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Scientists see most extreme gamma-ray blast

(China Daily)
Updated: 2009-02-21 08:05

The US space agency's 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 September in the Carina constellation, produced energies 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 said.

"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.

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 is eight light minutes from Earth, and Pluto is 12 light hours away.

Taking into account the huge distance from earth of the burst, scientists worked out that the blast was stronger than 9,000 supernovae -powerful explosions that occur at the end of a star's lifetime - and that the gas jets emitting the initial gamma rays moved at nearly the speed of light.

"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.

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

Long bursts, which last more than two seconds, occur in massive stars that are undergoing collapse, while short bursts lasting less than two seconds occur in smaller stars.

In short gamma-ray bursts, stars simply explode and form supernovae, but in long bursts, the enormous bulk of the star leads its core to collapse and form a blackhole, into which the rest of the star falls.

Agencies

(China Daily 02/21/2009 page11)