Binary star found near Milky Way's supermassive black hole surprises astronomers

An international team of researchers has recently detected a binary star system orbiting close to Sagittarius A*, the supermassive black hole at the center of our galaxy. 

This marks the first time a stellar pair has been identified in the vicinity of a supermassive black hole. 

The findings, based on data from the European Southern Observatory’s Very Large Telescope (ESO’s VLT), provide new insights into how stars survive in extreme gravitational environments and pave the way for future studies on planets near Sagittarius A*.

“Black holes are not as destructive as we thought,” said Florian Peißker, a researcher at the University of Cologne, Germany, and lead author of the study.

Binary stars, which consist of two stars orbiting each other, are common throughout the universe. However, none had ever been found so close to a supermassive black hole, where intense gravity typically destabilizes such systems.

Understanding binary stars — the basics

A binary star is a system where two stars orbit around a common center of mass, acting like cosmic dance partners.

Instead of having just one star like our Sun, binary systems have two stars that are gravitationally linked, keeping each other in their paths.

These pairs can vary a lot — in some cases, the stars are so close they even exchange material, leading to fascinating events like nova explosions.

Other binary stars are spaced far apart, each shining brightly on their own while still moving in harmony with their partner. It’s like having a stellar buddy system up there in space!

By studying these binary star pairs, scientists can accurately measure the masses of stars, which is tricky to do with single stars. Plus, binary systems can influence the formation of planets and other celestial bodies around them.

Young binary star near a black hole

This discovery reveals that some binary stars can briefly persist even under such harsh conditions. The newly identified binary star, named D9, is estimated to be just 2.7 million years old. 

However, its close proximity to the supermassive black hole means the immense gravitational forces will likely cause it to merge into a single star within one million years – a fleeting moment on cosmic timescales.

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

Black holes and star formation

For decades, scientists believed that the extreme gravitational environment near supermassive black holes prevented the formation of new stars.

However, the discovery of several young stars near Sagittarius A* in recent years has overturned that assumption. 

The D9 binary system now adds another layer to this understanding, suggesting that even pairs of stars can form in such challenging conditions.

Study co-author Michal Zajaček is a researcher at Masaryk University and the University of Cologne.

“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,” explained Zajaček.

The binary was found within the S cluster — a dense grouping of stars and objects orbiting near Sagittarius A*.

Among the most puzzling objects in this cluster are the G objects, which appear like clouds of gas and dust but behave more like stars.

Confirmation of the binary star

The team’s observations of the G objects led them to identify the binary nature of D9. Data from the VLT’s ERIS instrument, combined with archival data from the SINFONI instrument, showed recurring velocity variations in D9, indicating that it consists of two stars orbiting each other.

“I thought that my analysis was wrong, but the spectroscopic pattern covered about 15 years, and it was clear this detection is indeed the first binary observed in the S cluster,” said Peißker.

This discovery has implications for the enigmatic G objects as well. The team hypothesizes that these could be either binary stars that have yet to merge or remnants of stars that have already merged.

Looking ahead: The hunt for planets

Despite this breakthrough, many questions remain about the origins and characteristics of objects near Sagittarius A*. 

The GRAVITY+ upgrade to the VLT Interferometer and the METIS instrument on ESO’s Extremely Large Telescope (ELT), currently under construction in Chile, are expected to revolutionize studies of the Galactic center. 

These tools will allow researchers to conduct even more detailed observations, uncovering additional binary systems and young stars.

“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,” Peißker concluded.

This discovery not only advances our understanding of binary stars but also opens up exciting possibilities for future discoveries in one of the most extreme environments in our galaxy.

The study is published in the journal Nature Communications. 

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