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Volume 46 | Issue 2 | March 2004



Chandra's data point to new class of black holes

Mysterious, powerful X-ray sources found in nearby galaxies may represent a new class of celestial objects, according to data from NASA's Chandra X-ray Observatory. These sources, which are not as hot as typical neutron-star or black-hole X-ray sources, could be a large new population of black holes with masses several hundred times that of the sun.

"The challenge raised by the discovery of these sources is to understand how they produce so much X-ray power at temperatures of a few million degrees," said Rosanne Di Stefano of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and Tufts University in Medford, Mass.

Until a few years ago, astronomers knew of only two sizes of black holes: stellar black holes, with masses about 10 times the sun, and supermassive black holes located at the centers of galaxies, with masses ranging from millions to billions times that of the sun. Recent evidence suggests a class of "intermediate-mass" black holes may also exist.