A group of Southampton scientists have discovered a star in the closest known orbit to what is believed to be a black hole.
Astronomers, including a team from the University of Southampton, have found evidence that the star whips around a black hole about twice an hour. It is thought this may be the tightest orbital dance ever witnessed for a likely black hole and a companion star.
This discovery was made using NASA’s Chandra X-ray Observatory as well as NASA’s NuSTAR and CSIRO’s Australia Telescope Compact Array (ATCA).
The close-in stellar couple – known as a binary – is in the globular cluster 47 Tucanae, a dense cluster of stars in our galaxy about 14,800 light years from Earth.
While astronomers have observed it for many years, it wasn’t until 2015 that radio revealed the pair was likely to contain a black hole.
Professor of Astrophysics, at the University of Southampton, which found that the X9 system was an accreting compact object in a close binary system.
Professor Knigge, professor of astrophysics at the University of Southampton, who is one of the authors on the paper, said: “This is an extremely exciting result, because this may be the first black hole discovered to date that is fed by a white dwarf companion in this kind of ultra-compact configuration.”
Although the white dwarf does not appear to be in danger of falling in or being torn apart by the black hole, its fate remains uncertain.
First author Arash Bahramian, of the University of Alberta in Edmonton, Canada, and Michigan State University in East Lansing, said: “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.
“Luckily for this star, we don’t think it will follow this path into oblivion, but instead will stay in orbit.”
A copy of the research paper is available at https://academic.oup.com/mnras/article/467/2/2199/3052451/The-ultracompact-nature-of-the-black-hole?searchresult=1.