Apr 13 1999
From The Space Library
NASA announced the discovery of a "mysterious class of `middleweight' black holes." Two teams of astronomers studying x-ray light at NASA and Carnegie Mellon University had independently found evidence of this new class of black hole. Astronomers did not know what process had formed the newly discovered black holes, 100 to 10,000 times as massive as the Sun and located in spiral-shaped galaxies throughout the universe. Before this discovery, astronomers had known of only two types of black holes: 1) stellar black holes, formed from the "remains of dead stars several times heavier than the Sun" and compressed to a "diameter of a few miles or less"; and 2) supermassive black holes, which have masses equal to 1 million to 1 billion Suns and likely formed in the "early universe from giant gas clouds or from the collapse of clusters of immense numbers of stars." Edward H. Colbert and Richard F. Mushotzky of NASA's Goddard Space Flight Center (GSFC) had observed hints of the black holes while studying x-rays from 39 nearby galaxies. Andrew Ptak and Richard Griffiths of Carnegie Mellon University had studied x-ray light in galaxy M82, which was not one of the set of galaxies that the Goddard team had studied. Both teams had identified unique x-ray light indicative of a class of black holes that was neither stellar nor supermassive.
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