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Red glimmer reveals most distant galaxy.

Astronomers have glimpsed a galaxy so far from Earth that it ranks as the most distant object in the known universe.

Researchers found the collection of stars by detecting light that left it more than 12.2 billion years ago -- only 820 million years after the universe formed, according to some estimates. The team of observational astronomers will report the findings in May in the Astrophysical Journal Letters.

Astronomers have been searching for primordial galaxies for the last 20 or 30 years, says theorist David N. Spergel of Princeton University (SN: 2/7/98, p. 92). Observing galaxies formed so soon after the birth of the cosmos will help researchers figure out how these clusters, including our own Milky Way, evolved.

"The most important science facing astronomers today is how galaxies formed. At the moment, there are lots of theories but no observations to constrain any of these theories," says team member Arjun Dey of Johns Hopkins University in Baltimore, Md.

Dey collaborated with researchers from the University of California, Berkeley and the W.M. Keck Observatory on Hawaii's Mauna Kea.

Although astronomers spotted another juvenile galaxy last year, the newly observed one, 0140+326RD1 -- or RD1 for short -- is the first found beyond what they refer to as redshift 5.

As the universe expands, light from distant objects is shifted to longer, or redder, wavelengths. The phenomenon is similar to the way in which the sound of a police siren changes pitch as a squad car speeds away. Astronomers use the degree to which a celestial object's light has redshifted to calculate distance. The redder the light, the farther the object is from Earth. Thus, redshift 5 indicates that the expanding universe stretched an object's light by a factor of 5.

Going beyond redshift 5 represented both a psychological and technological barrier, Dey says. "It's not necessarily such a huge gain in look-back time, but 5 was thought of as one of the earliest epochs in which galaxies might form."

The latest generation of telescopes, such as the Keck telescopes in Hawaii, has made the search easier. Even so, the discovery of RD1 was an accident. Dey and his team were using the Keck II telescope to study an area of the sky where other astronomers had found objects with redshifts not much beyond 4.

"But right next to them was another object that had escaped our original detection because it was very faint," Dey says. Just an edge of the fuzzy blob appeared in their field of view, he adds.

Those first observations were made in September 1997, but the scientists didn't realize then that the blob was the most distant object known, says team member Hyron Spinrad of the University of California., Berkeley. By January 1998, the group had homed in on RD1 and confirmed that it has a redshift of 5.34.

Although the team needs more data to be certain, RD1 may be "our best candidate so far" for a galaxy just beginning to make stars, says Dey.
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Title Annotation:astronomers discover collection of stars by detecting light they emitted 12.2 billion years ago
Author:Jensen, M.N.
Publication:Science News
Article Type:Brief Article
Date:Mar 21, 1998
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