Saturday, October 15, 2005
Ancient Interstellar Collision Helps Explain Source of Radiation
NYTimes
By DENNIS OVERBYE
Published: October 5, 2005
With a screech of high-energy radiation brighter than a million billion suns, a pair of stars in a faraway galaxy collided two billion years ago and disappeared into a black hole.
That cataclysm, recorded by a battery of telescopes and NASA satellites on July 9, has provided scientists with the answer to the last remaining piece of 35-year-old astronomical mystery: the origin of explosions that sporadically shower outer space with gamma rays, the most energetic and deadly form of electromagnetic radiation.
"This is the real deal," said Donald Lamb of the University of Chicago, a co-author of one of four papers by an international cast of astronomers being published on Thursday in the journal Nature...
.....
Gamma ray bursts come in two types: long and short. Two years ago, astronomers were able to trace the long bursts, which last from two seconds up to a minute or more, to certain kinds of supernova explosions in very distant galaxies.
But about 10 percent of the bursts are shorter, often lasting less than a second, and have thus been harder to study. Theorists have speculated that they could originate in double-star systems where a pair of neutrons stars or a neutron star and a black hole spiral ever tighter in a death dance toward merger and oblivion.
But on May 9, by homing in on the X-ray afterglow of a short burst, a team using NASA's Swift satellite was able to trace a 70-millisecond burst to the vicinity of an elliptical galaxy about 2.9 billion light-years away in the constellation Coma Berenices. This was significant, because such galaxies lack the massive young stars that give rise to the more violent core-collapse explosions...
...
By DENNIS OVERBYE
Published: October 5, 2005
With a screech of high-energy radiation brighter than a million billion suns, a pair of stars in a faraway galaxy collided two billion years ago and disappeared into a black hole.
That cataclysm, recorded by a battery of telescopes and NASA satellites on July 9, has provided scientists with the answer to the last remaining piece of 35-year-old astronomical mystery: the origin of explosions that sporadically shower outer space with gamma rays, the most energetic and deadly form of electromagnetic radiation.
"This is the real deal," said Donald Lamb of the University of Chicago, a co-author of one of four papers by an international cast of astronomers being published on Thursday in the journal Nature...
.....
Gamma ray bursts come in two types: long and short. Two years ago, astronomers were able to trace the long bursts, which last from two seconds up to a minute or more, to certain kinds of supernova explosions in very distant galaxies.
But about 10 percent of the bursts are shorter, often lasting less than a second, and have thus been harder to study. Theorists have speculated that they could originate in double-star systems where a pair of neutrons stars or a neutron star and a black hole spiral ever tighter in a death dance toward merger and oblivion.
But on May 9, by homing in on the X-ray afterglow of a short burst, a team using NASA's Swift satellite was able to trace a 70-millisecond burst to the vicinity of an elliptical galaxy about 2.9 billion light-years away in the constellation Coma Berenices. This was significant, because such galaxies lack the massive young stars that give rise to the more violent core-collapse explosions...
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