First-ever binary star discovered near our galaxy’s supermassive black hole

An international team of researchers has detected a binary star orbiting close to Sagittarius A*, the supermassive black hole at the center of our galaxy. This is the first time that a pair of stars has been discovered near a supermassive black hole.

This discovery, based on data collected by the European Southern Observatory’s Very Large Telescope (ESO VLT), helps us understand how stars survive in extreme gravity environments and could pave the way for detecting planets close to Sagittarius A*.

“Black holes are not as destructive as previously thought,” says Florian Peißker, a researcher at the University of Cologne, Germany, and lead author of the study published in Natural communications.

Binary stars, pairs of stars orbiting each other, are very common in the universe, but they have never before been found near a supermassive black hole, where intense gravity can make star systems unstable.

This new discovery shows that some binaries can thrive briefly, even under destructive conditions. D9, as the newly discovered binary star is called, was detected just in time: it is estimated to be only 2.7 million years old, and the strong gravitational force of the neighboring black hole will likely cause it to merge into a single star in just a few days. a million years, a very short period of time for such a young system.

“This only provides a brief window on cosmic timescales to observe such a binary system – and we succeeded,” says co-author Emma Bordier, also a researcher at the University of Cologne and a former student at the ESO.

For many years, scientists also thought that the extreme environment near a supermassive black hole prevented new stars from forming. Several young stars found near Sagittarius A* refuted this hypothesis. The discovery of the young binary star now shows that even pairs of stars have the potential to form under these harsh conditions.

“The D9 system shows clear signs of gas and dust around the stars, suggesting that it may be a very young star system that should have formed near the supermassive black hole,” says co-author Michal Zajaček, a researcher at Masaryk University, Czechia, and the University of Cologne.

The newly discovered binary was found in a dense cluster of stars and other objects orbiting Sagittarius A*, called the S cluster. The most enigmatic objects in this cluster are the G objects, which behave like stars but resemble clouds of gas and dust.

It was during their observations of these mysterious objects that the team discovered a surprising pattern in D9. Data obtained with the VLT’s ERIS instrument, combined with archival data from the SINFONI instrument, revealed recurring variations in the star’s velocity, indicating that D9 was actually two stars orbiting each other. on the other.

“I thought my analysis was wrong,” says Peißker, “but the spectroscopic model covered about 15 years and it was clear that this detection was indeed the first binary observed in the S cluster.”

The results shed new light on what the mysterious G objects might be. The team proposes that they might actually be a combination of binary stars that have not yet merged and leftover material from stars already merged.

The precise nature of many of the objects orbiting Sagittarius A*, as well as how they could have formed so close to the supermassive black hole, remains a mystery. But soon, the GRAVITY+ upgrade of the VLT interferometer and the METIS instrument on ESO’s Extremely Large Telescope (ELT), under construction in Chile, could change the situation.

Both facilities will allow the team to make even more detailed observations of the galactic center, revealing the nature of known objects and undoubtedly discovering more binary stars and young systems.

“Our discovery allows us to speculate on the presence of planets, because these often form around young stars. It seems plausible that the detection of planets at the galactic center is only a matter of time,” concludes Peißker.