Star and black hole in dizzying dance

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PARIS, March 19 (UPI) -- A star and a black hole are orbiting each other at the rate of once every 2.4 hours, smashing the previous record by nearly an hour, European astronomers say.

The black hole in this compact pairing discovered by the European Space Agency's XMM-Newton space telescope is at least three times more massive than the Sun while its red dwarf companion star has a mass only 20 percent that of the Sun, and the pair is separated by only around 600,00 miles, a release from ESA's Paris headquarters reported Tuesday.

The duo were discovered in September 2010 by NASA's Swift space telescope and were initially thought to be a gamma-ray burst, but more observations, including those by XMM-Newton, revealed that the radiation was coming from a black hole feeding off material ripped from a tiny companion.

Astronomers were able to determine the pair's orbital period was just 2.4 hours, setting a record for black hole X-ray binary systems. The previous recordholder has a period of 3.2 hours, they said.

The short orbital period results in the companion red dwarf star moving at a speed of 1.2 million miles per hour, making it the fastest moving star ever seen in an X-ray binary system, researchers said.

"The companion star revolves around the common center of mass at a dizzying rate, almost 20 times faster than Earth orbits the Sun," lead author Erik Kuulkers of ESA's European Space Astronomy Center in Spain said.

"You really wouldn't like to be on such a merry-go-round in this galactic fair!"