2009-11-11

Study finds new middleweight class of black hole

Astronomers have found new evidence that supports the existence of a middleweight class of black holes, not like the either little or big variety in previous studies, according to media reports Wednesday.

NGC 5408 X-1, the newly found object, is an X-ray source in the NGC 5408 galaxy, 15.8 million light-years away from Earth in the constellation Centaurus.

"Intermediate-mass black holes contain between 100 and 10,000 times the sun's mass," said Tod Strohmayer, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

The new study used the European Space Agency's orbiting XMM-Newton observatory to observe the black hole in 2006 and in 2008. It found further proof that the signal is a medium-sized black hole.

Black hole is infinitely dense and it could trap matter and even light with its gravity. Though astronomers can't see it directly, they detect a black hole by its gravitational pull on other objects, and by the ray it emitted when massive things fall into it.

NGC 5408 X-1 emits more X-rays than a typical star, but less than supermassive black holes. And its flickering is about 100 times slower than that seen from stellar-mass black holes. Based on this, the researchers consider it probably a middleweight.

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