January 12, 2011 - Science News
Astronomers have determined with high precision that the black hole at the heart of the nearby galaxy M87 weighs the equivalent of 6.6 billion suns. The finding makes the monster the most massive known in Earth’s cosmic neighborhood and the heaviest black hole measured so far using the orbits of stars.
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To weigh M87’s black hole, Gebhardt’s team used precision optics on the Gemini North telescope atop Hawaii’s Mauna Kea to measure the speeds of groups of stars orbiting the galaxy’s core at different distances. The speedup of stars closest to the center gives a precise measure of the black hole’s pull, allowing researchers to calculate its mass. The researchers also used data gathered by a telescope at the McDonald Observatory in west Texas.
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