Experts at the Space Telescope Science Institute said on Tuesday the image dated back 13bn years to just 700mn years after the Big Bang.

Hubble has looked back in time before, but this image, known as the Ultra Deep Field, is the most profound vision the orbiting telescope has ever captured.

The new picture looks like a scattering of jewels on black velvet, but is in fact 10,000 galaxies crammed into a section of sky about one-tenth the size of the full moon.

It peers only 300mn miles deeper into the ancient universe than similar Hubble images made in the 1990s.

Cosmic dark age

But this extra distance sees back to when the very first infant galaxies were forming, a time of great interest to astronomers because it marks a transition point from a cosmic dark age.

"This is the deepest view of the visible ever taken. It's an amazing time to be an astrophysicist"

Rodger Thompson,
astronomer

"This is the deepest view of the visible ever taken," said Rodger Thompson, one of a team of astronomers who put the image together with two of Hubble's sophisticated instruments.

"It's an amazing time to be an astrophysicist."

Thompson and other scientists emphasised the importance of looking at the earliest times of galactic development, which can be more dramatic and sweeping than the evolution of galaxies as they age.

"It doesn't seem like much ... but when you realise that this is a time when a phase transition occurred in the universe ... this is a very critical time, you want to have details on that critical time," Hubble astronomer Mario Livio said.

Giant leap

Livio and other astronomers likened the development of the universe to the development of a human being.

They noted the most dramatic changes occur at the earliest ages, making even a seemingly slight increase in the depth of observation a giant leap for basic study of the cosmos.

Hubble produced the picture over
four months as it orbited earth

The quality of the image is so fine that galaxies billions of miles away show features that scientists formerly had seen only in galaxies in Earth's cosmic neighbourhood.

These early galaxies are shown to be more chaotic, to interact more with each other, and to be less well-formed than our own Milky Way, the astronomers said.

Hubble made the picture over four months as it orbited Earth, from 24 September 2003 to 26 January of this year, over a total of one 11.3 days of viewing time.

The production of the image was shrouded in such secrecy that until Tuesday only four people had seen the whole picture, said Steven Beckwith, director of the telescope institute.

Hubble's final act?

This was done to create a level field for research, since any scientist who saw the whole picture in advance could begin studying the vast wealth of data it contained.

"It's like the great land rush, where the gun is fired and everybody takes off," Beckwith said. "There was no advantage to the home team."

Beckwith and others noted this could be the last such image made by Hubble.

NASA has decided to forego a scheduled servicing mission for the telescope, which means its gyroscopes and battery could doom it to an early demise.

"There is not a final act, there is kind of a denouement," Beckwith said of Hubble's ultimate fate.