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US: Space telescope spots biggest-ever gamma-ray blast

20 Feb 2009 3:34 AM
EDS: Embargoed until 0600 (AEDT) Friday

WASHINGTON, Feb 19 AFP - The US Fermi telescope has detected a massive explosion in space which scientists say is the biggest gamma-ray burst ever detected, a report published on Thursday in Science Express said.

The spectacular blast, which occurred in the Carina constellation, produced energy ranging from 3,000 to more than five billion times that of visible light, astrophysicists said.

"Visible light has an energy range of between two and three electron volts and these were in the millions to billions of electron volts," astrophysicist Frank Reddy of US space agency NASA told AFP.

"If you think about it in terms of energy, X-rays are more energetic because they penetrate matter. These things don't stop for anything - they just bore through and that's why we can see them from enormous distances," Reddy said.

Gamma-ray bursts are the universe's most luminous explosions, which astronomers believe occur when massive stars run out of nuclear fuel.

As a star's core collapses into a black hole, jets of material powered by processes not yet fully understood blast outward.

The jets bore through the collapsing star and continue into space, where they interact with gas previously shed by the star, generating bright afterglows that fade with time.

Using the Gamma-Ray Burst Optical/Near-Infrared Detector (GROND) on a telescope at the European Southern Observatory in Chile, a team led by Jochen Greiner of Germany's Max Planck Institute for Extraterrestrial Physics determined that the huge gamma-ray burst occurred 12.2 billion light years away.

The sun, by comparison, is eight light minutes from earth.

With the extraordinary distance taken into account, scientists worked out that the blast exceeded the power of nearly 9,000 ordinary supernovae, some of the most energetic explosions known, which occur at the end of a star's lifetime.

The gas jets emitting the initial gamma rays moved at one-ten-thousandth of a percentage point less than the speed of light, the scientists said.

"This burst's tremendous power and speed make it the most extreme recorded to date," a statement issued by the US Department of Energy said.