January 7, 2014
Today at the news conference, scientists presented three findings based on Hubble Space Telescope data. The conference was a part of the 223rd meeting of the American Astronomical Society (AAS) that began on Sunday and will last until Friday this week.
Four ultra-bright objects, circled and designated A-D on this picture, are galaxies only 500 million years old. Credit: NASA/ESA/Illingworth,Oesch,UC-SC/Bouwens, Labb,Leiden U.
Using data from Hubble and Spitzer space telescopes, astronomers have discovered four very distant, extremely bright galaxies as they appeared some 13 billion years ago.
Bear in mind that when looking at very distant objects, we're also looking at objects that existed in our universe's distant past and their light is only now reaching us. These four galaxies appear as they were when the universe was only 500 million years old. The universe was smaller then, so you shouldn't be surprised that these galaxies are 20 times smaller than our Milky Way, containing 1 billion stars crowded together.
We have discovered galaxies from this era of the universe before, but it is surprising to find those shining 10 to 20 times brighter than anything before. The reason for such brightness is the rate at which their stars are born – the brightest one has stars forming 50 times faster than the stars in the Milky Way.
"These just stuck out like a sore thumb because they are far brighter than we anticipated," said Garth Illingworth of the University of California, Santa Cruz, USA. "There are strange things happening regardless of what these sources are. We're suddenly seeing luminous, massive galaxies quickly build up at such an early time. This was quite unexpected."
Furthermore, using data from Spitzer space telescope, astronomers have estimated stellar masses of these objects, making it the first such measurement for objects at such a huge distance.
Abell 2744 galaxy cluster in the foreground and newly discovered, very faint galaxies in the background that would be invisible if not for the gravitational lensing. Credit: NASA/ESA/J.Lotz, M.Mountain, A.Koekemoer/STScI HFF Team
As reported previously here, there's a collaborative project called The Frontier Fields where three great telescopes are used to discover some of the youngest (and thus oldest) and more importantly some of the faintest galaxies ever detected, by using a natural phenomenon called gravitational lensing.
In gravitational lensing, a massive object in the foreground is used to focus the light of the fainter and more distant objects in the background, thus rendering them visible. In the discovery announced today, the object in the foreground is a massive galaxy cluster called Abell 2744, some 3.5 billion light-years away.
In the background scientists discovered some 3,000 very distant, young galaxies that we normally couldn't see. These are more than 12 billion light-years away. In the picture above, they appear magnified, smeared and duplicated, all side effects of gravitational lensing. Nevertheless, we can see objects 10 to 20 times fainter than any previously observed.
By combining images from Hubble with those from Spitzer space telescope and Chandra X-ray Observatory, the team hopes to gain new insight into the evolution of early galaxies and black holes that each of them has at its centre.
Again, by using gravitational lensing of a galaxy cluster in the foreground (Abell 1689 in this picture), astronomers discovered faint objects in the background, here 58 galaxies. Credit: NASA/ESA/B.Siana, A.Alavi, UC Riverside
Related to the discovery above, by using gravitational lensing of another galaxy cluster called Abell 1689 some 2.3 billion light-years away, the Hubble Frontier Fields team discovered 58 small, very young galaxies.
They are the type of galaxies thought to be responsible for the birth of the majority of distant stars we see in the sky today. At distance of over 10 billion light-years from us, these tiny, faint galaxies outnumber their larger counterparts by 100 to 1. That means that in the early ages of the universe, most of the stars formed in such small, unseen galaxies.
"There's always been a concern that we've only found the brightest of the distant galaxies," said Brian Siana of the University of California, Riverside, USA. "The bright galaxies, however, represent the tip of the iceberg. We believe most of the stars forming in the early universe are occurring in galaxies we normally can't see at all. Now we have found those 'unseen' galaxies, and we're really confident that we're seeing the rest of the iceberg."