A group of international researchers have discovered a binary star orbiting near a supermassive black hole at the centre of our galaxy, the Milky Way.
The study, published in the peer-reviewed journal Nature Communications, was based on data collected by the European Southern Observatory's Very Large Telescope (ESO's VLT).
Researchers said their discovery was the first time a stellar pair had been found near a supermassive black hole.
"Black holes are not as destructive as we thought," lead author Florian Peißker from the University of Cologne said.
The 'D9' binary star forms in harsh conditions
A binary star is a system of two stars orbiting around a common centre of mass, leaving them bound together by the force of gravity.
Their existence is quite common in the universe.
However, researchers said that before their discovery, binary stars had never been found near a supermassive black hole because the intense gravity could make stellar systems unstable.
For years, scientists believed that the extreme conditions near a supermassive black hole would prevent new stars from forming.
But the newly discovered binary star orbiting Sagittarius A* has shown that stars can form even in those environments.
The binary star has been called "D9", and is estimated to be about 2.7 million years old.
Co-author Michal Zajacek from the University of Cologne said the D9 system showed signs 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," he said.
Researchers anticipate that due to the strong gravitational force of the black hole, the two stars will likely merge into one in about a million years, which is a short time for a young system.
What does this mean?
In 2020, US researchers discovered what they called four bizarre objects forming near our galaxy.
The new class of objects were later called G objects.
At the time, the authors of the study from the UCLA Galactic Center Group said "these objects looked like gas but behaved like stars".
Astrophysicist Dr Clare Kenyon explained that G objects were a population of dusty weird objects that were close to the supermassive black hole, Sagittarius A*.
"Extrapolating these discoveries, the scientists expect that this population of G objects are probably objects like D9 — yet to merge binary systems," Dr Kenyon from the University of Melbourne said.
"Up until now, it's been a bit unclear what these G objects are. It's just another tiny piece of the enormous puzzle of our Universe — how it works, its past, present and future. There's still so much to understand."
Researchers said there were still many unknowns about the nature of the objects orbiting Sagittarius A*, and how these were able to form near a supermassive black hole.
But the discovery of the binary star near a Sagittarius A* has challenged the view that black holes were completely destructive.
Professor Geraint Lewis from the Sydney Institute for Astronomy said black holes were misunderstood.
"[Black holes] come across as being these beasts that devour everything. But in reality, a black hole has a lot of gravity, which is strong nearby, and then sort of drops off as you head away from the object," Professor Lewis said.
"So the environment of a black hole, while quite different to, say, the environment in our solar system, is not completely destructive.
"It doesn't tear things apart as soon as things exist, but there are more subtle effects that you need to take into account because it's an extreme environment."
The discovery leaves open the possibility of detecting planets
Professor Lewis said that a young star tended to be surrounded by lots of debris from its birth, such as gas and dust.
Those stars would have had a disc of this material out of which planets could form.
"So if that sort of material is close enough to the star that it doesn't feel the really strong gravitational pull from the black hole, then your planets will form more or less oblivious to the fact that it's near a black hole," he said.
"If so, if that stuff is spread out on a much larger volume, then the gravity from the black hole itself can start to pull things apart. So, yeah, this is kind of showing that if you have stars near the centre of the galaxy, then the gravitational conditions are not too nasty for their planets to form."
Lead author Dr Florian Peißker said their discovery had allowed them to speculate about the existence of planets because they were often formed around young stars.
"It seems plausible that the detection of planets in the galactic centre is just a matter of time," Dr Peißker said.
