Big Isle team assesses star burst


POSTED: Friday, January 09, 2009

HILO » When a gamma ray burst goes off someplace in the universe, earthly viewers have no more than a few hundred seconds to spot it.

On the night of last June 7, alerted by the gamma-spotting Swift satellite, astronomers at Keck Observatory on Mauna Kea dropped their main project and refocused on the gamma burst within 15 minutes, the National Aeronautics and Space Administration said.

Gamma rays had already passed, but X-rays and visible light were still streaming from the far distance.

The Keck team eventually determined that the gamma burst originated 11.5 billion light-years away, the most distant such burst of energy ever seen. The estimated age of the universe is 13.7 billion years.

Team members Xavier Prochaska of the University of California, Santa Cruz, and Yaron Sheffer of the University of Toledo, Ohio, announced their findings Tuesday at the American Astronomical Society meeting in Long Beach, Calif.

NASA described gamma bursts as “;the universe's most luminous explosions.”; Most are believed to be created when massive stars, very different from Earth's sun, end their short lives while shooting out jets of gas that trigger the bursts, NASA said.

Since the big stars live just a few tens of millions of years, the cloud of molecules that created them is still around them when they die.

The cloud was so dense around last June's burst that only 1 percent of the light from the burst was able to escape, NASA said.

The light of the gamma burst shining through the dust tells astronomers what that part of the universe was made out of back then, when the universe was just a youngster at 2.2 billion years old.

This was the first time astronomers were able to make an analysis of gas surrounding a gamma burst.

The Keck team quickly identified hydrogen and carbon monoxide, gases associated with star formation right here in the Milky Way galaxy.

But nearly half of the tell-tale absorption lines in the gamma burst light were unidentified, leaving lots of new discoveries waiting for the astronomers.