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Thursday, 14 March, 2002, 11:38 GMT
Far away stars light early cosmos
Esther Hu holds the filter used to detect the most distant galaxy
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By Dr David Whitehouse
BBC News Online science editor
The most distant galaxy yet found is giving astronomers a glimpse of what the early Universe was like.

"This galaxy is forming stars at a time speculated to be in the so-called Dark Ages of the Universe, when galaxies began to turn on," said University of Hawaii Professor Esther Hu.

When the first galaxies form, it's like turning on lights to clear out a fog bank

Len Cowie, Hawaii astronomer
"You want to catch galaxies in their infancy and see how they develop.

"Scaling the age of the Universe to a person's lifetime, we're showing you baby pictures. The last snapshot we obtained showed a toddler just past his fourth birthday. This new one is three and a half."

The newly discovered galaxy has a redshift of 6.56, which means it is about 14 billion light-years distant and its light set off when the Universe was about 780 million years old.

Zoom lens

This is about 50 million years earlier than the view supplied by the most distant quasar found so far (redshift = 6.28).

Until this discovery, the most distant objects and hence the earliest probes of the Universe had been quasars - extremely luminous galactic cores, believed to be powered by black holes. Ordinary galaxies are fainter and much harder to detect at such distances.

Galaxy, Ifa
Most distant galaxy: Barely visible behind the cluster
To capture the image of the distant galaxy researchers used two techniques.

To reach faint and very distant galaxies they looked through a "gravitational lens" - a massive cluster of galaxies that bends and amplifies light from more distant objects behind. It is like a zoom lens that allows astronomers to peer even further into the depths of the Universe.

In this case, the scientists used the galaxy cluster Abell 370, which is six billion light-years away and whose core contains a mass of several hundred galaxies. It magnified light from a galaxy behind it that is 15.5 billion light-years distant, almost at the edge of the observable Universe.

Zoom lens

The researchers then concentrated on a particular part of the light, where a bright hydrogen line called Lyman alpha could be seen. This line is usually prominent in galaxies that are undergoing large bursts of star formation.

Galaxy, Keck
The view by the Keck Observatory
The detection of a Lyman alpha emitter galaxy whose light has been amplified by Abell 370 was accomplished using one of the giant Keck 10-metre telescopes in Hawaii.

Hawaii astronomer Len Cowie said: "The fact that this is a galaxy, and not a quasar, is important. When the first galaxies form, it's like turning on lights to clear out a fog bank.

"Quasars are really bright though rare, so they can make large clear cavities around themselves, but the fact that light from the fainter but much more numerous galaxies is getting out means that a significant amount of early star formation has already taken place and much of the general fog has already dissipated."

See also:

14 Apr 00 | Sci/Tech
Astronomers see further than ever
09 Jan 01 | Sci/Tech
Huge galaxy grouping detected
11 Jul 01 | Sci/Tech
Most distant objects observed
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