Swift Deep Image of the Galactic center
Credit: NASA/Swift/N. Degenaar (Univ. of Michigan)

Swift Action at the Galactic Center

The center of the Milky Way is where the action is. It contains a wild assortment of weird residents and shady characters: extremely massive stars, a swarm of stellar corpses, and most notoriously, Sgr A*, the Milky Way's supermassive black hole. Sgr A* is a gravitational monster containing as much mass as 4 million suns in a tiny region only one fifth the size of Mercury's orbit. Sgr A* is peculiar, though, since it's a particularly quiet and unassuming monster. It's very faint, suggesting that it's not feeding very much on nearby gas clouds or stars. But how quiet is it, really? There's some evidence that Sgr A* may undergo periods of increased activity. To help determine how active Sgr A* really is, for the past seven years the Swift observatory has been monitoring the high-energy X-ray output of Sgr A*. High-energy X-ray emission is a believed to be a good tracer of Sgr A*'s feeding habits, since, if material falls into a black hole, it should heat to extreme X-ray emitting temperatures. This Swift campaign shows that Sgr A* exhibits surprising intervals of X-ray activity. Swift detected six X-ray flares from Sgr A*, in which the X-ray emission brightened by up to 150 times. These observations also detected the presence of other X-ray sources (shown in the image above), including SGR J1745-29, a strange type of neutron star called a magnetar. The Swift monitoring campaign is ongoing, and astronomers are eagerly awaiting an upcoming event later this year, when Sgr A* should swallow a large gas cloud which is believed to be on a collision course with the black hole.
Published: January 27, 2014

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Page Author: Dr. Michael F. Corcoran
Last modified Sunday, 02-Feb-2014 23:26:21 EST