Posted on 04/04/2002 4:08:20 AM PST by kattracks
LEICESTER, England, Apr 03, 2002 (United Press International via COMTEX) -- Super-hot gas streaking across space may be the smoking gun evidence that solves one of the key mysteries in astronomy -- the identity of the culprits behind the most powerful explosions in the universe, researchers said Wednesday.
"There's been all sorts of wild theories -- alien spacecraft, nuclear explosions -- but now we have some real evidence that nails these things," said lead researcher James Reeves of the University of Leicester in Britain. "We think we can now prove supernovae cause them."
Gamma ray bursts are flashes of deadly radiation that can unleash more energy in a few seconds or minutes than the sun can over its entire 10-billion-year lifespan.
"For a short period of time, they are the most powerful events happening in the universe," explained astrophysicist Ken Pounds of the University of Leicester.
These explosions were first discovered accidentally some 35 years ago by military satellites monitoring for secret nuclear weapons tests in space. Details about their origins have eluded astronomers ever since -- they happen daily but there is no way of telling from which direction the next one will come.
Last December, however, the most powerful X-ray telescope ever placed in orbit, the European Space Agency's X-ray Multi-Mirror satellite, managed to catch a glimpse of the afterglow of a gamma ray burst some 10 billion light years away. The pictures revealed the presence of a lot of superheated gas -- nearly 10,000 times hotter than the sun's surface, and enough to make up one tenth of the sun's mass.
More important, the spectra or wavelengths of light from this massive fireball reveal its ingredients are a mix of magnesium, argon, sulfur, calcium and silicon, with traces of nickel. This is just the kind of elemental blend that would be expected to see hurled from a supernova -- the explosive collapse of a dying star that results in a black hole.
The gas also is apparently traveling at nearly 10 percent the speed of light or 67 million miles per hour -- exactly what might be expected from an expanding supernova's shell.
"When a massive star comes to the end of its lifetime it can go supernova," Pounds told United Press International. "Its outer part explodes while there's a simultaneous collapse of its core. What we think we are seeing is the ejecta, the material blown off by the supernova, lit up by the gamma ray burst.
"We think the exploding part forms a thick shell of material that travels at high velocity for a time. After a few hours of whirling around, the core finally implodes to form a black hole, releasing a gamma ray burst that catches up with the ejecta and heats it up so that it emits X-rays," Pounds said.
Although supernovae probably will not explain all gamma ray bursts -- the one studied lasted about four minutes, while others are only fractions of a second long -- "this is an important step," said astrophysicist Herman Marshall of the Massachusetts Institute of Technology in Cambridge. "I think many scientists will now try the method the researchers used, which helped provide a much better clue to what's actually happening."
The researchers described their findings in the scientific journal Nature.
(Reported by Charles Choi in New York.)
Copyright 2002 by United Press International.
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