Press Release

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

17 December 2024

The image shows a section of our galaxy, the Milky Way, in the night sky. This is where the supermassive blackhole and the newly discovered binary star around it are located. The Milky Way traverses the image diagonally and is a spectacle of light and darkness. Its millions of stars illuminate the picture, but light is often blocked by large dark clouds of gas and dust that create eerie shapes. It also contains stars and small nebulae of red, pink and blue colours. In the background, the sky is dark, but full of stars of different sizes and colours. The centre of the galaxy with the binary star appears in a close-up on one corner of the image. This is a pixelated mapping of the hydrogen emission of the region around the star pair D9. Bright orange to white patches represent high hydrogen levels (indicating stars), black, represents very low hydrogen emission. Most of the centre of the image is dark with a few wisps of dark orange. The black hole and the binary D9 are indicated.

An international team of researchers has detected a binary star orbiting close to Sagittarius A*, the supermassive black hole at the centre of our galaxy. It is the first time a stellar pair has been found in the vicinity of a supermassive black hole. The discovery, based on data collected by the European Southern Observatory’s Very Large Telescope (ESO’s VLT), helps us understand how stars survive in environments with extreme gravity, and could pave the way for the detection of planets close to 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, pairs of stars orbiting each other, are very common in the Universe, but they had never before been found near a supermassive black hole, where the intense gravity can make stellar systems unstable.

This new discovery shows that some binaries can briefly thrive, 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 nearby black hole will probably cause it to merge into a single star within just one million years, a very narrow timespan for such a young system.

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

For many years, scientists also thought that the extreme environment near a supermassive black hole prevented new stars from forming there. Several young stars found in close proximity to Sagittarius A* have disproved this assumption. The discovery of the young binary star now shows that even stellar pairs have the potential to form in these harsh conditions. “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,” explains 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. Most enigmatic in this cluster are the G objects, which behave like stars but look like clouds of gas and dust. 

It was during their observations of these mysterious objects that the team found a surprising pattern in D9. The data obtained with the VLT’s ERIS instrument, combined with archival data from the SINFONI instrument, revealed recurring variations in the velocity of the star, indicating D9 was actually two stars orbiting each other. “I thought that my analysis was wrong,” Peißker says, “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 shed new light on what the mysterious G objects could be. The team proposes that they might actually be a combination of binary stars that have not yet merged and the leftover material from already merged stars.

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, remain a mystery. But soon, the GRAVITY+ upgrade to the VLT Interferometer and the METIS instrument on ESO’s Extremely Large Telescope (ELT), under construction in Chile, could change this. Both facilities will allow the team to carry out even more detailed observations of the Galactic centre, revealing the nature of known objects and undoubtedly uncovering more binary stars and young systems. “Our discovery lets us speculate about the presence of planets, since these are often formed around young stars. It seems plausible that the detection of planets in the Galactic centre is just a matter of time,” concludes Peißker.

More information

This research was presented in the paper “A binary system in the S cluster close to the supermassive black hole Sagittarius A*” published today in Nature Communications (doi: 10.1038/s41467-024-54748-3).

The team is composed of F. Peißker (Institute of Physics I, University of Cologne, Germany [University of Cologne]), M. Zajaček (Department of Theoretical Physics and Astrophysics, Masaryk University, Brno, Czechia; University of Cologne), L. Labadie (University of Cologne), E. Bordier (University of Cologne), A. Eckart (University of Cologne; Max Planck Institute for Radio Astronomy, Bonn, Germany), M. Melamed (University of Cologne), and V. Karas (Astronomical Institute, Czech Academy of Sciences, Prague, Czechia).

The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration for astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 16 Member States (Austria, Belgium, Czechia, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom), along with the host state of Chile and with Australia as a Strategic Partner. ESO’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its Very Large Telescope Interferometer, as well as survey telescopes such as VISTA. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. Together with international partners, ESO operates ALMA on Chajnantor, a facility that observes the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society. 

Links

Contacts

Florian Peißker
Institute of Physics 1, University of Cologne
Cologne, Germany
Tel: +49 221 470 7791
Email: peissker@ph1.uni-koeln.de

Emma Bordier
Institute of Physics 1, University of Cologne
Cologne, Germany
Tel: +49 221 470 3548
Email: bordier@ph1.uni-koeln.de

Michal Zajaček
Department of Theoretical Physics and Astrophysics, Masaryk University
Brno, Czechia
Tel: +420 549 49 8773
Email: zajacek@physics.muni.cz

Bárbara Ferreira
ESO Media Manager
Garching bei München, Germany
Tel: +49 89 3200 6670
Cell: +49 151 241 664 00
Email: press@eso.org

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About the Release

Release No.:eso2418
Name:D9
Type:Milky Way : Star : Grouping : Binary
Facility:Very Large Telescope
Instruments:ERIS, SINFONI

Images

The image shows a section of our galaxy, the Milky Way, in the night sky. This is where the supermassive blackhole and the newly discovered binary star around it are located. The Milky Way traverses the image diagonally and is a spectacle of light and darkness. Its millions of stars illuminate the picture, but light is often blocked by large dark clouds of gas and dust that create eerie shapes. It also contains stars and small nebulae of red, pink and blue colours. In the background, the sky is dark, but full of stars of different sizes and colours. The centre of the galaxy with the binary star appears in a close-up on one corner of the image. This is a pixelated mapping of the hydrogen emission of the region around the star pair D9. Bright orange to white patches represent high hydrogen levels (indicating stars), black, represents very low hydrogen emission. Most of the centre of the image is dark with a few wisps of dark orange. The black hole and the binary D9 are indicated.
Location of binary star D9 in the Milky Way
The image is a pixelated mapping of the hydrogen emission of the region around the star pair D9. Bright orange to white patches represent high hydrogen levels (indicating stars), black, represents very low hydrogen emission. Most of the centre of the image is dark with a few wisps of dark orange. The location of the supermassive black hole Sagittarius A* is indicated by two lines in the middle of the image, in a black patch. Two lines indicate the location of the star pair D9, which is showing as a bright orange patch. Most of the image is dark, with three bright orange-reddish patches at the right, and one at the bottom left.
Image of the binary star D9 close to Sagittarius A* (annotated)
The image is a pixelated mapping of the hydrogen emission of the region around the star pair D9. Bright orange to white patches represent high hydrogen levels (indicating stars), black, represents very low hydrogen emission. Most of the centre of the image is dark with a few wisps of dark orange. The supermassive black hole Sagittarius A* is not discernable. D9 is showing as a bright orange patch near the top right of the image. Two other bright orange-reddish patches are at the right, another is at the bottom left.
Image of the binary star D9 close to Sagittarius A*
A 340-million pixel starscape from Paranal
A 340-million pixel starscape from Paranal
Straight to the Milky Way's heart
Straight to the Milky Way's heart
Sagittarius A* in the constellation of Sagittarius
Sagittarius A* in the constellation of Sagittarius

Videos

First ever binary star found near Sgr A* | ESO News
First ever binary star found near Sgr A* | ESO News
Star pair D9 orbiting the supermassive black hole Sgr A* (artist's animation)
Star pair D9 orbiting the supermassive black hole Sgr A* (artist's animation)
Artist's animation of star pair D9 orbiting the supermassive black hole Sgr A*
Artist's animation of star pair D9 orbiting the supermassive black hole Sgr A*
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