PBS Newshour - December 5, 2011
Researchers have discovered a monster black hole that appears to be the most massive found to date, as massive as 21 billion suns. This is one of two black holes found in elliptical galaxies some 300 million light years away -- both believed to be the biggest yet.
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Scientists calculate the mass of black holes by studying the matter swirling around them. In this case, researchers used state-of-the-art spectrographs on Hawaii's Gemini North and Keck 2 telescopes to determine the speed and motion of stars orbiting around the black holes. The more massive the black hole, the faster objects will orbit around it.
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