January 13, 2011 - Science Now
Even among cosmic heavyweights, the black hole in the core of galaxy M87 stands out. New observations reveal that the object weighs in at a whopping 6.6 billion suns, making it the most massive black hole for which a precise mass has ever been measured. "It could swallow our solar system whole," says astronomer Karl Gebhardt of the University of Texas, Austin, who presented the new results here Wednesday afternoon at the 217th meeting of the American Astronomical Society.
Previous estimates put the mass of the black hole at some 3 billion times the mass of our sun, still nearly 1000 times as massive as the black hole at the center of the Milky Way. To compensate for the blurring effects of Earth's atmosphere and obtain a more accurate measurement, Gebhardt and colleagues utilized the adaptive optics capability of the 8.1-meter Frederick C. Gillett Gemini Telescope on Mauna Kea, Hawaii. That enabled the astronomers to measure how fast stars orbit the black hole, which lies some 50 million light-years away, in the direction of the constellation Virgo. From the observed speeds—up to almost 500 kilometers per second—they could then calculate the hole's mass. "It's the most accurate mass estimate ever obtained" for a supermassive black hole, says Gebhardt.
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