Sue Hartigan <[EMAIL PROTECTED]> writes:
Stargazers Set Distance Record
> WASHINGTON (AP) -- Astronomers have detected a small
> galaxy 12.3 billion light-years from Earth -- the most
> distant object ever seen -- and say they are on the
> brink of seeing things even farther away and closer to
> the big bang beginning of the universe.
>
> ``We've already got some candidate objects that are
> even farther away,'' said Esther M. Hu, a University of
> Hawaii astronomer and co-discoverer of the most distant
> object. ``We are looking about 94 percent of the
> distance back to the big bang.''
>
> The discovery was first announced in Science News, a
> weekly journal of research reports. The journal is to
> publish the story on Saturday.
>
> The big-bang theory holds that the universe started
> with a huge explosion and has been expanding ever
> since. In the billions of years since, the hydrogen and
> helium in the big bang have been processed through
> stars to form other chemicals. Just when the big bang
> happened is controversial, but most astronomers say it
> was about 13 billion years ago.
>
> Just six weeks ago, another team of astronomers found a
> small galaxy about 12.2 billion light-years away to
> establish a most-distant mark. Both teams used the Keck
> telescopes in Hawaii. A light-year is the distance
> light travels in a vacuum in one year, about 5.8
> trillion miles.
>
> ``The records for most distant galaxies have become
> really fragile,'' said Bruce Margon, a University of
> Washington astronomy professor. ``Once they would stand
> for six or seven years. Now it changes in a matter of
> months.''
>
> Margon said the latest discovery is important because
> it continues to push back the time when it is known
> that stars and galaxies formed after the big bang,
> giving more understanding of the developmental history
> of the universe.
>
> Hu and her colleagues, Lennox L. Cowie of Hawaii and
> Richard G. McMahon of the University of Cambridge,
> England, sighted the distant galaxy by analyzing a
> particular wavelength of light emitted by hydrogen
> atoms.
>
> This technique, said Hu, will enable the group to probe
> even farther back in time and distance.
>
> One way astronomers measure distance and time is by a
> value called the redshift. This is the amount that a
> wavelength of light has been stretched, or shifted, by
> the expanding universe. The new most-distant galaxy
> found by the Hu team is at a redshift of 5.64. This is
> about 60 million years earlier than the previous mark,
> which was a redshift of 5.34.
>
> ``We already have candidates at redshift 6.5 and I
> think we'll eventually push it back to a redshift of
> 7,'' said Hu. This would push the viewed universe back
> to within 4.4 percent, or about 500 million years, of
> the big bang, she said.
>
> Galaxies at that distance, said Hu, will all be young,
> only a few tens of millions of years old, since the
> universe at that point is also very young.
>
> Margon said there is a physical limit on just how far
> back toward the big bang astronomers will see. For
> about the first million years after the big bang, when
> the universe was just beginning to expand, the matter
> was still so dense that if there was light it could not
> travel very far before being absorbed.
>
> Additionally, it is believed that it took several
> million years for stars to form, and without stars,
> said Margon, there was no light to be seen. One
> question to be solved, he said, by looking for fainter
> and fainter starlight is to discover how soon after the
> big bang galaxies began to form.
--
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