Gamma ray finding may open new window on universe
Artist's conception of an early stage of a gamma-ray burst.
November 25, 1999
Web posted at: 9:49 a.m. EST (1449 GMT)
By David Nordan
Special to CNN Interactive
(CNN) -- NASA scientists say a new finding on the properties of gamma-ray bursts could open "a new window on the distant universe" and offer fresh insight into its beginnings -- and perhaps its eventual demise.
Astronomers say the revelation could make it possible to determine the geometry of the universe throughout its various epochs, as well as when and where massive stars formed in its very early stages.
The work was reported in mid-October by Jay Norris, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, at the Fifth Huntsville (Alabama) Gamma-Ray Burst Symposium.
At the same meeting, related findings emphasizing the same principles but coming from a slightly different approach were reported by Edward Fenimore, an astrophysicist at Los Alamos National Laboratory, and fellow researcher Enrico Ramirez-Ruiz.
Norris issued the "new window" analogy. If the findings hold up, he said, "many gamma-ray bursts can be detected beyond the farthest supernovae and quasars we can now see."
In an interview, Los Alamos' Fenimore agreed, noting that either or both approaches have the potential of vastly expanding the amount of the universe that can be measured.
"We may get a much better idea of where we came from, and where we're going," he said. Fenimore predicted that other scientists "will be all over this" with expansions of the theories. "We've given them something that smells like physics to work with," he said.
Gamma-ray bursts occur randomly several times a day. Typically, they last only a few seconds to a minute and apparently release vastly more energy than any explosions in the universe -- other than the Big Bang itself. Scientists have likened the phenomena to the simultaneous explosion of a thousand supernovas.
New tools to measure with
Where gamma rays come from and how far they travel have remained elusive facts. But the findings from the Goddard scientists may provide the tools needed to pinpoint their point of origin, distance traveled and age.
Norris explained that, in a single burst, gamma rays of different energies reached Earth-orbiting detectors at slightly different times. The higher-energy gamma rays arrived before the lower-energy gamma rays. The amount of lag time between the two corresponded to the to the burst's peak brightness and distance.
Gamma-ray bursts were discovered in the late 1960s. Only recently have most astronomers agreed that many of them originate in the very distant, early universe. The bursts fade quickly and are hard to pinpoint, making it difficult to observe a burst's optical afterglow and determine a distance, or "redshift."
Redshift is a common measurement of astronomical distances. The more
distant an object is from Earth, the faster it is receding due to the expansion of the universe, and the more its light is stretched, or redshifted. Objects at high redshift thus serve as probes to the early universe because their light has taken billions of years to reach Earth.
A future with more gamma data
Appropriate methods of measuring gamma-ray redshift have thus far been elusive. Of the thousands of gamma-ray bursts detected, fewer than 10 had an afterglow or host galaxy whose redshift could be determined with optical telescopes.
Goddard scientists say their new method of comparative measurement of the time between high energy and low energy rays has the potential to gauge the distance of many bursts.
This could give scientists vastly more burst data to work with in the future, NASA officials say.
The team performed the new analysis using data from NASA's Compton
Gamma Ray Observatory and several optical telescopes.
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Goddard Space Flight Center
Huntsville Gamma-Ray Burst Symposium
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