VLT eyes up a dark horse

March 15, 2002

Astronomers have been able to catch a glimpse of the most distant galactic neighbourhood discovered by taking a peek through a gravitational "porthole".

Their findings are helping to illuminate what the universe looked like in its earliest days.

The European Southern Observatory's Very Large Telescope was trained on MS 1512-cB58, a fairly average-looking galaxy that was unusual in just one regard - it sits almost 12 billion light years from the Earth.

Normally, this would make it too faint to be seen by terrestrial observers.

But a massive cluster of galaxies sits about halfway between the distant galaxy and the Earth. This cluster distorts the path of the light passing through it and acts like a vast lens in the sky.

As a result, the image of MS 1512-cB58 appears 50 times brighter than it would otherwise.

By using the 8.2m VLT, the team, led by Sandra Savaglio at Johns Hopkins University in the United States, gathered sufficient light not only to see the galaxy but also to collect spectrographic data about the dust that lies between it and the Earth. In effect, the astronomers are looking at the equivalent of smoke caught in a beam of light. This has allowed the astronomers to subject the galaxy's surroundings to unprecedented scrutiny.

What has emerged, according to the study, which will be published in the Astrophysical Journal , is detail of intergalactic gas clouds near MS 1512-cB58.

This suggests that the distant galaxy is itself part of a cluster, giving the astronomers information on the structure of the young universe that was previously beyond their reach.

It further hints that large structures - such as clusters of galaxies - were formed from the gas that emerged from the big bang earlier than many scientists had thought.

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