A group of international astronomers using NASA’s NuSTAR telescope, the Australia Telescope Compact Array (ATCA), and the Chandra X-Ray Observatory has found a star that orbits around a black hole twice an hour at a distance two and a half times that of the Earth and the moon.
This is an exciting discovery because it is the first time a star has been found so close to a black hole. The team found it by looking at the X-ray fluctuations in X9, a white dwarf/black hole binary system in a thick cluster of stars located 14,800 light years from Earth.
While researchers have long known about the system, they did not realize it may be composed of materials under the influence of a nearby black hole until 2015, Tech Times reports. They also observed that the star cluster fluctuates in brightness once every 28 minutes and contains a large amount of oxygen, suggesting it contains a white dwarf star.
The star sits very close to the black hole — so close that the team first believed they were simply watching two different stars moving around the Earth. However, closer inspection of the system revealed a black hole that appears to be ripping material from a white dwarf.
“Due to the proximity of the white dwarf to the black hole, the immense gravitational pull of the black hole rips off matter from the surface of the star,” said study co-author Slavko Bogdanov, associate research scientist in the Columbia Astrophysics Laboratory at Columbia University, in a statement. “This matter accumulates in a disk of matter before spiraling in past the black hole event horizon, never to be seen again. While it is unlikely that the entire white dwarf will be devoured by the black hole, it is not entirely clear what its ultimate fate will be.”
While black holes normally consume and tear apart any stars that get too close to them, the white dwarf appears to be intact for now, though researchers are not sure why. The team believes it could be the result of a major collision with a massive red star, which would have led to the release of the gas from the external region of the star and formed a binary system that held both the black hole and white dwarf.
“For a long time astronomers thought that black holes were rare or totally absent in globular star clusters,” said study co-author Jay Strader, an astronomer at Michigan State University, according to Popular Mechanics. “This discovery is additional evidence that, rather than being one of the worst places to look for black holes, globular clusters might be one of the best.”
The findings are outlined in a recent study published in the Monthly Notices of the Royal Astronomical Society.