Astronomers observe new type of cosmic explosion

A new type of cosmic explosion that occurred late last year could shed light on the death of massive stars, astronomers said on Wednesday.
It was more powerful than supernovae, explosions marking the death of a huge star, but weaker than gamma-ray bursts (GRB), the mysterious and most brilliant blasts in the universe.
"I was stunned that my observations ... showed that this event confirmed the existence of a new class of bursts," said Alicia Soderberg, of the California Institute of Technology in Pasadena, who reported the finding in the science journal Nature.
"It was like hitting the jackpot."
Scientists had thought all gamma-ray bursts had a standard energy and the same intrinsic brightness until the discovery of the cosmic blast that occurred on December 3, 2003 and is known by its date of birth, GRB 031203.
"With this new event we realise it is not true. There are sub-energetic bursts that are less luminous with fainter emission, which means there is a not a standard energy," Soderberg said in an interview.
"Perhaps there is some sort of continuum between the two explosions that we didn't realise before," she added. The new blast occurred about 1.6 billion light years away. A light-year is about 6 trillion miles (10 trillion km), the distance light travels in a year. It was also much closer than other gamma-ray bursts and about a thousand times weaker.
Astronomers do not know what causes gamma-ray bursts. They are thought to occur when stars collapse possibly to become a black hole, creating a huge gravitational pull from which nothing can escape.
But last month, cosmologist Stephen Hawking said he believes some material oozes out of black holes over billions of years through irregularities on their surface.
Scientists from the Space Research Institute of the Russian Academy of Sciences, in Moscow, who also observed the cosmic blast and reported it in Nature, believe other similar blasts have occurred but have not been detected. In 1998 astronomers reported an extremely faint gamma-ray burst called GRB 980425.
NASA's Swift mission in the Autumn, which will study gamma ray bursts, could provide more information about the explosions.
"This is an intriguing discovery," said Shrinivas Kulkarni, a professor of astronomy and planetary science at the California Institute of Technology and a co-author of one of the reports. "I expect a treasure trove of such events to be identified by NASA's Swift mission..," he said in a statement.