Correction appended
Two University researchers hope to shed some light on a little-known phenomenon.
Gamma rays, or light emissions that originate beyond the solar system and can last as little as a fraction of a second, have puzzled scientists since they were discovered. University researchers Raymond Frey and Isabel Leonor are involved in an international science group that helped discover where a gamma ray may have come from – or at least where it did not come from. The findings could one day give scientists a better understanding of the universe outside the solar system.
Scientists believe gamma rays come from powerful supernovae, caused by either collisions between two neutron stars or between a neutron star and a black hole.
“Right now during the past decade or so, we’ve had some good progress in understanding what causes them,” Leonor said.
Physicists involved in the Laser Interferometer Gravitational-Wave Observatory, which is made up of hundreds of researchers across the world and funded by the National Science Foundation, discovered a February burst of gamma rays possibly from the Andromeda Galaxy, the closest galaxy to the Milky Way. But the burst lacked a gravitational wave.
That means the gamma ray likely didn’t come from merging neutron stars or black holes within Andromeda, Leonor said.
Leonor recently presented the findings at the Gravitational Wave Data Analysis Workshop in Cambridge, Mass.
LIGO gamma ray satellites, located in orbit, measured a short burst of gamma rays in February and collected data about the event, but the group didn’t detect any gravitational wave, Leonor said. Scientists previously thought the merger of two neuron stars or black holes formed the gamma ray.
“The fact that we didn’t see gravitational waves – I call it ‘the dog that didn’t bark’ – means we didn’t have the right model,” Frey said, adding there may be other possible explanations.
The gamma ray may have formed in a “box” near the Andromeda Galaxy, the nearest galaxy of comparable size to the Milky Way, or from a source beyond the Andromeda Galaxy in a distant galaxy, Frey said.
Frey said he wants to learn more about gravitational waves and gamma rays because they could be a telling piece on how the universe evolved.
“Gamma ray bursts are still such a mystery that everything we learn is part of the puzzle,” Frey said. “Probably five years from now this will be a more obvious piece of the puzzle when all the pieces are put together. Right now, though, it’s just another piece of evidence.”
LIGO hopes to one day detect a gravitational wave using its satellites. It would be the first to ever do so.
“Our goal is to use these gravitational waves to probe the universe or look at the universe in a way that no astronomical tool can,” LIGO spokesman David Reitze said, adding that other tools such as optical and radio telescopes rely on electromagnetic radiation. “Gravitational waves are fundamentally different and are literally ripples in the fabric of space-time and provide complementary and completely new information that we can’t get anywhere else.”
Leonor said she’s hopeful the group will detect a gravitational wave one day.
“It will help us understand the universe,” Leonor said. “We’re all contributing different bits and pieces to understand what the universe is.”
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Because of a reporter’s error, details on gamma ray discoveries were incorrect. The February burst of gamma rays were discovered by detectors on satellites in orbit, not the Laser Interferometer Gravitational-Wave Observatory facilities in the United States. Also, the Andromeda galaxy is the nearest galaxy of comparable size to the Milky Way. The Emerald regrets the error.
Illuminating the final frontier
Daily Emerald
January 27, 2008
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