Researchers have found evidence of a white dwarf star orbiting a likely black hole at a distance of only 961,000 km — just about 2.5 times the distance between the Earth and the Moon.
In a tightest orbital dance ever witnessed for a black hole and a companion star, the star whips around the black hole at an astonishing speed — about two orbits an hour, said the study published in the journal Monthly Notices of the Royal Astronomical Society.
“This white dwarf is so close to the black hole that material is being pulled away from the star and dumped onto a disk of matter around the black hole before falling in,” said study lead author Arash Bahramian, affiliated with the University of Alberta in Canada and Michigan State University in the US.
“Luckily for this star, we don’t think it will follow this path into oblivion, but instead will stay in orbit,” Bahramian said. Although the white dwarf does not appear to be in danger of falling in or being torn apart by the black hole, its fate is uncertain.
The stellar system, known as X9, is located in the globular cluster 47 Tucanae, a dense cluster of stars in our galaxy about 14,800 light years away from the Earth. “For a long time astronomers thought that black holes were rare or totally absent in globular star clusters,” study co-author Jay Strader from Michigan State University said.
“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,” Strader added. For the study, the researchers used data from the Australia Telescope Compact Array as well as NASA’s Chandra X-ray Observatory and NuSTAR telescope.