Astronomers have managed to boldly see what no human has seen before: the deepest view ever obtained over a large area of the sky.

These observations are part of the Ultra-Deep Survey (UDS), which covers an area four times the size of the Moon and includes over 250,000 galaxies that formed during the first billion years of the universe. The project was presented at the National Astronomy Meeting in Nottingham.

"With the UDS we can study distant galaxies in large numbers, and observe how they evolved at different stages in the history of the universe," said UDS team leader Professor Omar Almaini in a statement. "We see most of the galaxies in our image as they were billions of years before the Earth was formed."

The project began in 2005 as part of the UKIRT Infrared Deep Sky Survey, and it was possible by observing the same patch of sky repeatedly, achieving 1,000 hours of exposure.

Since the universe is expanding, the light from distant galaxies is stretched out towards longer wavelengths. For this reason, infrared allows us to look at far-away galaxies that are in their prime. UDS covers a huge number of galaxies during several periods of the Universe. Most of the galaxies that have now been surveyed formed billions of years before Earth.

"We are particularly keen to understand the dramatic transformation that many massive galaxies underwent around 10 billion years ago," said Dr William Hartley, a postdoctoral researcher at University College London. “At that time many galaxies appear to have abruptly stopped forming stars, and they also changed shape to form spheroidal-looking galaxies. We still don’t fully understand why this happens. With our new UDS images, we expect to find large numbers of these galaxies, caught in the act of transformation, so we can study them in detail to solve this important puzzle.”

^{Zooming into a small section of the UDS field. Omar Almaini, University of Nottingham}