Scientists Announce New Class of Stellar Events: Ultra-Long Gamma Ray Bursts

Scientists have introduced a previously-unknown astronomical phenomenon --- the ultra-long gamma ray burst.

The Astrophysics Spectator defines gamma ray bursts as "events that last from less than a second to many thousands of seconds, and as their name implies, they are random bursts of gamma-rays."

But, three unusually long examples of the stellar explosions were recently discovered using the Swift satellite and other international telescopes, according to Universe Today.

The astronomers who discovered them said the three GRBs represented a previously unrecognized class of stellar explosions, which occur amid the catastrophic deaths of supergiant stars hundreds of times larger than Earth's own sun.

One of the three new phenomena, named GRB 111209A, was longest GRB ever detected, with a duration of about 7 hours.

"We have observed the longest gamma ray burst in modern history, and think this event is caused by the death of a blue supergiant," said Bruce Gendre, the researcher who led the study at the Italian Space Agency's Science Data Center in Frascati, Italy.

"It caused the most powerful stellar explosion in recent history, and likely since the Big Bang occurred," added Gendre, who now works with the French National Center for Scientific Research.

GRBs are the most luminous and mysterious explosions in the universe. The blasts emit surges of gamma rays, which are the most powerful known form of light, as well as X-rays, and can produce afterglows, slowly fading light emissions at longer wavelengths created by collisions between the material blasted out by the explosion and interstellar gas that can be observed at optical and radio wavelengths.

Swift, the Fermi telescope and other spacecraft detect an average of about one GRB each day.

Andrew Levan, an associate professor in the physic department at the University of Warwick in Coventry, England, said the new GRB type appears to be difficult to find because, well, it lasts so long.

"Gamma ray telescopes usually detect a quick spike, and you look for a burst - at how many gamma rays come from the sky," Levan told Universe Today. "But these new GRBs put out energy over a long period of time, over 10,000 seconds instead of the usual 100 seconds."

Because such GRBs are spread out, " it is harder to spot, and only since Swift launched [in 2004] do we have the ability to build up images of GBSs across the sky," he said. "To detect this new kind, you have to add up all the light over a long period of time."

Levan added long-lasting GRBs were likely more common in the universe's past.