September 12, 2005

Astronomers detect most distant cosmic explosion

WASHINGTON (Reuters) - Astronomers said on Monday they have
detected a cosmic explosion at the very edge of the visible
universe, a 13-billion-year-old blast that could help them
learn more about the earliest stars.

The brilliant blast -- known as a gamma ray burst -- was
probably caused by the death of a massive star soon after the
Big Bang, but was glimpsed on September 4 by NASA's new Swift
satellite and later by ground-based telescopes.

The explosion occurred soon after the first stars and
galaxies formed, perhaps 500 million to 1 billion years after
the Big Bang explosion that scientists believe gave birth to
the cosmos. The current scientific estimate for the age of the
universe is 13.7 billion years.

"We are finally starting to see the remnants of some of the
oldest objects in the universe," said Daniel Reichart of the
University of North Carolina at Chapel Hill. Reichart led the
team that measured the distance of the blast from Earth.

This gamma ray burst, or GRB for short, could be the first
of dozens or hundreds that might soon be unveiled to
scientists, and these expected discoveries could help them
learn more about the early universe, astronomer Donald Lamb
said in a telephone news conference.

"This burst opens the door to the use of GRBs as unique and
powerful probes of the early universe," said Lamb, a professor
at the University of Chicago. "This is what we've all been
waiting and hoping for and now the fun begins."

Scientists had theorized that such bursts could be
detected, and the Swift spacecraft, launched last year, aimed
to find them.

In cosmic terms, distance equals time, so this explosion
occurred 13 billion light-years away, with its light just
reaching earthly observers. One light-year is about 6 trillion
miles, the distance light travels in a year.

"We designed Swift to look for faint bursts coming from the
edge of the universe," Neil Gehrels, of NASA's Goddard Space
Flight Center outside Washington, said in a statement. "... For
the first time we can learn about individual stars from near
the beginning of time. There are surely many more out there."

The earliest stars no longer exist, but debris from their
destruction can still be detected with Swift and other
telescopes; by studying the remnants of these ancient
explosions, scientists may be able to tell what these stars
were made of and how they formed.

While this gamma ray burst is the most distant explosion
ever detected, scientists have found one object that is even
further away from Earth -- a previously discovered quasar.
Quasars are believed to be produced by gas falling into a
massive black hole.