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that if it were burning in the manner of a coal fire, the Sun would last only for a few thousands of years, whereas in fact the age of the Sun must be measured in thousands of millions of years.
Geologists can tell us the age of our own Earth with fair certainty. It proves to be at least 3,000 million years, and the Sun is older still, so that the 'burning' theory is obviously wrong. (It is worth adding that ages are relative newcomers to the scene. If we discount the time which has represented the age of the Earth by eighty hours, the whole story of human civilization will have to be crammed into a single second.)
A better idea was put forward by Sir Norman Lockyer in 1890. Lockyer, the pioneer spectroscopist who paid such attention to the prominences of the Sun, was deeply concerned with the life-story of the stars, and he believed that his observations sounded thrillingly straightforward. We know now that it was not correct, but nevertheless it provided a useful working basis.
Lockyer began by supposing that a star condensed out of material scattered in space as dust and gas. We know of such material; the Orion Nebula, close to the three bright stars of the Hunter's Belt, is made up of it, and this part of Lockyer's scheme is still accepted today.
Lockyer suggested that as the material drew together it would form a spherical mass, and its inner temperature would rise. Gravitational force would tend to make all the material condense towards a point in the centre of the mass, and so the temperature would increase steadily. At first the star would be a Red Giant of vast diameter, and relatively low surface temperature; as it shrank, it would become a Yellow Giant, and then a smaller but still bluish star called a Blue Giant. That would reach peak of its career. The gravitational shrinking could go on, until the temperature would drop also, and the star would become successively a Yellow Dwarf (such as the Sun) and finally a Red Dwarf. Eventually all its heat would leave it, and it would become a cold, dead globe.
When Lockyer put forward this theory, the giant and dwarf division had not been recognized. The later work of Hertzprung and Russell seemed to provide splendid confirmation, but still there was something wrong. A star which radiated only because it was shrinking under the influence of gravity could not last for more than 50 million years, which was not enough.
Russell tried to put matters right by introducing the idea of atomic energy. He knew of course that an atom contains protons, each of which carry a unit positive charge by electricity, and electrons, each of which carry a unit negative charge. If a proton and an electron met, he suggested, they would 'cancel each other out', and both would vanish, with the emission of energy. Could it be that a star shone because it was annihilating its material?
Russell's theory was published in 1913, and seemed to be satisfactory. A star would begin as a Red Giant, as Lockyer had supposed, and would turn into a hot white star, after which it would cool down to become a Yellow Dwarf. If it remained up as a Red Dwarf. Unfortunately there were difficulties of another sort. So much energy would be available that a star could last for at least 10 million million years, and this was as obviously
THE TRIFID NEBULA IN SAGIT-
TARIUM: photograph taken on '1929'
with the 100-inch Hooker reflector at Mount Wilson; exposure 23 hours. A nebula of this sort is a mass of dust and gas, and is entirely different from any galaxy known to science. Spiral, since it is a member of our own Galaxy. The old name for external galaxies, 'spiral nebulae', is now obsolete. It was in any case somewhat misleading, since by no means all the galaxies are spiral in form.
![]() A photograph showing a nebula with several bright spots.
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too long as Lockyer's 50 million years had been too short. To make things worse, further studies of the atom showed that a proton and an electron could not annihilate each other as Russell had supposed.
Astronomers such as Sir Arthur Eddington, who had been born at Kewal, in Westmorland, in 1882 and who was responsible for great advances in our knowledge of a star's interior, puzzled over the whole problem of stellar evolution; yet almost up to the outbreak of the Second World War, the chief mystery—the source of stellar energy—remained unsolved.
The vital clue was discovered in 1938 by two astrophysicists working quite independently of each other, Hans Bethe in America and Hans Albrecht Bethe in Germany. Apparently Bethe had been attending a conference in Washington, and was returning by train to Cornell University when he started wondering whether he could calculate any 'nuclear reactions' which would explain the reason why the Sun shone. Before he got out of the train, he had broken the back of the whole problem.
Hydrogen is much the most plentiful substance in the whole universe, and it is also the lightest element in it. Near the Sun's centre, where the temperature is around 20,000,000 degrees and the pressure is colossal, strange things happen to the hydrogen nuclei. They band together to form nuclei of the second lightest element, helium. It takes four hydrogen nuclei to make one nucleus of helium, and the process is a complicated one, but the net result may be summed up quite simply: hydrogen is changed into helium by a nuclear reaction. This is the process. It is that which is responsible for the Sun's radiation.
If it were possible to balance four hydrogen nuclei against the single helium nucleus formed from them, we would find that the helium is slightly the less massive. Therefore, mass has been lost in the energy production process. It appears that the Sun is losing mass by 4,000,000 tons every second. The figure seems
**PROFESSORSIRARTHUREDDINGTON.**
One of the greatest of British astrophysicists,
Sir Arthur Eddington was responsible for many important advances. He was moreover a distinguished writer on astronomy, and wrote a number of popular books on astronomy and allied subjects. Modern theories of stellar evolution was much in his pioneer work in the earlier part of the present century.
**STELLAR EVOLUTION ACCORDING TO LOCKYER. In its final development, Lockyer's theory gave what appeared to be a very plausible explanation of stellar evolution. A star begins life as a Red Giant such as Betelgeuse, pass down the giant branch until becoming a very luminous star of type B (Rigel), then passing through a Blue Star stage before becoming a Red Dwarf (Proxima) and finally, a cold dark globe. It is now known that the whole theory is incorrect, and modern theories have straightened it out.
Nevertheless, Lockyer's theory provided a useful working basis**
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| A (White) |
(Orange-red) |
| F G K M |
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| 3000 |
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| 6000 |
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| Very Hot Star |
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| Old Star |
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| Young Star |
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unbelievable, but we may be sure that it is not very wide of the mark.
Hydrogen is the essential 'fuel', at least for stars such as the Sun, and of course the hydrogen supplies will not last for ever. Moreover, the very luminous stars are losing mass at an even more staggering rate. It has been estimated that Rigel in Orion does so at the rate of 0.0000000000000000000000000000001 gram per second, and it cannot go on radiating so energetically for more than a few thousand years yet.
In view of this new work, it is still possible to look at the Hertzsprung-Russell Diagram and to decide whether we can still retain the attractive Red Giant to Red Dwarf sequence. Rather reluctantly, astronomers have decided that we cannot.
There is no choice but to start afresh.
A whole class of beautiful nebulae such as the Sword of Orion. Local condensations appear, and the newly-born star contracts under gravitational force. As soon as the central temperature is high enough, nuclear reactions begin, and by the time the star has reached the Main Sequence we find that it is drawing its energy from the conversion of hydrogen into helium.
The main difference between modern and older theories is that a star like our Sun is becoming more luminous as it uses up its hydrogen fuel. We do not know how long this will continue, but it now seems certain that the energy output is becoming greater instead of smaller, so that the final fate of life on Earth will be destruction by heat instead of by cold.
Once a Main Sequence star has almost exhausted its hydrogen it is left with a central core of helium, which cannot be used for energy production. According to one theory this core will then 'quench' itself, and become invisible to us, and the star will rearrange itself drastically. The outer layers will swell, and cool as they do so, until we are left with a star consisting of a small, very hot core surrounded by a huge rarefied 'atmosphere'. In other words, the star will become a Red Giant.
Not all authorities agree with this picture. A Red Giant may be in a different pattern, and its source of energy is not yet properly understood. But whatever happens, it is certainly involved. But we can see that on modern theories a Red Giant is not a young star at all; it has reached a late stage in its career, and there is a strong possibility that our own Sun will become a Red Giant in something like 10,000 million years from now.
The giant stage cannot last for ever, and once the star has used up all its hydrogen it must die. We do not know what happens. It may be that there is a tremendous explosion producing a supernova similar to the star seen by Tycho Brahe in 1572; it may be that supernovae are the exception and not the rule. At any rate, some astronomers believe that a Red Giant changes rather suddenly, on the astronomical scale, into a very different object--a White Dwarf. This brings us on to the remarkable story of Sirius B.
Sirius itself is the most brilliant star in our skies. It is by no means particularly luminous; admittedly it is 66 times as powerful as the Sun, but this does not seem much when we remember that we know of stars which have a million Sun-power. Sirius is conspicuous mainly because it is only 84 light-years away. Of
THE HORSE'S-HEAD NEBULA IN ORION, near the bright star Zeta Orionis. This nebula, known officially as LC. 434 or Barnard 33, is made up of dark material, and is 14 light-years across. It contains the 'Horse'-Head'. The photograph was taken in red light with the 200-inch Hale reflector at Palomar
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the 1st-magnitude stars, only Alpha Centauri, at 4$\frac{1}{2}$ light-years is nearer.
This closeness means that Sirius has an exceptionally rapid proper motion. In 1834, Friedrich Bessel realized that its behavior was peculiar. Its motion relative to its neighbor seemed to be erratic, instead of moving uniformly, it was 'waving' its way along, as shown in the diagram. Each 'wave' was very tiny, and took about fifty years to complete, but there seemed to be no doubt about it.
Bessel decided that there was only one explanation. Sirius must have a faint companion which was pulling on it and making it travel in a curve. On the other side of a straight line, Jean-Adrien and Le Verrier had tracked down the planet Neptune because of its effects on Uranus, so Bessel worked out where the companion of Sirius must be. He had no hopes of seeing it himself; he realized that it must be overpowered by the glare of the bright star. When Bessel died, in 1844, the Companion was still undiscovered.
Then, in 1862, a well-known American instrument-maker named Clark decided to test a new 7-inch telescope by looking at Sirius. To his surprise he saw a twinkling of light beside the bright star. It proved to be the long-expected Companion, almost exactly where Bessel had said it would be.
According to its effects on Sirius itself, the Companion was estimated to be almost as massive as the Sun. Since it was only of magnitude 8$\frac{1}{2}$, it was 10,000 times less luminous than its brilliant neighbor, and was assumed to be cool and red, with a large diameter.
The real shock came in 1915. At Mount Wilson, Walter Sydney Adams examined the spectrum of the Companion, and found to his surprise that the star was not cool at all. It was white, and its surface temperature was 8,000 degrees—2,000 degrees greater than the Sun's!
Astronomers all over the world were deeply interested. The Companion was very faint, so that it sent out relatively little light—and yet its surface was at white heat! The only way to make the observations fit was to assume that it was a dwarf with a diameter of only 24,000 miles. This meant that it was smaller than a planet such as Uranus or Neptune.
On the other hand the Companion was about as massive as the Sun, and so was quite unlike a planet. It was amazingly 'heavy' for something so small—it contains something like 70,000 times that of water. Comparing it with Sirius was rather like comparing a small, dense bullet with a distended cream puff.
Other 'White Dwarfs' were found, some of them even more extraordinary. One star studied by G. P. Kuiper in America proved to be only 4,000 miles across, about the size of Mars, and yet as massive as the Sun. If it were possible to take a cube of material from Kuiper's star and carry it across this country weighing one cubic inch, and bring it back to Earth, the weight would be about half a ton. Many tons could be packed into a thimble.
To explain this 'super-dense' matter we must go back to our description of the way in which an atom is built up. There is a central nucleus, round which move circling or planetary electrons.
APPARENT MOVEMENT OF SIRIUS (Diagram). The wavy line of the bright component, shown by the thick wavy line, showed that there must be an unseen companion affecting its motion.
![]() A diagram showing the apparent movement of Sirius.
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SIZES OF DWARF STARS. The Sun, with its diameter of 86,000 miles, is regarded as a dwarf star, but some of the White Dwarfs are much smaller than the Sun. These are shown together with the planets Uranus, the Earth and Mars, and two White Dwarfs—Sirius A and B. It is interesting to find that Kuiper's Star, with a diameter slightly less than that of Mars, has a mass equal to that of the Sun, so that its matter is remarkably dense.
(It is not easy to explain atomic structure in non-mathematical language, since the nucleus and the electrons are not, strictly speaking, solid lumps of material; but the picture is good enough for our present purpose.) It is clear, then, that most of the atom is empty space. High temperatures and pressures break up the atom by breaking off some of the planetary electrons; an atom damaged in this way becomes a White Dwarf. In a White Dwarf, the ionization is complete. Every planetary electron is broken off and the result is a chaotic jumble of atomic nuclei and unattached electrons. Waste space is eliminated, and the broken pieces of the atom may be crammed close together. This accounts for the incredibly high densities.
There seems little doubt that a White Dwarf has used up all its nuclear fuel, and is continuing to shine only because it is still shrinking slowly under the influence of gravitation. It is a
![]()
Uranus
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'bankrupt' star, and has sunk into a long-drawn-out old age. No more supplies of energy are left to it, and eventually it must die.
Do all stars turn into White Dwarfs eventually? Some authorities believe so, in which case the life-story of a star may be summed up quite neatly. The star begins by condensing out of interstellar matter into a 'Giant' Star. Soon after this it becomes very luminous; it turns into a Red Giant as its hydrogen is exhausted, and when it has used up its other fuels also it collapses into a White Dwarf. This may well be the fate in store for the Sun.
The picture may be completely wrong. Theories change every few years, and new discoveries may cause us to alter our ideas completely. For the moment, however, we can say no more. There is a possibility that the Sun will pass through a period of glory before it collapses and becomes a 'stellar glow-worm' similar to the strange, super-dense Companion of Sirius.
![]() STAR-CLOUDS IN THE MILKY WAY:
Sagittarius region. Photographed with a
Teasar lens of 10-inch focus
Earth
Mars
Kuiper's Star
Sun
48-INCH SCHMIDT CAMERA-TELESCOPE AT PALOMAR
24
**the variety of the stars**
WE HAVE SEEN how men such as Hipparchus, Ptolemy and Tycho Brahe drew up star catalogues, using observations made with the naked eye. The later application of telescopic sights allowed Flamsteed and his successors to draw up far better catalogues. In this connection it would be unfair not to mention Friedrich Argelander, who was born at Memel in Germany in 1799, and became Director of the Bonn Observatory. Between 1830 and 1865 he drew up a sky catalogue of 300,000 stars down to the 9th magnitude—a grand total of over 300,000. The Bonn Durchmusterung became a standard work.
Argelander was assisted by another German astronomer, Eduard Schönfeld, who later extended the catalogue to the southern skies and chartered about 133,000 stars. Schönfeld became Director of the Bonn Observatory after Argelander died, and continued to make detailed surveys.
Nowadays, of course, photography has enabled us to produce very detailed sky surveys. Particularly useful is the Schmidt camera, invented as recently as 1930, which has a rather complicated optical system which makes it possible to photograph large areas of the sky with each exposure. Large Schmidt cameras have been set up at Palomar and elsewhere. Bernhard Schmidt, who developed the camera, had to give up his own telescope, but having hurt himself so badly that he lost an arm he turned to astronomy as being rather safer. Astronomers throughout the world have every reason to be grateful that he did, since Schmidt cameras have proved to be of the greatest value.
Among the stars catalogued in early times were some which proved to behave in a curious way, since they did not shine steadily. These stars are altered in brightness by an extent of several magnitudes. Perhaps one of the most famous of these variable stars is Mira, in the constellation of Cetus, the sea-monster of the Perseus legend.
One of the early pioneers of telescopic astronomy was David Fabricius, a Dutch pastor who lived at Oostel in Holland. He was a friend of Tycho and Kepler, and father of Johann Fabricius, who discovered Jupiter's moons independently of Galileo and Scheiner but who died young.
On August 13, 1595, David Fabricius was looking at stars in Cetus when he noticed an object of the 3rd magnitude. He paid no particular attention to it, since it looked just like a normal star, but by October it had disappeared. It is rather curious that Fabricius made no attempt to follow the matter up. (Incidentally he received an informal letter in January 1601 preaching a sermon in which he said that one of his guests had been stolen and hinted that he knew who was responsible. Evidently he was right, since he was murdered before he could give the name of the thief.)
When Johann Bayer was drawing up his own catalogue, in 1603, he recorded a star in the same place as Fabricius had done. This time it was of the 4th magnitude, and Bayer gave it the
THE DOUBLE STAR-CLUSTER IN PERSEUS. These objects are not included in Messier's famous catalogue, and are known officially as H.VI.33 and 34, from their position. The photograph given here was taken in 1922 by W.S. Franks, using a 6-inch refractor. The clusters are so close together that they are liable to be confused with the Sword of Orion; are beauti-
ful objects, excellently seen in a small tele-
scope
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the variety of the stars
![]() A diagram showing the constellation Cetus with the position of the long-period variable Mira marked.
THE CONSTELLATION OF CETUS,
showing the position of the long-period variable Mira
Greek letter Omicron. He did not associate it with Fabricius' vanishing star; neither did Wilhelm Schickard, Professor of Mathematics at Tübingen University, who saw it again in 1631.
Then, in 1638, another Dutchman—Johann Phocylides Holwarda, a professor at Franeker University—began a series of observations which showed that Omicron Ceti appeared and vanished regularly. The results were remarkable, and his first observations by Hevelius from 1648 onward showed that it had a period of about 331 days. At maximum it may reach the 2nd magnitude, and has been known to outshine Polaris. At minimum it drops to magnitude 9.3, so that even binoculars will not show it. It has an M-type spectrum, and is strongly orange-red; like Betelgeux, it is a Red Giant of vast diameter. Moreover it has a fairly short life.
Omicron Ceti was the first variable star to be identified, and was well named Mira, or 'the Wonderful'. Neither the period nor the maximum magnitude are constant. In some years Mira has failed to become brighter than the 5th magnitude, and on an average it is only visible to the naked eye for about 18 weeks out of its 47-week period.
Many other 'long-period variables' have been detected, a notable example being Chi Cygni in the Swan, which has a period of 409 days. At maximum it is of magnitude 4.3, and is an easy naked-eye object, but at minimum it sinks to magnitude 14, and a telescope of some size is needed to show it. Chi Cygni, too, has an M-type spectrum, and is a Red Giant. Most (though not all) of the long-period variables are of the same type. A small instrument will show many of them, and it is fascinating to watch their slow but obvious changes.
Rather different are the irregular variables, which have no definite periods at all. The most conspicuous of them is of course Betelgeux in Orion, which sometimes matches Rigel, but may
![]() A high-dispersion spectrum of Omicron Ceti.
SPECTRUM OF O CETI, High Dispersion.
Spectral Type M0a
3700-4400A
MIRA CETI
RICH STAR-FIELD IN THE MILKY WAY REGION
HIGH-DISPERSION SPECTRUM OF
MIRA CETI
the variety of the stars 185
![]() A diagram showing the constellation Cepheus, with lines connecting stars to indicate their positions. The labels "Alderamin" and "Cassiopeia" are shown near the stars they represent. A line labeled "CEPHEUS" extends from Alderamin to Cassiopeia.
THE CONSTELLATION OF CEPHEUS, showing the positions of the famous variables Delta and Mu. Cepheus is not a prominent group, but the W. C. Curtis star at its center, the brightest star is Alderamin. Delta Cephei is not conspicuous, but is always an easy naked-eye object, and may be seen through a telescope. Epsilon and Zeta, with which it forms a small triangle. Mu is sometimes easy to see without a telescope, being about 6th magnitude, almost the 6th magnitude. The strong red color which led to Herschel's christening it 'the Garnet Star' is not evident with the naked eye, but any small telescope will show it excellently.
![]() A light-curve graph of Delta Cephei. The x-axis represents days, ranging from 0 to 6. The y-axis represents magnitude, starting from -3.9 and going up to +4.5. The curve shows fluctuations around a central value, with maxima occurring at intervals of approximately 5 days.
LIGHT-CURVE OF DELTA CEPHEI.
The fluctuations are perfectly regular. This star is the most famous member of its class.
fade until it is no brighter than Aldebaran in the Bull. There is a rough period of about 5 years, but we can never tell just how Betelgeux is going to behave. This applies also to Mu Cephei, in the far north, and to Eta Aquila, in the south, whose magni-
tudes 4 and 6. It is so highly-colored that Sir William Herschel nicknamed it 'the Garnet Star', and it is a lovely object in bin-
oculars or a small telescope.
Some faint variables are even more unpredictable. R Corona Borealis in the Northern Crown is usually easy to see in a low-
powered instrument, sometimes it drops abruptly by as much as 8 magnitudes, remaining at minimum for some time before brightening again. Another faint variable in the Giraffe normally shows semi-regular rises and falls, but sometimes be-
comes perfectly steady for months on end before starting to fluctuate again. Stars such as SS Cygni and U Geminorum have
periodical 'outbursts', and are sometimes termed dwarf nova'.
There seems to be no end to the different types.
On the other hand there are some variable stars which are as regular as clockwork, and can be forecast their bright-
ness with complete accuracy. The most famous of them is Delta
Cephei, whose changes were first detected in 1784 by a most
unusual astronomer—John Goodricke.
Goodricke was born in Holland, of English parents, in 1764.
He was deaf and dumb, and remained so all through his life, but
there was nothing the matter with either his eyesight or his brain,
and he became one of the best observers of his day. Unfor-
tunately he lived only to the age of twenty-one. In spite of his
handicap, he had shown every sign of becoming one of the
leading astronomers of his time.
Goodricke was studying the stars in Cepheus when he was
attracted by the changes of Delta, which forms a small triangle
with its neighbours Alpha and Beta Cephei. He found that similar
rises and falls occurred soon Goodricke found that maxima occurred at intervals of 5 days or so. The magnitude range was from 3:7 to
4:3, so that the star was always an easy naked-eye object even though it was never particularly conspicuous.
In the same year another English astronomer, Pigott, found that Eta Aquila, not far from the brilliant star Altair, varied from magnitude 3:7 to 4:3 in a period of just over 7 days. Like Delta Cephei it could not be regarded as a variable star also to
many other variable stars their real luminosities: the longer the interval between one maximum and the next, the more luminous
the Cepheid. For instance Delta Cephei, with a period of 5 days
9 hours, shines 660 times as brightly as the Sun when at its bright-
est. Eta Aquila, with a period of over 7 days, is more luminous.
A southern Cepheid, I Carinae, with a period of 35$\frac{1}{2}$ days, has a maximum luminosity as great as 5,500 Suns.
5
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![]() A diagram showing the position of the Cepheid variable Eta Aquila within the constellation of Aquila.
THE CONSTITUTION OF AQUILA, showing the position of the Cepheid variable Eta Aquila
The reason for this period-luminosity law is quite unknown, but it is remarkably useful. As soon as we know the period of a Cepheid, which we can find out merely by studying it with a telescope, we can tell its luminosity. By comparing the luminosity with the apparent magnitude, we can calculate the distance of the star's distance. Since Cepheids are powerful stars, they remain visible over vast distances, and have been named the 'standard candles' of the Galaxy. By using them we can gauge distances which are so great that the old parallax method would be utterly useless.
It is interesting to find that the Pole Star is a Cepheid variable. Its changes in magnitude are very slight, and its period is almost 4 days, which tells us that its luminosity is about 550 times that of the Sun.
Related to the Cepheids are the RR Lyrae variables, which are just as regular but which have shorter periods. All are remote, and so all appear faint. The strange thing about them is that all seem to have about the same luminosity, 90 times as great as the Sun's. They are so called because RR Lyrae, in the small but interesting constellation of Lyra (the Lyre) was the first to be discovered.
Many astronomers have been forward to explain the reasons why some stars are variable. Our knowledge is still incomplete, but we do know that the variables swell out and contract, so that their fluctuations are due to actual changes in the stars themselves. Unlike the Sun they are not completely stable. It has been suggested that all stars become 'variables' for a period in their careers, but this may or may not be the case. It is certainly fortunate that the Sun does not change much during our lifetime, since temperature changes on Earth would make our world unfit for habitation.
Neither do we know the exact cause of nova, or 'new stars' - which, as we have seen, are not genuinely 'new' at all, but represent some tremendous upheaval in a previously faint object. The very brilliant stars seen by the Chinese in 1054, by Tycho in 1572 and by Kepler in 1604 were more cataclysmic still; in such supernova the star seems to blow most of its material away into space, so that it never returns to its former state. That was one of the Chinese supernova, for instance, may still be seen as a gas-cloud, noticed by Messier and known to astronomers as the Crab Nebula.
It lies near the third magnitude star Zeta Tauri, and may be seen with a small telescope, though large instruments are needed to show its full beauty.
Nova novae are much more common. A particularly interesting one appeared in 1934, when J. P. M. Prentice, an English amateur famous for his work on meteors, discovered a bright 'new star' in Hercules, not far from the head of the Dragon. It reached the 1st magnitude before fading away again, and is still visible in powerful telescopes. Other bright nove of the present century appeared in 1901, in Perseus; 1918, in Aquila; 1925, in Pictor; 1930, in Bootes; and 1945 in Argo Navis. The first two became very conspicuous and formed a sort of constellation between them and the bright star from Sirius and Canopus. Nova Persei later developed a 'shell' of gas, which expanded outward and showed many interesting features. Nova Lacerta also ejected gaseous shells at a speed of something like 2,400 miles per second.
The last bright nova was discovered on March 7, 1960 by the
![]() A photograph of a supernova in NGC 4598 taken with a 36-inch reflector at Mount Wilson.
SUPERNOVA IN THE GALAXY NGC 4598 photographed with the 36-inch Hooker reflector at Mount Wilson. (Top) August 23, 1937, when the supernova was at maximum. (Middle) November 24, 1938, six months after maximum. (Bottom) January 19, 1942; the supernova can no longer be seen. Supernovae of this sort have often been recorded in external galaxies
Norwegian astronomer Olaf Hassell. It reached the 5th magnitude, and I remember seeing it clearly with the naked eye, but it faded quickly. A new bright nova may appear at any moment, and it is only by the most careful observation that anyone who sees a bright star which he cannot identify would be unwise to report the discovery of a nova until very careful checks have been made.
Mention must also be made of an extraordinary star in the southern hemisphere, Eta Argus. It seems to be a variable and not a true nova, but its light-changes have been remarkable. About 1840 it was brighter than any star in the sky apart from Sirius; for the last half-century it has been too faint to be seen
NOVA HERCULIS 1934, photographed in ultra-violet, green and red light in 1951.
Photographs with the 200-inch Hale reflector at Palomar
EXPANDING NEBULOSITY ROUND NOVA PERSEI, photographed with the 200-inch Hale reflector at Palomar
![]()
A diagram showing the positions of Vega, Nova Herculis, and Hercules. The head of Draco is also shown.
**HEAD OF DRACO**
**LYRA**
**Vega**
**NOVA**
**HERCULES**
POSITION OF NOVA (DQ) HERCULIS 1934, in the region of Vega and the head of Draco
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without a telescope. It is associated with the lovely gaseous Keyhole Nebula, and northern astronomers always regret that it never rises above the horizon in Europe or the Northern United States.
Most bright variables and novae are a long way off, which means that our telescopes cannot see them out of date. Prentice's nova of 1934, for instance, is 800 light-years away. This means that the outburst actually took place not in 1934, but about 1134, during the reign of William the Conqueror's son Henry I.
In 1669 Geminano Montanari, Professor of Mathematics at the Italian University of Bologna, found that Algol (Beta Persei) was apparently variable. At this time Mira was the only variable star
THE KEYHOLE NEBULA IN ARGO.
Nebulosity in the region of the famous interstellar nebula is so faintly visible that apparently the area is too far south in the sky to be seen from Europe or the northern United States
LIGHT-CURVE OF BETA LYRAE. The secondary minimum is much more pronounced than in the case of Algol
![]() A diagram showing the constellation of Perseus with Algodol labeled.
**THE CONSTELLATION OF PERSEUS**
![]() A graph showing the light-curve of Algol. The small secondary minimum cannot be detected without instruments.
**LIGHT-CURVE OF ALGOL. The small secondary minimum cannot be detected without instruments**
![]() A diagram showing the constellation of Lyra with Beta Lyrae labeled.
**THE CONSTELLATION OF LYRA**
![]() A graph showing the light-curve of Beta Lyrae. Days are on the x-axis and magnitude on the y-axis.
**Beta Lyrae**
the variety of the stars 189
known, so that Montanari's discovery caused great interest, particularly as Algol behaved in a way of its own. Usually it was steady at just below the 2nd magnitude, and showed no changes for several years. Then it would suddenly drop to magnitude 3, taking 5 hours to do so; it remained faint for a short period, and then took a further 5 hours to climb back to maximum.
Goodricke, painstaking as ever, studied Algol closely and came to the conclusion that the star was not a genuine variable at all. Admittedly it showed fluctuations in light, but Goodricke believed that these changes were due to the daily orbital period between Algol and its companion. In this case Algol would be a binary, with one bright and one dimmer component; when the dimmer star passed between the bright component and ourselves, it would eclipse the main star, and the total brightness would drop.
As we now know, Goodricke was quite right. The bright member of the Algol pair has a B8-type spectrum and a surface temperature of 12,000 degrees with a diameter of about 1.7 million miles. The other member is fainter than 16th magnitude. When the bright star eclipses the faint star there is a much smaller fall in brilliancy, so slight that even Goodricke did not notice it.
Strictly speaking, then, Algol is not a proper variable, but an eclipsing binary. There is no difference between it and an ordinary binary of short period except that the plane of the orbit happens to lie in our line of sight. Were the orbit differently tilted, no eclipse would occur.
Another eclipsing variable easily visible to the naked eye is Beta Lyrae, close to the brilliant Vega. Here the light-changes are always going on. Both components are very hot and luminous, and are so close together that they almost touch. They raise huge tides in each other, and each star is distorted into the shape of an egg-shaped ellipsoid. As they revolve round each other some of this material streams out to produce a shell of gas rounding the pair. Fewer than 200 Beta Lyrae-type variables are known, but eclipsing binaries similar to Algol are much more common.
Perhaps the most remarkable of the eclipsing binaries are Zeta and Epsilon Aurigae, which with Eta Aurigae form a triangle of stars beside Capella. Zeta consists of a B8 giant over 100 times as luminous as the Sun, accompanied by a K4-type star with much lower brilliance. The two stars revolve round each other at least 200 million miles. The period is 972 days, as against less than 4 days for Algol, which shows that the components are much farther apart. When the red star eclipses the hot giant, interesting changes in the spectrum are noted; the hot star seems to dim slightly, showing that it is shining through the vast tenuous atmosphere of its companion, and it is some time before the spectrum of the hot star disappears. From this we can calculate that the outer part of both components has a density of no more than about one-five-millionth that of water.
Epsilon Aurigae consists of a particularly luminous yellow star 60,000 times the power of the Sun, together with a companion whose surface is much cooler (only 1200 degrees), but whose diameter is around 1,360 million miles—larger than the orbit of Saturn! A jet-aircraft moving at a constant speed of 1,000 m.p.h.
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the variety of the stars
![]() A diagram showing the positions of Capella, Nath, and Zeta Aurigae in the constellation Auriga. Capella is at the top left, Nath is at the bottom right, and Zeta Aurigae is near the center. The diagram also shows the positions of two stars in a binary system, labeled A and B. The diagram is annotated with labels indicating the positions of these stars.
THE CONSTELLATION OF AURIGA,
showing the positions of the two remarkable
eclipsing binaries Epsilon and Zeta Aurigae
would take over 6,000 years to go once round the red star of Epsilon Aurigae. Eclipses are infrequent, since the revolution period is 27 years. As long ago as 1821 Fritsch found Epsilon Aurigae to be a variable, but the fact that it is actually an eclipsing binary was not discovered until astrophysical methods were used much later.
Eclipsing binaries prove that some apparently single stars are in fact pairs, with components so close together that no telescope will divide them. However, the German astronomer Vogel, who acted as Director of Potsdam Observatory between 1882 and his death in 1907, found that where the telescope fails the spectroscopic can succeed. We come back once more to our reliably able the Doppler Effect.
Suppose that we have a very close binary whose components appear as a single mass? If the orbital plane is almost edge-on to us, as shown in the diagram, there will be times when one star (A) is approaching us, while the other (B) is receding. The spectrum of A will therefore yield a Doppler shift towards the violet, while the spectrum of B will give a red shift. At other times, when A is receding and B is approaching, the shifts will be reversed; when the motion of the components is perpendicular to our line of sight, there will be no Doppler shifts due to orbital motion.
If therefore we find a star whose spectrum lines regularly become double, we may be sure that we are dealing with a close *spectroscopic binary*. Capella is one such star, while the bright companion of Mizar in the Great Bear is another.
Visual binoculars show many common types optical pairs of the kind shown in the diagram on page 354. Some of them show contrasting colors, and are really beautiful. Perhaps the loveliest of all is Albireo in the Swan, which has a yellow primary and a bluish-green companion and is well seen in a small telescope. Antares, the bright red star in the Scorpion, has a green companion called Castorletti in Hercules, which is one of the largest stars known to us and may even have a diameter greater than that of Epsilon Aurigae.
The stars of a binary system move round their common centre of gravity. The periods range from a few hours for close spectroscopic pairs up to millions of years for wide visual pairs. As we have seen, the stars are not so unequal in weight as might be supposed; even Mizar Ceti, with its vast diameter of about 300 million miles, is less than 20 times the mass of the Sun. Therefore the centre of gravity for a normal binary system is not very far from the mid-point of an imaginary line joining the centres of the two stars.
Multiple stars also occur. The most spectacular is Epsilon Lyrae, near Vega. To the naked eye it appears as a double, and a 3-inch refractor is enough to show that each component is again double, so that this forms a quadruple system. Castor, the senior though fainter member of this system, has a four-fold system made up of four bright components and two dim stars.
Only a few of the most interesting objects in the stellar heavens have been mentioned here. There is endless variety among the stars, and it is clear that we have learned much since the new science of astrophysics came into its own less than a century ago.
DETECTION OF A SPECTROSCOPIC
BINARY. In the positions shown, component
A is approaching and will show a violet shift;
B is receding, and will show a red shift
![]() A diagram showing the positions of several stars, including Aldebaran, in Taurus (the Bull). The Hyades, which appear as a V-shape of relatively faint stars near the brilliant red Aldebaran, is also shown.
**Aldebaran**
THE HYADES, which appear as a V-shape of relatively faint stars near the brilliant red Aldebaran, in Taurus (the Bull)
**25 the galaxies**
LOOK UP AT THE SKY on a clear night, and you may think that you will see millions of stars. This is not the case. At any one moment, nobody can see more than a few thousands of stars without using optical aid. However, the actual number of stars in our Galaxy really does amount to millions; indeed, the best modern estimate gives a grand total of 100 thousand million.
Astronomers speak of 'open' or 'galactic clusters', of which the best examples are the Pleiades or Seven Sisters, round the 3rd-magnitude star Alcyone in Taurus, and the Hyades, round Aldebaran—also in Taurus. Another interesting cluster visible to the naked eye is Persepe in Cancer, nicknamed the 'Beehive', while southern observers have the 'Jewel Box' in the Southern Cross.
| Pleiades |
Asterope |
Taygeto |
| Maus |
Celano |
|
| Atlas |
Alcyone |
Electra |
|
Merope |
|
THE PLEIADES or 'Seven Sisters'. All the stars named are visible with the naked eye on a clear night. The brightest of them, Alcyone, is of the 3rd magnitude
SPIRAL GALAXY N.G.C. 3841, IN Ursa Major. The spiral form is well shown. Like most external galaxies, the object is too small seen through even moderate telescopes. Photography with very large instruments is needed to bring out the details properly. This picture was taken with the 200-inch Hale reflector at Palomar
![]() Spiral galaxy Messier 64 (NGC 4825) in Coma Berenices, as photographed with the 60-inch reflector at Mount Wilson.
Spiral Galaxy Messier 64 (NGC 4825) in Coma Berenices, as photographed with the 60-inch reflector at Mount Wilson
the galaxies 193
There are also the nebulae, which are less conspicuous. The first mention of them goes back to the tenth century, when Al-Sufi recorded the Great Spiral in Andromeda, though to him it appeared as a faint star. The name Nebula was first used when it was mentioned in 1612 by Peiresc, and the work of Messier, Herschel and others led to the detection of large numbers of nebulae of all kinds. Herschel, as we have seen, regarded some of them as 'starry' and others as non-stellar. In 1791, writing about the Orion Nebula, he stated: 'Our judgment, I venture to say, will be that the nebulousness around this star is not of a starry nature.'
One great advance in the experiment had to wait until the development of the spectroscope. It was made on August 29, 1864, by Sir William Huggins.
A star yields a spectrum with a rainbow background and dark absorption lines. If therefore a nebula is made up of stars, the result will be a jumble of all the separate star-spectra together, and the main absorption lines should be made out. If a nebula is made up of gas it will give an emission spectrum consisting of isolated bright lines.
Huggins turned his spectroscope towards an 'irresolvable' nebula in Draco. At once he saw bright emission lines, but no rainbow background. Herschel had been right; the nebula was gaseous, and was not made up of stars.
Objects of this sort are known as gaseous or galactic nebula.
NGC 205, companion of the Andromeda Nebula, photographed in red light with the 500-inch Hale reflector at Palomar
MESSIER 15: NEBULA IN SCUTUM SOBIESKI, photographed in red light with the 200-inch Hale reflector at Palomar
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the galaxies
![]() A black and white photograph of a dumb-bell nebula in Vulpecula, a famous planetary, photographed at the Lick Observatory.
THE DUMB-BELL NEBULA IN VULPECULA, a famous planetary, photographed at the Lick Observatory.
PLANETARY NEBULA N.G.C. 7293 IN AQUARIUS, photographed in red light with the 200-inch Hale reflector at Palomar.
The Sword of Orion is the best known of them; it surrounds a famous multiple star, Theta Orionis (known as the Trapezium, because of the arrangement of its four main components), and is of tremendous extent. A ray of light would take twenty years to cross from one side to the other. It is in nebulae of this sort that, according to modern theory, fresh stars are being created out of the dust and gas.
Herschel also noted various different objects which he christened 'planetary nebula', because they showed planet-like disks. The brightest of them, the Ring Nebula, is conveniently placed between the famous eclipsing binary Beta Lyrae and its neighbor Gamma, and is easy to see in a moderate telescope. Actually a planetary nebula is a very rare thing; it consists of a compact, faint central star, possibly not unlike a White Dwarf, surrounded by a tremendous, expanding shell of gas. Some authorities believe that a planetary nebula represents the final stage of a nova or supernova, but of this there is no proof. The gas is very rarefied; if we could take a cupful of air and spread it around a vast enclosure 5 miles in diameter, the resulting density would be about the same as that of a planet's atmosphere.
All Herschel's most important work was concerned with the distribution of stars in our Galaxy. He believed the system to be shaped like a double-convex lens, with the Sun near the middle,
the galaxies 195
and at the time his idea seemed perfectly reasonable. It was not until well into the twentieth century that a more accurate picture was given by the American astronomer Harlow Shapley.
Shapley—who is still alive and active—was born at Nashville, in Missouri, in 1865, after completing his university education he went to work for George Washington大的大学教授，of Russell Diagram fame. In 1914 he moved to Mount Wilson, and stayed there until 1921, when he was appointed Director of Harvard College Observatory. He continued to work as hard as ever even after he officially retired.
While at Mount Wilson, Shapley used the 60-inch reflector there to study the objects known as globular clusters. These are immense collections of stars, which are found around the centre of the clusters, and are magnificent in large instruments. About 100 of them are known. Messier 13, in Hercules, is visible to the naked eye, and is a familiar sight to European astronomers, but the brightest globular clusters—Omega Centauri and 47 Tucanae—lie too far south to be seen from our latitudes.
Shapley knew that the globulars are very distant; and seem to form a kind of 'outer framework' to the Galaxy. They were so remote that they could not be measured by parallaxes, and Shapley turned to less direct methods. Moreover he saw that most of the globulars were in the southern sky, particularly in the region of the constellations Scorpio and Sagittarius. Such a 'lop-sided' distribution could hardly be due to chance.
The essential clue was found when Shapley detected RR Lyrae
MESSEY (3): THE GLOBULAR CLUSTER IN HERCULES, photographed with the 60-inch reflector at Mount Wilson. The first photograph was given an exposure of 15 minutes; the second, 37 minutes; the third, 94. The increase in number of stars shown with increasing exposure is very obvious. In this respect the photographic plate is far superior to the eye; the longer the exposure, the more it records.
THE OWL NEBULA, Messier 97 in Ursa Major. Another planetary, photographed with the 60-inch reflector at Mount Wilson
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![]()
A diagram showing the relative distances of stars within the Milky Way Galaxy. The Sun is shown at the center, with a star cluster labeled "SUN" to its left. A large star labeled "2000 light years" is shown to the right of the Sun, and another star labeled "100000 light years" is shown further to the right. The diagram also shows a line labeled "Main Plane" running horizontally across the middle.
THE GLOBULAR CLUSTER OMEGA CENTAURI, photographed at Royal Observatories, Greenwich, on February 19, 1903 (exposure 50 minutes). This is the brightest globular cluster in the sky. Unfortunately it lies too far south in the sky to be seen from Europe or the northern United States.
GALAXY N.G.C. 4565, a system seen almost 'edge-on' to us
variables inside the globular clusters. It was known that these stars obeyed a period-luminosity law, and that each was about ninety times as luminous as the Sun. Once RR Lyrae variables had been found, then, their distances could be worked out—and hence, the distances of the globulars in which they lay.
Shapley's results gave astronomers something of a shock. By studying the globulars and measuring their distances it has been shown that the Galaxy has a diameter of about 100,000 light-years, with a greatest width of about 20,000 light-years. The Sun lies well within this circle, but it is not clear whether it lies close to or far from the galactic nucleus, which at once explains the lop-sided distribution of the globular clusters. The galactic nucleus lies in the direction of the glorious rich star-clouds in Sagittarius.
Unfortunately we cannot see right through the nucleus, or even to the galactic centre. There is a great deal of obscuring material in the way, and light-waves cannot penetrate it. Radio waves can do so, however, and have been used for this purpose since after the end of the First World War, radio astronomy still lay in the future.
Following on from this research, it was found that the whole Galaxy is rotating. The Sun is moving round the nucleus, taking over 225,000,000 years to complete one journey. This period is sometimes termed the cosmic year. One cosmic year ago, the most advanced life-forms on Earth were amphibians; the Coal Measu- sures were being laid down; and men had not yet appeared. Two cosmic years ago, life only lived on Echinodermata of tiny creatures in the oceans. It is interesting to speculate as to what 'men' will be like in one cosmic year from now—if, indeed, men still exist.
Now let us go back to Herschel's second guess: that the starry or resolvable nebulae are 'island universes', far beyond the bound-aries of our own system.
The clusters, as well as the gaseous nebulae such as the Sword of Orion and all the stars visible to the naked eye, were known to be members of our Galaxy, but it was difficult to be so sure about the spirals and other objects of similar type. Were they, too, members of one large system—or were they not? The only way to decide was to measure the distance of at least one of them, and the most promising was undoubtedly the Great Spiral in Andromeda, M31. When it was bright enough to be seen without a tele- scope, it was likely to be nearer than the rest.
The matter was settled in 1923 by Edwin P. Hubble, who had been assistant at Yerkes Observatory from 1914 to 1917, and had
The 'Saturn Galaxy' NGC 4504, photographed with the 60-inch reflector at Mount Wilson. The nickname is due to a superficial resemblance to Saturn and its system of rings.
**DIAGRAM OF THE GALAXY AS IT WOULD BE SEEN EDGE-ON. The galactic centre lies about 25,000 light-years away, and the stars in the outer regions drift out toward the edge of the system, and is not near the centre, as Herschel believed. When we look along the main axis of the galaxy, we appear to see approximately the same direction, and this causes the Milky Way effect**
![]() Messier 87, a globular galaxy in Virgo, photographed with the 200-inch Hale reflector at Palomar
**the galaxies** 197
then moved to Mount Wilson. Using the 100-inch Hooker reflector, much the most powerful telescope in the world at that time, he searched for Cepheid variables inside the Andromeda Spiral, and indeed he found them. He looked for half a dozen, and worked out their distances. The result was conclusive. The Cepheids, and hence the spiral, were hundreds of thousands of light-years away, and so the Spiral was in fact a separate system, containing stars, clusters, gaseous nebulae and other features known in our Galaxy.
A new system of naming came into force. The term 'nebule'
was confined to the gaseous objects in our stellar system, while the spirals and other resolvable objects became known simply as 'galaxies'.
Originally, Hubble estimated the distance of the Andromeda Galaxy as 750,000 light-years. He later increased this to 900,000 light-years. In 1936 he received another shock. W. Baade, using the 200-inch Palomar reflector, announced that there had been a mistake in the Cepheid scale, and that all the galaxies were at least twice as remote as had been thought. The distance of the Andromeda Spiral was not 900,000 light-years, but about two million. This meant that it was a system even larger than the Galaxy in which we live.
Astronomers themselves pointed out that there seem to be two kinds of 'star populations'. The brightest stars of Population I are very luminous, and are of spectral types O and B; in these regions there is considerable dust and gas spread through space. With Population II the brightest stars are red supergiants, and there is almost no interstellar material. Globular clusters and the centres of galaxies are mainly Population II, while the spiral arms of galaxies are mainly Population I.
When mapping the Galaxy, Shapley had used RR Lyrae stars, not 'classical' Cepheids; and his results were correct, since his estimates of the luminosities of RR Lyrae stars were valid. What neither he nor anyone else had realized was that there are two types of short-period variables; those of Population I (including RR Lyrae stars) and those of Population II (including the classical
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the galaxies
STELLAR POPULATIONS I AND II.
The Andromeda Galaxy, photographed in blue light, shows giant and supergiant stars as Population I variable stars. The patch at the upper left is composed of unresolved Population II stars. N.G.C. 205, companion to the Andromeda Galaxy, photographed in yellow light, shows stars of Popula-
tion II; the brightest stars are reddish, and only 1/1000 as bright as the blue giants of Population I. The scattered and randomly distributed stars in both pictures are fore-
ground stars belonging to our own Galaxy.
Photographed with the 200-inch Hale reflector at Palomar
NUCLEUS OF THE ANDROMEDA
GALAXY, showing Population II stars
resolved. Photographed with the 200-inch
Hale reflector at Palomar
Cepheids), and there is a great difference between them. A
Population I variable is much more luminous than a Population II
variable of the same period.
The Cepheids used by Hubble to measure the distance of the
Andromeda Spiral were of Type I, but the distances had been
worked out on the assumption that they were of Type II. There-
fore since the Cepheids were more luminous than had been
thought, they must also be more remote; and this led to a
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complete revision of our ideas of the scale of the universe. It also explained why RR Lyrae stars did not appear in the Andromeda Spiral. Undoubtedly they existed there, but they are less powerful than the RR Lyrae, and were too faint to be seen even with the Palomar reflector.
Not all the outer galaxies are spiral, and in fact spirals seem to be in the minority. Some, such as the two Nebulae or Magellanic Clouds, are more or less irregular (though it has been suggested that there are vague indications of spiral structure). The Nebulae, are too far south to be seen from Europe, or the Northern United States, and are the closest of our neighbor systems. They lie about 150 million light-years from us. They seem to be "satellites" of our Galaxy, and are magnificent objects visible to the naked eye. The Large Cloud (Nebula Major) is particularly splendid, and contains stars of high luminosity. One of them, S Doradus, is thought to be about a million times as powerful as the Sun—and yet from Earth it cannot be seen at all without optical aid.
We next meet with elliptical galaxies, which look at first sight not unlike globular clusters, though they are of course entirely different in nature. Then there are the extraordinary barred spirals, as well as the spectacular 'Catherine wheels' such as Messier 51 in Canes Venatici (the Hunting Dogs). The only way to study these various objects properly is to take photographs of them with large telescopes, and it is true to say that even the Andromeda Galaxy is rather disappointing when observed with a modest instrument unless like nothing more than a fuzzy patch. However, pictures taken with the great reflectors show the galaxies in all their glory.
THE NUBECULA OR MAGELLANIC CLOUDS. The Large Cloud is on the right; the Small Cloud upper left. The Magellanic cluster in Tucana is also shown (lower left)
THE NUBECULA MINOR, or Small Magellanic Cloud
THE NUBECULA MAJOR, or Large Magellanic Cloud
THE WHIRLPOOL GALAXY, Messier 51 in Canes Venatici, photographed by Ritchey with the 60-inch reflector at Mount Wilson
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the galaxies
![]() A spiral galaxy in Leo, NGC 3903, photographed with the 200-inch Hale reflector at Palomar.
Another important discovery was that the galaxies tend to collect in clusters. Among the members of our local cluster are the Galaxy in which we live, the Nebulcule, the Andromeda Spiral, the fainter spiral in Triangulum, and more than a dozen other systems. Beyond these we can see an immense distance before we come to the next group of galaxies.
Since the members of the local group are comparatively near on the comical scale, the Cepheids in them show up plainly. As we probe farther and farther into space, the Cepheids merge into the general background blur, but supergiants are still visible, and by taking their average luminosity for a supergiant star we can estimate the distances of galaxies as far out as 20 to 25 million light-years.
In the constellation of Virgo lies a whole group of galaxies known as the Virgo Cluster (not really a happy term, since a cluster of galaxies is in no way related to a star-cluster such as the Pleiades or the Hercules globular). By observing the supergiants in the Virgo galaxies, we can work out the distances of the galaxies and then deduce how far they are. From this, it is possible to estimate the average size of galaxies of different kinds. Beyond about 25 million light-years we lose even the supergiants, but if we know the shape of a more remote galaxy we can get some idea of its distance—though probably not with much accuracy. The most distant galaxy yet studied optically, gC-295 in Bootes, is about 5,000 million light-years away.
Five billion years ago our Sun was indeed looking through both space and time. When we study the Boötes galaxy, we are seeing it not as it is now, but as it used to be 5,000 million years ago, long before life on Earth began.
On a photograph these remote galaxies appear as tiny, blurred patches, and it is difficult to realize that each is a tremendous system containing at least two thousand million stars, many of
![]() The veil nebula in Cygnus. The colors radiated by these filaments of gas result from collisions between atoms and electrons from an exploding star more than 50,000 years ago with an initial velocity of nearly 5,000 miles per second. The gas has been slowed down to a speed of only one mile per second by constant collisions with atoms in interstellar space. The force of these collisions causes the atoms to emit characteristic colors shown here. Clouds ejected in the opposite direction at the time of the explosion were now 786 trillion miles from this part of the universe. The decline in velocity caused by these collisions, the nebula will cease to glow in another 50 billion years.
THE VEIL NEBULA IN CYGNUS. The colors radiated by these filaments of gas result from collisions between atoms and electrons from an exploding star more than 50,000 years ago with an initial velocity of nearly 5,000 miles per second. The gas has been slowed down to a speed of only one mile per second by constant collisions with atoms in interstellar space. The force of these collisions causes the atoms to emit characteristic colors shown here. Clouds ejected in the opposite direction at the time of the explosion were now 786 trillion miles from this part of the universe. The decline in velocity caused by these collisions, the nebula will cease to glow in another 50 billion years.
SPIRAL GALAXY IN LEO, N.G.C. 3903, PHOTOGRAPHED WITH THE 200-INCH HALE REFLECTOR AT PALOMAR.
CLUSTER OF GALAXIES IN COMA BERENICEIS, PHOTOGRAPHED WITH THE 200-INCH HALE REFLECTOR AT PALOMAR. THE CLUSTER IS ABOUT 40,000,000 LIGHT-YEARS AWAY.
THE VEIL NEBULA IN CYGNUS. THE COLORS RADIATED BY THESE FILAMENTS OF GAS RESULT FROM COLLISIONS BETWEEN ATOMS AND ELECTRONS FROM AN EXPLODING STAR MORE THAN 50,000 YEARS AGO WITH AN INITIAL VELOCITY OF NEARLY 5,000 MILES PER SECOND. THE GAS HAS BEEN SLOWED DOWN TO A SPEED OF ONLY ONE MILE PER SECOND BY CONSTANT COLLISIONS WITH ATOMS IN INTERSTELLAR SPACE. THE FORCE OF THESE COLLISIONS CAUSES THE ATOMS TO EMIT CHARACTERISTIC COLORS SHOWN HERE. CLOUDS EJECTED IN THE OPPOSITE DIRECTION AT THE TIME OF THE EXPLOSION WERE NOW 786 TRILLION MILES FROM THIS PART OF THE UNIVERSE. THE DECLINE IN VELOCITY CAUSED BY THESE COLLISIONS, THE NEBULA WILL CEASE TO GLOW IN ANOTHER 50 BILLION YEARS.
THE VEIL NEBULA IN CYGNUS. THE COLORS RADIATED BY THESE FILAMENTS OF GAS RESULT FROM COLLISIONS BETWEEN ATOMS AND ELECTRONS FROM AN EXPLODING STAR MORE THAN 50,000 YEARS AGO WITH AN INITIAL VELOCITY OF NEARLY 5,000 MILES PER SECOND. THE GAS HAS BEEN SLOWED DOWN TO A SPEED OF ONLY ONE MILE PER SECOND BY CONSTANT COLLISIONS WITH ATOMS IN INTERSTELLAR SPACE. THE FORCE OF THESE COLLISIONS CAUSES THE ATOMS TO EMIT CHARACTERISTIC COLORS SHOWN HERE. CLOUDS EJECTED IN THE OPPOSITE DIRECTION AT THE TIME OF THE EXPLOSION WERE NOW 786 TRILLION MILES FROM THIS PART OF THE UNIVERSE. THE DECLINE IN VELOCITY CAUSED BY THESE COLLISIONS, THE NEBULA WILL CEASE TO GLOW IN ANOTHER 50 BILLION YEARS.
THE VEIL NEBULA IN CYGNUS. THE COLORS RADIATED BY THESE FILAMENTS OF GAS RESULT FROM COLLISIONS BETWEEN ATOMS AND ELECTRONS FROM AN EXPLODING STAR MORE THAN 50,000 YEARS AGO WITH AN INITIAL VELOCITY OF NEARLY 5,000 MILES PER SECOND. THE GAS HAS BEEN SLOWED DOWN TO A SPEED OF ONLY ONE MILE PER SECOND BY CONSTANT COLLISIONS WITH ATOMS IN INTERSTELLAR SPACE. THE FORCE OF THESE COLLISIONS CAUSES THE ATOMS TO EMIT CHARACTERISTIC COLORS SHOWN HERE. CLOUDS EJECTED IN THE OPPOSITE DIRECTION AT THE TIME OF THE EXPLOSION WERE NOW 786 TRILLION MILES FROM THIS PART OF THE UNIVERSE. THE DECLINE IN VELOCITY CAUSED BY THESE COLLISIONS, THE NEBULA WILL CEASE TO GLOW IN ANOTHER 50 BILLION YEARS.
THE VEIL NEBULA IN CYGNUS. THE COLORS RADIATED BY THESE FILAMENTS OF GAS RESULT FROM COLLISIONS BETWEEN ATOMS AND ELECTRONS FROM AN EXPLODING STAR MORE THAN 50,000 YEARS AGO WITH AN INITIAL VELOCITY OF NEARLY 5,000 MILES PER SECOND. THE GAS HAS BEEN SLOWED DOWN TO A SPEED OF ONLY ONE MILE PER SECOND BY CONSTANT COLLISIONS WITH ATOMS IN INTERSTELLAR SPACE. THE FORCE OF THESE COLLISIONS CAUSES THE ATOMS TO EMIT CHARACTERISTIC COLORS SHOWN HERE. CLOUDS EJECTED IN THE OPPOSITE DIRECTION AT THE TIME OF THE EXPLOSION WERE NOW 786 TRILLION MILES FROM THIS PART OF THE UNIVERSE. THE DECLINE IN VELOCITY CAUSED BY THESE COLLISIONS, THE NEBULA WILL CEASE TO GLOW IN ANOTHER 50 BILLION YEARS.
THE VEIL NEBULA IN CYGNUS. THE COLORS RADIATED BY THESE FILAMENTS OF GAS RESULT FROM COLLISIONS BETWEEN ATOMS AND ELECTRONS FROM AN EXPLODING STAR MORE THAN 50,000 YEARS AGO WITH AN INITIAL VELOCITY OF NEARLY 5,000 MILES PER SECOND. THE GAS HAS BEEN SLOWED DOWN TO A SPEED OF ONLY ONE MILE PER SECOND BY CONSTANT COLLISIONS WITH ATOMS IN INTERSTELLAR SPACE. THE FORCE OF THESE COLLISIONS CAUSES THE ATOMS TO EMIT CHARACTERISTIC COLORS SHOWN HERE. CLOUDS EJECTED IN THE OPPOSITE DIRECTION AT THE TIME OF THE EXPLOSION WERE NOW 786 TRILLION MILES FROM THIS PART OF THE UNIVERSE. THE DECLINE IN VELOCITY CAUSED BY THESE COLLISIONS, THE NEBULA WILL CEASE TO GLOW IN ANOTHER 50 BILLION YEARS.
THE VEIL NEBULA IN CYGNUS. THE COLORS RADIATED BY THESE FILAMENTS OF GAS RESULT FROM COLLISIONS BETWEEN ATOMS AND ELECTRONS FROM AN EXPLODING STAR MORE THAN 50,000 YEARS AGO WITH AN INITIAL VELOCITY OF NEARLY 5,000 MILES PER SECOND. THE GAS HAS BEEN SLOWED DOWN TO A SPEED OF ONLY ONE MILE PER SECOND BY CONSTANT COLLISIONS WITH ATOMS IN INTERSTELLAR SPACE. THE FORCE OF THESE COLLISIONS CAUSES THE ATOMS TO EMIT CHARACTERISTIC COLORS SHOWN HERE. CLOUDS EJECTED IN THE OPPOSITE DIRECTION AT THE TIME OF THE EXPLOSION WERE NOW 786 TRILLION MILES FROM THIS PART OF THE UNIVERSE. THE DECLINE IN VELOCITY CAUSED BY THESE COLLISIONS, THE NEBULA WILL CEASE TO GLOW IN ANOTHER 50 BILLION YEARS.
THE VEIL NEBULA IN CYGNUS. THE COLORS RADIATED BY THESE FILAMENTS OF GAS RESULT FROM COLLISIONS BETWEEN ATOMS AND ELECTRONS FROM AN EXPLODING STAR MORE THAN 50,000 YEARS AGO WITH AN INITIAL VELOCITY OF NEARLY 5,000 MILES PER SECOND. THE GAS HAS BEEN SLOWED DOWN TO A SPEED OF ONLY ONE MILE PER SECOND BY CONSTANT COLLISIONS WITH ATOMS IN INTERSTELLAR SPACE. THE FORCE OF THESE COLLISIONS CAUSES THE ATOMS TO EMIT CHARACTERISTIC COLORS SHOWN HERE. CLOUDS EJECTED IN THE OPPOSITE DIRECTION AT THE TIME OF THE EXPLOSION WERE NOW 786 TRILLION MILES FROM THIS PART OF THE UNIVERSE. THE DECLINE IN VELOCITY CAUSED BY THESE COLLISIONS, THE NEBULA WILL CEASE TO GLOW IN ANOTHER 50 BILLION YEARS.
THE VEIL NEBULA IN CYGNUS. THE COLORS RADIATED BY THESE FILAMENTS OF GAS RESULT FROM COLLISIONS BETWEEN ATOMS AND ELECTRONS FROM AN EXPLODING STAR MORE THAN 50,000 YEARS AGO WITH AN INITIAL VELOCITY OF NEARLY 5,000 MILES PER SECOND. THE GAS HAS BEEN SLOWED DOWN TO A SPEED OF ONLY ONE MILE PER SECOND BY CONSTANT COLLISIONS WITH ATOMS IN INTERSTELLAR SPACE. THE FORCE OF THESE COLLISIONS CAUSES THE ATOMS TO EMIT CHARACTERISTIC COLORS SHOWN HERE. CLOUDS EJECTED IN THE OPPOSITE DIRECTION AT THE TIME OF THE EXPLOSION WERE NOW 786 TRILLION MILES FROM THIS PART OF THE UNIVERSE. THE DECLINE IN VELOCITY CAUSED BY THESE COLLISIONS, THE NEBULA WILL CEASE TO GLOW IN ANOTHER 50 BILLION YEARS.
THE VEIL NEBULA IN CYGNUS. THE COLORS RADIATED BY THESE FILAMENTS OF GAS RESULT FROM COLLISIONS BETWEEN ATOMS AND ELECTRONS FROM AN EXPLODING STAR MORE THAN 50,000 YEARS AGO WITH AN INITIAL VELOCITY OF NEARLY 5,
![]() A starry sky with a prominent, dark nebula shape that resembles a dragon's tail. The nebula has a reddish hue and is illuminated by bright stars. The background is filled with numerous other stars.
![]()
A spectrogram showing the spectrum of a distant galaxy. The top part shows the spectrum of a galaxy, with several bright lines indicating emission from hydrogen gas. The bottom part shows the spectrum of a star, with a single sharp line indicating absorption by oxygen.
THE MOST REMOTE GALAXIES SO FAR MEASURED 3C-295 IN BOÖTES. These objects, with the greatest distance yet determined (June 1960) comprise the cluster of faint galaxies shown in the central area of the front below. The small, hazy spots are the galaxies; the sharp round dots are stars in our own Galaxy. First detected by large radio telescopes as a source of radio noise, this distant cluster of galaxies was identified by a photograph taken with the 300-inch Hale telescope at Palomar on a red-sensitive plate. The photograph shows two bright spots separated by about one arc minute. It is believed that these two spots may represent two galaxies in collision. The unusual amount of energy released by this collision creates the radio noise, and causes certain spectral lines to appear in emission rather than the usual absorption. One such line is shown in the spectrum, just to the left of the strong line due to light from the night sky. The marked line is due to oxygen; its normal wavelength is 3,727 Angstroms, but due to the energy release, resonance lines are displaced by 1,371 Angstroms, and appears at 5,498 Angstroms. The spectrum was photographed by a very fast spectrograph. Long times and bands in the spectrum are due to the night sky; only the single, small line below the marker originates in the galaxy
the galaxies 203
![]() A black and white photograph of the Andromeda Spiral galaxy.
ED NGC 5577 E2 NGC 230 (M34)
E5 NGC 4621 (M58) C1 NGC 375
VARIOUS TYPES OF GALAXIES: elliptical and irregular. Photographed with the 60-inch reflector at Mount Wilson
![]() A black and white photograph of the Andromeda Spiral galaxy.
Sb NGC 4994 Sba NGC 2999
Sb NGC 2841 Sba NGC 5870
VARIOUS TYPES OF GALAXIES: spiral and barred spiral. Photographed with the 60-inch reflector at Mount Wilson
203
them much more brilliant than the Sun. Such a conception would have been regarded as absurd even sixty years ago, but we know it to be true.
Our galaxy appears to be a fairly typical system. The Andro-
meda Spiral is admittedly rather big, but it contains all the
familiar features, including globular clusters and even satellite
galaxies which appear to be of much the same size as our Nebulcule.
This must also apply to many of the rest, even though only a few
are close enough to be studied in any detail.
Many problems remain to be solved. For instance, we have as yet no idea why some of the galaxies are spiral, and only recently have we learned that others have the spiral arms trailing. Neither do we know for certain whether an irregular galaxy turns into a spiral, or vice versa; and we cannot be sure whether all galaxies go through a spiral stage during their evolution.
It is significant that elliptical galaxies are mainly Population II.
Most of the interstellar material has presumably been used up,
and the hot early-type supergiants have disappeared, to be replaced by cooler red stars which are more advanced in their careers. It is tempting to suppose that they will pass through an earlier stage than ellipticals. According to one theory a galaxy begins as an irregular, turns into a spiral because of its rotation, and becomes elliptical as its rotation slows down, ending up as a spherical system. It has also been suggested that the key to the problem is the original rate of spin, so that quick-spinners will become spiral and slow-spinners will become elliptical. At the moment we have no definite answer, and our ideas are changing as time goes on.
Meanwhile, there is another point to be considered—the move-
ments of the galaxies. Proper motions are too small to be measured,
but radial velocities are not, and in 1920 V. M. Slipher, working at the observatory which had been founded in Arizona by Percival Lowell, made yet another remarkable discovery. Apart from the Andromeda Spiral and a few others which we now know to be members of our own group, all the galaxies showed Doppler shifts to the red end of the spectrum. This meant that all were receding from us.
The discovery was a complete puzzle at the time, because it was still not certain whether or not the galaxies were true external systems. When Hubble made his classic observations of Cepheids in the Andromeda Spiral, the situation became even stranger. If the red shifts were real, then all the groups beyond the local group were running away; and the more remote they were, the faster they seemed to go.
Using the 100-inch Hooker reflector, Hubble and his colleague Milton Humason probed to 700 million light-years, which was the distance of a cluster of galaxies in Ursa Major. The speed of recession turned out to be 26,000 miles per second. After the Second World War Walter Baade began work with its superior light-grasp it could reach out still farther, and the red shifts showed that the faint galaxy g-295 is racing away at 90,000 miles per second.
It seems unbelievable. If you listen to a grandfather clock which ticks once per second, it is hard to realize that between each pair of ticks the Boötes galaxy recedes another 90,000 miles. Yet all the
THE NORTH AMERICA NEBULA IN CYGNUS. So called because its shape is slightly reminiscent of North America, this vast mass of gas shines by the same mechanism of fluorescence which causes the gas in neon signs to shine; ultra-violet light is absorbed by the gas and re-emitted in visible colors. The North America Nebula appears to be red, due to the filtering action of intervening material in space which removes the other colors radiated by the gas. The relatively dark areas in the nebula are regions where the gas is ionized, which cuts out the light of the nebula as well as background stars.
Photographed with the 40-inch Schmidt camera at Palomar
THE RING NEBULA IN LYRA, MESSIER 57. The famous planetary; a familiar object to most amateur astronomers, since it can be seen with relatively small telescopes. Even in large instruments, however, it appears as an almost colorless ring, due to the fact that it is composed entirely of hydrogen.
Only high-speed color film, exposed in powerful telescopes, can record these delicate hues. The blue star at the centre of the ring is the source of powerful ultra-violet light, which causes the gas on either side of it to glow. Hydrogen and oxygen are the major constituent gases in such nebulae. Photographed with the 200-inch Hale reflector at Palomar
![]() A bright, ring-shaped nebula with a blue center and reddish outer rings, set against a starry background.
206
![]()
A diagram showing Hubble's classification of galaxies.
- E: Ellipticals (Eo to E7)
- S: Spirals (Sa, Sb, Sc)
- SB: Barred Spirals (SBa, SBb, SBc)
HUBBLE'S CLASSIFICATION OF THE GALAXIES: ellipticals (Eo to E7), spirals (Sa, Sb, Sc), and barred spirals (SBa, SBb, SBc)
evidence points the same way. Unless there is a major mistake, and the red shifts are not Doppler effects at all, the estimated velocities must be at least of the right order.
There is no suggestion that our Galaxy is in any way a special case. The spectroscopic measures show that each cluster of galaxies is receding from each other cluster, so that the whole universe is expanding.
Light moves at 186,000 miles per second, and therefore the Boötes galaxy is speeding away at almost half of optic velocity. Very recent work indicates that we may have probed even farther, and photographed galaxies which have a motion of recession greater than this. There must be a limit; if the speeds continue to grow with increasing distance, there will come a time when we cannot see any more galaxies moving away from us at the speed of light per second. This raises even more difficulties, but at least we can be sure that a galaxy moving away from us at the speed of light would not be visible at all. Its light would never reach us, and it would have passed over the boundary of the observable universe.
No telescope in the world is capable of photographing galaxies much beyond 5,000 million light-years; even the Russian 236-inch reflector, now under construction, will be inadequate, though of course it will add greatly to our knowledge. But perhaps we have a new development which may help us to solve at least some of the outstanding problems. This is radio astronomy, which began only in the 1930's but which has already more than proved its worth.
CLUSTER OF GALAXIES IN HYDRA, photographed with the 300-inch Hale reflector at Palomar. Foreground stars of our own Galaxy are shown, but many of the blurred patches are due to remote external galaxies, each of which is composed of perhaps 100,000 million Suns
26
# the story of radio astronomy
![]() A YAGI ARRAY, the simplest form of radio telescope
**THE COLOR OF LIGHT depends on its wavelength. As we have seen, red light has a longer wavelength than blue or violet. The unit of length is the Angström, named in honor of the Swedish physicist Anders Ångström, who was born in 1814 and died in 1874, and who followed up the work of Kirchhoff, carrying out many valuable experiments. One Angström unit is equal to one hundred-millionth of a centimetre. Red light has a wavelength of about 6000 Angströms.
Now suppose that we have radiation whose wavelength is longer than 7600 Å? It will not affect our eyes, and so we will not be able to see it, but it will be measurable in other ways. Most people are familiar with the lamps used in hospitals. The radiation emitted by these lamps is infra-red, and is simply too 'long' to be seen visually. Similarly, short waves below 4000 Å, the ultra-violet, are invisible to the eye.
It is rather surprising to find that the range of visible light, from 7600 to 4000 Å, is only a very small part of the electromagnetic spectrum. Beyond the ultra-violet, we have the invisible X-rays and gamma-rays; beyond the infra-red, we have radio waves.
To make matters worse, there are layers in the upper part of the Earth's atmosphere which block out most of the electromagnetic spectrum. In other words, all the radiation coming from space does not reach us at all, but is stopped by the atmosphere. We have the so-called optical window, which includes the visible light from red to violet, and some distance into the infra-red and ultra-violet; we have the radio window, which allows some of the much longer waves to pass through. But this window is not a 'window' at all—nothing—so long as we stay on the surface of the Earth. To study the universe from space, we must send our instruments up above the troublesome absorbing layers. Modern rockets are able to do this without the slightest difficulty, but the situation was very different in the year 1931, when a young research worker named
**THE ELECTROMAGNETIC SPECTRUM.**
The central strip is the 'optical window', indicated by a dotted line. This means that 'see' only a very small part of the total electromagnetic spectrum. The Earth's atmosphere will pass only visible light (the optical window), and some infra-red and ultra-violet (the radio window). This is one reason why research with high-altitude instrumented rockets and space-probes is now so important.
**OPTICAL WINDOW**
| ATMOSPHERIC ABSORPTION |
ATMOSPHERIC ABSORPTION |
RADIO WINDOW |
IONOSPHERIC ABSORPTION |
| Y-RAYS |
X-RAYS |
ULTRA-VIOLET |
INFRA-RED |
RADIO WAVES |
| 100,000,000 cm. |
| 1,000,000 cm. |
| 4100,000 cm. |
| 2 cm. |
| 10,000 m. |
THE 250-FOOT RADIO TELESCOPE OF THE UNIVERSITY OF MANCHESTER,
which was opened at Jodrell Bank, in Cheshire, in 1957. It is the largest 'disk'-type radio
telescope in the world, and is designed for automatic following of celestial objects across the
sky. It is made of steel, and weighs 2,000 tons
the story of radio astronomy 209
Above left
RADIO TELESCOPE AT ARCETRI.
One of the Italian radio telescopes, at Arcetri Observatory, is very different in type from the 'dish' instrument such as the 250-foot paraboloid at Jodrell Bank. Photography by Colin Roman, 1963
Above right
TOTAL ECLIPSE OF THE SUN, October 2, 1959, photographed from a McDonnell F-8J jet aircraft at an altitude of 45,000 feet. Radio astronomers are particularly interested in solar eclipses.
SOLAR RECORDING RADIO TELESCOPE at F. W. Hyde's private radio astronomy observatory at Clacton, Essex. Photograph by Patrick Moore, June 1961
Karl Jansky made a discovery which ranked among the most important of the twentieth century.
Karl Guth, Jansky was born in Oklahoma, in the United States, in 1905. His father was of Czech descent, but had settled permanently in America and had become a Professor in the University of Wisconsin. Karl Jansky took his degree in physics at the same University, and then joined the Bell Telephone Laboratories. His main work was to carry out research into problems of short-wave radio communication, and he was particularly concerned with 'static'. Static, known commonly as 'hiss', and more specifically as 'hisising and crackling', is the radio operator's worst enemy, and the Bell authorities wanted to find out as much about it as they could.
Jansky set up a strange contraption on a farm at Holmdel, New Jersey. It was an experimental radio aerial, looking somewhat like the shape of an aircraft wing, and it was driven round by means of a motor-driven wheel. The wheel was a modified Ford car. Jansky's 'merry-go-round', as it was nicknamed, was designed to investigate static, but it achieved something much greater than anyone could have hoped.
There was plenty of static. There was radio noise due to near-by thunderstorm activity, and more noise due to more distant storms over 100 miles off. There was also a third noise; a very weak, steady hissing that remained. The cause of this noise presented a puzzle for some time. It was not close at hand, and it seemed to come from a definite point in the sky. The source-point moved from day to day, and eventually Jansky found the answer. The hiss came from the Milky Way; more accurately, from that part of the Milky Way which lies in the constellation Sagittarius.
Let us go back for a moment to the shape of the Galaxy. We
KARL JANSKY'S 'MERRY-GO-ROUND', the first true radio telescope. It was with this equipment that Jansky first detected radio waves from the Sun, and so founded the science of radio astronomy.
Jansky believed so, and he published his results. Technical journals referred to them, and on May 5, 1933, when the news was released, the world was shocked about it. It is very curious, then, that little attempt was made to follow the matter up. It is even stranger that Jansky himself did almost no further research in radio astronomy, the science which he had created. He published a few more results in 1937, but after that he abandoned the problem altogether. He died in 1949.
One thing must be made clear at once. Sound-waves are carried by air. There is no such thing as sound-waves above 30 miles above the Earth at most, and so no sound-waves can cross space. Jansky's radio hiss was produced inside the instrument itself, and was merely a means of recording the long-wavelength radiations. This also applies to modern radio telescopes of all kinds. We cannot 'hear' noise from space, but merely pick up the radiation and then convert it into a hiss. (In these days, better recording methods are available.)
Professional astronomers of the time were uninterested, and Jansky's pioneer work was almost ignored. Fortunately it was followed up by a brilliant amateur, Grote Reber, who was by profession an electrical engineer. He had been born in Chicago in 1911, and even when still a boy had built powerful transmitters with which he communicated with other radio enthusiasts all over the world.
In 1937 Reber turned his attention to the problems of what he called 'cosmic static', and he built the first modern-type radio telescope. It consisted of a 'dish' or parabolic metal mirror, 31 feet 5 inches in diameter, operating on a wavelength of about 2 metres. The mirror focused radio waves just as the mirror of an ordinary telescope focuses light waves, but of course no visible image was produced. One does not 'look through a radio telescope'.
Reber confirmed Jansky's discovery of radio waves from the Sagittarius star-clouds. He also found other sources in Cygnus, Cassiopeia, Canis Major and Argo. What did surprise him was
STAR-FIELDS IN THE MILKY WAY,
photographed at Mount Wilson
the story of radio astronomy 211
![]() A 17-foot "dish"-type radio telescope in Australia. It operates at a wavelength of 1 to 2 meters.
17-FOOT 'DISH'-TYPE RADIO TELESCOPE IN AUSTRALIA. IT OPERATES AT A WAVELENGTH OF 1 TO 2 METERS.
that these sources did not agree with the positions of visible stars.
For instance, no radio waves could be detected from Sirius, Vega or other brilliant objects; yet a part of the sky in Cassiopeia, unmarked by any bright star, seemed to send out strong radio waves.
Reber published some of his findings during the years between 1940 and 1945, when the war was going on. Later he set up some equipment on Haleakala, an extinct volcano in the Hawaiian Islands, to study radiation of even longer wavelength, and in 1954 he went to Australia to continue his researches. Modern radio telescopes make his original 31-foot 'dish' look very small, but there can be no doubt that the greatest pioneer of radio astronomy was Reber.
One of Reber's early ideas was to bounce energy waves off the Moon and record the 'echo'. He was not successful at the time, but radar developments during the war paved the way for spectacular advances in true radio astronomy.
If you go into a darkened room and shine a torch on to the far wall, you will see the wall, because it reflects the light back to your eyes. But if you shine a torch on to a mirror, you do not get a complete one,
with the way in which a tennis-ball rebounds from a wall and so may be caught. If then we send out a radio 'pulse', it ought to be possible to record the 'echo' as the pulse hits a solid object and is reflected back to the transmitter.
This is the principle of radar, originally known as radiolocation.
The method was developed during the Second World War, mainly by British scientists. It allowed the various ground forces to detect enemy aircraft and to give the range and direction of attacking machines; it also led to various new instruments used in navigation.
To give further details about radar would be beyond the scope of the present book; suffice to say that it was discussed by R. A. Watson Watt as long ago as 1855, so that it is almost as old as radio itself. The first recorded use of radar echoes have indeed been received from various celestial bodies. The Moons echoes were first recorded in 1946 by the Hungarian scientist Z. Bay, and since then many experiments have been carried out in Britain, Australia, the United States and Russia. Radar echoes have also been received from Venus. In addition, meteors may be studied by radar, since the trail left by a meteor as it plunges through the atmosphere is similar to that left by a meteorite and follows the manner of a solid body--though of course, it lasts for only a second or two. One interesting discovery has been that many meteor showers occur in the daytime. Such meteors cannot be seen (unless they are exceptionally brilliant), but radar is unaffected by the lightness of the sky and is equally unaffected by cloud. In consequence, radar has largely superseded the old method of visual meteor-watching.
Radar was first used for navigation swinging during the year 1942,
when the war was at its height. British anti-aircraft gunners were using radar to detect approaching German machines, but it was found that some mysterious 'jamming' was periodically upsetting all the equipment. It was suggested that the Nazis might have invented some means of putting the radar out of action, and a
![]() PULKOVO RADIO TELESCOPE. One of two Russian radio telescopes at Pulkovo Observatory in Leningrad. The feature is a 'rail' aerial of 90 separate sheets; it has high resolution, and works at a wavelength of 2 to 5 c.m. Photograph by Patrick Moore, 1960
PULKOVO RADIO TELESCOPE. ONE OF TWO RUSSIAN RADIO TELESCOPES AT PULKIVO OBSERVATORY IN LENINGRAD. THE FEATURE IS A 'RAIL' AERIAL OF 90 SEPARATE SHEETS; IT HAS HIGH RESOLUTION, AND WORKS AT A WAVELENGTH OF 2 TO 5 C.M. PHOTOGRAPH BY PATRICK MOORE, 1960
THE JODRELL BANK RADIO TELESCOPE, viewed from the control desk. As well as recording radio waves from space, the telescope has been used to track the various artificial satellites and space-probes launched since 1957
THE SATELLITE TRACKING STATION
AT ZVENIGOROD, U.S.S.R. This
station, near Moscow, is used by Soviet
scientists for optical tracking of both Russian
and American space vehicles. Photograph by
Patrick Moore, 1960
![]() A view of a satellite tracking station with several small buildings and a large telescope in the foreground.
THE MAIN CAMERA-TELESCOPE AT
ZVENIGOROD TRACKING STATION. A
more detailed view of the main instrument at
Zvenigorod. There are, of course, a number of
camera-telescopes at the tracking station.
Photograph by Patrick Moore, 1960
214
research team under J. S. Hey undertook to find out what was happening.
It did not take Hey and his colleagues long to find out the source of the jamming. It did not come from a German transmitter; it came from the Sun.
Years earlier Karl Jansky had looked for radio noise from the Sun, and had failed to find it. This was not Jansky's fault. His work had been done near the time of a sunspot minimum, when the Sun was at its least active. In the early 1940's, when Hey investigated the matter again, there were more frequent large sun-spots, and these produced bursts of radio noise. Most powerful of all were the flares, short-lived phenomena at a higher level than the spots.
When Hey first made his discovery, it came under the heading of a military secret. Other nations on both sides were busy working at radar development, and very little more research in pure radio astronomy could be done until the war was over. As soon as possible after the end of fighting, scientists turned back to the radio-investigations which they had begun. By now it was clear that the new methods could add tremendously to our knowledge, and the importance of the pioneer work of Jansky and Reber was at last realized.
An American, George Ellery Hale, was mainly responsible for the world's greatest optical telescopes, including the Palomar 400-inch. In radio astronomy Hale's role has been played by a Briton - Professor Sir Bernard Lovell, one of the radar pioneers. Just as Hale planned instruments of greater size and power than any built in earlier years, so did Lovell. The aim this time was a giant radio telescope with a 'dish' 250 feet in diameter.
Lovell had to face immense difficulties. There were the usual money troubles; Britain, after all, had been financially crippled by the war. Moreover, radio astronomy was still a relatively new science, and there were many problems of design and construction of design problems. By his personal enthusiasm and technical skill, and helped by a brilliant research team including R. Hanbury Brown, another of the radar pioneers, Lovell overcame the difficulties one by one. The 250-foot 'dish' was built, and set up at the Jodrell Bank Research Station near Manchester.
I remember going to Jodrell Bank when the construction had barely started. It was a vast site; there was a vast circular track, and complex equipment of all kinds. I felt that the telescope is complete, it is more impressive still, and there is nothing else in the world to compare with it. Other similar telescopes are under construction in America and (presumably) in Russia, and there are excellent instruments in Holland also. But all these owe a great deal to the work of Lovell and his team on the Jodrell Bank site.
The 'dish' focuses radio waves, just as an optical mirror focuses light waves. The focal point is the tip of a 60-foot-long metal rod or dipole which sticks out from the centre of the disk; the radio waves coming from space are reflected to this point, and are amplified. They are then passed to an automatic pen which records them on a moving chart paper.
Not all radio telescopes have 'dishes'. There is, for instance,
LONG-ENDURING METEOR TRAILS,
which act as reflectors of radar pulses. By radar studies, our information about meteors has been vastly extended during the last two decades
the story of radio astronomy 215
MILLS CROSS. Not all radio telescopes are dishes. The Jodrell Bank 20-foot instru-
ment is of course a paraboloid, the Anctcri
radio telescope and the instrument at the
Crater are quite different in nature. This
photograph shows a Mills Cross, set up in
Australia
![]() A record of the radio emission from Jupiter, showing time-intervals in seconds.
RECORD OF RADIO EMISSIONS FROM JUPITER. The scale gives time-intervals in seconds
STRONG RUMBLE DOUBLE CRACK WEAK RUMBLE
30 20 10 0
A record of the radio emission from Jupiter (observed from the Ohio State University Radio Observatory).
MILLS CROSS: looking along the north-
south arm
the Mills Cross type, named in honor of the Australian scientist Bernard Y. Mills, who was one of the main designers (another was Britton, M. Ryle). Here we have two rows of aerials set up perpendicular to each other. The first receives the radio waves from one area of the sky; the second receives the waves from another part. If both rows are receiving together, there will be double strength signals corresponding to the centre of the cross. If the rows are connected so as to work in opposition, the strength in the centre of the cross will be zero, since one row will cancel out the other. By rapidly changing the position of these rows, frequencies are rapidly changed from one position to the other, and the current in the centre of the cross will vary up and down when a radio source lies in the position defined by the centre of the cross. By this method the position of the radio source itself can be worked out.
Now let us see what sorts of objects send out radio waves.
The Sun is one source. Another, surprisingly, is the planet Jupiter; it is thought that the waves from the Giant Planet may be due to electrical 'thunderstorm' activity in the Jovian atmosphere. Radio waves from Saturn have also been reported. If these are confirmed, they too may be due to 'thunderstorms' in the planet's atmosphere.
Yet most radio sources lie far beyond the Solar System. One, of particular interest, is the Crab Nebula, Messier 1 in Taurus—the wreck of the supernova observed by Chinese astronomers in 1574. There is also a radio source which corresponds closely to the position of the supernova studied by Kepler in 1604, and it is suggested that yet another source, in Cassiopeia, may be due to the remains of Tycho's Star of 1572. There is nothing surprising in this. Supernovae are the most tremendous cosmic outbursts known to us, and the disturbed gases and materials may be ex-
pected to emit radio waves for many centuries after the 'explosion'.
![]() A starry night sky with a nebula in the center, surrounded by numerous stars.
THE CRAB NEBULA, MEISSNER I IN TAURUS. Here we see the result of a stellar explosion which occurred nearly 5,000 years ago. In the year 1680, with the explosion was not observed until nearly 4,000 years after it had taken place. On the morning of March 13, 1680, the Chinese observers, shining with a brightness 100 million times greater than previously. After several months it faded below naked-eye visibility. The Crab Nebula is still expanding at a rate which would take it to the nearest star in about 70,000,000 miles each day. High-energy electrons, still moving about rapidly as a result of the explosion, cause the centre of the nebula to emit light and at the same time cause the wispy filaments of gas to shine with characteristic color. Photographed with the 200-inch Hale reflector at Palomar.
Another very strong radio source is known as Cassiopeia A. It does not correspond with any bright star, or with any recorded supernova. It seems to be about 10,000 light-years away, and the Palomar reflector has been able to photograph a very faint luminous cloud of gas in the exact position of the source, but the reason why this gas-cloud is so powerful a radio emitter is not definitely known. Then, too, there is the source located at the galactic centre, first recorded by Jansky.
We know that there is a great deal of gas spread through the Galaxy. Of this gas, hydrogen is by far the most plentiful, and tens of thousands of hydrogen clouds, each some 30 light-years across. It is of course extremely cold, and also extremely rarefied; there are less than ten atoms per cubic centimetre, which is a low density judged by any standards. Nevertheless, in 1944 a Dutch scientist, Hendrik van de Hulst, predicted that this hydrogen should be sending out radio waves on a length of 21-t centimetres. He knew that it would be weak and hard to detect, but he believed that it would be found.
At the time, van de Hulst was unable to carry out experimental work. The Germans occupied Holland, and scientific research was at a standstill. It was not until 1951 that two Americans, H. Ewen and E. Purcell, managed to detect the 21-t-centimetre radiation; but when they did, it proved to be most important.
Interesting gas clouds plentiful in all arms of any galaxy. Moreover, if it is ionized, it will yield Doppler shifts in the same way as visible light. By plotting the positions of the hydrogen clouds, and observing their Doppler shifts, radio astronomers were able to prove what had already been suspected—that our own Galaxy is spiral in form. By now five definite spiral arms have been traced, and in addition we can receive radio waves from the galactic nucleus—since these waves are not blocked by obscuring matter.
We can see the way in which the story has unfolded. Herschel gave a good idea of the disk-shape of the Galaxy; the distribution of bright stars of early spectral type indicated the possibility of a spiral form, and radio astronomy proved it. There is, after all, a strong link between Herschel and van de Hulst.
Beyond the Galaxy lie other radio sources. One of these is the Great Radio Nebula in Cygnus A. In 1932 Van Allen predicted that radio waves would one day be received from the Spiral, and his forecast has come true. But what of the remarkable source in the Swan, known as Cygnus A? Apart from Cassiopeia A, it is the most intense radio source in the sky—but its distance is much greater. One estimate places it at 200 million light-years.
The answer has been found. Cygnus A is not one object, but two. It consists of two galaxies which are colliding and are passing through each other at a speed of something like 600 miles per second.
The idea of colliding galaxies conjures up a picture of a super-inferno, with stars meeting each other head-on. This is a long way from the truth. Even in the most densely-populated part of a galaxy, the stars are still widely separated, and actual collisions can seldom occur. There is an analogy with two orderly crowds moving through each other, and passing in different directions.
the story of radio astronomy 217
RADIO SOURCE CASSIOPEIA A., a particularly intense source. (This is a negative photograph.) The emission is due to distributed masses of gas, and there is no bright visual object
218
the story of radio astronomy
![]() A negative photograph of a starry sky, with a faint object labeled "RADIO SOURCE CYGNUS A. Another intense radio source. This is a negative photograph, obtained at Palomar".
Unless the people are very closely packed, there will be no actual collisions, and there is no close packing in the stellar population.
However, the dust and gas between the stars will be colliding all the time during an encounter between two galaxies, and it is this which produces the radio waves received by our instruments. Other radio sources too have now been identified with colliding galaxies.
In some ways a radio telescope is more powerful than an optical telescope. (In other ways it is of course, much less efficient, as it has much lower resolving power.) Cygnus A is a faint object even with the Palomar reflector. If it lay at ten times its actual distance it would be 2,000 million light-years off, which is about what the real distance of Cygnus A is. Galaxies in Hydras Optically Cygnus A would then be well beyond the range of the Palomar telescope, but its radio emission could still be detected. In fact, radio astronomy can reach out farther than optical astronomy—and this brings us to our best hope of clearing up one of the major problems of modern science.
We can trace the life-story of a star: we may make many errors, but at least we seem to be on the right track. All theories begin with 'gas and dust', out of which the stars condense. But what about the galaxies themselves? How did they begin, and what is the origin of the universe?
So far nobody has the answer, but there are two theories which have caused strong (and sometimes heated) discussion in recent years. One is the 'evolutionary' theory, based on the work of men such as the British physicist George Lemaître. It is supposed that all the material in the universe was originally concentrated into immensely dense 'primeval atom', and that between 20,000 million and 60,000 million years ago this 'primeval atom' exploded, sending its material outward in all directions. Expansion went on for thousands of millions of years, and gradually the clusters of galaxies were formed. For a time there was a balance between expansion and contraction; then, about 9,000 million years ago, something happened tipping the balance in favour of expansion, so that the galaxies are still receding from each other.
We can indeed show that if the present rates of expansion have gone on far into the past, all the galaxies must have been relatively close together 9,000 million years ago. Unfortunately we are still quite in the dark as to how all the material was created in the first place.
On the evolutionary theory, the universe had a definite beginning, and will have a definite end; eventually the galaxies will be so far apart that they will be receding from each other at the speed of light, and will be unobservable from each other. Eventually, too, all the stars in the galaxies will die, and we will be left with a dead universe.
The second theory is that of the 'steady-state' universe. It is due to a group of astronomers who worked at Cambridge, including F. Hoyle, T. Gold and H. Bondi. Here we have no definite beginning; the universe has always existed, and will exist forever. New matter is being created out of 'nothingness' all the time, so that as old galaxies die, new ones will take their place. Of course, the process will be very gradual. Matter is created in the form of
![]() A black-and-white photograph showing a cluster of galaxies with a bright central galaxy labeled "N.G.C. 1275; ONE OF THE MEMBERS OF THE PERSIUS CLUSTER GALAXIES", photographed with the 200-inch Hale reflector at Palomar. This galaxy is a radio source".
hydrogen atoms, and there is no chance of our being able to detect it, any more than one could detect the formation of a single grain of new sand in the Sahara Desert.
We have here another case where the difficulty that nobody can suggest why fresh material should appear out of nothingness; but this also applies to the evolutionary theory. If, as Lemaître supposed, we began with the primeval atom, this primeval atom must similarly have been created out of nothing. On this score, the one idea is as reasonable as the other.
On the steady-state theory, the average amount of matter in any given volume of space has always been the same, so that (say) 9,000 million light-years away, it would have been as wide apart as they are now. Yet on the evolutionary theory, the galaxies were much more crowded 9,000 million years ago.
We cannot travel in time—but we can look back through time. If we observe a galaxy 9,000 million light-years away, we are seeing it as it used to be 9,000 million years ago. Suppose, then, that we study galaxies at this distance! If they prove to be more closely crowded than those which are nearer to us, then the evolutionary theory is right. If there is no crowding, then the steady-state theory wins the day.
The Palomar reflector can reach out only about 5,000 million light-years, which is not enough. Neither is it certain that we can build optical telescopes of sufficient light-gathering power, at least until we can set them up beyond the Earth's atmosphere—either in space or on the ground. Radio telescopes are not similarly hand-capped, and it is to radio astronomy that we must turn for any hopes of a speedy solution.
In 1961 M. Ryle, at Cambridge, announced some important results obtained by the radio astronomers at the University. Analysis of very weak—and so, presumably, very distant—radio sources indicated that they were "colliding", which sup- ported the evolutionary theory rather than the steady-state. It seems, therefore, that the steady-state theory has failed its first direct test. Yet the observations are incomplete and uncertain, and there may be a considerable margin of error, so that the last word has by no means been said. We cannot yet say definitely whether the universe resembles a giant clock which is running down, or whether it is more like a clock which is being continuously re-constructed.
Whether we will ever solve the mystery of the creation of the universe remains to be seen. Meanwhile, investigations continue all the time, and our first successes are due to radio astronomy—the young science which was born on that day in 1931 when Karl Jansky used his 'merry-go-round' to detect the weak emission due to radio sources in the Milky Way.
the story of radio astronomy 219
**CHRISTIANSEN INTERFEROMETER AT SYDNEY, AUSTRALIA. This is yet another type of radio telescope; it may be com- pared with the instruments at Jodrell Bank, Arcetri, de Grasse and elsewhere**
**S.G.C. 4998-2: COLLIDING GALAXIES photographed with the 4-inch Schmidt camera at Palomar. The two galaxies are 'passing through' each other, and the gas and dust between the stars is colliding all the time, so producing the radio emission**
# 27 Life in the universe
A DIATOM. Diatoms are microscopic plant-like organisms which surround themselves with elaborate silicate shells. Like other plants they can trap solar energy at light and use it for building themselves up from simple chemicals.
MODERN TELESCOPES, both optical and radio, can reach far out into space. We can photograph galaxies thousands of millions of light-years away, and we can measure the luminosities of stars whose light started on its journey towards the Earth long before life appeared on our world. Yet what of 'life' itself? Are we alone in the universe, or is our civilization only one of many?
Before we go any further, let us make sure what we know about 'life', so that we can narrow down our search as much as possible. We know that life in the universe is made up of a comparatively few fundamental substances or elements; ninety-two are known to occur in nature.
Of all the various types of atoms, only one is able to produce the very complex atom-groups which are needed for living matter. This is the atom of carbon. All organic material, then, must be based on carbon. Many other elements are involved, but carbon is the fundamental element for this purpose, wherever it may be found, is similarly dependent on the carbon atom. In this case it must be of the same kind as the life we know on Earth.
This may seem a sweeping statement—and indeed it is; may well prove to be much too sweeping. First, it is worth noting that the silicon atom is a fairly good 'builder'. It is not nearly so efficient as carbon, and we have no evidence of the existence of silicified life; but according to some scientists, the possibility does exist.
There is another argument which is always raised in any discussion of life on other worlds. It runs as follows: 'Why should we say that all life in the universe must be built on the same pattern as ours? There may be intelligent races of quite different kind.'
The argument is plausible enough, and is impossible to disprove. Yet it has no real evidence to have, and gives the most reasonable interpretation on which we have got. That these alien creatures do not seem at all probable, either in our Solar System or beyond. If they exist, they must be built upon a pattern which we cannot understand, and so it is pointless to speculate. There is no proof that alien life-forms exist anywhere, and there is considerable indirect proof that they do not.
We can conclude that life need not be of human form. All we can say is that according to modern evidence, an extra-terrestrial being would be made up of familiar elements, and would be based—as we ourselves are—upon carbon.
Having made this point, we can start to look round for worlds which might be expected to support life.
There are two essential qualifications. A life-bearing world must be neither too hot nor too cold; intense heat breaks up organic molecules and destroys their vital activity. It is also necessary to have an atmosphere, preferably one which contains a reasonable amount of oxygen and water-vapor.
Obviously we can rule out the stars, which have surface temperatures of several thousands of degrees. Of the nine planets in the
![]() A COLLECTION OF MICRO-ORGANISMS WILDBLINDS AND DAMP SOILS. Most of these are minute with plant-like organisms, and because they possess chlorophyll they can trap and use the energy of sunlight. Organisms like these require a lot of energy must form an important part of the world of life on any planet, and it is reasonable to expect them to appear on planets identical forms as plants other than Earth. Unlike terrestrial plants, photosynthetic organisms such as cyanobacteria do not release free oxygen, and in this way may resemble our photosynthetic bacteria.
![]() A DIATOM. Diatoms are microscopic plant-like organisms which surround themselves with elaborate silicate shells. Like other plants they can trap solar energy at light and use it for building themselves up from simple chemicals.
life in the universe 221
Solar System, five (the giants, and Pluto) are too cold, while Mercury has practically no atmosphere. The asteroids are airless, and so are the satellites—except for Titan, which must be rejected because of its low temperature.
Apart from the Earth, the only Venus and Mars seem to be worlds resembling Earth. Mars has always been regarded as the most promising as we have seen, many astronomers believe the dark tracts to be due to living organisms. Few scientists now believe in Lowell's intelligent Martian canal-builders, and analysis has shown that the atmosphere of the planet is too thin and too poor in oxygen to support men or animals of Earth type, but it would be unsafe to rule out the possibility of much more primitive creatures than man. Venus is a world of carbon dioxide, probably no more advanced than our mosses or lichens. Whether it is genuinely like any Earth plants remains to be seen.
With Venus, our knowledge is so slight that we are reduced to little more than guesswork. If oceans exist there, there may be simple marine life. We must remember that life on Earth began in the seas, and that in the Pre-Cambrian period, more than 500 million years ago, the Earth's atmosphere contained mainly carbon dioxide and water vapour than is the case now. In fact a modern man would be unable to breathe a 'Pre-Cambrian' atmosphere. It was only in later ages that plants spread on to the land and removed much of the carbon dioxide, replacing it by free oxygen by the process known to scientists as photosynthesis. Animals breathe in oxygen and expel carbon dioxide; plants do the reverse, taking in carbon dioxide and supplying oxygen, so that the amount of oxygen on our times remains more or less constant.
Venus may be a world in a 'Pre-Cambrian' state, and it is at least possible that life will eventually develop there just as has happened on Earth, though we cannot be at all certain.
To sum up: in the Solar System, there are only two planets apart from the Earth which might possibly support life. On Mars there seems no vegetation', but intelligent being are improbable. (Whether a Martian civilization exists or not has now died out we do not know, but the evidence is rather against it.) Venus seems unsuitable for anything except, possibly, very lowly single-celled marine creatures. Yet can there be planetary systems circling other stars?
There have been many theories about the origin of the Solar System. One such popular Hypothetical, was put forward in 1796 by Pierre Simon Laplace, a leading French mathematician. According to Laplace the system began as a vast gas-cloud, disk-shaped and in rotation. As the cloud cooled down, it shrank; and as it shrank its rate of spin increased, until the centrifugal force at the edge became equal to the gravitational pull there. At this stage a ring of matter broke away from the main mass, and gradually this ring condensed into a planet. As the shrinkage continued, another ring broke away from this planet and broke away from this planet and condensed into another planet, and so on. The final result was a central Sun surrounded by a family of smaller bodies.
The theory seems reasonable enough, but unfortunately there are strong objections to it. For one thing, a gaseous ring formed in such a way could not possibly condense into a planet.
![]() A circular diagram showing a polar view of Mars with canals drawn around it.
THE SOUTH POLAR AREA OF MARS,
1888, according to Schiaparelli; many
canals are shown
![]() A drawing of a bird-like creature flying over a landscape.
DRAWING OF MARS BY LOWELL.
Here we see the canal network in its most
developed form
MARS, 1909, DRAWN BY E. M.
ANTONIADI. The telescope used was the
Mendon 35-inch refractor. The difference
between Antoniadi's drawing and those
of Schiaparelli and Lowell is very obvious.
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life in the universe
In 1900 two American scientists, Chamberlin and Moulton, put forward another theory, according to which the planet-forming material was pulled off the Sun by the action of a second star which passed near by. This 'tidal' theory was modified by Sir James Jeans, and will be well remembered by many people not only for his astrophysical researches but also for his popular books and broadcasts.
This time we have an encounter between the Sun and a passing star which resulted in a 'tongue' of matter being pulled away from the Sun. After the second star had gone on its way, the 'tongue' broke up into pieces, each of which became a planet. An attractive feature of Jeans' idea is that the 'tongue' would have been thickest in the middle, which is where we find the largest planets, Jupiter and Saturn.
Here again there are mathematical difficulties. Although the tidal theory still has its supporters, most scientists agree that it cannot be correct.
F. Hoyle once suggested that the Sun formerly had a binary companion, which turned into a supernova. Hoyle went on to calculate that the effects of the explosion would give what was left of the star a velocity of about 30 miles per second due to gravitational pull of the Sun. He suggested that just before its final departure it ejected a cloud of gas which the Sun managed to retain, and that the planets then condensed out of this material.
The most favored theory at present is based on work by a German, Carl von Weizsacker, and a Russian, Otto Schmidt. They said it supposed that some thousands of millions of years ago the Sun passed through an interstellar cloud, and collected an envelope of matter out of which the planets and other bodies of the Sun's family were formed.
It is too early to say whether this last theory is correct, but at least it seems to be promising. If we accept it, planetary systems must be common in space. What can happen to the Sun can happen to other stars as well.
But one curious point is that a planet has no light of its own, and even a large body accompanying a relatively close star would be too faint to be seen even from Palomar. The only way in which such a body could be detected would be by its gravitational pull on the parent star.
In 1942, K. A. Strand published results which showed that the fainter member of the 61 Cygni binary seemed to be 'wobbling very slightly'. It might be supposed that this might be due to the presence of a massive planet. The calculations showed that the mass of the invisible body ought to be about sixteen times as great as that of Jupiter. Another near star, 70 Ophiuchi, may be attended by a somewhat less massive planet.
If two of our stellar neighbors prove to have planet-families of their own, we are entitled to suppose that many others exist. Indeed, it would be unreasonable to believe otherwise. Our Sun is one of them. The reason why we see it is because Galileo's telescope reflector is capable of photographing 1000 million galaxies. Therefore, the number of stars which we know to exist is 100 thousand million multiplied by 1000 million—and even this represents only one part of the universe. It is surely absurd to suggest
JEANS' TIDAL THEORY OF THE ORIGIN OF THE SOLAR SYSTEM. The theory was accepted for many years until mathematical investigations have revealed so many weaknesses in it that it has now been rejected
![]() A diagram showing the relative sizes and positions of various planets in relation to the Sun.
that in all this host, the Sun is unique in possessing a system of planets.
If the number of planet-families runs into hundreds of millions, some of these worlds must be suitable to support life. Where the conditions are right, life may be expected to appear. At this moment, some astronomer living on a planet circling a far-away star may be turning his telescope towards the yellow star we call the Sun, and wondering whether it also may be the centre of a 'Solar System'.
Interplanetary travel is a real possibility, but reaching the stars is another matter altogether, and may always remain beyond our power. The only way of contacting distant races would be by means of radio signals, which travel at 186,000 miles per second—and in 1960 some interesting experiments were begun by an American scientist, Frank Drake, using the 85-foot radio telescope at Green Bank, in Virginia.
Drake surveyed all the comparatively close stars in an attempt to decide which of them might be attended by Earthlike planets. Very few of these stars, as the Red Dwarfs held out little hope; it was better to search for stars which are not too unlike the Sun. Two in particular caught his attention: Tau Ceti and Epsilon Eridani. Both are of magnitude $3\frac{1}{2}$, so that they are clearly visible to the naked eye; both are of spectrum type K$\alpha$, and both are about 11 light-years away. Tau Ceti is nearly half as luminous as the Sun, while Epsilon Eridani has about one-third of its solar luminosity.
If these stars have planet-families able to support intelligent beings, radio astronomers may live there. In this case they will know about the cold hydrogen clouds in the Galaxy, and will be 'listening out' on a wavelength of 21-1 centimetres, which is the frequency of the radiation emitted by the hydrogen. Drake's scheme is to send out messages and see if anyone can arrange them so that they are obviously artificial transmissions.
The idea is not entirely absurd, but it must be said that the chances of success are remarkably slight. For one thing, a radio wave will take eleven years to reach either Tau Ceti or Epsilon Eridani. If we assume that our transmission is received by a radio astronomer there, it will take another eleven years for a 'reply' to be received. Consequently, messages sent out in 1961 cannot bear any reply until 1972—so that even if we had no idea whether either star has a planet-family, or whether there is any real chance of intelligent life there. Reluctantly, we have to admit that the whole experiment is 'the longest of long shots'.
Even so, there is no reason to doubt that intelligent life is widely scattered through the universe. The Sun is an ordinary star; the Earth is an ordinary planet; and neither is there anything remarkable about us when judged in terms of local biological intelligence scale, but it is a measure of our scientific advance during the last few centuries that we have come to realize how unimportant we really are.
GROUP OF GALAXIES IN LEO, PHOTOGRAPHED WITH THE 200-INCH HALE REFLECTOR AT PALOMAR
THE 85-FOOT RADIO TELESCOPE AT GREEN BANK, VIRGINIA, OPERATED BY THE ASSOCIATED UNIVERSITIES, INC., UNDER CONTRACT WITH THE NATIONAL SCIENCE FOUNDATION. NATIONAL RADIO ASTRONOMY OBSERVATORY, GREEN BANK, WEST VIRGINIA
![]() EXOSPACEHIRE 250 MILES UPWARDS
# 28 rockets into space
TO BRING OUR STORY up to date we must consider one more new development. This is rocket astronomy, which began a quarter of a century ago but which did not become a serious research tool until after the end of the Second World War.
Hardly a month now passes without some startling new development. Rocket vehicles have been put round the Earth and also round the Moon; others have been sent into paths round the Sun, and many have been sent into space at enormous speed as a result. Yet it is commonly thought that the only purposes behind rocket research are to provide military weapons, and to send men to other worlds. Nothing could be further from the truth. Few scientists now doubt that it will be possible to reach the Moon within the next half-century or so, but at the moment our most valuable information comes from understanding the nature of the upper atmosphere.
As long ago as the second century A.D., a Greek writer, Lucian of Samosata, wrote a story in which his heroes were sent to the Moon by the action of a waterspout, which caught the ship in which they were sailing and hurled it upward. Centuries later, a story by no less a man than Johannes Kepler described a lunar voyage. At about the same time an English bishop, Godwin, published an interesting fantasy in which a journey to the Moon was made on a raft towed by wild swans. Of course, these stories and other tales were what we now call 'science fiction', and although some of them (notably Kepler's 'Somnium') contained some interesting scientific forecasts, the suggested methods of space-travel were—to put it mildly—impracticable.
In 1865 Jules Verne, the great French story-teller, in his book *From The Earth to The Moon* Verne planned to send his voyagers on their way by means of a space-gun. The projectile containing the travellers was put into the barrel of a vast cannon, and fired moonward at a speed of 7 miles per second.
Verne always kept to the proper facts as much as he could, and many of the calculations in his story were correct. For instance, he selected the right starting velocity. Seven miles per second is enough to enable a projectile to break free of the Earth's gravitational pull. It corresponds to about 25,000 m.p.h., and is termed escape velocity. Unfortunately there were two things which Verne failed to take into account. If a solid body were made to move through the dense lower atmosphere at such a speed, it would be so violently heated by friction that it would be destroyed at once. Moreover, the choice of starting at seven miles per second would certainly kill the luckless pioneers. No human frame could endure so tremendous a jolt.
Space-guns, then, are out of the question. Neither can we travel to the Moon by 'conventional' machines such as aircraft. An aircraft cannot function unless there is air round it, and above a height of a few miles there is so little atmosphere that for most
![]() METEOR BURN-OUT
NOCTILUCENT CLOUDS
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NACREOUS CLOUDS
CIRRUS CLOUDS
CUMULUS
TROPOSPHERE CLOUDS
SEA-LEVEL
CROSS-SECTION OF THE EARTH'S ATMOSPHERE
![]() IONOSPHERE
AURORA POLARIS (40-600 MILES)
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NOCILUCENT CLOUDS
HIGH TEMPERATURE BELT
NACREOUS CLOUDS
CIRRUS CLOUDS
CUMULUS
TROPOSPHERE CLOUDS
SEA-LEVEL
NO MOVEMENT
EQUAL
PRESSURE
OF DIRECTION MOVEMENT
THrust NO PRESSURE
ESCAPING GAS
PRINCIPLE OF REACTION
rocks into space 225
purposes it may be disregarded. Most of the quarter-million mile flight to the Moon must be done in airless space. (Modern jet-aircraft are similarly limited, since their engines depend on being able to draw air into them.)
Around the turn of the last century two men independently realized that the only way to reach the Moon was to use vehicles propelled according to what Sir Isaac Newton had termed the principle of reaction. In Germany, Hermann Ganswindt designed an extraordinary machine propelled by dynamite; in Russia, Konstantin Eduardovich Tiolkoski published the first papers outlining his ideas.
Ganswindt must have been a good approximation to the traditional inventor of the story-books. Most of his ideas were wild in the extreme, and few of his inventions really worked. For instance, he designed a helicopter, driven by a falling weight; but as he could not provide it with an engine, it was hardly likely to prove successful. He also described a new type of fire-engine, and even an unusual method of shooting bullets from a pack with heavy steel cartridges filled with dynamite. Ganswindt's plan was to fire the explosive so that the upper part of the cartridge would bang against the top of the vehicle, thus knocking it up-ward. . . . A succession of such charges would, he reasoned, send the projectile into space, though in a rather jerky fashion.
Ganswindt's space-ship is as far-fetched as Lucian's waterspout launcher. It is not unreasonable than Jules Verne's space-gun. Yet the germ of an idea was there, and it was fortunate that Ganswindt had neither the patience nor the clear-headedness to follow it up. He died in 1834.
Tiolkoski was a very different sort of man. Unlike Ganswindt, he put forward his proposals in a truly scientific manner, and many of his theories still hold good today.
DESIGN FOR A SPACE-SHIP BY TIOLKOSKI: K. E. Tiolkoski, the great Russian pioneer, produced various space-ship designs; this one is on exhibition at the Tiolkoski Museum at Kaluga, where he taught for many years.
РАКЕТА К.Э. ЦИОЛКОВСКОГО
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
![]() A diagram showing the principles of reaction propulsion.
PREPARATIONS FOR FIRING VANGUARD
PIONEER V. LAUNCHER. A 4-stage Thor-Able rocket blasting off from Cape Canaveral, Florida, carrying the space-probe Pioneer V in its nose. The 948-lb. (429 kg.) sphere, packed with scientific instruments was launched into a 361-day orbit round the Sun between the orbits of the Earth and Venus. This was the third of the artificial planets; the first two were the American vehicle Pioneer IV, and the Soviet Lunik I
![]() A rocket launching from Cape Canaveral, Florida.
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rockets into space
![]() A diagram illustrating the principle of the rocket. It shows a rocket with a fuel tank at the top, an oxidant tank below it, pumps to move the propellants, and exhaust gases coming out of the bottom. The diagram also includes a combustion chamber and a chamber labeled "EXHAUST GASES".
**PRINCIPLE OF THE ROCKET**
He was the son of a forester, and was born at Izhhevsk, in the Russian province of Ryazanskii, in 1857. When he was a boy of ten he caught scarlet fever, and was left permanently deaf, which handicapped him all through his life. However, he was a skilful musician and learned to play the piano first at a small country school and then in the town of Kaluga.
Tsniokovski's first published article on the possibilities of space travel appeared in 1903 in a monthly journal called *No-vitchimje Obserenije* (Science Survey). It caused almost no interest even in Russia, and nobody outside that country heard about it until years later. Yet it was of great importance, since it laid down many of the principles of the science we now term *aerodynamics*.
What Tsniokovski had in mind was that a rocket does not need to be surrounded by air. The diagram will make this clear. The inside of a firework rocket, for instance, is packed with gunpowder; when the gunpowder is lit, hot gas is produced, and this hot gas rushes out through the exhaust, so propelling the rocket-body in the opposite direction.
Tsniokovski realized that gunpowder rockets of this kind are inefficient. For this reason, he planned to use liquid pro-pellants. The two liquids, a fuel (such as petrol) and an oxidant (such as liquid oxygen) would be pumped separately into a combustion chamber; ignition would take place, and gas would be sent out of the exhaust as with the firework. Using a rocket motor of this kind would, he wrote, open up endless possibilities.
He was certainly right. Moreover, his claim to fame does not rest on this invention alone; he did much else. Later he published many articles, containing ideas which seemed absurd at the time but which seem very far from absurd now. Of course he made mistakes, but generally speaking he was well ahead of his time.
Tsniokovski retired from teaching in 1920. Four years later, when the idea of space-flight had really started to take hold of people's minds again, he published another article containing his original article, following it with new productions of many of his other works. Suddenly the shy, deaf ex-teacher became almost a national hero. His seventy-fifth birthday, in 1932—three years before his death—was marked by public celebrations, and Stalin sent him a telegram of congratulation.
![]() A photograph of the Earth from high altitude, taken from a rocket. It is a composite picture, but the curvature of the Earth's surface is clearly shown.
PHOTOGRAPH OF THE EARTH FROM HIGH ALTITUDE, taken from a rocket.
It is a composite picture, but the curvature of the Earth's surface is clearly shown.
W
SOUTH
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rockets into space 229
Tsiolkovskii was not a practical experimenter. He never fired a rocket in his life, and probably never seriously considered doing so. Yet nobody is likely to dispute his right to the title of 'father of astronautics'.
Some years after the publication of Tsiolkovskii's first article, an American scientist, Robert Hutchings Goddard, began to turn his attention to rocketry. He had been born in 1882, at Worcester in Massachusetts, and had become Professor of Physics at Clark University. In 1914 he started serious experimental work, but the war intervened, and not until after the Armistice was he able to continue with his own research. Then, in 1919, he published a monograph entitled *A Method of Reaching Extreme Altitudes*, in which he discussed the use of rockets for upper atmosphere studies, and also suggested that it might be possible to send a vehicle to the Moon. He did not discuss a manned rocket; he was concerned with something much less ambitious—a small vehicle carrying a charge of flash powder which would cause a visible spark as it hit the lunar surface.
The Moon-rocket proposal caused a tremendous amount of interest, and was reported in various American daily papers. Goddard was not pleased. He hated publicity in any form, and in any case he thought—rightly—that the Press was paying too much attention to the 'lunar shot' idea and too little to the immediate task of exploring the upper atmosphere of our own world. After that, he did his best to keep himself out of the public eye.
On March 16, 1936 he actually fired the first liquid-propellant rocket. It contained liquid hydrogen and liquid oxygen, and rose modestly to a height of 200 feet, attaining a maximum speed of 60 m.p.h. It caused no comment at the time simply because almost nobody knew about it. Goddard published a report four years later, but it was not until 1936 that the date and nature of his pioneer experiment became generally known.
Meanwhile a remarkable book had been produced by a Russian teacher, Hans von Oberth. Oberth appeared in 1923 under the title of *Rakete zu den Planetenrümmen* (The Rocket into Interplanetary Space). It was mainly mathematical, but it quickly became something of a best-seller, because Oberth treated the whole space-travel problem in a properly scientific way.
![]() GODDARD'S ROCKET LAUNCHER AT ROSWELL, 1934. Goddard, the first man to fire a liquid-propelled rocket, was one of the greatest of the pioneers in this field.
T NORTH MILES
TOTAL ECLIPSE OF THE SUN, February 15, 1961,
photographed from Florence by Colin Roman. The corona,
shown here, is visible only on the Sun's surface only
during totality; full investigations of the Sun's surround-
ings depend on future research with rocket vehicles.
PHOTOGRAPHS OF THE AURORA
BOREALIS (Northern Lights)
ORBIT OF THE AMERICAN SATELLITE ECHO 1, launched on August 12, 1960.
This was a sphere 100 feet in diameter, and in its first journeys round the Earth had a period of 18 minutes, with a height varying between 345 and 170 miles. It took the form of a hollow sphere, because the radiation pressure of the highly reflective metallic lamina-
tion. Its mass was therefore very slight, and it was perturbed by the effects of light-pressure from the Sun; this radiation pressure is virtually negligible for more conventional satellites with their much larger masses. The Echo was also subject to atmospheric absorption atten-
tion, since it shone more brightly than a 15-magnitude star. In this plate an accurate globe of the Earth has been photographed and the orbit of the Echo added. The inclination of the orbit to the Earth's equator is shown as 47 degrees
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rockets into space
(Incidentally, his work was independent of Tsailkovskii's. He could not read Russian—and still cannot, as he told me recently—
and at that time Tsailkovskii's works had not been translated into any other language.)
Oberth's book led to a surge of interest in astronautics, and
Interplanetary Societies were formed in various countries. Parti-
cularly important was the German 'Verein für Raumschiffahrt',
or Society for Space-Travel. Its leading members, such as Wernher
von Braun and Willy Ley, decided to fire liquid-fuel rockets of
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rockets into space
![]() NIGHT LAUNCHING OF VIKING 13, in the United States
WOOMERA. This is the main Commonwealth rocket range, and is situated in Australia. The photograph gives a general view.
their own, and actually did so. They knew nothing about God-ard's experiment of 1926, and naturally assumed that their vehicles were first in the field.
When the Nazi Party came to power in Germany, the military authorities saw that there might be a chance of turning the new rockets into weapons of war. The Verein für Raumschiffahrt ceased to exist. Some of its leaders, including Ley, left Germany; others, such as Von Braun, joined the official rocket station which was set up at Peenemünde, a small village on the Baltic island of Usedom. Work was continued, but this time for destruction instead of scientific progress. In 1937 came the first successful launches, and on October 5, 1942, a much larger and more efficient vehicle, the V2, was launched.
As the war turned against Germany, the Nazis sent their V2 rockets against Britain. Between September 1944 and March 1945 vehicles carrying explosive charges fell on London and the Home Counties, and did considerable damage. The attacks ended when the launching sites were captured by the advancing Allied armies. Some of the German scientists, notably Von Braun, went to America after the war. Many V2s were shipped across the Atlantic to be used for scientific purposes.
Though the V2 was designed as a military weapon, it may be regarded as the ancestor of the space-ship. It could reach a height of well over 100 miles, which is beyond most of the Earth's atmosphere, and it was easy to adapt for high-altitude research.
There are many reasons for wanting to explore the upper part of the air. We do not do so merely because we hope to have a full knowledge of the atmospheric mantle. Moreover, remember that there are various absorbing layers which block out many of the radiations emitted by the Sun and stars. If we want to examine these radiations, we must send our instruments above the absorbing layers, and rockets give us our only means of doing so.
In addition to cosmic rays—high-velocity particles, mainly atomic nuclei—which come from the depths of space, and which are bombarding the Earth all the time. When a cosmic ray primary smashes into the upper air it breaks up some of
233
the air-particles, and is itself broken up. A whole series of collisions takes place, and only the broken pieces of the primaries reach the ground. This is fortunate for us, since the primaries may well be dangerous to living matter, but cosmic rays are clearly of fundamental importance, and scientists are anxious to study them as closely as possible.
As soon as the war was over the Americans began a serious programme of rocket research. The German V2s were improved, and new rockets soared high into the atmosphere—Aerobees, Vikings and the rest, each more powerful and more efficient than its predecessor. In 1949 came the first *step-vehicle*, a development which requires no explanation.
Even our best liquid propellants are not powerful enough to send a single-stage rocket beyond the atmosphere. Unlike the projectile of Verne's fictional space-gun, a rocket does not start off at full escape velocity, since if it were to do so it would be destroyed by frictional heating. It has to work up to maximum velocity more gradually, so that it travels through the dense lower air without burning up.
A step-vehicle consists of several rockets mounted one on top of the other. At the start of the flight, the bottom rocket does all the 'lifting'. When it has used up all its fuel, it breaks away and falls back to the ground; the second 'step' continues the journey under the power of its own motors, so that it has the double advantage of being well above the densest part of the atmosphere, and also of having a greater power available for its third stage into play. The second stage in turn can carry a third, and so on, though the design difficulties increase with each new step and there is a practical limit to the number of separate rockets.
The 1949 vehicle fired from the American proving ground at White Sands, New Mexico, consisted of a German V2 carrying a smaller rocket known as a WAC Corporal. Unlaided, the WAC Corporal would have been able to reach fifty miles. Launched by the V2, it soared to almost 250 miles, which was a record at that time.
High-altitude rockets provided a tremendous amount of valuable information, but in some ways they were not satisfactory. No rocket can stay up for more than a few minutes. When it has reached the peak of its flight it plunges back to earth, and lands with a force sufficient to destroy it completely. Often enough the instrument equipment is damaged or broken before it reaches free during the descent and brought down by parachute. On July 29, 1955, the Americans therefore announced that they planned to send up a man-made moon or artificial satellite.
This was indeed a new departure. It meant that for the first time, men were planning to send proper scientific vehicles to carry out a research programme from above the Earth's atmosphere; it also meant that the true space age was about to open.
![]()
A small rocket with a cylindrical body and fins.
**THE FIRST AMERICAN EXPLORER SATELLITE** Though much smaller than the German vehicles which preceded it, these satellites carried complex instrumentation, and provided a great deal of valuable scientific information
![]()
A small rocket with a cylindrical body and fins.
29 Earth satellites
THE IDEA of an artificial Earth satellite was not new. It had been discussed by most of the rocket pioneers, including Goddard and Oberth. Yet in 1957, when the Americans made their announce-
ment, many people still regarded it as fantastic. The usual question asked by non-scientists was: 'Even if the satellite can be taken up by rocket power, what is to stop it falling down again—just as an ordinary rocket does?'
To explain this, let us look at the case of the real Moon, which moves round the Earth at a distance of about 239,000 miles. It is travelling at a speed, relative to the Earth, of just over half a mile per second, and so it does not fall to the ground. As Newton showed so long ago, it is theoretically 'falling' all the time, but its distance from us remains the same. Moreover, it keeps moving simply because there is nothing to stop it. The same arguments apply to the Earth in its journey round the Sun.
Suppose we could take up a satellite inside a rocket, and start it moving round the Earth at that incredible speed? What would behave in the same manner as a natural astronomical body, and would be subject to the same laws of motion. It too would enter an orbit round the Earth, and would not fall back to the ground.
This, then, was what the Americans planned to do: build a small instrumented vehicle, send it up by rocket, and start it moving round the Earth above the top of the air-mantle. It was an easy proposition: it travelled at such a speed around all over the world. The progress of 'Project Vanguard' was keenly followed, and scientists in every continent waited for news.
Yet when success came, it was from an unexpected quarter—an unexpected, that is to say, in Western Europe and the United States. On October 4, 1957, Russian scientists launched the first artificial satellite known generally as 'Sputnik I'. It took the form of a sphere 2 inches in diameter with a radio transmitter on its pole-top and it was sent up in a multi-stage rocket. It carried a radio transmitter and almost at once its 'Bleep! bleep!' signals were picked up by wireless operators in various parts of the globe.
Its orbit, naturally enough, was elliptical. At its farthest point or apogee it was 588 miles above the ground; at its nearest, or perigee, only 142 miles. The time taken for it to complete one journey around the Earth was exactly 90 minutes. The last stage of the rocket launcher also entered a closed orbit.
The news was surprising in view of the fact that no previous Russian announcements of a satellite programme had been made, but it was at once clear that the Soviet techniques were ahead of the American—despite the help given to the United States team by German pioneers such as von Braun. Unfortunately a launch like this could not be repeated without some means to carry a military weapon, and the political situation prevented any further interchange of ideas so far as the launchers were concerned. This is still the case, and scientific progress is handicapped as a result.
![]() SPUTNIK I. The first artificial satellite, launched by Soviet scientists on October 4, 1957.
TRAIL OF SPUTNIK I, near one of the Nebulae or Magellanic Clouds. Photograph by K. G. Herring at the Mount Stromlo Observatory in Australia, on October 8, 1957. 19:37 E.A.T.
ОПЕРАТІВА
2-ГАРАНТИЙНАЯ
339 км
ORIGINAL ORBIT OF SPUTNIK II, the second Russian satellite
![]() A black and white photograph of a satellite being launched into space.
**TRAIL OF SPUTNIK II. Dunfermline Abbey is shown in this photograph by Morris Allan**
**CAMERA-END OF THE MAIN SATELLITE TRACKING CAMERA AT ZVENIGOROD, U.S.S.R. Photograph by Patrick Moore, 1960**
Sputnik I was not designed to remain in orbit permanently. When near apogee it was virtually above the resisting atmosphere, but at its perigree distance of less than 150 miles there was still appreciable air, and resistance had to be taken into account. As expected, the Sputnik's orbit was gradually changed. Finally, on July 4, 1958, it dropped into the main part of the atmosphere and was destroyed in an explosion much like a shooting-star. Meanwhile, new developments had taken place.
Sputnik II, sent up by the Russians on November 3, 1957, was altogether more ambitious than its predecessor. It took the form of a cylinder 70 or 80 feet long, and weighed well over 1,000 pounds, so that great power was needed to launch it. It carried a variety of instruments to study phenomena such as cosmic rays and solar ultra-violet.
Sputnik II moved in a relatively eccentric orbit, so that its distance from the ground varied between 140 and 1,038 miles. During its first circuits it had a period of 104 minutes, and it lasted until April 14, 1958, when it too entered the denser air and was destroyed. It was easily visible to the naked eye, and appeared as a bright starlike point moving slowly and steadily across the horizon. The Russians claimed that an artificial satellite loom as large as a balloon were surprised to find that it looked like nothing more than a luminous dot.
American scientists carried on with their own programme as quickly as they could, but at first they had no success. The first attempt at a Vanguard launching, on December 6, 1957, resulted in an explosion which completely destroyed the rocket. Then, on January 31, 1958, the American team at JPL successfully launched a satellite, Explorer I, which carried various instruments as well as a radio transmitter. It was a dwarf compared with the Sputniks, since it weighed only 31 pounds, but at least it was encouraging.
Three more satellites were launched by the American teams during 1958, as well as two unsuccessful moon probes which will be described below. One of these, the first Vanguard to enter orbit, is expected to remain circling the Earth for several centuries, but since it weighs only 3 pounds and is no larger than a croquet ball all contact with it has long since been lost.
On May 15, 1958, the Russians again stressed their technical superiority when they launched the cone-shaped, 2,925-pound Sputnik III. This satellite carried instruments comparable up to that time. The instrumentation was varied, including magnetic and cosmic-ray recorders; research into micro-meteorites was also included in the programme. Like Sputnik II it was easily seen with the naked eye, and it continued orbiting the Earth until well into 1960.
Various methods for tracking the satellites, both Russian and American, were adopted. Amateur observers formed themselves into "Moonwatch" teams, and did excellent visual work. More important, however, were radio and radar observations; and in this field Britain took the lead. The 250-foot 'dish' at Jodrell Bank was far more powerful than any radio telescope in America, and neither, apparently, did the Russians have anything to compare with it. Under Lovell's direction, the Jodrell Bank team carried
Earth satellites 235
236 Earth satellites
NOSE-CONE OF SPUTNIK III. This is a replica of the nose-cone on display in Moscow.
THE PADDLE-WHEEL SATELLITE The four solar cell 'paddle-wheels' are extended before the launching at Cape Canaveral, Florida. During take-off, and until orbital height was reached, the wheels were folded 'birdlike' beneath the satellite. They then came into place through the force of springs and centrifugal force as Explorer VI went into orbit. Symbolically, this vehicle was one of the most valuable of the early satellites.
out invaluable work in the early days of practical space research. This was all the more creditable because the telescope had been designed to study objects far away beyond the Solar System, and during its construction there had been no direct provision for such purposes.
It would be both tedious and unnecessary to list the details of all the various artificial satellites which have been launched since the first Sputnik. Particularly notable, however, was the American 'Paddle-wheel', sent up on August 13, 1959. All things considered, the satellites have more than justified the money and time spent on them. We now know far more about the upper part of the Earth's atmosphere than we did a few years ago, and we also have an increased appreciation of conditions in what is popularly termed 'outer space'.
One fact cannot be too strongly emphasized: though the Russian vehicles are, so far, much more massive and complex than the American, it would be both wrong and unjust to minimize the great contributions which have come from Western countries. For instance, it was an American satellite which first detected an important radiation belt around the Earth, known today as the Van Allen Belt. In the field of radio astronomy Britain has a pride of place. The exploration of space is an international study, and we can only hope that before long all the various security regulations will be abandoned. Only then can scientists of all countries combine to make the best possible use of their knowledge.
![]() A black-and-white photograph showing a replica of a satellite nose-cone on display.
![]() A black-and-white photograph showing a satellite with its solar panels extended.
![]() A black-and-white photograph showing a satellite with its solar panels folded up.
30 space probes and Luniks
ARTIFICIAL SATELLITES are not designed to go far from Earth. They are set in closed orbits, and can never break free to journey across space on their own. Yet they must lead on to true space probes, and new experiments which carry our researches well beyond the Earth-Moon system.
In 1959 the Americans planned the first lunar probe, the PIONEER. By placing the probe in orbit round Earth it was designed to go right round the Moon, taking photographs of the mysterious hidden side and then sending its pictures back by means of television. The Moon, as we know, has what is termed a captured rotation; 41 per cent of its surface is permanently turned away from us, and so long as we have to carry out our studies from our Earth-based observatories we can never have a complete knowledge of the lunar surface.
The Pioneer was also intended to carry out researches into the possibility of a magnetic field round the Moon. This is an important problem, and only direct measurements from a rocket could be of use in solving it. The Earth's magnetic field may well be
PIONEER. Ascent of the American lunar probe on October 11, 1958
PREPARATIONS FOR LAUNCHING PIONEER, November 10, 1958. Photographed by C. Rogers
SODIUM CLOUD FROM LUNIK I. A chart of the region in the sky where the sodium cloud was observed on January 5, 1959
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space probes and Luniks
PHOTOGRAPH OF THE LUNIK I SODIUM CLOUD. This photograph was taken at 9h. 50m. 20sec. on January 3, 1959, by the Soviet Academy of Sciences Observatory outside Kislovodsk, by the station's director, M. N. Gnevishen. The faint stars surrounding the artificial satellite were photographed through a special filter. The position of the sodium cloud could be measured with great precision.
Six successive photographs of the sodium cloud emitted by Lunik II
associated with the conditions deep inside the globe, where there is a high content of iron in what is thought to be a liquid condition. If the Moon lacks a comparable core, it may also be expected to lack a powerful magnetic field.
The American team had set themselves a difficult task. Unless the whole launching mechanism went off perfectly, the Pioneer would not approach the Moon close enough. There was no margin for slightest error, and in any case it would be hard to receive the televised information. There was clearly no chance of recovering the rocket itself. As soon as it re-entered the Earth's atmosphere, it would be destroyed in the usual way.
Pioneer I was launched on October 11, 1958. For a time all seemed well, but then news came that the rocket was not keeping to its planned course. Its starting velocity had not been great enough, and it travelled only part of the way to the Moon. After reaching an altitude of 71,000 miles it dropped back, and is thought to have disintegrated in the atmosphere, with its broken pieces falling into the Pacific Ocean. Its journey into space had lasted for 43 hours. Two more Pioneers launched before the end of 1958 proved unsuccessful.
As with the Earth's satellites America accomplished what America had initially failed to do, and during 1959 the three Lunik rockets opened the second stage in man's exploration of space.
Lunik I was launched on January 2, 1959. It was not designed to go round the Moon, and in this respect was less ambitious than the Pioneer; it was given a speed greater than escape velocity, and so as to pass by the Moon it continued onward into space, never to return. Thirty-four hours after launch it had passed within 4,000 miles of the Moon, sending back wireless messages all the time, and yielding priceless information about conditions in those regions of space. Subsequently it moved away from both Earth and Moon, so becoming a tiny artificial planet or sun-satellite. The last contact with it was made on January 5, 62 hours after launch had been launched. At that time it was 371,000 miles away from the Earth.
We cannot tell where Lunik I is now. According to calculations it is moving round the Sun in a period of about two years, and its distance varies from 91 million to 120 million miles from the Sun itself. Its radio transmitters have of course ceased to work, and the chances of our finding it again are very slight, even though it may sometimes come within a few millions of miles of us. Yet unless something happens we shall never know whether Lunik I will continue indefinitely. Millions of years hence Lunik I will still be circling the Sun, looking just the same as it did when launched from Soviet Russia in our own time.
Lunik II followed on September 12. This time the Russians meant to hit the Moon, and they were successful in doing so.
The first reports after launching showed that everything was going according to plan until a few minutes later clouds swept from the vehicle was photographed, and signals from the Lunik were picked up at Jodrell Bank and elsewhere. Scientists all over the world waited expectantly, and then came an announcement from Moscow that the rocket was due to land at 21 hours 1 minute GMT on September 13.
![]() Lunik III, the Soviet vehicle which sent back the first photographs of the reverse side of the Moon
The timing was almost perfect. Less than 1½ minutes after the predicted moment, the radio signals from Lunik II ceased, and there can be no doubt that the rocket had in fact hit the Moon. For the first time a vehicle had been sent from one world to another.
At least the first Luniks cleared up the question of the Moon's magnetic field. It is known that on Earth it is extremely weak, and in no way comparable with that of the Earth. Neither are there any definite signs of lunar radiation belts similar to the Van Allen zone which surrounds our own world.
On October 4, 1959, exactly two years after the ascent of Sputnik I, the Russians launched a still more complex vehicle —Lunik III.
As it passed away from Earth, Lunik III duly passed by the Moon on October 6, approaching the lunar surface to within 4,400 miles. On the following day the Russians announced that the far side of the Moon had been photographed. Meanwhile the vehicle continued to recede; it reached its greatest distance from Earth—293,000 miles—on October 10, and then began to approach once more. By October 28 it was only 25,000 miles away, and the photographs were sent back by means of specially-adapted equipment.
The historic pictures of the far side of the Moon were released on October 26.
![]() The visible and reverse sides of the Moon. Some features, such as the Mare Grisium, may be identified on both photographs
The photographs had been taken when the Lunik was thousands of miles away—between 30,000 and 40,000 miles beyond the Moon—and had been automatically developed and processed inside the vehicle. Under these circumstances they were of amazingly good quality. Various dark areas were revealed, including a well-marked plain which the Soviet authorities named the Marc Moscovianum (Moscow Sca). Among other features were several objects which seemed to be craters, as well as a long mountain chain or ridge. Astronomers had been right in supposing that the
240
space probes and Luniks
![]() A detailed map of the Moon's surface, showing various craters, maria, and other features. The map is oriented with the North Pole at the top left corner.
THE REVERSE SIDE OF THE MOON. Over thirty photographs were received from Lunik III in October 1959, transmitted back to the Earth by complex television techniques. Though the photographs are naturally lacking in definition judged by ordinary standards, they have been most successfully interpreted, and certainly rank among the most remarkable scientific pictures ever obtained. Analysis of the photographs has been carried out by Soviet astronomers at Moscow, Leningrad and other universities. A chart of the reverse hemisphere—or rather, that portion of it covered by the Lunik photographs—has been drawn up by Y. N. Lipshits of the Leningrad Academy of Sciences. Several hundreds of features are shown. It may be assumed that the chart is of satisfactory precision, though future rockets will presumably lead to more detailed maps.
The Soviet scientists have allotted names to some of the new features, and have followed Riccioli's old system very closely. The names chosen are extremely suitable, and are moreover international; there are some Russians (Tsiolkovskii, Lomonossov); Britons (Clark Maxwell); and Italians (Bruno).
![]() A legend explaining the names on the map of the Moon's reverse side.
![]() A legend explaining the names on the map of the Moon's reverse side.
![]() A legend explaining the names on the map of the Moon's reverse side.
![]() A legend explaining the names on the map of the Moon's reverse side.
![]() A legend explaining the names on the map of the Moon's reverse side.
![]() A legend explaining the names on the map of the Moon's reverse side.
![]() A legend explaining the names on the map of the Moon's reverse side.
![]() A legend explaining the names on the map of the Moon's reverse side.
![]() A legend explaining the names on the map of the Moon's reverse side.
space probes and Luniks 241
far side of the Moon is basically similar to the side we have always known.
The Russians followed Riccioli's old system of naming the craters after famous men and women. Among the new 'personalities' now honoured by such a way are Jules Verne, Lomonosov, Clerk Maxwell, Giordano Bruno, Edison, and—fittingly enough—Tsiolkovskii.
The next step in space research was, of course, manned flight. The Russians tackled the problem with great skill, and were wise enough not to make any attempt to rush matters. Three prototype space-ships were sent up in 1960. The first of these was launched on October 3rd, but was destroyed when its radio transmitter failed as well as a great deal of equipment. By May 19 its planned programme had been completed, and efforts were made to bring it back into the atmosphere at a speed low enough to avoid excessive frictional heating. At this point the Russian plans went wrong; instead of returning, the space-ship continued circling the Earth. Its radio transmitter ceased to function on July 8.
Space-probes were also sent up in 1960. They were of much the same size, but carried two live dogs—Strelka and Belka—as well as other, smaller creatures. The vehicle orbited the Earth eighteen times, covering a total of over 430,000 miles, and was then brought safely down. (Belka, incidentally, has since had a litter of six puppies!) This was in itself a great achievement; it meant that the Russians had solved the problem of re-entering the atmosphere. Such difficulties could still occur, and the test vehicle, sent up on December 17th, was put into a path which had remained under control, it departed from its calculated path, and was burned up in the atmosphere.
Progress was fully maintained in the first part of 1961. On February 4 the Russians sent up Sputnik IV, which weighed over six tons; the main idea was to study problems in connection with the launching of really heavy vehicles, and there was no attempt at a successful landing. Then, eight days later, came the famous Venus Probe.
This was not a new departure, since the Americans had already sent out a smaller vehicle toward Venus, but it held out great promise. The launching was successful, and the orbit appeared to be very much as planned, but most unfortunately radio contact was lost after the end of the month.
The probe continued on its set path, and passed within 70,000 miles of Venus on February 27. Probably the vehicle continued on its set path, and passed within 70,000 miles of Venus in mid-May, but it is impossible to be certain. Just why the radio failed is not known. It may have been the result of a simple power fault; it is also possible that a meteor hit was responsible. In June, 1961, radio astronomers at Jodrell Bank together with the Russian scientists, made renewed efforts to contact the vehicle. Some unidentified signals were received; but only whole it seems unlikely that these came from the Venus Probe.
Then, after two more satellite launches and successful landings—one on March 9, the other on March 25—came the greatest Soviet triumph to date. On April 12, Major Yuri Gagarin, in the space-ship Vostok, orbited the Earth at a distance ranging between
POSITION OF LUNIK III DURING THE PHOTOGRAPHING OF THE MOON'S REVERSE SIDE. The Sun's rays come from the lower right, and the Earth is assumed to be at the upper left
VENUS PROBE. In February 1961 Soviet scientists launched a rocket vehicle toward the orbit of Venus. It was expected that the probe would be able to enter Venus' orbit within 70,000 miles. In March 1961, however, con-
tact with it was not maintained as had been hoped
242
space probes and Luniks
ANOTHER PHOTOGRAPH OF THE MOON'S REVERSE SIDE, obtained by Lunik III. The features shown include the Mare Crisium and the Mare Moscovianum.
MAJOR YURI GAGARIN, The first space-traveller. Major Gagarin made his pioneer flight on April 12, 1961, and orbited the Earth in the vehicle Vostok, landing safely in the prearranged position. He suffered no ill effects from his flight; his whole experiment was a complete success
108 and 188 miles, and came down safely. He experienced weightlessness, he saw the Earth from beyond the atmosphere, and he had the honor of being mankind's first space-traveller. At dawn on April 12, he was unknown except to his friends and colleagues; by sunset he had been assured of a permanent place in history.
No praise can be too high for the Russian scientists, whose achievements had been brilliant indeed. Yet space research was beginning to spread to other States also, and the flight of the Vostok was followed by the famous American astronaut Alan Shepard, from Cape Canaveral. Unlike Gagarin, Shepard did not orbit the Earth, and his flight was relatively brief, but the experiment--watched by all America on television, and heard by other countries on the radio--was a complete success. It showed that the United States programme was well under way.
It proved so rapid that it is dangerous to make forecasts as to what is likely to happen next. Yet we may close this book with the first space-flights; they so obviously mark the end of one era and the beginning of another. The way to the planets is open, if only we use our scientific knowledge in the proper way. Nobody can deny that we are living in the most exciting period in all history.
COMMANDER ALAN SHEPARD. The flight of the Vostok was followed by the successful ascent of Commander Shepard from Cape Canaveral, Florida. Unlike Major Gagarin, Commander Shepard did not orbit the Earth; his flight was relatively brief, but it was nevertheless successful. The experiment was shown on television, and a running commentary given on sound radio was heard by listeners all over the world.
![]() A black-and-white photograph of a man in a military uniform smiling at the camera.
![]() A black-and-white photograph of a man in a space suit standing on a rocky surface.
243
# conclusion
WE HAVE SURVEYED the history of astronomy from its dim beginnings up to modern times. Much has been left out, but perhaps enough has been said to show that the tale is indeed a wonderful one.
A thousand years ago the Earth was believed to be all-important, and to lie in the very centre of the universe. Even 400 years ago, scientists who taught otherwise did so at the peril of their lives. We are wiser now, in this respect at least. We have found that our world is no more important in the cosmos than a single drop of water in the Atlantic; we know that even the Sun is a very junior member of the Galaxy, and that we ourselves are only a tiny speck in the vastness of space. We have studied star-systems so remote that their light started on its journey towards us before life on Earth began; we have picked up radio waves across vast stretches of space, and we have even sent our messengers to begin the direct exploration of the Solar System.
If we use our knowledge in the right way, there is no limit to what we can do. Yet we should never forget that we owe everything to those who came before us. Aristotle . . . Ptolemy . . . Tycho Brahe . . . Kepler . . . Newton . . . Herschel . . . Tsiolkovskii . . . Jansky. . . What would Tycho for instance, have thought about the Palomar reflector, the Jodrell Bank 'dish', and the Russian Luniks? Yet Tycho lived less than four centuries ago. Four centuries hence, men may look back at the pioneers of today, and say the same of them.
The story of astronomy is not over. Indeed, it may only just be starting.
244
B.C. (All dates rather uncertain)
**2000** Constellations first drawn up by the old star-watchers.
**580** Pythagoras speculates as to the nature of the sun and planets.
**280** Aristarchus suggests that the Earth revolves around the Sun.
**270** Eratosthenes measures the size of the Earth.
**130** Hipparchus draws up his star catalogue.
A.D.
**140** Ptolemy writes his *Almagest*.
**813** Al-Mamun founds the Baghdad school of astronomy, and has the catalogue of the stars printed.
**905** Al-Sufi draws up his star catalogue.
**1054** Supernova in Taurus recorded by Tycho Brahe.
**1270** Alphonsine Tables published by order of Alphonso X of Castile.
**1433** Ulugh Beg builds an observatory at Samarkand.
**1440** Nikolaus Kopernikus (Nebulae of Cana) advances the theory of the Earth's rotation.
**1474** Regiomontanus suggests the 'lunar distance' method of determining longitude.
**1543** Copernicus De Revolutionibus Orbium Celestium published.
**1576** Tycho Brahe observes a supernova in Cassiopeia.
**1576** Tycho finds the observatory at Uraniborg.
**1596** Tycho leaves Denmark; Uraniborg abandoned.
**1595** Mira Ceti observed by David Fabricius.
**1600** Giordano Bruno burned at the stake.
**1606** Publication of Johann Bayer's star catalogue, *Cæmiaresia*.
**1606** Kepler publishes *De revolutionibus orbium coelestium*.
**1608** Lipperhey develops the telescope.
**1609** Galileo first uses the telescope for astronomical observations.
First two of Kepler's Laws of Planetary Motion published.
**1612** Surveys of the stars by Johannes Hevelius, Scheiner and Johann Fabricius.
The Orion Nebula first reported by N. L. de Chéseaux.
**1618** Kepler's Third Law published.
Kepler publishes the Rudolphine Tables.
Transit of Mercury, predicted by Keplar, observed by Edmund Halley.
**1632** Publication of Galileo's Dialogue on the Tumultuous World at Rome, and forced to recant.
Variability of Mira Ceti discovered by John Flamsteed; Richard Wollaston; Jeremiah Horrocks observes the transit of Venus.
![]() A diagram showing a celestial sphere with various constellations marked.
Landmarks in the story of astronomy
rsc Publication of Hevelius' map of the Moon.
r66 Publication of Riccioli's map of the Moon.
r67 Huygens discovers Titan, the largest satellite of Saturn, and also their true nature of Saturn's rings.
r65b Founding of the Copenhagen Observatory by Tycho Brahe.
r65g Markings on Mars first seen by Huygens.
r65h Principle of the reflecting telescope put forward by James Gregory, Newton and others; laws of reflection and gravitation, at Woolsthorpe, Lincolnshire; Polar caps on Mars observed by H. G. Rosse; Newton builds the first reflecting telescope.
r66b Variations of Algol discovered by Montanari.
Paris Observatory founded; discovery of Phobos and Deimos, satellites of Mars; Lagrange, the eighteenth satellite of Saturn. Greenwich Observatory founded; discovery of Uranus; discovery of Neptune; main division in Saturn's rings; O. Remez measures the velocity of light; Halley goes to St. Helena to cata-
logue comets; Cassini observes the Zodiacal Light; Publication of Newton's Principia; Halley predicts the return of Halley's Comet for 1758; Publication of a new version of Flamsteed's star catalogue.
r77b James Bradley discovers the aberration of light; Chester More Hall discovers the principle of the achromatic refracting telescope; Transit of Venus across the Auro-
sphere of Venus discovered by Lomonosov; Discovery of Bradley's measures of the positions of 60,000 stars; Nevil Maskelyne founds the National Maritime Museum at Greenwich; Transit of Venus observed. Mean motion and distance between Earth and Sun determined by Bode's Law publicized by Johann Elert Bode; First recorded astronomical observation of William Herschel.
r77b Lunar map published by Tobias Mayer in 1779. Johann Schröter founds his observatory at Jena in 1784. Publication of Menier's catalogue of stars, clusters and nebulae. r784 Goodricke puts forward his theory of the variability of Algol. r784 Goodricke publishes the variability of Delta Cephei. r78b Herschel puts forward his "disk" theory about our Galaxy. r78b Completion of Herschel's 40-foot telescope. r79b Publication of Laplace's Nebrular Hypothesis. r801 Publication of Corels, first of the minor planets. Publication of Lalande's catalogue of minor planets. r803 Herschel announces the discovery of binary star systems. W. Huggins detects dark lines in the solar spectrum. r803 Fall of meteors at L'Aigle, France. r803 The comet returns every 75 years. r803 Others put forward his theory of comets-in-continuity. r813 Discovery of Schröter's observa-
tory at Lilienfeld. r813 Franz Bessel discovers the dark lines in the spectrum of the Sun. r824 Enoch Comet discovered by Pons; Bessel completes the reduction of Bradley's observations of 5,000 stars. r824 Erection of Fraunhofer's "Great Dorpal Refractor". r824 Discovery that Jupiter is a Comet, inde-
pendently by Biela and Gambart. r829 John Herschel begins his observa-
tions at Birnau near Vienna, at Cape. r83g Great Comet shower (the Leonids). r83g Bessel discovers the irregularity of the proper motion of Sirius, and attributes it to its presence as a binary system. r83g Publication of Beer and Mädler's Astronomical Ephemeris giving a really accurate map of the Moon. r83g Bessel measures the distance of a star (Sirius) (by Gyms). r84o Draper takes his first photograph on glass plate. r84a Announcement, by C. Doppler, of Doppler's Principle. r84a Sunspots discovered by H. Schwabe. r843 Completion of Lord Rose's 7x-
inch refractor at Birnau Castle. Hencke discovers the fifth minor planet, Astrea. Sun photos taken by Fizeau and Foucault.
![]() A diagram showing a celestial sphere with various constellations marked.
some landmarks in the story of astronomy 245
| 1845 |
Breaking-up of Biela's Comet ob- served. |
1896 |
33-inch refractor erected at Mu- ldowney Observatory. |
1934 |
White spot discovered on Saturn by W. T. Hay. |
| 1846 |
Discovery of Neptune by Adams and Le Verrier. |
1897 |
Yorkes Observatory opened. |
1938 |
Appearance of a bright nova in Hercules, discovered by J. Pren- cer. |
| 1847 |
The first observatory set up at Cam- bridge, Massachusetts, U.S.A. |
1900 |
Lebedev establishes the reality of the Solar System. |
1937 |
Grote Reber builds his 'dish' radio telescope. |
| 1848 |
Roche proves that Saturn's rings are composed of ice and rock. |
1901 |
New theory of the origin of the Solar System put forward by H. G. von Miehanen. |
1938 |
Nature of stellar energy pro- posed by H. Bethe, and indepen- dently by C. Von Weizsäcker. |
| 1850 |
Crepé Ring of Saturn discovered by Bond. |
1903 |
Appearance of Tsiolkovski's first rocket. |
1942 |
K. G. Tsiolkovsky's 6i Cygni B is attended by a massive planet. |
| 1854 |
The meteorite discovered by the Danish astronomer T. Bronson. |
1905 |
Mount Wilson Observatory founded. |
1944 |
| 1855 |
The appearance of the comet in the spectra of the Sun and stars. |
| 1861 |
| 1862 |
| Sirius B discovered by Clark, in the period forecast by Besel. |
| 1863 |
| some landmarks in the story of astronomy
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's outbreak an outback", "page": "<>"},
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]
```
246
**list of illustrations**
* Indicate four-color illustrations
| Group of Nebulae in Leo |
12 |
Apparent Path of Mars in May |
160 |
Apparent Movement of Mars among the Stars, three photographs |
68 |
| The Andromeda Spiral |
6, 13 |
Leo, the Lion |
Johannes Kepler |
Statue of Newton |
69 |
| The Position of the Andromeda Spiral |
13 |
Johannes Kepler |
43 |
Astronomical Spectrum |
70 |
| Comparative Sizes of the Sun and Planets |
14 |
Drawing an Ellipse |
March, September 30, 1956 |
A 1.2-inch Newtonian Re- flexor |
70 |
| Star Trails |
15 |
Drawing an Ellipse |
44 |
A 1.2-inch Newtonian Re- flexor |
70 |
| Orion |
15 |
Drawing an Ellipse |
44 |
A 2.5-inch Newtonian Re- flexor |
70 |
| Scale of the Solar System |
16 |
Keppler's Second Law |
Keppler's Second Law |
Newton's First Reflector |
71 |
| The Heli Reflector |
17 |
Finding Dates of an Eclipse of the Moon |
Finding Dates of an Eclipse of the Moon |
The Mount Wilson 60-inch Reflector |
71 |
| Total Eclipse of the Sun, 1936 |
19 |
Theory of an Eclipse of the Sun, 1936 Total Eclipse of the Sun, 1936 Theory of an Eclipse of the Sun Galileo The Leaning Tower of Pisa Galileo's Telescopes The Pleiades The Principle of the Refractor A Refractor A Modern Refractor Movements of Venus according to Newton's Theory Correct Theory of the Move- ments of Venus The Milky Way in Cygnus The Lunar Mare Crisium The Lunar Mare Tranquillitatis The Green and Red Flashes Solar Domes at Falkwok Sumptograph by Scheiner Sumptograph drawing by Hevelius Sumptograph Rotation of the Sun Sumptograph Photographs Sumptograph No. 1 Marine Chronometer The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation The Great Samson Group of 1947: continuation Transits from Mercury, November, July, August, September, October, November, December, January, February, March, April, May, June, July, August, September, October, November, December, January, February, March, April, May, June, July, August, September, October, November, December, January, February, March, April, May, June, July, August, September, October, November, December, January, February, March, April, May, June, July, August, September, October, November, December, January, February, March, April, May, June, July, August, September, October, November, December, |
* Indicate four-color illustrations
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The Universe according to Ptolemy
Babylonian Table for estimating Positions
Taxonomic Constellations
Arabian Almagest
A Diagram to show the use an Astronomer
Star Magnitudes
Ulugh Beigh Memorial
Geminis; the Twins
Phases
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun...
List of illustrations 247
**Principle of the Herschelian Reflector**
Herschel's 40-Foot Reflector
Engraving of the 40-Foot Reflector
* *Framed House*
The Old Royal Observatory, Greenwich
Optical Double Star
External Galaxy NGC 805
Distances of the nearest stars from the Sun according to Bode's Law
Plan of Schröter's Observatory at Llanfair
Path of Ceres among the Stars
Inclination of the Trojan Orbit of Pallas
Orbits of the Trojan Asteroids
Sizes of the Minor Planets compared with the British Isles
Trail of Icarus, 1949
Telescope used by Schröter
Orbits of Interesting Minor Planets
Size of Eros Compared with Mars
**Discovery of Neptune**
The Telescope with which Galileo discovered Neptune
Positions of Uranus and Ncp- tures in 1640
* *Neptune*
Discovery of Pluto, 1930: two photographs
Perseval Lowell
Lowell's Telescope by Short
Another Grödinger Telescope
Palomar Observatory
**Discovery of the 1st Reflector at the Crimine Astronomical Observatory**
Bach's Reflector
2.5-inch Reflector on Equatorial Mount
The 7-inch Reflector at Birr Castle
The Whirlpool Galaxy, M.51 in Canes Venatici
Dome of the 33-inch Reflec- tor at Mount Wilson
The 10-inch Reflector; iron floor of the dome
* *The 200-inch Hale Reflector at Palomar*
* *The 6-inch Schmidt at Palo- man*
* *The 50-inch Zeiss Reflector at the Crimine Astronomical Observatory*
* *Mirror End of the 50-inch Zeiss Reflector at the Cri- mine Astronomical Observatory*
* *Dome of the 50-inch Reflector at the Crimine Astronomical Ob- servatory*
* *Dome of the 74-inch Reflector at the Commonwealth Ob- servatory*
* *Mars and its Shadow*
* *The Volcanic Crater of Hver- jökull, in Iceland*
* *Tychos, a Comet, in Tycho*
* *The Lunar Crater Aristillus*
* *The Mare Crisium, as drawn by Galileo*
* *The Hyginus Cliff*
* *The Lunar Craters Prolo- natus, Aegir and Ar- zachel*
* *Sunspots on Lunar Craters*
* *Some of some Lunar Craters Region of Pluto*
* *A Profile of the Lunar Crater Alphonsus*
* *The Western Marc Nobium*
* *Linné’s Map of the Moon*
* *106 & 107: The Moon’s Craters Copernicus and Serenitatis.*
* *The Southern Uplands of the Moon.*
* *Spectrogram of Alphonsus.*
* *Region of the Craters Mercator and Clavius.*
* *The Lunar Craters Apergatus and Alphonsus.*
* *Alpargatus and Alphonsus: Spectrograms of Venus by J. W. M. Baxter.*
* *Six photographs of Venus by Appian’s Size of Venus.*
* *Photograph of Venus, 1961.*
* *Venus, 1929 (and 1959) Opposite Size of Mars.*
* *Oppositions of Mars Apparent Size of Mars.*
* *March and Pleiades.*
* *March and Pleiades: Solar Prominence.*
* *March, October 12, 1936 Seasonal Decrease of the North Pole.*
* *Lowell’s Map of Mars The ‘Canals’ of Mars*
**The Martian ‘Canals’ accord- ing to A. Dollfus**
Sizes of Phobos and Deimos
Mars and its two Satellites
Jupiter’s Ring System
**The Changing Aspects Of Jupiter’s Belt**
Rotation Periods of the Vari- ants Saturn (Flaigstall)
Saturn (Palomar)
Saturn’s Moons Photographs of Jupiter Diagram of Saturn’s Ring System
**Saturn in 1949**
Various Aspects of Saturn’s Ring System
**Inclination of the Rotation Axes of the Planets**
Orbits and Asymmetrical Pla- nets
**Planets, Showing Apparent Motion over 24 Hours**
Campanus’s Comet of 1940
Campanus’s Comet of 1957 Great Comet 1811 Alcock’s First Comet of 1959 The Great Comet of 1811 Chetner’s Comet, 1844 Drawing of Bielet’s Comet Behavior of a Comet’s Tail Perseid Meteor Shower Photographs of the Motorway Mt. L. Spectrum of a Taurid Meteor Exploding Andromedine Me- teorite
**The Hola West Meteorite in Africa**
Region where the Siberian Meteorite landed, 1908 The Arizona Meteor Crater The Parallax Method of mecha- nizing orbits Star-Celebrants in the Milky Way Position of Gamma Draconis Position of Gyi Cygni Position of Beta Centauri Position of Vega The Scorpion The Quadrantilementary Orion Solar Prominences Sunspot Group Sunspots, September 17, 1959 Three Stages of the Solar Eclipse February 15, 1961 Part II: Solar Spots Total Eclipse before the Sun June 30, 1924 The Solar Flare, a periodical phenomenon The Solar Flare August 8, 1957 Total Eclipse of the Sun June 30, 1954 Solar Prominence, 1959
248
list of illustrations
The 120-Inch Tower Tele-
scope at Mount Wilson
Orion and his Retinue
Typical Stellar Spectra
The Doppler Effect
Stellar Spectra
Giant and Dwarf Stars
The Hertzsprung-Russell Dia-
gram
The Trifid Nebula in Sagit-
tarius
Professor Sir Arthur Eddington
Stellar Evolution according to Lockyer
The Horse's-Head Nebula in Orion
Apparent Movement of Sirius in the Sky
Spires of the Great Star-
Star-Clouds in the Milky Way
8x3inch Schmidt Camera-
Telescope at Palomar
The Double Star-Cluster in Perseus
The Constellation of Cetus
Rich Star-Field in the Milky Way
High-Dispersion Spectrum of Mira Ceti
The Constellation of Cepheus Light-Curve of Delta Cephei The Constellation of Aquila Supernova in the Galaxy LC.
4168 Position of Nova (DQ) Her-
cula 1934 Nova Hercula, 1954 Expansion of Heliochronic Order Nova Persei The Keyhole Nebula in Argo The Comet of 1861 Perseus Light-Curve of Alpha Lyrae The Constellation of Auriga Detection of a Spectroscopic Binary The Hyades The Pleiades Spiral Galaxy NG.C. 2841 in Ursa Major Spiral Galaxy Messier 64 (NG.C. 306) in Coma Berenices Galaxy NG.C. 295 Messier 17 Veil nebula in Scutum Sobieski's Dumb-Bell Nebula in Vulpeculae Planetary Nebula NG.C. 293 in Aquarius Messier 13 Globular Cluster in Hercules; three photographs The Owl Nebula Diagram of the Galaxy as it would be seen edge-on The Globular Cluster Omega Centauri
Galaxy N.G.C. 4365 196
The Saturn's Galaxy N.G.C. 197
4594 Menier 87 198
Galaxies: Conjunctions I and II 198
Nucleus of the Andromeda Galaxy 198
The Taurus nebule or Magellanic Clouds 199
The Nebulace Minor 199
The Nebulace Major 199
Spiral Galaxy in Leo 200
The Andromeda Galaxy, Coma Berenices 201
The Veil Nebula in Cygnus far measured: g-c-293; in Boötes Various types of Galaxies: 202
Various types of Galaxies: 203
The North America Nebula in Cygnus 204
The Crab Nebula in Lyra, Messier 57 204
Hubble's Classification of the Universe 205
Cluster of Galaxies in Hydra Yagi Array Aneurysmatic Spex-
trum 207
The 4-inch Fores Radio Telescope at the University of Man-
chester 207
Radio Telescope at Ascot Total Eclipse of October 2, 1959 The First American Radio Teles-
cope Karl Jansky's "Merry-Go-
Round" Star-Fields in the Milky Way "Dish-Type" Radio Telescope in Australia Pulkovo Radio Telescope The Lowell Ranch Radio Tele-
scope The Satellite Tracking Station at Cape Canaveral The Main Camera-Teloscope Station The Venierough Observatory Long-Enduring Meteor Trail, Cheshire Photographs Mills Cross Record of Radio Emissions from Jupiter Mills Cross: north-south arm The Crab Nebula, Messier 13 215
Radio Source Casiopeia A Radio Source Cygnus II NGC 6888: a member of the Perseus Cluster of Galaxies Interferometer at Sydney, Australia 218
N.G.C. 409l-g: Colliding Ga-
laxies 219
A Diatom 219
A Collection of Micro-Organ-
isms which grow in Water and Damp Soil 220
The South Polar Area of Mars, 1880 (Schiaparelli) 221
Photograph by William Lowell Mars, 1900, drawn by E. M. Aitken 221
Jansen' tidal Theory of the Origin of the Solar System Grouping by Tidal Forces The 8-foot Radio Telescope at Green Bank, Virginia Cosmosography of the Earth's Atmosphere Principle of Reaction Designs for a Space-Ship by Tsaiokovski 224
Preparations for firing Van-
keres' rocket Pioneer V. Launcher V. Rocket Pocket Photograph of the Earth from High Altitude Goddard Rocket Launcher at Roswell, 1953 Total Eclipse of the Sun, 1966 Two photographs: Borealis, two photographs Orbit of the American Satellite Sputnik I Night Launching of Viking 3 Moskva Sputnik III Rocket The First American Explorer Satellite Sputnik I Trail of Spurritik I Sputnik II Trail of Sputnik II Camera-Earth Film Camera-Earth Film Camera at Zvenigorod, U.S.S.R. Non-Core of Spurritik III Pioneering Wheel-Satellite Pioneer Nothurn Cloud from Lunik I Pioneers for launching Pioneers Photographs of the Lunik I series Six Succive photographs of the Moon's Bean Cloud emitted by Lunik II Lunik II The Moon's Ecliptic and Reverie Sides of the Moon The Reverse Side of the Moon Photos taken on July III during the photographic eclipse, the Moon's Reverse Side Your Photograph Another photograph of the Moon's Reverse Side Commander Alan Shepard
![]() A diagram showing various types and characteristics of galaxies.
| Description |
Page Number(s) |
The North America Nebula in Cygnus
Messier 57
Hubble's Classification of the Universe
The Crab Nebula in Lyra
The Veil Nebula in Cygnus
The Andromeda Galaxy, Coma Berenices
The Taurus nebule or Magellanic Clouds
The Nebulace Minor
The Nebulace Major
Spiral Galaxy in Leo
The Andromeda Galaxy, Coma Berenices
The Veil Nebula in Cygnus far measured: g-c-293; in Boötes
Various types of Galaxies: |
204, 205, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207, 207 |
N.G.C. 4365,
N.G.C. 4594,
Messier 87,
Messier 57,
Messier 64,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68,
Messier 68, |
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249
**Acknowledgments**
Illustrations are keyed by the appropriate page number followed by positioning symbol U for Upper, C for Centre, L for Lower, r for Left, e for Right
Oldbourne Book Co. Ltd; 134, 154, 16, 18, 19, 202, 220.
233, 234, 44, 45, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80.
81a, 81b, 82a, b83a, b84a, b85a, b86a, b87a, b88a.
U.S. Naval Observatory; Washington; n.d.
United States Weather Bureau and Information Bureau; n.d.
Brian Gullery; n.d.
Pic du Midi Observatory; n.d.
N. A. Koszirsky; n.d.
K. Sagiaki; Tokyo Museum of Science; n.d.
G. V. Schiaparelli; n.d.
H. E. Dall; n.d.
Raimund Schein; n.d.
D. Deloffe; n.d.
W. T. Hay; n.d.
E. A. Whittaker; n.d.
G. E. D. Alocek; n.d.
H. H. Moulton; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.; n.d.;
D. E. Blackwell and M. F. Ingham; n.d.
P-A Reuter; n.n.
Professor Ake Wallenquist; nd
Royal Greenwich Observatory; nd
U.S.N.R. Academy of Sciences; nd
Elliot and Fry Ltd; nd
W. S. Franks; nd
Astronomical Society of the Pacific; nd
Central Office of Information; nd
McDonnell Aircraft Corporation; nd
Karl Januskiy; nd
D. G. Rushton; nd
F.J. Jackson; nd
National Radio Astronomy Observatory, Green Bank; nd
National Radio Astronomy Observatory; nd
J.C. Weekley; nd
U.S. Embassy London; nd
British Interplanetary Society; nd
National Film Board of Canada; nd
George Philip's Globe by Rand McNally & Company;
New York; nd
U.S. Army Air Force; nd
K.Gottlieb,Mount Stromlo-Observatory,Canberra;
Photograph Picture by Morris Allan,
DefenceMinistry;
U.S.AirForce Missile and Test Centre Florida;
Society for Cultural Relations with the U.S.S.R.;
Planet News; nd.
Science Museum London. Reproduced by courtesy of the Royal Society; nd.
Port Elizabeth Observatory, South Africa; nd.
Colin Roman; nd.
U.S.Naval Observatory, Washington; nd.
United States Weather Bureau and Information Bureau; nd.
Brian Gullery; nd.
Pic du Midi Observatory; nd.
N.A.Koszirsky; nd.
K.Sagiaki,TokyoMuseumofScience;n d.
G.V.Schiaparelli;n d.
H.E.Dall;n d.
RaimundSchein;n d.
D.Deloffe;n d.
W.T.Hay;n d.
E.A.Whittaker;n d.
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F.J.Achiefford,FforestHallObservatory,Northumberland: nd
F.J.Achiefford,FforestHallObservatory,Northumberland: nd
H.E.Wood,UrsinObservatory,Johannesburg: nd
Radio Times and Huton Picture Library: nd
Deutsches Museum: nd
Deutsches Museum: nd
Copyright Science Museum: nd
Science Museum London: nd
Science Museum London: nd
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Gösta Persson; nsd
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
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Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
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Patrick Moore's Astronomy for Everyone (1990) pgs:
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Patrick Moore's Astronomy for Everyone (1990) pgs:
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Patrick Moore's Astronomy for Everyone (1990) pgs:
Patrick Moore's Astronomy for Everyone (1990) pgs:
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Dominic Fisher; nsd
Lowell Observatory; nsd
Lick Observatory; nsd
Lick Observatory; nsd
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W.M.Baxter;
W.M.Baxter;
W.M.Baxter;
W.M.Baxter;
W.M.Baxter;
W.M.Baxter;
W.M.Baxter;
W.M.Baxter;
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W.M.Baxter;
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W.M.Baxter;
W.M.Baxter;
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W.M.Baxter;
W.M.Baxter;
W.M.Baxter;
W.M.B Baxter,
Daily Express:
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Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Express:
Daily Expression.
British Interplanetary Society.
National Film Board of Canada.
George Philip’s Globe by Rand McNally & Company.
New York.
U.S. Army Air Force.
Photograph Picture by Morris Allan,
Defence Ministry.
U.S.AirForce Missile and Test Centre.
Society For Cultural Relations With The U.S.S.R.
Planet News.
British Interplanetary Society.
National Film Board of Canada.
George Philip’s Globe by Rand McNally & Company.
New York.
U.S. Army Air Force.
Photograph Picture by Morris Allan,
Defence Ministry.
U.S.AirForce Missile and Test Centre.
Society For Cultural Relations With The U.S.S.R.
Planet News.
British Interplanetary Society.
National Film Board of Canada.
George Philip’s Globe by Rand McNally & Company.
New York.
U.S. Army Air Force.
Photograph Picture by Morris Allan,
Defence Ministry.
U.S.AirForce Missile and Test Centre.
Society For Cultural Relations With The U.S.S.R.
Planet News.
British Interplanetary Society.
National Film Board of Canada.
George Philip’s Globe by Rand McNally & Company.
New York.
U.S. Army Air Force.
Photograph Picture by Morris Allan,
Defence Ministry.
U.S.AirForce Missile and Test Centre.
Society For Cultural Relations With The U.S.S.R.
Planet News.
British Interplanetary Society.
National Film Board of Canada.
George Philip’s Globe by Rand McNally & Company.
New York.
U.S. Army Air Force.
Photograph Picture by Morris Allan,
Defence Ministry.
U.S.AirForce Missile and Test Centre.
Society For Cultural Relations With The U.S.S.R.
Planet News.
British Interplanetary Society.
National Film Board of Canada.
George Philip’s Globe by Rand McNally & Company.
New York.
U.S. Army Air Force.
Photograph Picture by Morris Allan,
Defence Ministry.
U.S.AirForce Missile and Test Centre.
Society For Cultural Relations With The U.S.S.R.
Planet News.
British Interplanetary Society.
National Film Board of Canada.
George Philip’s Globe by Rand McNally & Company.
New York.
U.S. Army Air Force.
Photograph Picture by Morris Allan,
Defence Ministry.
U.S.AirForce Missile and Test Centre.
Society For Cultural Relations With The U.S.S.R.
Planet News.
250
**index**
**AERATION** of light, 160
Adams, J. C., 103-104
Adams, W. S., 176-179
Acrobates, 180-182
Aerolites, 194
Airy, G. B., 103-104, 111
Alberto (Eta Tauri), 191
Al-Cayman (Eta Tauri), 191
Al-Battani, 27
Alchemy, 27
Alcock, G. E. D., 153
Aldebaran, 169, 172, 193
Alexandrian Library, 25, 26
Algol, 188-9
Alkaid, 200-201
Amagat, the, 25, 27
Al-Mamoun, 27
Alpha Centauri, 29, 161-2, 178
Alphonsine Tables, 28
Alphonsus (lunar crater), 125-126
Alpina (Vega), 25
Alps (lunar), 126
Al-Sufi, 27, 28
Altair, 27-28
Altitudinous mountings for telescopes, 110
Andromeda, Great Galaxy in, 13, 193,
286-287
Andromeda, legend of, 39-40
Angestrom, A., 207
Anguieras, 34-35
Antaratsis, 162-163
Antaratsis II, 344-345
Apeironia (lunar), 346-347
Arab astronomy, 26, 27-28
Araxes, I., 350-351
Arcetri Observatory, 169
Arcturus, 28s, 89-90
Argelander, J., 350-351
Arizadus Clef, 353
Aries, 41-42
Aries Point of see Vernal Equinox
Aristarchus, 24
Aristarchus (lunar crater), 63
Arnoldi, P., 350-351
Arrhenius, S., 376-378
Ashen Light, 198
Aspera (Minor Planet), Astrum, 100
Astrolabe, see Astrolabe Astronomy,
Astrology, 22.
Athens Observatory, 198.
Atmospheric Structure of Earth's Atmosphere,
Aurorae, 85.
Auzout, A., 62, 67.
Babbage, W., 197.
Bacon, R., c.49.
Baghdad School of astronomy, c.57.
Bailly, J. S., 88.
Baily (lunar crater), 124.
Barbados (lunar crater), 131.
Barnard's Ecliptic Star Cluster,
Barnard's Star, 74.
Barrow's Star Cluster,
Baye's Star Cluster,
Bavasos Tapastery,
Beer's Star Cluster,
Bessel's Star Cluster,
Beta Lyrae,
Betelgeux,
Beta Lyrae,
Beuchet's Star Cluster,
Bourget's Star Cluster,
Bowl of the Astronomers,
Cassini's Star Cluster,
Cassiopeia (lunar crater),
Cassiopeia (lunar cluster),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star),
Cassiopeia (lunar star)
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light,
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculus of light，
Calculation by the use of a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadrant and a quadratic equation with two variables,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant,
Quadrant
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use of an equatorially mounted telescope with an equatorial mounting for telescopes.
Calculation by the use
![]() Colliding galaxies.
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxies
Colliding galaxie
index 251
**Eratosthenes,** 24
Eratosthenes, 139
Erythraeanum, Mare, 139
Escape velocity, 224
Eta Aquilae, 185
Eratosthenes, 137-8
Euler, L., 167
Europe, 147
Evolutionary theory of the universe, 218-9
Ewen, H., 217
Explorer I, American satellite, 234
**fabriciusi,** D., 183
Fabricius, J., 53, 183
Fahrenheit, 100
First Point of Aries, see Vernal Equinox
Fizziu, H., 110
Flamsteed, John, 124
Hamstedt, J., 70-80, 91, 102, 183
Hamstedt House, 97
Hannibal, 100
Fourcoudt, C., 110
Fox Talbot, L., 130
Freyre, E., 226-7
Fraunhofer Lines, 165, 166
Frageris, Marq, 123
**G.** g.
**g.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
**G.** g.
Juno, too
Juno Caesar, 27
Vulcanus (Juno Crater), 63
Jupiter, 13, 117; 145-7; 173; 222
Lunar rotation of $6^\circ$, $64^\circ$;
Lunar satellites of $3^\circ$, $49$, $68$, $147$
KANT, J., 90
Kappa Pappanu, 185
Kappa Pappanu, 185
Kelvin, Lord, 175
Kirkwood's Law of $3^{\circ}$ to $6^{\circ}$; $58$, $158$, $224$
Keppler's Laws, 45
Keppler's Star, $q$, $86$, $215$;
Keppler's Star, $q$, $86$, $215$;
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,
Kirchhoff's Law of Absorption and Emission,![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength on the x-axis and intensity on the y-axis.![]() A diagram showing Kirchhoff's law of absorption and emission with a black body at different temperatures on a graph with wavelength
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical paths.
![]() An illustration depicting Kepler’s laws: The first shows three planets orbiting around their star in elliptical paths; The second shows two planets orbiting around their star in elliptical paths; The third shows two planets orbiting around their star in elliptical
![]() An illustration depicting Kepler’s laws: Three bodies (planets) are shown revolving about each other (the sun) following ellipses rather than circles.
The innermost planet is shown moving counterclockwise.
The middle planet is shown moving clockwise.
The outermost planet is shown moving counterclockwise.
The orbits are depicted as ellipses rather than perfect circles.
The sun is located slightly off-center to one side.
The relative sizes are not to scale.
The innermost planet has an orbital period that is less than that required for circular motion.
The middle planet has an orbital period that is greater than that required for circular motion.
The outermost planet has an orbital period that is greater than that required for circular motion.
The orbits are depicted as ellipses rather than perfect circles.
The sun is located slightly off-center to one side.
The relative sizes are not to scale.
The innermost planet has an orbital period that is less than that required for circular motion.
The middle planet has an orbital period that is greater than that required for circular motion.
The outermost planet has an orbital period that is greater than that required for circular motion.
The orbits are depicted as ellipses rather than perfect circles.
The sun is located slightly off-center to one side.
The relative sizes are not to scale.
The innermost planet has an orbital period that is less than that required for circular motion.
The middle planet has an orbital period that is greater than that required for circular motion.
The outermost planet has an orbital period that is greater than that required for circular motion.
The orbits are depicted as ellipses rather than perfect circles.
The sun is located slightly off-center to one side.
The relative sizes are not to scale.
The innermost planet has an orbital period that is less than that required for circular motion.
The middle planet has an orbital period that is greater than that required for circular motion.
The outermost planet has an orbital period that is greater than that required for circular motion.
The orbits are depicted as ellipses rather than perfect circles.
The sun is located slightly off-center to one side.
The relative sizes are not to scale.
The innermost planet has an orbital period that is less than that required for circular motion.
The middle planet has an orbital period that is greater than that required for circular motion.
The outermost planet has an orbital period that is greater than that required for circular motion.
The orbits are depicted as ellipses rather than perfect circles.
The sun is located slightly off-center to one side.
The relative sizes are not to scale.
The innermost planet has an orbital period that is less than that required for circular motion.
The middle planet has an orbital period that is greater than that required for circular motion.
The outermost planet has an orbital period that is greater than that required for circular motion.
The orbits are depicted as ellipses rather than perfect circles.
The sun is located slightly off-center to one side.
The relative sizes are not to scale.
The innermost planet has an orbital period that is less than that required for circular motion.
The middle planet has an orbital period that is greater than that required for circular motion.
The outermost planet has an orbital period that is greater than that required for circular motion.
The orbits are depicted as ellipses rather than perfect circles.
The sun is located slightly off-center to one side.
The relative sizes are not to scale.
The innermost planet has an orbital period that is less than that required for circular motion.
The middle planet has an orbital period that is greater than that required for circular motion.
The outermost planet has an orbital period that is greater than that required for circular motion.
The orbits are depicted as ellipses rather than perfect circles.
The sun is located slightly off-center to one side.
The relative sizes are not to scale.
The innermost planet has an orbital period that is less than that required for circular motion.
The middle planet has an orbital period that is greater than that required for circular motion.
The outermost planet has an orbital period that is greater than that required for circular motion.
The orbits are depicted as ellipses rather than perfect circles.
The sun is located slightly off-center to one side.
The relative sizes are not to scale.
The innermost planet has an orbital period that is less than that required for circular motion.
The middle planet has an orbital period that is greater than that required for circular motion.
The outermost planet has an orbital period that is greater than that required for circular motion.
The orbits are depicted as ellipses rather than perfect circles.
The sun is located slightly off-center to one side.
The relative sizes are not to scale.
The innermost planet has an orbital period that is less than
![]() An illustration depicting Kepler’s laws: Three bodies (planets) are shown revolving about each other (the sun) following ellipses rather than circles.
Each ellipse represents an eccentricity varying from left to right (from smaller to larger).
In this depiction:
- **Innermost Planet:** Orbits closer to circle (smaller eccentricity).
- **Middle Planet:** Orbits more elongated (larger eccentricity).
- **Outermost Planet:** Orbits even more elongated (larger eccentricity).
This illustrates how eccentricity affects planetary orbits over time.
252
index
Maya astronomy, 36
Mayes, S., 40
Mayes, R., 181
Mars, 138-43, 145, 221
canals, 147
caps, polar, 66-7, 139
clouds, 141-42
mooncraters, 34, 46-66, 72-78, 83
organisms, living, 190-192, 143-145
rotation, 66
satellites, 143-145
temperature of, 139, 141
Makenseyne, N., 93, 115
Matter, atomic, see Atomic matter
McDonald Observatory, 118
Mecca, Holy Stone at, 157
Michelson, A., 200
Menzel, D. H., 138
Mercury, see Mercury
Mercury transit of Earth, 47-48, 227-229
transits of, 38-40, 85
Meridians, 47
Messier, J. E., 551
catalogue of nebulae, 551
Meteor Crater in Arizona, 198
Metempsychosis, 357
Meteorites, 355-57
radiants, 156
radio astronomical studies of, 211
Metsu, 109
Mesudon Refractor, 125-149
Mitchell's telescope, see Mitchell's telescope
Milky Way, 49
radio waves from, 209
Mills, B. V., 234
Mills Crows, 214-15
Mimas, see Mimas
Minor Planets, 69-102
Mira Ceti', 183-4; 190
Mira Ceti', see Mira Ceti'
Montanari G., 188
Moon, I33-132; albedo; atmosphere; cielis; craters; diameter; distance; Earthshine on; ephemerides; equinoxes; origin of; phases of; photographing; rays; tides; rotation of; surface features; stars; temperature; transit of Moonwatch Project, 234 Moore, A. L., see Moore A. L.
Moscowian Mare, 239
Mohounl F. R., see Mohounl F. R.
Moonlight and Atmospheric Light, 124 Mount Wilson Observatory, 117 Mu Cephei', see Mu Cephei'
Multiple Stars and Variable Stars Munich Optical Institute, 108
NAMSYTH', J., 128;
Nautical Almanac,
Nicholas' table (see Table)
Nickle's table (see Table)
Nebula in Orion, see Orion Nebula in Nebular Hypothesis,
Neptune,
Neurodegeneration,
Neridat,
Nero (Roman emperor), see Nero (Roman emperor)
Nero (Roman emperor), see Nero (Roman emperor)
Nero (Roman emperor), see Nero (Roman emperor)
Nero (Roman emperor), see Nero (Roman emperor)
Nero (Roman emperor), see Nero (Roman emperor)
Nero (Roman emperor), see Nero (Roman emperor)
Nero (Roman emperor), see Nero (Roman emperor)
Nero (Roman emperor), see Nero (Roman emperor)
Nero (Roman emperor), see Nero (Roman emperor)
Nero (Roman emperor), see Nero (Roman emperor)
Nero (Roman emperor), see Nero (Roman emperor)
Nero (Roman emperor), see Nero (Roman emperor)
Nero (Roman emperor), see Nero (Roman emperor)
Nero (Roman emperor), see Nero (Roman emperor)
Nero (Roman emperor), see Nero (roman emperor)
Nero (roman emperor), see Nero (roman emperor)
Nero (roman emperor), see Nero (roman emperor)
Nero (roman emperor), see Nero (roman emperor)
Nero (roman emperor), see Nero (roman emperor)
Nero (roman emperor), see Nero (roman emperor)
Nero (roman emperor), see Nero (roman emperor)
Nero (roman emperor), see Nero (roman emperor)
Nero (roman emperor), see Nero (roman emperor)
Nero (roman emperor), see Nero (roman emperor)
Nero (roman emperor), see Nero (roman emperor)
Nero (roman emperor), see Nero (roman emperor)
Nero (roman emperor), see Nero (roman emperor)
Nero (roman emperor), see Nero (roman emper...
Nero (roman emper..., see Nero...
Nero...
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Neptune,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto,
Pluto，
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polaris.
Polar...
index 253
**LADY TRIBUNAL**, 195
Saint-Pierre, p8
Saros Period, 20
Satellites of planets, 13, 49
Saturn, 64-65, 72-73, 237
Saturn, 50-64, 147-150, 159, 173, 222
rings of, 64, 148-149
radio waves of, 15
satellites of, 66, 67, 95
Schiaparelli, G. V., 134, 135, 139, 143
Schmidt, B., 184
Schmidt, B., 181
Schmidt, J., 125, 128
Schmidt Camera, 183
Schmidt Camera, 184
Schmidt Camera, 185
Schmidts Camera, 186
Schmidts Camera, 187
Schmidts Camera, 188
Schmidts Camera, 189
Schmidts Camera, 190
Schmidts Camera, 191
Schmidts Camera, 192
Schmidts Camera, 193
Schmidts Camera, 194
Schmidts Camera, 195
Schmidts Camera, 196
Schmidts Camera, 197
Schmidts Camera, 198
Schmidts Camera, 199
Schmidts Camera, 200
Schmidts Camera, 201
Schmidts Camera, 202
Schmidts Camera, 203
Schmidts Camera, 204
Schmidts Camera, 205
Schmidts Camera, 206
Schmidts Camera, 207
Schmidts Camera, 208
Schmidts Camera, 209
Schmidts Camera, 210
Schmidts Camera, 211
Schmidts Camera, 212
Schmidts Camera, 213
Schmidts Camera, 214
Schmidts Camera, 215
Schmidts Camera, 216
Schmidts Camera, 217
Schmidts Camera, 218
Schmidts Camera, 219
Schmidts Camera, 220
Schmidts Camera, 221
Schmidts Camera, 222
Schmidts Camera, 223
Schmidts Camera, 224
Schmidts Camera, 225
Schmidts Camera, 226
Schmidts Camera, 227
Schmidts Camera, 228
Schmidts Camera, 229
Schmidts Camera, 230
Schmidts Camera, 231
Schmidts Camera, 232
Schmidts Camera, 233
Schmidts Camera, 234
Schmidts Camera, 235
Schmidts Camera, 236
Schmidts Camera, 237
Schmidts Camera, 238
Schmidts Camera, 239
Schmidts Camera, 240
![]() A close-up view of Earth from space, showing the western coast of Europe and North Africa. The landmasses are detailed with varying shades of green and brown, indicating different terrains. The ocean is depicted in blue, with some white clouds visible in the sky.
![]() A large, detailed moon with dark craters and a pinkish hue is set against a starry background.
Patrick Moore
ASTRONOMY
McGraw-Hill
![]() Saturn with rings
Astronomy
PATRICK MOORE
ASTRONOMY
PATRICK MOORE
OLDBOURNE LONDON |
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