Astrophysicists are marveling at the latest celestial discovery made near the Milky Way’s supermassive black hole.
Scientists have uncovered the existence of a binary star system close to the black hole near the center of the Milky Way galaxy, confirming a hypothesis made by happenstance nearly a century ago, according to a paper published in Nature Communications on Wednesday.
The second of three images of ESO’s GigaGalaxy Zoom project is a new and wonderful 340-million-pixel vista of the central parts of our galactic home, a 34 by 20-degree wide image that provides us with a view as experienced by amateur astronomers around the world.
ESO/S. Guisard
Scientists have previously predicted the existence of a binary star system — one in which two stars are gravitationally bound to one another around a common center of gravity — in the vicinity of the black hole at the center of the galaxy, called Sagittarius A*, the paper states.
In the 1930s, American engineer Karl Jansky made the accidental observation while attempting to research whether there was any interference in radio signals between Europe and the United States, Florian Peissker, an astrophysicist at the University of Cologne in Germany and author of the paper, told ABC News.
Within the scope of that research, Jansky discovered Sagittarius A*, a supermassive black hole about 26,000 light-years from Earth. Follow-up observations showed bright emissions coming from the region, but scientists at the time couldn’t figure out what the “bright blob” was, Peissker said.
It wasn’t until the 1990s that researchers first documented detailed observations of stars orbiting the bright emission, and the first time that stars have been observed close to a supermassive black hole, Peissker said. In the early 2000s, Andrea Ghez, an astrophysicist at UCLA, discovered a very young star in the region, estimated to be just a few million years old.
D9 is the first star pair ever found near Sagittarius A*, the supermassive black hole at the centre of the Milky Way. This image shows an emission line of hydrogen mapped by the SINFONI instrument on ESO’s Very Large Telescope. The instrument provides a spectrum for every single pixel; over the years, the emission around D9 was found to oscillate periodically towards red and blue wavelengths which revealed that D9 is actually two stars orbiting each other.
ESO/F. Peißker et al
Since stars typically form in pairs or triplets, rather than a single star, scientists deduced that binary star systems were orbiting near the black hole, Peissker said.
The high-velocity stars and other dusty objects that orbit Sagittarius A* are collectively known as the “S-cluster.” Scientists have never been able to detect the binary star system within the S-cluster — until now.
Peissker and his colleagues used the European Southern Observatory’s “Very Large Telescope” — one of the world’s most advanced optical telescopes — to detect the binary star system.
Peissker described the new findings as an “amazing” development in mapping out the evolution of the Milky Way.
This chart shows the location of the field of view within which Sagittarius A* resides — the black hole is marked with a red circle within the constellation of Sagittarius (The Archer). This map shows most of the stars visible to the unaided eye under good conditions.
ESO, IAU and Sky & Telescope
The researchers believe the binary star system will merge soon. When the binary star system disappears, one single star will remain.
“We calculated that it could be tomorrow, next week or maybe in a million years — which, from an astrophysical point of view, is really soon,” Peissker said.
The S-cluster is a “highly dynamical system” with stars that interact with each other as they come within each other’s gravitational pull, Peissker said.
The researchers hypothesize that all of the stars in the close vicinity of the supermassive black hole were binary systems that have since merged, Peissker said. The influence of the supermassive black hole allows the binary star systems to reside within the S-cluster for about 1 million years after they migrate from outside the cluster.
This image indicates the location of the newly discovered binary star D9, which is orbiting Sagittarius A*, the supermassive black hole at the centre of our galaxy. It is the first star pair ever found near a supermassive black hole.
ESO/F. Peißker et al., S. Guisard
The presence of the supermassive black hole could speed up the merging process of the binary star systems, Peissker said.
The findings are “big news” and provide a missing link to the mystery of the evolution of our galaxy, as well as others out there — like the Andromeda galaxy, the closest to the Milky Way about 2.5 million light-years away, Peissker said.
“We get a much better understanding about the evolution of stars in the vicinity of a supermassive black hole, so we can actually use that knowledge also to, at some point in the future, understand how stars ended up close to a supermassive hole in other galaxies,” he said.