Magazine article Science News

Chandra Eyes Low-Temperature Black Hole

Magazine article Science News

Chandra Eyes Low-Temperature Black Hole

Article excerpt

From Atlanta, at a meeting of the American Astronomical Society

Black holes rank among the most intriguing objects in the universe. Now, astronomers have found a really cool one.

Homing in on the supermassive black hole at the heart of the Andromeda galaxy, the sharp eye of the Chandra X-ray Observatory has found that gas falling into the dense object has a temperature of a few million kelvins. That's the lowest temperature ever found for emissions from a galactic black hole. Sucking in hot, X-ray-emitting gas at nearly the speed of light, the black holes that scientists have previously studied have temperatures typically of about a billion kelvins.

Andromeda lies just 2 million light-years away from the Milky Way. The two galaxies are similar in size and shape, and astronomers have gathered evidence that each harbors a central black hole. Besides having a lower temperature, Andromeda's black hole emits radiation with a much lower ratio of X rays to radio waves than the Milky Way's black hole does.

Standard models can't explain this surprising behavior, reports Stephen S. Murray of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

One explanation for the cool observations may be that much less hot gas than cold gas is falling onto the black hole, says theorist Eliot Quataert of the Institute for Advanced Study in Princeton, N.J. That could occur if large pockets of hot gas boil and swirl around the black hole instead of falling directly onto it, he suggests. …

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