Astronomers detect distant cosmic explosion

WASHINGTON - Astronomers 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 theorised 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.

- REUTERS