COMETS 441 - 450
|441. COMET SIDING SPRING C/2007 Q3 Perihelion: 2009 October 7.26, q = 2.252 AU
As I discuss on my statistics page, the length of time that I follow the comets I observe varies widely; the "average" time span (depending upon how one wants to define that term) is in the general vicinity of three months, but there are comets that I may follow for considerably longer, or considerably shorter, than that time span. Of the 440 comets that I've observed up until now, I've followed 26 of them (6%) for over a year; of all the other ones still ongoing, at least one more, and possibly as many as three others, should eventually go over the one-year mark. This is yet another one that should easily go over one year (and possibly as long as two years); when I first picked it up on the morning of October 7, 2008 it was exactly one year, to the day, before its perihelion passage (although, if one wants to split hairs, I missed observing it one year before perihelion by 4 1/2 hours).
The comet was discovered back on August 25, 2007 by Donna Burton with the Siding Spring survey based in New South Wales. Because it was so distant (over 7 AU from both the sun and Earth) it did not appear cometary on the discovery images, and it wasn't until images were taken several days later with other telescopes that its cometary nature was revealed -- hence, the name "Siding Spring" as opposed to that of the individual discoverer. (This is the third comet I have observed with the name "Siding Spring.") At that time it was located at a moderately high southerly declination (near -47 degrees) and is has remained in the southern sky ever since; when I first saw it its declination was again near -47 degrees, only a few degrees above my southern horizon. I had a fairly strong suspect (magnitude 13 1/2, small and condensed) on the morning of the 7th, and verified this suspect the following morning.
Presently the comet is located in southwestern Puppis, and is heading almost due southward at ten arcminutes per day. For the time being I may very well be done with it, since the weather forecasts are indicating some storm activity may be moving into the area, and once that's done there will be the full moon; once the morning sky is dark again the comet's declination will be south of -50 degrees, which for all practical purposes is too far south for me to observe. (I have occasionally observed bright comets at that declination from here, but this one isn't bright enough to be in that category.) After crossing into western Carina in early November the comet passes just over a degree west of the bright star Canopus in the middle of that month, then continues its southward motion until it reaches a maximum southerly declination of -54.3 degrees in mid-December, at which time it will also be near opposition. It then begins heading back north, and should again become accessible from my latitude by the latter part of February 2009, by which time it may have brightened to about 12th magnitude. It might brighten an additional half-magnitude or so by the time I lose it in twilight near the beginning of May (at which time it will be located near the star Beta Canis Majoris, or Mirzam); comet-watchers in the southern hemisphere should be able to follow it for perhaps an additional month.
After conjunction with the sun Comet Siding Spring emerges into the morning sky by the latter part of October, when it will be located in southeastern Leo and perhaps as bright as 10th magnitude. It should maintain something close to this brightness for the next several months, as it travels northeastward through Virgo (passing through the northern section of the Virgo galaxy cluster during the latter half of November), Coma Berenices, and Bootes, and enters Draco in early March 2010. The comet is nearest Earth (2.19 AU) in early February 2010, and is at opposition in early May when it will also be at its most northerly declination of +64 degrees. It will probably have faded to about 12th magnitude by about that point, and should continue fading as it turns back south; on the second anniversary of my initial observation it will be located low in the northwestern evening sky in Corona Borealis, and should probably have faded back to 14th magnitude.
Comet Siding Spring turns out to be the 30th comet I have observed in 2008. This is the fourth time I have reached that total during a calendar year, and this is by far the earliest I have ever reached it. My all-time record for most comets observed in a single calendar year is 34, which I accomplished in 2002; with over 2 1/2 months to go in 2008 it is entirely possible that I may tie or break that record this year. There aren't any comets that I definitely expect to observe before the end of the year, but there are several "maybes" (a handful of which I have already attempted unsuccessfully), and of course there is always the possibility of one or more unexpected discoveries taking place between now and then. We shall see . . .
UPDATE: As expected, I picked up this comet in mid-February 2009 after its passage through more southerly skies. Its brightness was around magnitude 12 1/2 -- not dramatically different from the scenario described above -- so at this time it appears that the initial expectations still hold.
UPDATE: After its conjunction with the sun I picked up this comet low in the morning sky in mid-October 2009. It appeared as a relatively condensed object between magnitudes 10 1/2 and 11 -- reasonably close to the projected brightness for this time -- so the scenario described above for the uncoming few months continues to appear likely.
UPDATE: An infrared image of Comet Siding Spring is featured among the initial set of images taken by the Wide-field Infrared Survey Explorer (WISE) spacecraft that was released in mid-February 2010. The image in question, taken on January 10, shows a bright and distinct dust tail, and in fact appears fairly similar to the visual appearance that the comet was exhibiting at that time.
It may seem that I'm adding comets to "Countdown" at a pretty rapid rate, but in theory I could be adding them even faster; I am constantly attempting additional comets that are too faint for me to observe successfully (or are unobservable for other reasons). Since I began "Countdown" in March 2007 there are 22 comets that I have unsuccesfully attempted to observe visually; I've managed to image a couple of these with CCD, and there are another couple that I might successfully detect visually sometime in the not-too-distant future.
On the evening of October 21 I decided to attempt several very faint comets that I haven't observed yet, and frankly I didn't really expect to see. I failed to detect the first three comets I attempted that night, but when I turned to the fourth one I did seem to be seeing an extremely faint "something" in the expected position. After again seeing this "something" in the correct position on both of the two subsequent nights (including distinct motion on the last night) and after seeing a CCD image taken by "Countdown" mentor Vitali Nevski just a few hours before my first sighting I became convinced that I was indeed observing this comet. It was an extremely faint object of magnitude 14 1/2, right around the "diffuse comet" limit of the 41 cm telescope.
The comet was initially discovered in September 1949 independently by Pelageja Shajn at the Crimean Astrophysical Observatory in the then-Soviet Union and by Robert Schaldach at the Lowell Observatory in Arizona. This was the only comet discovery for either of these two individuals, although Shajn's husband, Grigory Shajn, was also an astronomer who specialized in the study of galactic nebulae and who made a comet discovery of his own, Comet Shajn-Comas Sola 1925a. The comet had passed only 0.18 AU from Jupiter three years earlier (which, among other things, decreased its perihelion distance from 4.3 AU to 2.2 AU and shortened its orbital period from 10.6 years to 7.3 years) and apparently had undergone an outburst before its discovery, as the reports from that time indicated a brightness of about 12th magnitude, much brighter than it has ever appeared since. It was missed at the subsequent two returns (perhaps in part because it wasn't as bright as expected) but was finally recovered in 1971 and has been seen at every return since then. A moderately close approach to Jupiter (1.0 AU) in early 2006 decreased the perihelion distance to the present value and shortened the orbital period to the current 7.05 years. At the current return it was recovered on June 6, 2008 by the Italian duo of Ernesto Guido and Giovanni Sostero utilizing a remote-control telescope in Mayhill, New Mexico.
Comet Shajn-Schaldach is now a month and a half past perihelion passage and will be closest to Earth (1.18 AU) on November 3 before being at opposition a week later, and accordingly is about as bright as it is going to get. Unless something strange happens, then, at most I will only obtain a few observations of it, and in fact it is entirely possible that the observations I've made so far will be the only ones that I get. The comet is currently located in western Taurus half a degree west of the star 6 Tauri, and it is traveling slowly towards the southwest; it crosses into northeastern Cetus in early November but will probably be too faint to observe by then. I suspect that very few "Countdown" participants will see this comet, at least visually; those who attempt it should keep in mind that it is very easy for the eye to "manufacture" very dim "fuzzies" and thus should take care to ensure that they are indeed seeing it.
I've attempted this comet unsuccessfully on two previous returns, in 1986 and in 1993. There are several other numbered periodic comets that I've attempted unsuccessfuly on two returns, and a handful where I've been unsuccessful on three returns; P/Shajn-Schaldach is the only "third time's the charm" comet I've had so far. It also has the distinction of having the longest interval between first attempt and first successful observation -- over 22 years. Meanwhile, the next two returns, in 2015 and 2022, take place under slightly more favorable geometry than this year's and the comet should accordingly be slightly brighter, so perhaps I will be able to grab a few more observations of it before all is said and done.
It seems that a lot of the periodic comets that I'm adding to my tally these days hearken back to "interesting" times of my life during previous returns, and are reinforcing the changes that are underway in my life right now (which I'm still not quite ready to share in these pages yet -- but that day will come). This is yet another one of those objects . . .
The comet was originally discovered in January 1994 by a Japanese amateur astronomer, Yoshio Kushida, who found it via film photography (kind of a dying art these days) -- only one month after he had co-discovered another comet (another short-period object now known as 147P/Kushida-Muramatsu). This newer comet was already almost a month past perihelion when discovered but was still a month away from opposition, and thus it remained well placed for observation for some time. I followed it (no. 184) for about two months after its discovery, and despite its receding from both sun and Earth during that time it maintained a fairly constant brightness near 10th magnitude before fading abruptly in March. This all happened during a relatively short period of time -- a little over 18 months -- in my life when I was living in El Paso, Texas, working hard on getting what is now the Earthrise Institute started and running, and also scouting out potential homesites in the Sacramento Mountains near Cloudcroft, New Mexico, where I would move to the following year.
Comet Kushida's current orbital period is 7.6 years. It returned to perihelion in mid-2001, but this was a very poor return geometrically, and I did not attempt it; only a handful of observations of any kind were reported. On the current return it was recovered as long ago as June 18, 2007 by Karen Meech and Jana Pittichova with the Keck II 10-meter telescope at Mauna Kea in Hawaii, and it was also observed the following July 9 and 10 by a team led by Michael Kelley utilizing the Spitzer Space Telescope. These observations weren't announced until July of this year, and curiously there were no additional observations reported until this past September, although it has been observed regularly since then.
To be truthful, I wasn't quite sure what to expect from Comet Kushida this time around. The geometry at this return is quite favorable -- similar to that at the discovery return -- which at face value suggests a peak brightness near 10th magnitude; however, in my mind the comet's behavior suggested it might have experienced an outburst shortly before its discovery. (On the other hand, there weren't any close approaches to Jupiter or any other apparent "trigger" events prior to that return.) The complete lack of any observations for over a year following its recovery in mid-2007 didn't seem particularly encouraging, nor did the fact that it was being reported as faint as 20th magnitude once observations did resume. However, recent CCD reports (and even a couple of visual reports) suggested that it has recently been brightening rapidly, and when I tried it for the first time on the evening of November 16 I easily saw it as a fairly condensed object near magnitude 12 1/2.
The comet was at opposition just before mid-November, but is still two months away from perihelion passage, and will be nearest Earth (0.59 AU) in mid-December. We know very little about its overall brightness behavior and thus it is difficult to make any definitive predictions; if we use the post-discovery brightness in 1994 as a baseline then we might expect a peak brightness between 10th and 11th magnitude from late December through perhaps early February, and it might remain visually detectable until perhaps sometime in March. Whatever it does, it remains well placed for viewing in the evening sky for some time; currently it is located in eastern Aries some seven degrees southwest of the Pleiades star cluster M45, and after reaching its stationary point in early December it begins traveling eastward, crossing into western Taurus late that month. The comet spends the next two months passing through Taurus (including crossing directly across the Hyades star cluster during the first week of February) before entering northeastern Orion in early March and southwestern Gemini two weeks later.
Although I'm still not ready to share the major events taking place in my life right now, there are plenty of life's little events, both good and bad, going on. On the negative side, on Saturday evening (the night before my first Kushida observation) I was involved in a minor car accident when I struck a cow on one of the mountain roads here. (It was a completely unavoidable accident, as just prior to hitting the cow I had been blinded by the headlights of an oncoming car.) No injuries -- at least, to those of us in the car -- but although the damage wasn't extensive, because it's an old car that I've been driving for a long time it has been declared totaled. Thus, I will have to get a new(er) car sometime soon. On the plus side, shortly after the Kushida observation I happily watched my favorite football team (the Dallas Cowboys) defeat its archrival, the Washington Redskins. (Apologies to any Redskins fans out there . . . ) Meanwhile, I'm planning to attend a performance of the musical Jesus Christ Superstar in a couple of days, and then going to a Trans-Siberian Orchestra concert early next week. Next week is also, of course, Thanksgiving week here in the U.S., and my older son Zachary will be coming home for a few days. So, amidst the comets and everything else, life goes on . . .
I first became interested in astronomy while in elementary school, and observed a handful of astronomical events (including a few eclipses as well as the great Leonid meteor shower of 1966) during those early years, but it was in early 1970 when I acquired my first telescope that my interest really took off. At around the same time -- due in large part to my best friend at the time, Mark Bakke -- I discovered the magazine Sky & Telescope at a local newstand. The first issues I ever had were the November and December issues from 1969, and I completely devoured these from cover to cover. (I actually still have these, although they are so wrinkled from overuse that I've had to replace them for my overall collection.) Among many, many other items, the December issue carried a brief article about a new comet that had been recently discovered from the Alma Ata Observatory in the then-Soviet Union (now Kazakhstan) by Klim Churyumov and Svetlana Gerasimenko, coincidentally on a photograph that had been taken of Comet 32P/Comas Sola. (This would be Gerasimenko's only comet discovery, but Churyumov (officially with the Kiev University) would later be one of the discoverers of the long-period Comet Churyumov-Solodovnikov 1986i (no. 94 -- the first comet I added to my tally after moving back to New Mexico from California). I had the pleasure of meeting him at an Asteroids Comets Meteors (ACM) conference in Flagstaff, Arizona in 1991.)
The new comet was found to be periodic (current period 6.45 years) and it has been recovered at every subsequent return. I successfully observed it during its returns in 1982 (no. 53), 1996 (no. 206), and 2002 (no. 315); the 1982 return was very favorable geometrically and it reached 9th magnitude, displaying in a telescope some of the most remarkable tail structure I've ever seen on a comet of that brightness. On the current return it was recovered on June 1, 2008 by Gustavo Muler at the Nazaret Observatory in Spain (although I've read that it was apparently observed with the Spitzer Space Telescope as far back as July/August 2006, but these reports have not yet been published).
67P's current return is rather unfavorable, and in fact I'm a little bit surprised that I was able to pick it up at all. But some of the recent CCD observations, as well as a couple of visual observation reports, suggested it might be worth attempting, and I've been doing so since about the beginning of October. Finally, on the evening of November 18 I saw an extremely faint (magnitude 14 1/2) tiny and condensed comet moving through the expected star field over the course of 1 1/2 hours.
The comet was already at opposition back in mid-August, and was nearest Earth (just under 1.40 AU) in early September. It is currently located in the southwestern evening sky in Capricornus, and over the coming few months it tracks steadily towards the northeast, crossing into Aquarius in early December, into Pisces towards the latter part of January, and finally into Aries in early March. By then its elongation will have shrunk to slightly under 50 degrees, although since it will then be near perihelion it may have brightened to about 13th magnitude. After that the elongation will slowly continue shrinking and the comet will likely begin fading, and thus it probably won't be visible for much longer.
Although this return of 67P is at best a nondescript and mediocre one, the next one, in 2015 (perihelion mid-August) will be most interesting. While it isn't especially favorable geometrically and the comet probably won't get any brighter than magnitude 12 to 12 1/2, this is the return where it will be visited by the European Space Agency's Rosetta mission, which was launched in March 2004. Rosetta will arrive at Comet 67P in early 2014 and stay with it as it approaches and passes through perihelion, and among other things will deploy a small lander onto the comet's nucleus. When that return is over, then, we'll probably know more about this particular comet than we've ever learned about any other.
And meanwhile, while there aren't any expected visitors for the subsequent return in 2021 (perihelion early November), the geometry then is excellent -- very similar to that in 1982 -- so at least we'll have an interesting comet to observe again.
Amazingly, I have now tied my personal record for most comets observed in a calendar year, 34. I achieved this record in 2002, when I added my last two comets on the morning of New Year's Eve; since there is still a month to go in 2008 and I can think of at least one comet that I might potentially observe before year's end there is a pretty reasonable chance that this will be a record-breaking year for me.
The record-tying comet is a long-period object that was discovered on October 1, 2008 by Rob Cardinal, who is based at the Rothney Astrophysical Observatory at the University of Calgary in Alberta. (This is his first comet discovery, and in fact this is the first comet ever to be discovered from the Rothney Observatory.) At the time of its discovery the comet was about 16th magnitude, and it was located in far northern circumpolar skies at a declination of +80 degrees. Since that time it has slowly traveled northward and has gradually brightened, and after several unsuccessful attempts I finally spotted it on the evening of November 29, when it was located 50 arcminutes from the north celestial pole and appeared as a very faint object of magnitude 14 1/2. Comet Cardinal thus has the unusual distinction of being the farthest north of any comet that I've added to my tally; it is only the fourth comet that I have ever observed north of declination of +89 degrees, although -- curiously -- this comes barely over a month after I observed Comet Boattini C/2008 J1 (no. 430) when it was only four arcminutes from the north celestial pole in late October.
The comet remains in far northern circumpolar skies for some time, reaching a peak declination of +89.5 degrees on December 3 and then passing just five arcminutes north of the star Polaris two days later. As it moves away from the pole it technically becomes an evening object, although it remains north of declination +80 degrees until the second week of January 2009; it then spends the second half of January and all of February in eastern Cassiopeia. Thereafter the comet travels southeastward through Camelopardalis, Perseus, Auriga, and Gemini, roughly paralleling and close to the galactic equator (thus remaining in fairly rich Milky Way star fields throughout that time). It is nearest Earth (1.73 AU) shortly after mid-March when it may be 10th or 11th magnitude, and by the end of May when it will be located in Canis Minor it will probably have brightened an additional one to two magnitudes.
At around that time Comet Cardinal will cease being visible from the northern hemisphere, but should then be fairly easily accessible from the southern. It passes 1 1/2 degrees southwest of the star Procyon during the second week of June and will be three degrees south of that star when it goes through perihelion. Thereafter it continues southeastward along the Milky Way, passing through Monoceros, Hydra, Antlia, and Vela, finally entering Centaurus in late August when it may still be 11th magnitude. The comet reaches a peak southerly declination of -55.5 degrees in late October and may remain visually detectable for perhaps another month before fading away.
Life continues on here in Cloudcroft. The then-upcoming events that I discussed in the entry for Comet 144P/Kushida have now taken place (all generally on a positive note), and I'm still in the process of going through the major changes in my life that I've been continuously hinting at. By the time I've finished observing Comet Cardinal I suspect that those will have finally come to pass.
The new year of 2009 has now begun on Planet Earth! For astronomers, 2009 is an especially important year, as it has been designated as the "International Year of Astronomy" in commemoration of the 400th anniversary of the first astronomical use of a telescope by the Italian astronomer Galileo Galilei. There are numerous "cornerstone" projects being conducted under the banner of the IYA, and one of these is something called the "Cosmic Diary," which is an effort to show the personal and human side of those of us who do astronomy for a living. I'm one of the participants of the Cosmic Diary, and I'll be maintaining a personal blog there throughout the course of the year. I encourage all "Countdown" participants to check out my blog -- and those of all the other Cosmic Diary astronomers -- regularly throughout 2009.
This year of 2009 will almost certainly be an "interesting" one for me. It has already had one very notable happening: my younger son Tyler was selected to be in the Bands of America Honor Band that marched in the Tournament of Roses Parade in Pasadena, California on New Year's Day. (I wasn't able to go to Pasadena to see him march, but I did watch the parade on television; I was a little bit disappointed in the coverage of this particular segment, however.) Meanwhile, those changes in my personal life that I've been hinting at for the past several months are now well underway, and I suspect should come to fruition within perhaps the next two to three months, at which point I'll finally be able to share those with the "Countdown" participants.
"Countdown" itself starts off with a "bang!" in 2009, with Comet Lulin C/2007 N3 now visible in the morning sky and running brighter than predicted -- and thus the signs are good for a fairly bright display when it's closest to Earth next month. And, I've already added a new comet to my tally -- and a most interesting comet it is. This is a comet that was originally discovered on May 26, 2003 by Eric Christensen during the course of the Catalina Sky Survey, his first of what would eventually be 19 comets that he discovered via that program. It was about 14th or 15th magnitude when discovered, and may have been identical to a possible comet that was reported in images taken with the SWAN ultraviolet telescope aboard SOHO the previous month but which several observers, myself among them, were unable to confirm. The comet was found to be periodic, with an orbital period of 5.7 years (and an unusually small perihelion distance for a previously-unknown short-period comet). Despite its faintness I was actually able to obtain a couple of visual observations of it (no. 335), however I was only able to do so by taking CCD images of it and thereby knowing exactly where to look and what to look for.
Comet Christensen was expected to pass perihelion again in early 2009, but several searches that were conducted for it during the latter months of 2008 were unsuccessful. However, in mid-December Australian researcher Alan Watson discovered an apparent comet in images taken December 8 with the Heliospheric Imager instrument aboard the STEREO-B spacecraft. German astronomer Rainer Kracht was able to determine a rough orbit from positions he measured of the comet, and subsequently another German astronomer, Maik Meyer, suggested that Watson's STEREO comet might in fact be the expected Comet Christensen -- a suggestion that was quickly verified. The initial prediction turned out to be off by 22 days, an unusually large amount in this day and age. Incidentally, this turns out to be the first time that a first-return periodic comet was recovered in images taken with a spacecraft.
At the time of its recovery Comet Christensen was already at a pretty small elongation from the sun, and ground-based observations were essentially impossible. As it went through perihelion (passing between the Earth and the sun and coming to within 0.44 AU of Earth as it did so) it was visible for a few days in both the LASCO C3 and C2 coronagraphs aboard SOHO, becoming moderately bright in the process because of forward scattering of sunlight (the same phenomenon one encounters when driving into the sunset with a dusty windshield). After exiting the LASCO field-of-view Comet Christensen began to emerge into the morning sky at the very end of 2008, and the first ground-based images were obtained on December 30. I attempted it unsuccesfully with a 20-cm telescope on the morning of New Year's Day (when its elongation from the sun was 24 degrees), but easily saw it the following morning (when the elongation had increased to 27 degrees) with the 41-cm telescope; its overall brightness was about 11th magnitude.
The comet is currently located in southern Ophiuchus a few degrees west of the star Eta Ophiuchi, and over the coming few weeks will track northwestward across Ophiuchus, initially quite rapidly but slowing down as it recedes from the sun and Earth. We don't know very much about its brightness behavior, but it will most likely fade fairly rapidly; my suspicion is that it will probably fade beyond the range of visual detectability by perhaps early February. I thus probably won't be getting more than a handful of observations of it. Still, this is the most favorable return of Comet Christensen for some time -- not until 2025 (perihelion late November) is there a similarly favorable one -- so we should take advantage of the opportunities we do have to see it this time around.
Incidentally, at this writing the "210P" designation is still unofficial; it hasn't been formally assigned yet. That should happen sometime within the next couple of weeks.
UPDATE: As of mid-January the "210P" designation is now official.
For the third time in all my years of comet observing, I've added two comets to my tally during the first week of a new year. This newest addition is an old friend; it was originally discovered in January 1990 by Paul Wild at the University of Berne in Switzerland, the seventh and last of his comet discoveries between 1957 and 1990. (Curiously, he holds the unusual distinction of having discovered at least one comet during each of the 1950s, 1960s, 1970s, 1980s, and 1990s.) In addition to his comet discoveries Wild also discovered several asteroids (including the possible extinct comet (3552) Don Quixote, which will be passing moderately close to Earth later this year and which should reach 15th magnitude) and numerous supernovae.
Comet P/Wild 4 has a current orbital period of 6.48 years, and this is its third predicted return following its original discovery. I've managed to see it at every return so far, including its discovery return (no. 138) as well as those in 1996 (no. 208) and 2003 (no. 327). Following its 1996 return it was followed through aphelion and thus can properly be considered an "annual" comet; the first observations at the current return were obtained by the Spacewatch program in Arizona on September 24, 2006, only five months after being at aphelion. I began trying for it this past December, and on the morning of January 7 I suspected a faint object of 14th magnitude which I was able to verify the following morning.
The comet has reached a peak brightness between 12th and 13th magnitude each time around so far, and should do so again this year. It is currently an early-morning object in western Leo some five degrees north-northwest of the bright star Regulus; it has just passed its stationary point and is beginning apparent retrograde (westward) motion. Over the coming several weeks it will track westward across Leo and eastern Cancer, being at opposition in mid-February. The comet will reach its other stationary point in late March and will begin tracking eastward again, and should also be near its peak brightness throughout March and April. Afterwards it should slowly fade as it gradually sinks lower into the western evening sky, and it should remain accessible until sometime around the end of July.
Provided that I continue observing comets through the foreseeable future, I should probably see Comet P/Wild 4 a few more times. The next return, in 2016 (perihelion mid-January), is very similar to that in 2003, while the one after that, in 2022 (perihelion mid-July), is essentially identical to this year's. Again, the comet should reach somewhere between 12th and 13th magnitude both times.
On the home front, my son Tyler's band exploits (discussed some in the previous entry) are far from finished. He was selected (for the third consecutive year) to participate in the New Mexico All-State Music Festival, and is performing in the All-State Symphonic Band in Albuquerque on Saturday; I plan to go see him perform. Several other interesting things are also happening around here, involving both Earthrise and me personally, and I'll share those in future entries . . .
It's Super Bowl weekend here in the U.S., and I've been watching the big game (which was a good one, although I wish my Dallas Cowboys had been playing in it, but oh well . . . ). I've also added another comet to my tally this weekend, and like several of the other recent ones this is an old friend.
The comet was originally discovered in August 1906 by August Kopff at the Konigstuhl Observatory in Heidelberg, Germany, the second of two comets he found that year (the only two comet discoveries he had, although he also discovered numerous asteroids, including two of the earliest-known Jupiter Trojans). It was missed on the subsequent return but was recovered in 1919, and has been seen at every return since then. Its current orbital period is 6.44 years, and the present return is the 16th at which it has been observed. This time around it was recovered on January 30, 2008 by the Catalina Sky Survey in Arizona.
As far as Jupiter-family periodic comets go, P/Kopff is, intrinsically, fairly bright, and usually becomes bright enough to be visually detectable on most returns. I've seen it three times previously: in 1983 (no. 55), 1996 (no. 213) and 2002 (no. 313). The 1983 and 1996 returns were quite favorable and I followed it for several months both times, with the comet achieving a peak brightness near 8th magnitude; the 2002 return was quite unfavorable but I still managed to glimpse it a couple of times several months before perihelion as a very faint object. In 1983 it had the distinction of being the first comet that I ever observed from a country outside the U.S., when I saw it from a beach on the island of Bali in Indonesia a few days before I observed a total solar eclipse from the neighboring island of Java. The 1996 return is also somewhat distinctive in that, early on, I observed it on one occasion in the same telescopic field as Comet 65P/Gunn (no. 210) -- the second (and, so far, last) occasion when I've observed two comets in the same telescopic field of view. Later on I saw it in the same binocular field as Comet Hale-Bopp C/1995 O1 (no. 199) -- the only occasion when I've observed two comets in the same binocular field of view.
The current return is a relatively favorable one similar to those in 1983 and 1996, and it should again reach a peak brightness of 8th or 9th magnitude. After being in conjunction with the sun the comet began emerging into the morning sky during the latter part of 2008, and I began searching for it in late December; there were a couple of occasions earlier in January when it was in fairly busy star fields and I possibly suspected "something" but could never convince myself I was actually seeing it. Finally, on the morning of January 31 I clearly saw the comet as a diffuse and slightly condensed object of magnitude 13 1/2 (somewhat fainter than I was expecting it to be).
P/Kopff is currently located in southern Ophiuchus, some eight degrees north of the bright star Antares. Over the coming months it tracks eastward along the ecliptic, and for a while is going to continue traveling through some very busy star fields, entering Sagittarius at the end of this month and passing over (or at least very close to) the star clusters M23, M24, and M25 during the first half of March. During the latter part of April it travels into Capricornus and then enters Aquarius in early June, where it remains for the next several months; it is at opposition near the beginning of September. Historically, P/Kopff tends to brighten fairly rapidly and to remain near its peak brightness for several months; if it follows the same basic pattern this time around it should remain 9th magnitude or brighter from perhaps the latter part of April through about August, and may remain visually detectable until sometime in October or November.
Provided that I keep up my comet observing, I will probably see P/Kopff a few more times before all is said and done. The next two returns, in 2015 (perihelion late October) and 2022 (perihelion mid-March) are both somewhat mediocre, but the comet should still reach perhaps 11th magnitude both times. Meanwhile, in 2026 it passes close to Jupiter and its perihelion distance gets shortened down to 1.32 AU, and at the next return in 2028 (perihelion late June) it passes just over 0.35 AU from Earth and should reach naked-eye brightness (4th or 5th magnitude). I'll be 70 then, and one can only speculate about the changes that I and the world will see during the intervening two decades.
Yet another "tally addition by outburst!" This is the latest in a series of comets that I never would have seen had it not been for its undergoing a dramatic outburst event. In fact, this is a numbered periodic comet that I'm not sure I would have ever observed, with only a return fifteen years from now even offering a slim opportunity for possible visual observations.
The comet was originally discovered in December 1909 -- almost exactly one century ago -- by Zaccheus Daniel from the Halsted Observatory on the campus of Princeton University in New Jersey, the last of three comets he discovered there during the final years of the 20th Century's first decade. (The Halsted Observatory apparently is no more, and considering the light pollution endemic to that area nowadays it would seem unlikely that any additional comets will be discovered from there.) The comet was reported as being 9th magnitude at discovery, and it was found to be periodic with an orbital period of 6.5 years. It was missed at the next several returns, however, and for a while was considered lost, but through the calculations by Japanese astronomer Hideo Hirose it was finally recovered in 1937. It has been recovered at most returns since then, and the current return is the 10th at which it has been observed; as a result of approaches to Jupiter its current orbital period is 8.1 years.
One of the intervening approaches to Jupiter -- in 1959 -- placed the comet into an orbit with a period of just over 7 years, and furthermore brought it to perihelion when it was on the opposite side of the sun from Earth. The next several returns were thus very poor from an observational standpoint, although they progressively got slightly better, to the point where I attempted it a few times (unsuccessfully) during the 1992 return. An additional close approach to Jupiter in 1995, unfortunately, "reset" this pattern and increased the orbital period by almost exactly one year, once again keeping it in this poor viewing geometry. When at perihelion last July its elongation from the sun was only 24 degrees, and this had increased to 42 degrees by the time it was tentatively recovered on August 31 by Austrian amateur astronomer Michael Jaeger; this recovery was confirmed four mornings later by Timur Kryachko, Stanislav Korotkiy and B. Satovski at the Zelenchukskaya Observatory in Russia.
Comet P/Daniel was reported as being around 19th magnitude at recovery, and it has slowly faded away since then. However, James Schofer in California reported it as undergoing an apparent outburst at the end of January, being around 16th magnitude; I visually attempted it once, unsuccessfully. The comet faded from this outburst, but on February 20 Leonid Elenin, remotely utilizing the Tzec Maun Observatory in New Mexico, reported a newer, even brighter outburst event. Two nights later, shortly after midnight on the night of February 21-22, I easily detected the comet visually as a small and relatively condensed object of 14th magnitude.
The comet is currently well placed for viewing, being located in Ursa Major five degrees southeast of the star Psi Ursae Majoris and some ten degrees south of the "bowl" of the Big Dipper. It remains in this same part of the sky for the next few months, being at opposition during the second week of March, and eventually travels southward into Leo and Coma Berenices, disappearing into evening twilight towards the latter part of July. Since its current visibility is due to an outburst it is difficult to predict just how long it will remain detectable; my suspicion is that it will probably fade away fairly quickly, although since this is the second outburst event within a month it is possible that we might see additional ones during the coming weeks.
It is entirely possible that the observations I obtain now will be the only ones I ever get of P/Daniel. An additional approach to Jupiter in 2018 increases the perihelion distance to slightly over 2.2 AU and the orbital period to 8.3 years, and as I alluded to earlier the return in 2024 (perihelion mid-November) is moderately favorable. Even then the comet will probably remain quite faint, and since the subsequent returns are less favorable than that, there does not seem much in the way of likely observations within the foreseeable future. It is always possible, of course, that the comet will undergo outbursts at these future returns just as it has done now, so one never knows . . .
Halfway through "Countdown!" Just barely over two years after I reached comet number 400, and actually slightly less than two years after I formally launched "Countdown," I'm at the halfway point -- quite a bit earlier than I had expected to be here. The comet activity has indeed been unusually busy for some time now, and the incredible number of tally additions I had during the last few months of 2007 (the last quarter of that year being the busiest I have ever had in that context) has certainly played a part in getting to this point so soon. My original estimate was that it would take me between five and seven years to reach number 500, and I still hold to that; but if I continue to remain as active as I have been the past two years the date for that accomplishment will obviously be toward the shorter end of that timeframe.
My "halfway" comet is an old friend. It was originally discovered in October 1970 by James Gunn, a renowned astrophysicist based at Princeton University in New Jersey (who specializes in the study of galaxies and cosmology and who also has developed some unique astronomical instrumentation -- this was his only comet discovery), who found it on a photograph he had taken of the galaxy cluster Abell 194 in Cetus with the 1.2-meter Schmidt telescope at Palomar Observatory in California. The comet was found to be already a year and a half past perihelion, and to be traveling in a fairly low-eccentricity (0.32) short-period orbit (6.8 years). Two years later it was observed when close to aphelion, and it has remained under almost continuous observation ever since; at the current return it was first imaged by German amateur astronomer Werner Hasubick at the Buchloe Observatory on October 31, 2006, when it was less than a month past aphelion.
P/Gunn is, incidentally, one of five comets that were "discovered" on first-generation Palomar Sky Survey images by a team of astronomers led by R. Weinberger at the Institut fur Astronomie in Innsbruck, Austria during the late 1970s and early 1980s; it appeared as a faint (19th magnitude) object on two Sky Survey plates taken in August 1954. A few months later this particular comet was identified as P/Gunn by Japanese astronomer T. Nomura at Waseda University in Tokyo. At the time it appeared on the Sky Survey plates the comet was in a more distant orbit (perihelion distance 3.3 AU, period 8.0 years, eccentricity 0.18), and a close approach to Jupiter (0.35 AU) in 1965 placed it into the smaller orbit that it occupies today.
I have observed P/Gunn on each of the previous four returns: in 1982 (no. 50), 1989 (no. 126), 1996 (no. 210), and 2003 (no. 331) -- on each return it has reached a peak brightness between magnitudes 12 1/2 and 13. (Curiously, at its 2003 return it passed very close to the globular star cluster M70, the same cluster near which I had discovered Comet Hale-Bopp C/1995 O1 (no. 199) eight years earlier.) This time around I picked it up quite a bit earlier than I had expected to (slightly over a year before perihelion passage), but the reported CCD magnitudes on recent "Observations of Comets" Minor Planet Electronic Circulars suggested it might be bright enough to attempt visually. On my first attempt, during the late evening of February 24, I suspected a faint object of 14th magnitude, but clouds moved in before I could verify this as being the comet; I succesfully did so the following night. On both nights the comet was located just a few arcminutes from the "Siamese Twins" galaxies NGC 4567 and 4568 in Virgo.
Over the course of the next month P/Gunn will travel westward across the densest part of the Virgo galaxy cluster, and will be at opposition during the last week of March. After reaching its stationary point two degrees south of the star Denebola (Beta Leonis) in mid-May the comet turns toward the southeast, passing through the southern region of the Virgo cluster during July before disappearing into dusk by sometime in August. The comet will remain faint during this time, probably brightening by only half a magnitude or less.
After being in conjunction with the sun in mid-November P/Gunn emerges into the morning sky around late February 2010, when it will be located in dense star fields in central Sagittarius. Over the subsequent months it travels eastward into Capricornus and then southward into Microscopium, being at opposition in early August and reaching a maximum southerly declination of -32 1/2 degrees late that month. The comet should reach a peak brightness -- again, between magnitudes 12 1/2 and 13 -- during the middle months of 2010, but should begin to fade fairly rapidly once it is past opposition, dropping beyond the range of visual detectability by October or November.
I've had a pretty good run of observations of P/Gunn over the past quarter-century and more, but that may come to an end with this return. In Decenber 2012 the comet again passes closes to Jupiter (0.56 AU) and this will increase its perihelion distance to 2.91 AU and its orbital period to 7.6 years. It may still be visually detectable at the next two returns, in 2017 (perihelion mid-October) and 2025 (perihelion mid-June), but it will probably not become any brighter than 14th magnitude.
Meanwhile, though, I seem to have gotten a pretty quick start on the second half of "Countdown" . . .
UPDATE: After being in conjunction with the sun in late 2009 Comet P/Gunn began emerging into the morning sky in early 2010, and I successfully picked it in mid-March when it was low in my southeastern sky before dawn. (In the process it became the 31st comet that I have followed for more than one year.) At that time the comet appeared between magnitudes 13 and 13 1/2, and due to its low elevation was not too easy to see; as it climbs higher into the morning sky over the subsequent weeks it should become easier to observe, and it should also brighten some as it approaches opposition during the summer.