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5 December 2013 11:26 am ,
Vol. 342 ,
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Gamma Ray Needles May Pierce Space
12 September 2003 (All day)
Gamma ray bursts (GRBs) and other cosmic explosions called x-ray flashes are the same phenomenon in different guises. That's the prediction of a disputed new model in which GRBs--the most powerful explosions in the universe--aim their energy like a rifle shot, whereas x-ray flashes emit broader fans of energy. If true, up to 100,000 GRBs could blow up in the universe for each one that astronomers see.
Satellites spot GRBs as flares of the most energetic radiation known. Astronomers reached a consensus about their origins earlier this year by finding the signature of an exploded star--a supernova--at the site of a nearby GRB (ScienceNOW, 14 April). Theorists now concur that massive stars must spew fantastic jets of energy into space when their cores collapse into black holes, but they disagree about what those jets look like. Clues lie in comparing GRBs to their seemingly less-energetic cousins, x-ray-rich GRBs and x-ray flashes, whose sources are more mysterious.
New research suggests all three types arise from supernovas that focus their fury in jets with drastically different shapes. Astrophysicist Donald Lamb of the University of Chicago and colleagues examined the energies of GRBs and their x-ray kin recorded by the High-Energy Transient Explorer-2 (HETE-2) satellite and earlier orbiters. The team saw a tight correlation between the total energy observed for each blast and the peak wavelength of the measured radiation. The bursts that appeared to be the most powerful churned out most of their energy in intense, short-wavelength gamma rays, while the weakest ones had peak energies at longer wavelength x-rays.
This striking pattern implies that the three types of explosions all have the same overall energy. If that's the case, says Lamb, an x-ray flash must spew radiation in nearly all directions, dimming its impact for a distant observer. However, a GRB would channel its outburst into a needlelike cone perhaps 1 angular degree wide, which we see as a far brighter flare. "Their jets are so tiny that we only see them if we are in the boresight," says Lamb, noting that we would detect just one of every 10,000 or 100,000 such blasts. Lamb spoke on 11 September at the GRB 2003 Symposium in Santa Fe, New Mexico.
His scenario earned a mixed reception. Astronomer Dale Frail of the National Radio Astronomy Observatory in Socorro, New Mexico, says the unified model "is so simple and elegant, you want it to be true." But astrophysicist Shrinivas Kulkarni of the California Institute of Technology in Pasadena objects to the "incredibly tiny" 1-degree beams. Rather, his group's research points to a range of gamma ray and x-ray energies emerging together in wider cones.