Astronomers have combined 10 years of Hubble Space Telescope views of the same region of space to look back in time 13.2 billion years, to view what the universe was like in its infancy.
The eXtreme Deep Field (XDF) was collected as a series of 2000 images, using Hubble's Advanced Camera for Surveys and the Wide Field Camera 3, with a total exposure time of 2 million seconds over 50 days. The XDF expands on a small patch of space at the centre of the 2004 Hubble Ultra Deep Field image.
"The XDF is the deepest image of the sky ever obtained and reveals the faintest and most distant galaxies ever seen. XDF allows us to explore further back in time than ever before," said Garth Illingworth, principal investigator of the Hubble Ultra Deep Field 2009 (HUDF09) program, according to NASA.
Seen within this small patch of space are close to 5,500 galaxies, some so faint that in order for you to see them with the naked eye, your eyes would have to be ten billion times more sensitive to light. The closest objects in the picture are probably less than 5 billion years old, but the oldest stretch back to 13.2 billion years old. These farthest and faintest galaxies are likely the first to form after the 'dark ages' of the universe — the time before the first stars formed and lit up space — and many are seen in their chaotic formation stages, after the stars began to swirl around the super-massive black holes that exist at the centre of most galaxies.
The best estimate of the age of the universe so far is 13.7 billion years. With the XDF, we can now see back in time to within about 500 million years of the Big Bang. For perspective on that time-scale, the first fish developed on Earth 500 million years ago. In the time-scales we're investigating here, that's actually fairly small.
NASA is expected to bring the James Webb space telescope — set to launch in 2018 — in on the project, because its infrared cameras can expand the XDF back further, into the 'dark ages' before stars formed. It's slow progress for those of us interested in this kind of work, but still exciting that we may reach a point where we'll be able to see the birth of the universe.