- Associated Press - Thursday, May 26, 2011

LONDON — A group of researchers say they have found the most distant explosion ever detected, a pulse of high-energy radiation sent by a disintegrating star near the very edge of the observable universe.

The stellar blast was first spotted by a NASA satellite in April 2009, and researchers announced Wednesday that they have since gathered data placing it more than 13 billion light years away - meaning that the event took place when the universe was still in its infancy.

Andrew Levan, one of the scientists behind the discovery, said this blast from the past blew open a window onto the universe’s early years, showing that massive stars were already dying within the first few hundred million years of the birth of the universe.

This particular explosion wasn’t a supernova but a gamma ray burst, the name given to a short but powerful pulse of high-energy radiation. Such bursts, thought to result from the collapse of massive stars into black holes, shoot jets of energy across the universe.

Charles Meegan, a researcher in gamma ray astronomy, said a typical burst “puts out in a few seconds the same energy expended the sun in its whole 10 billion-year life span.”

“You can’t get your arms around that very easily,” he said. “I can’t. And I’ve been thinking about it for decades.”

Not only are gamma ray bursts more powerful than supernovae, they’re faster too - typically lasting only a few seconds or minutes. They work differently as well. Whereas a supernova spreads its radiation all around, gamma ray bursts shoot it out in narrow beams, like a laser, which can make them hard to detect.

“We only see about one in 1,000 of all the gamma ray bursts that go off,” said NASA’s Neil Gehrels, who serves as the lead scientist on Swift, the gamma-ray detecting satellite that first picked up the distant burst’s signal.

Mr. Levan’s paper, due to published soon in Astrophysical Journal, stated with 90 percent certainty that the gamma ray burst was 13.11 billion to 13.16 billion light years away.

Mr. Gehrels, whose satellite identified the burst but who wasn’t involved in drawing up the paper, said he believes Mr. Levan is right - praising his team’s “careful analysis.”

But other outside experts are skeptical.

Richard Ellis, a professor of astronomy at the California Institute of Technology, called the discovery “potentially very exciting” but said that there wasn’t enough data to justify such a bullish estimate. In any case, he warned of the difficulties associated with peering across such a vast distance.

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