By Dr David Whitehouse BBC News Online science editor

Astronomers have obtained the deepest near-infrared image of the sky ever. They used one of the European Southern Observatory's Very Large Telescope (VLT) units.

The 8.2 metre Antu telescope spent more than 100 hours looking at a patch of sky previously studied by the Hubble Space Telescope (HST).

The resulting image reveals extremely distant galaxies, which are barely detected in the deepest optical images acquired with the HST.

Astronomer Marijn Franx from the University of Leiden said: "The new VLT images have opened a new research domain which has not been observationally accessible before."

Galaxy formation

The region of the sky observed is a tiny field only about 1% of the area of the full Moon. The HST observed it with a total exposure time of about one week, yielding the deepest optical images ever taken of the sky.

The new view was obtained by the VLT facility in Chile

Although the VLT observed it for less time, it was able to detect objects unseen in the Hubble Deep Field.

Astronomers will study the image with interest. Infra-red observations of distant objects are important because the optical light emitted by the distant galaxies has been redshifted to the near-infrared region of the spectrum.

From such observations, astronomers have discovered that galaxies existed already at that epoch which are clearly rather large, and some show spiral structure similar to that seen in very nearby galaxies.

This insight is having a profound impact on current attempts to understand the formation and evolution of galaxies.