Science & Tech

Streamers of gas feed beast at center of our galaxy

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Researchers seek to pinpoint source of black hole’s diet

Astronomers have long known that a supermassive black hole, more than 2 million times more massive than our Sun, lies at the center of the Milky Way Galaxy some 27,000 light-years from Earth. A point-like source of radio emission called Sagittarius A* (pronounced “A-star”) marks the location of this black hole. Now researchers Robin S. McGary and Paul T. P. Ho of the Harvard-Smithsonian Center for Astrophysics report that narrow “streamers” of ammonia gas appear to be flowing from giant clouds of gas toward the center of the galaxy. These findings, presented Jan. 12, 2000, at the American Astronomical Society meeting, could pinpoint the source of the black hole’s gluttonous diet. The black hole is surrounded by a ring of dust and gas orbiting Sagittarius A* (Sgr A*) at a radius of about 6.5 light-years from the black hole. This “circum-nuclear disk” revolves around the black hole at a velocity of 110 km/s. Gas and dust are stripped from the disk by the strong gravitational pull of the black hole and spiral towards Sgr A*.