Ellen Phiddian
Cosmos science journalist
Astronomers have detected a binary star right near the supermassive black hole at the mysterious centre of our galaxy.
The black hole, named Sagittarius A*, was thought to be too powerful to allow binary stars to form this close. But, despite its extreme gravitational pull, the pair of stars are managing to orbit each other – although they’ll likely merge in about a million years.
The discovery, according to a paper published in Nature Communications, could help to find planets near Sagittarius A*.
“Black holes are not as destructive as we thought,” says lead author Florian Peißker, from the University of Cologne, Germany.
The binary star, named D9, is roughly 2.7 million years old. While the stellar pair is holding out for now, the black hole’s gravity is eventually going to force them into one star.
“This provides only a brief window on cosmic timescales to observe such a binary system — and we succeeded!” says co-author Emma Bordier, also from the University of Cologne.
The team found the binary while studying a cluster of stellar objects around Sagittarius A*, called the S cluster, using the Very Large Telescope.
“The D9 system shows clear signs of the presence of gas and dust around the stars, which suggests that it could be a very young stellar system that must have formed in the vicinity of the supermassive black hole,” says co-author Michal Zajaček, a researcher at Masaryk University, Czechia, and the University of Cologne.
D9 was thought to be a single star, but the analysis revealed variations in its speed that didn’t make sense for an individual.
“I thought that my analysis was wrong,” says Peißker.
“But the spectroscopic pattern covered about 15 years, and it was clear this detection is indeed the first binary observed in the S cluster.”
The results could help to explain other mysterious things in the S cluster, which astronomers have dubbed G objects.
The researchers think they might be leftovers from merged binary stars, or binary stars that haven’t merged yet.
“Our discovery lets us speculate about the presence of planets, since these are often formed around young stars,” says Peißker.
“It seems plausible that the detection of planets in the Galactic centre is just a matter of time.”
