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.
The star whips around the black hole at an astonishing speed of 12 million kilometers an hour, said the study published in the journal Monthly Notices of the Royal Astronomical Society.
This is the tightest orbital dance ever witnessed for a black hole and a companion star.
“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.
The stellar dance between the two objects is taking place inside a globular cluster 47 Tucanae, a group of about a million stars orbiting the galactic centre about 15,000 light years from Earth.
Globular clusters have much higher stellar density than other galactic space, so a collision between a star and the black hole is the most likely process.
Astronomers made the discovery using the Australia Telescope Compact Array, operated by CSIRO near Narrabri in NSW, backed up with data from two of NASA’s space telescopes, Chandra X-ray Observatory and NuStar.
Associate Professor Miller-Jones said the next step will be to determine the mass of the objects.
He estimates the white dwarf star will only have a mass a few per cent that of the sun and have a planet-sized diameter.