September 12, 2005

Scientists Witness Farthest Known Gamma-Ray Burst

LONDON -- A team of Italian astronomers said on Monday they had witnessed the afterglow from one of the brightest and most distant gamma-ray bursts ever detected.

Gamma-ray bursts are the most powerful and most brilliant explosions known to man, other than the theoretical Big Bang that many astronomers believe gave birth to the universe -- but their cause remains unknown.

The burst known as GRB050904 was first detected on September 4 by the Swift satellite and was more than 12,500 million light years away, the most remote burst ever spotted.

A light year is about 6 trillion miles, the distance light travels in a year.

"Its luminosity is such that within a few minutes it must have released 300 times more energy than the sun will release during its entire life of 10,000 million years," said Guido Chincarini of the Osservatorio Astronomico di Brera and the University of Milano-Biocca in Italy, the leader of the team.

"The reason we were able to observe it and determine the distance is because we were able to see the optical afterglow," Chincarini explained.

Astronomers do not know what causes gamma-ray bursts. They are thought to occur when a star collapses, possibly to become a black hole, creating a huge gravitational pull from which nothing can escape.

The bursts last from less than a second to several minutes and release a tremendous amount of energy in a very short time.

"Some gamma-ray bursts originate in the farthest reaches, and hence the earliest epochs, of the universe," John Nousek, director of the Swift Mission, which is dedicated to studying gamma-ray bursts and their connection to black holes, said in a statement.

They said the discovery and study of gamma-ray bursts is fundamental to improve understanding of the universe when it was very young.