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Wednesday, January 27, 1999 Published at 11:52 GMT


Scientists snap deep space blast

What the sky looks like in gamma-rays

by BBC News Online's Science Editor Dr David Whitehouse

For the first time astronomers have been able to capture a mysterious deep space gamma-ray burst almost as it happened.

Last Saturday the orbiting Compton Gamma Ray Observatory was observing the sky. It is sensitive to gamma-rays, high energy radiation that usually comes from hot and violent parts of the cosmos.

[ image: The flash of light caused by the gamma ray burst]
The flash of light caused by the gamma ray burst
Suddenly, an intense flash of gamma-rays triggered detectors onboard the orbiting observatory.

Compton's BATSE instrument quickly relayed the approximate location of the burst to telescopes on the ground which began looking for the optical counterpart to the object.

"It was huge," according to NASA spokesman John Horack, "this is one of the brightest bursts we have ever seen."

Gamma-ray bursts were first detected 30 years ago. To this day they remain a mystery.

Some scientists believe that they occur when two small superdense stars called neutron stars collide releasing titanic amounts of energy.

[ image: A view of the region before the blast]
A view of the region before the blast
It is possible that they may occur when a neutron star is sucked into a black hole.

To get more information about them a detector called BATSE was placed aboard the Compton Gamma-Ray Observatory satellite which was launched in 1991.

Last Saturday night BATSE detected a gamma-ray burst and sent a message to a monitoring computer at NASA's Goddard Space Flight Centre in Maryland, USA.

Just 22 seconds later the doors were opened automatically at the ROTSE-I observatory in New Mexico and a telescope was swung towards the position of the flash.

Another orbiting satellite, the joint Italian-Dutch Beppo-SAX observatory, was also turned towards the spot and sent detailed co-ordinates to the New Mexico observatory.

[ image: Last May's burst - biggest since the Big Bang]
Last May's burst - biggest since the Big Bang
Other optical telescopes also looked towards the bright point of light that was associated with the gamma-ray flash.

For the first time ever the system worked and a glowing object was seen in the position of the gamma-rays.

"We are grabbing as much as we can, as fast as we can," Horack said.

The so-called optical counterpart was so bright that it could be seen in many amateur telescopes.

The latest observations of last Saturday's event, designated GRB 990123, suggests that it originated almost at the edge of the observable universe

Edge of the universe

Gamma-ray bursts are the most dramatic outbursts of energy in the universe.

More energy comes from them in 10 seconds than our Sun will release in ten billion years.

Last May NASA scientists announced that they had detected a burst that was second only to the Big Bang, the event that created the universe.

Black and wihte images courtesy of S. Odewahn, J. Bloom and S. Kulkarni: Palomar Observatory/California Institute of Technology.

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