A red dwarf star and a black hole are orbiting each other once every 2.4 hours, a new record for the fastest-spinning black-hole X-ray binary system ever found.
The star whirls around at 2 million kilometers per hour, while the much heavier black hole orbits at 150,000 kilometers per hour. They are about a million kilometers apart.
“The companion star revolves around the common center of mass at a dizzying rate, almost 20 times faster than Earth orbits the sun,” study lead author Erik Kuulkers of the European Space Agency (ESA) said in a press release.
“You really wouldn’t like to be on such a merry-go-round in this galactic fair!”
The speedy system, named MAXI J1659-152, contains a black hole that has three times the mass of our sun. The tiny star rushing around it has only 20 percent the mass of our sun.
When scientists first discovered the pair in 2010, they thought it was a gamma-ray burst. Then they detected some X-rays coming from it and realized that these rays were produced by a black hole feeding off a small star.
They spent over 14 hours observing the system with ESA’s telescope XMM-Newton. From the telescope’s point of view, the disk was nearly edge-on, so they were able to detect unevenness in the edge.
By watching the pattern of dips in the edge, they calculated how fast the system was orbiting. The result, one orbit every 2.4 hours, beat the previous record of 3.2 hours held by Swift J1753.5–0127.
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Both Swift J1753.5–0127 and MAXI J1659-152 are located far above the main disk of the Milky Way galaxy, an unusual place for black-hole binary systems.
“These high galactic latitude locations and short orbital periods are signatures of a potential new class of binary system, objects that may have been kicked out of the Galactic plane during the explosive formation of the black hole itself,” Kuulkers said.
