Scientists Unravel The Mysteries Of Large Gamma-Ray Bursts

Lee Rannals for redOrbit.com – Your Universe Online

Researchers unwrapped a little more of the mystery surrounding a new type of powerful cosmic explosion, creating a new theory around the death of supergiant stars.

These huge explosions create powerful blasts of high energy gamma rays, known as gamma-ray bursts. These larger blasts can last for several hours, compared to most gamma-ray bursts which rarely last more than a minute.

The new study has found several examples of these unusual cosmic explosions, and even pinpointed the place one event took place that eluded scientists. On Christmas Day 2010, astronomers saw the first example of these stellar explosions — but since they were unable to measure the distance of it, it remained a mystery. Now, researchers from the current study say this explosion took place in a galaxy much farther away than the two theories suggested.

Scientists calculated the huge gamma-ray burst using data from the Gemini Observatory telescope in Hawaii. They determined it sits about halfway between us and the edge of the observable universe, or roughly 7 billion light-years away.

They believe the Christmas 2010 burst was caused by a supergiant, which is a star 20 times more massive than the Sun. The team believes the ultra long duration of this explosion and two other similar bursts are due to the sheer size of the supergiants exploding in a supernova.

“These events are amongst the biggest explosions in nature, yet we’re only just beginning to find them,” said Dr. Andrew Levan of the University of Warwick, who led the scientists. “It really shows us that the universe is a much more violent and varied place than we’d imagined. Previously we’ve found lots of gamma-ray events with short durations, but in the past couple of years we’ve started to see the full picture.”

Nial Tanvir, a professor at the University of Leicester and second author of the study, said the team believes a newly formed black hole in the heart of the star could be powering the explosion.

“Predicting the detailed behavior of matter falling into a black hole in these circumstances turns out to be very difficult, and from a theoretical point of view we didn’t initially expect explosions at all,” said Tanvir in a statement. “The amazing thing is that nature seems to have found ways of blowing up a wide range of stars in the most dramatic and violent way.”

In a situation where a star collapses into a black hole, matter is drawn into it, but some of the stars’ energy escapes and is focused into a jet of material which blasts out in two directions. These jets are ejected nearly at the speed of light, otherwise the material would fall back into the black hole without escape.

“What the Christmas burst seems to be telling us is that the family of gamma-ray bursts is more diverse than we fully appreciate,” Christina Thoene of the Institute of Astrophysics of Andalusia in Granada, Spain, said in 2011 in a paper published in Nature about the original observation of the Christmas Day 2010 burst.

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