Astronomers get look at beginning of
light
By Kathy Sawyer, Washington Post, 1/11/2003
WASHINGTON - Astronomers have gained their first glimpses of
the cosmic dawn, a time more than 13 billion years ago when the
light of the earliest stars and galaxies came glimmering through
the remnants of a primordial fog.
Two independent teams of astronomers, pushing modern
technology to its limits, reported the discovery of multiple faint
galaxies and three blazing quasars that may have helped end the
cosmic ''dark ages.'' This murky period began perhaps 300
thousand years after the universe was born in the ''big bang,'' and
persisted for hundreds of millions of years. During this epoch, the
young universe was clouded with light-absorbing hydrogen gas.
''The question of when the first light formed was addressed by
religious texts for a long time before scientists could start to deal
with it,'' said Avi Loeb of Harvard University, a leading theorist in
this emerging field of inquiry, in a phone interview. ''This is the
first time in human history that we are able to address this
question scientifically.''
At a meeting of the American Astronomical Society in Seattle, a
group led by Xiaohui Fan of the University of Arizona, announced
on Thursday it had discovered the three new quasars, including
the most distant one ever detected. The quasar images show what
the scientists believe are the shadows of the last wisps of
obscuring hydrogen fog. The key observation was made by the 2.5
meter telescope of the Sloan Digital Sky Survey, at Apache Point
Observatory in New Mexico, and verified by telescopes in Hawaii,
Texas and Spain.
''These discoveries are giving us the first glimpse of the universe
when it was only 5 percent of its present age,'' said Michael
Strauss of Princeton University, a leader of the project.
Astronomers have been puzzled to find that quasars existed so
early in the evolution of the universe. The most luminous objects
known in the cosmos, quasars are thought to be young galaxies
powered by supermassive black holes.
Their brilliance - an energy equal to that of billions of suns -
comes from pulses of heat and light triggered at their margins as
they suck in gas and other material. The black hole itself is
invisible, a collapsed object so dense that not even light can
escape its gravity. But the quasars are only the dazzling tip of an
iceberg of much dimmer light sources.
A second group used the Hubble Space Telescope to capture
evidence of more than two dozen faint galaxies, a population that,
like the quasars, may have helped end the darkness. These dawn
galaxies are a billion times dimmer than the stars and other
objects that people can see with the naked eye in the night sky.
''The objects we found are in the epoch when the universe started
to produce stars in significant numbers - the hard-to-find young
galaxies,'' said Rogier Windhorst of Arizona State University.

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