Discovery of a binary star very close to our galaxy’s supermassive black hole – rts.ch

Binary star systems – two stars orbiting each other – are very common in the Universe and make up 50% of the stars in our galaxy.

But at the center of the Milky Way, where the supermassive black hole Sagittarius A* (Sgr A*) is located, they can be counted “on the fingers of one hand”: only five double systems have been detected there to date, explains Emma Bordier, astrophysicist at the German University of Cologne and co-author of thestudy published Tuesday in Nature Communications.

This region is considered “one of the most extreme” in our galaxy, due to “the immense gravitational influence of the supermassive black hole, which drives highly eccentric, high-speed stellar orbits, as well as tidal forces capable to disrupt and destroy potential binary systems,” adds the researcher.

The discovery of the binary star shows that black holes of this size “are not as destructive” as expected, summarizes in a press release from the European Southern Observatory (ESO) the main author of the study Florian Peissker, of the University of Cologne.

A very young star system

Named D9, this double system is located in a dense group of stars and other objects orbiting Sgr A*, called the “S cluster”. During its closest passes, it is only 0.12 light years from the black hole. In comparison, Proxima Centauri, the closest star to the Sun, is 40 times farther away than D9 from Sgr A*.

The detection of the double star was possible thanks to data obtained over a long period with two spectrographs of the Very Large Telescope (VLT) – SINFONI (2005-2019), then ERIS (commissioned in 2022).

According to Michal Zajacek, co-author of the study and researcher at Masaryk University in the Czech Republic and the University of Cologne, the D9 system “shows clear signs of the presence of gas and dust near the stars.” . Which suggests “that it could be a very young stellar system that must have formed near the supermassive black hole,” he adds.

The research team estimates that D9 is only 2.7 million years old, and the black hole’s gravitational force will likely cause it to merge into a single star within just a million years.

>> Lire : A very young star seen near the black hole at the center of our galaxy

This youth makes it even a little more unique of its kind, while the five other double systems discovered to date are massive, even very massive, more evolved stars.

Scientists believed that the extreme conditions near a black hole prevented new stars from forming and that those present there formed in more suitable regions before migrating to the galactic center during their lifetime.

Everything is possible around a supermassive black hole

However, observations showed that this region was “paradoxically populated by young stars”. The discovery of a young binary star “shows once again that everything is possible around a supermassive black hole”, underlines Emma Bordier.

This discovery also sheds new light on the “G objects“, the most mysterious objects in the S cluster, which behave like stars but look like clouds of gas and dust. The team suggests that it could be a combination of binary stars that have not yet merged and residual material from already merged stars.

The detection of D9 also allows us to speculate on the presence of planets in the galactic center, because these often form around young stars. “It seems plausible that the detection of planets in the galactic center is only a matter of time,” according to Florian Peissker.

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