for National Geographic News
An unusual gamma-ray burst has astronomers wondering what new type of cosmic explosion could have created the brilliant blast of light.
Gamma-ray bursts are brief explosions of super-energetic light at the most extreme range of the electromagnetic spectrum.
A single burst is a million trillion times brighter than the sun. It lasts only a short time—from a few milliseconds to a few minutes.
"They are the most violent events known in our universe," said Bing Zhang of the University of Nevada, Las Vegas.
"There are a lot of unknowns, but their study tells us about the extreme conditions found in the universe."
The bursts appear to be associated with supernovas—the massive explosions caused by the deaths of some stars that can spawn black holes.
But a gamma-ray burst observed by NASA's Swift satellite on June 14, 2006, defies any currently known theories, because it reveals no evidence of an associated supernova.
"The fact that this one didn't [associate with a supernova] is making us rethink our whole idea of what can cause gamma-ray bursts," said Neil Gehrels of the NASA Goddard Spaceflight Center in Greenbelt, Maryland.
Gehrels authored one of four studies of the mysterious burst that appear in tomorrow's issue of the journal Nature.
Explosion Defies Characterization
The prevailing theory is that a catastrophic explosion in the core of a star collapsing into a black hole launches a shock wave of energy that sends gamma rays surging from the star's surface.
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