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This discovery, based on data collected by the Very Large Telescope (VLT) of the European Southern Observatory (ESO), helps us understand how stars survive in environments with extreme gravity and could pave the way for detecting planets near Sagittarius A*.
"Black holes are not as destructive as we thought," says Florian Peißker, a researcher at the University of Cologne (Germany) and lead author of the study published today in Nature Communications. Binary stars, which are pairs of stars orbiting each other, are widespread in the Universe, but none had ever been found near a supermassive black hole, whose intense gravity can destabilize stellar systems.
This new discovery shows that some binaries can briefly develop even under destructive conditions. D9, the name of the newly discovered binary star, was detected just in time: it is estimated to be only 2.7 million years old, and the strong gravitational force of the nearby black hole will likely cause it to merge into a single star within just a million years, a very short timespan for such a young system.
"This is only a brief window in cosmic time to observe such a binary system—and we succeeded," explains Emma Bordier, co-author of the study, a researcher at the University of Cologne and a former student at ESO.
For many years, scientists also believed that the extreme environment near a supermassive black hole prevented the formation of new stars. Several young stars discovered near Sagittarius A* have refuted this hypothesis.
This animation shows how the two stars in the D9 system orbit each other, enveloped in a cloud of gas and dust. The blue line indicates the orbit of the binary system around Sagittarius A*, the supermassive black hole at the center of the Milky Way.
D9 is the first binary star discovered near a supermassive black hole. Its formation and survival in this extreme environment mean that black holes are not as destructive as previously thought.
D9 is the first binary star discovered near a supermassive black hole. Its formation and survival in this extreme environment mean that black holes are not as destructive as previously thought.
The discovery of the young binary star now shows that even stellar pairs can form under these harsh conditions. "The D9 system shows clear signs of gas and dust around the stars, suggesting it could be a very young stellar system that must have formed near the supermassive black hole," explains co-author Michal Zajaček, a researcher at Masaryk University in the Czech Republic and the University of Cologne.
The new binary was discovered 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 while observing these mysterious objects that the team discovered a surprising phenomenon 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. "I thought my analysis was wrong," explains Florian Peißker, "but the spectroscopic model covered about fifteen years, and it became clear that this detection was indeed the first binary observed in the S cluster."
These results shed new light on what the mysterious G objects might be. The team suggests they could be a combination of binary stars that have not yet merged and residual material from already merged stars.
This animation shows D9, the first pair of stars discovered near Sagittarius A*, the supermassive black hole at the center of the Milky Way. We zoom in and out of the black hole and the individual stars orbiting it, then move closer to D9, the first binary stellar system ever discovered in its vicinity.
The video, created by an artist from the Brno Observatory and Planetarium, shows how the stellar system orbits the black hole. It also reveals the dusty gas cloud in which the pair of stars is enveloped, suggesting it is a young stellar system.
The formation and survival of a binary stellar system in this extreme environment mean that black holes are not as destructive as we thought.
This animation was made possible by a Junior Star grant from the Czech Science Foundation (GM24-10599M).
The video, created by an artist from the Brno Observatory and Planetarium, shows how the stellar system orbits the black hole. It also reveals the dusty gas cloud in which the pair of stars is enveloped, suggesting it is a young stellar system.
The formation and survival of a binary stellar system in this extreme environment mean that black holes are not as destructive as we thought.
This animation was made possible by a Junior Star grant from the Czech Science Foundation (GM24-10599M).
The precise nature of many 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 to the VLT interferometer and the METIS instrument on ESO's Extremely Large Telescope (ELT), currently under construction in Chile, could change the game.
These two facilities will allow the team to conduct 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 about the presence of planets, as they often form around young stars. It seems plausible that detecting planets in the galactic center is only a matter of time," concludes Florian Peißker.