The Parasitic Bond Of Intimacy Between A Black Hole And A Massive, Dying Star

Using ESO's Very Large Telescope, astronomers have discovered the most distant black hole ever observed. Six million light years from Earth, it lies at the heart of a spiral galaxy, and is rapidly orbiting and eating a massive star.

According to a release about the new discovery:

The newly announced black hole lies in a spiral galaxy called NGC 300 . . . "This is the most distant stellar-mass black hole ever weighed, and it's the first one we've seen outside our own galactic neighbourhood, the Local Group," says Paul Crowther, Professor of Astrophysics at the University of Sheffield and lead author of the paper reporting the study. The black hole's curious partner is a Wolf–Rayet star, which also has a mass of about twenty times as much as the Sun. Wolf–Rayet stars are near the end of their lives and expel most of their outer layers into their surroundings before exploding as supernovae, with their cores imploding to form black holes.

In 2007, an X-ray instrument aboard NASA's Swift observatory scrutinised the surroundings of the brightest X-ray source in NGC 300 discovered earlier with the European Space Agency's XMM-Newton X-ray observatory. "We recorded periodic, extremely intense X-ray emission, a clue that a black hole might be lurking in the area," explains team member Stefania Carpano from ESA.

Thanks to new observations performed with the FORS2 instrument mounted on ESO's Very Large Telescope, astronomers have confirmed their earlier hunch. The new data show that the black hole and the Wolf–Rayet star dance around each other in a diabolic waltz, with a period of about 32 hours. The astronomers also found that the black hole is stripping matter away from the star as they orbit each other.

"This is indeed a very 'intimate' couple," notes collaborator Robin Barnard. "How such a tightly bound system has been formed is still a mystery."

See the scientific paper "NGC 300 X–1 is a Wolf-Rayet/Black-Hole binary" [PDF], to appear in Monthly Notices Of The Royal Astronomical Society