What a wind blows in NGC 3783
CAMBRIDGE, MASS — The highest gust of wind recorded on earth clocked in at 231 miles per hour on Mount Washington, N.H., in 1931. In galaxy NGC 3783, the fastest wind clocked in at a million miles per hour just outside of a black hole last January. Astonishingly, the wind was blowing away from the viselike grip of the black hole's gravity, which has a mass 10 million times that of our sun.
The discovery of the wind by NASA's orbiting Chandra X-ray observatory upsets black holes' fearsome reputation in the popular imagination as the mother-of-all vacuum cleaners, absorbing everything in their vicinity - even light. Scientists, however, have long theorized that a black hole creates almost as much outflow as it does inflow, according to Niel Brandt, of Penn State University, a member of the research team who analyzed the satellite's data at the Chandra Observatory center at the Massachusetts Institute of Technology, in Cambridge. He explains that the incredible radiation produced by matter rushing toward the black hole causes surrounding gasses to heat up to at least billions of degrees Celsius. The result is that wind, estimated to start about 20 light days away from the hole.
The Chandra satellite, launched last July, trained its gaze upon NGC 3783 - some 126 million light years away - because of the galaxy's abnormally clear rays, providing the clearest x-ray yet of a black hole. Researchers were able to detect a number of different elements in the wind such as oxygen, neon, magnesium, silicon, sulfur and iron. "Each has a distinctive pattern," explains Prof. Brandt. Chandra's x-ray beam produced a rainbow of different colors. A computer then plotted a graphic representation of the radiation energies. Dips in the absorption lines allowed scientists to pinpoint each element by identifying its individual pattern. Pinpointing the locations and widths of the dips also revealed the velocity of the wind. "It works on the same principle as a police radar gun," Brandt says.
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