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Hubble pinpoints oldest known galaxy

Discovery may aid study of how reionization occurs

LOS ANGELES – Scientists have found the most distant space object yet observed, a galaxy born just 500 million years after the Big Bang.

The record-breaking discovery, reported Wednesday in the journal Nature, may aid exploration of a crucial period in the early history of the cosmos – a time when light from the earliest stars broke up the fog of hydrogen gas that shrouded the universe shortly after the Big Bang. That process created the “reionized” universe that exists to this day, scientists believe.

“This is one of the most fundamental problems in astronomy – how the universe ionized,” said the study’s lead author, astronomer Matthew Lehnert of the Observatoire de Paris in France.

Lehnert said that while astronomers know reionization occurred, they don’t understand how, because they haven’t been able to observe the process under way. “That’s why (seeing this object) matters,” he said.

The Hubble Space Telescope first spotted the galaxy, named UDFy-38135539, after a new camera that permitted clearer images of distant objects was installed on the telescope in May 2009.

“It’s remarkable that in such a short time, well-developed galaxies already existed (in the universe),” said Michele Trenti, an astrophysicist at the Center for Astrophysics and Space Astronomy of the University of Colorado in Boulder.

Trenti, who wrote an editorial accompanying the Nature paper, said that it is likely there are more galaxies, yet unseen, lurking at these great distances.

Because UDFy-38135539’s glow is so faint, some scientists said they are skeptical of the results.

“The question of whether this is definitively the oldest is uncertain,” said California Institute of Technology astronomer Richard Ellis, who is co-author of a forthcoming review in Nature about the reionization of the universe. “This is an ambitious and difficult measurement. People have been wrong before.”


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