The University of Southampton

European astronomers create largest-ever catalogue of gamma-ray sources in the universe

23 February 2007

Using data from the European Space Agency's latest orbiting gamma-ray observatory, Integral, a European team of astronomers led by Dr Antony Bird of the University of Southampton (UK), has created an important new catalogue of gamma-ray sources in the universe.

With over 70 per cent of the sky now observed by Integral, this is the largest catalogue yet of individual gamma-ray-emitting celestial objects. And, according to the researchers, there is no end in sight for the discoveries to be made.

"We are in a golden age of gamma-ray astronomy," comments Dr Bird. "And ESA's Integral is at the forefront of this brave new universe."

"The gamma-ray sky is notoriously variable and extremely unpredictable," comments fellow researcher Anthony Dean, Professor of Astronomy at the University of Southampton, and one of the original proposers of the Integral mission.

"The constant observations undertaken by Integral are essential for monitoring and understanding the gamma-ray universe, and for maintaining an accurate catalogue of all gamma-ray sources. With this, astronomers can target individual gamma-ray objects for more detailed study. The information gathered by Integral is changing the way astronomers think of the high-energy cosmos."

The catalogue contains 421 gamma-ray objects, most of which have been identified as either binary stars in our galaxy containing exotic objects such as black holes and neutron stars, or active galaxies, far away in space. But a puzzling one quarter of sources remain unidentified so far.

"I think many of these will turn out to be either star systems enshrouded in dust and gas, or cataclysmic variable stars," continues Professor Dean.

Integral observes in the gamma-ray band so it can see through the intervening material. It has demonstrated that it can discover sources obscured at other wavelengths.

"Integral represents a milestone in gamma-ray astronomy," adds Professor Dean. "Thirty years ago, NASA's Einstein observatory produced a catalogue of X-ray sources that became the standard reference document for all X-ray observatories - including ESA's XMM-Newton. Integral is doing the same for gamma-ray astronomy."

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