The Hubble space telescope has allowed astronomers to look deeper into the universe than ever before and identified seven of the most distant galaxies on record.
One of the galaxies, UDFj-39546284, was observed as it looked when the universe was only about 380 million years old, which is the furthest back in time that any object has ever been witnessed.
Each of the seven galaxies, six of which were newly discovered, formed more than 13 billion years ago during the so-called “cosmic dawn” when the Universe was only about four per cent of its current age.
The study, by astronomers from the California Institute of Technology, is the first “census” of such a distant stage of the Universe’s history and supports our understanding of how the earliest galaxies formed.
Researchers found that the number of galaxies grew smoothly during this period, suggesting that the first galaxies assembled their stars steadily rather than in a sudden burst.
Because light takes so long to travel from such distant regions of the Universe the images captured by Hubble show the galaxies as they looked billions of years ago.
Richard Ellis, first author of the paper which will be published in the Astrophysical Journal Letters, said: “We’ve made the longest exposure that Hubble has ever taken, capturing some of the faintest and most distant galaxies.”
Brant Robertson of the University of Arizona, a co-author of the paper, said the study demonstrated that a process known as reionisation, when light from the first stars and galaxies began to interact with neutral hydrogen atoms, was “a drawn-out process occurring over several hundred million years with galaxies slowly building up their stars and chemical elements.”
“There wasn’t a single dramatic moment when galaxies formed; it’s a gradual process,” he added.
Astronomers hope to look even further back in time usint the James Webb Space Telescope, which is due to lanch in a few years’ time and will observe light at longer wavelengths than can be detected using Hubble.
Anton Koekemoer of the Space Telescope Science Institute in Baltimore said: “Although we may have reached back as far as Hubble will see, Hubble has, in a sense, set the stage for Webb.
“Our work indicates there is a rich field of even earlier galaxies that Webb will be able to study.”
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