Thousands of times more energetic than ordinary exploding stars, their visible light as bright as a million galaxies, gamma-ray bursts are the most violent events in the universe, and radiation from one of these events reaches the vicinity of Earth at a rate of about one a day.
Yet not until last January were astronomers able to capture the first images in visible light of a gamma-ray burst in progress. Now, the first results from the observations are being reported in the journals Science and Nature and are being described in interviews.The findings include surprises and new clues but still no solution to one of the most vexing mysteries in astrophysics: What is causing the cataclysmic events that produce these explosive flashes?
"For most phenomena, quasars, supernovas or black holes, maybe we have some notion of what they are," said Carl W. Akerlof, a University of Michigan astrophysicist and an author of one of the reports in Nature. "A gamma-ray burst is the most mysterious thing about which we still have so little information."
Astronomers recently learned that these bursts originated at extragalactic distances, but they were surprised by how far away was the source of this burst. In Friday's issue of Science, a team led by Michael Andersen of the Nordic Optical Telescope in the Canary Islands reported that an analysis of the visible light showed that its source had a "red shift" of at least 1.6, the equivalent to a distance of some nine billion light-years, or two-thirds of the way across the universe.
The farther away a cosmic object is, the greater its light is shifted toward the red end of the spectrum.
"We were stunned," George Djorgovski, an astrophysicist at the California Institute of Technology in Pasadena, said in a statement. "This was much farther than we expected."