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Physical Society Colloquium
Frederick Baganoff MIT Center for Space Research The center of the Milky Way is obscured from our view at optical wavelengths by clouds of dust. Telescopes operating at radio, infrared, X-ray, and gamma-ray wavelengths pierce this veil. Radio and infrared studies of the central few light-years of our galaxy indicate the presence of a large, dark object - presumably a supermassive black hole - with a mass of about 3 million suns. This object is spatially coincident with Sagittarius A*, the compact nonthermal radio source located at the dynamical center of the Milky Way. Sagittarius A* is thought to be powered by the gravitational potential energy released by matter as it falls into a supermassive black hole. It is, however, much fainter than expected in all wavebands, especially in X-rays. We present the discovery of rapid, large-amplitude X-ray flaring from the direction of Sagittarius A* with the Chandra X-ray Observatory. These data provide compelling evidence that the X-ray emission is coming from accretion onto a supermassive black hole at the Galactic center. This appears to be the first detection of violent activity from our local supermassive black hole, and the nature of the variations provides strong constraints on the astrophysical processes near the event horizon of the black hole.
Friday, November 2nd 2001, 15:30 |