Deep Space Eruption’s Energy Equals Thousands of Suns
The most powerful explosion ever observed, a deep space eruption detected in January, released in just seconds a burst of energy equal to billions of years of light from thousands of suns.
Researchers say in studies to be published today that the explosion, called a gamma ray burst, occurred 9 billion light-years from Earth. What caused the explosion is a mystery.
“It is probably something to do with massive stars,” said S. George Djorgovski, a Caltech astronomer. “The real truth is, we don’t know.”
The gamma ray burst was detected by Italian and U.S. science satellites that sent an alert to a network of ground instruments and telescopes. Within seconds, telescopes focused on the area of the sky where the burst originated and captured views in visible light. Later, more powerful telescopes photographed the explosion’s afterglow.
The alert enabled astronomers, for the first time in history, to capture optical views of a gamma ray burst as the detection was underway. Analyzing this light helped the scientists determine that the burst happened about 9 billion light-years from Earth. A light-year is about 6 trillion miles.
An international team of astronomers wrote a series of reports on their study of the gamma ray burst in two scientific journals, Nature and Science.
Djorgovski, co-author of a study in Nature, said an analysis of light and other energy spewing from the explosion suggests that, for a very brief instant, the explosion was more luminous and energetic than the rest of the universe.
“If the gamma rays were emitted equally in all directions, their energy would correspond to 10,000 times the energy emitted by our sun over its entire lifetime of about 5 billion years,” Djorgovski said in an interview. “Yet the burst lasted only a few tens of seconds.”
Djorgovski said there is some evidence the energy was detected as a concentrated beam pointed at Earth.
A beam would give an impression of greater energy in the explosion, just as a flashlight beam focused on one spot appears to be brighter than an uncovered bulb that scatters the same amount of light in all directions.
But even if the gamma ray energy were sent out in a beam, Djorgovski said, “it would still be the most powerful explosion ever observed.”
Gamma ray bursts were discovered in 1967, but the phenomenon remains mysterious. The bursts occur randomly across the sky several hundred times a year, lasting for only a few milliseconds to a few minutes. Because of the short duration, large telescopes in the past could not be focused in time to catch optical views. The satellite alert system now makes that possible.
Djorgovski said there have been more than 150 theories proposed to explain gamma ray bursts.
The two leading ideas, he said, both involve massive stars. One theory proposes that the burst occurs when two massive stars merge and form a black hole. Another theory proposes that the energy eruption comes from a hyper-supernova, a stellar explosion much larger than that of an ordinary supernova.
“It is perfectly possible that the source [of the burst] is even stranger and more unusual,” said Djorgovski, “but the circumstantial evidence suggests it involves massive stars.”
