Binary star found near our galaxy’s supermassive black hole

A first in astronomy

An international team of researchers has made a groundbreaking discovery near the supermassive black hole at the heart of our Milky Way galaxy, Sagittarius A*. They have detected a binary star system orbiting the black hole for the first time. This finding opens new avenues for understanding how stars and other celestial objects can survive in such an extreme gravitational environment.

The discovery, made using the European Southern Observatory’s (ESO) Very Large Telescope (VLT), marks a significant leap in astrophysics. It challenges previous assumptions about the destructive nature of black holes and provides a glimpse into how stars might form and persist near such an immense gravitational force.

Florian Peißker, a researcher at the University of Cologne and the study’s lead author, shared his excitement about the discovery: “Black holes are not as destructive as we thought.”

Binary stars, consisting of two stars orbiting each other, are standard throughout the universe. However, this is the first time a stellar pair has been observed so close to a supermassive black hole, where the immense gravity could theoretically tear such systems apart.

2.7 million years old

The binary star in question, D9, is estimated to be just 2.7 million years old. Due to its proximity to Sagittarius A*, the intense gravitational pull is expected to merge the two stars into one within a mere million years. Despite its youth, the system is rapidly evolving, and scientists have a small window to capture it before its eventual fate.

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“This discovery provides a brief glimpse into a unique cosmic timescale, and we succeeded just in time,” explained Emma Bordier, co-author of the study and a researcher at the University of Cologne. The short lifespan of this system within such extreme conditions adds to its scientific value, as it offers insights into the forces at play near black holes.

For years, scientists believed the hostile environment near a supermassive black hole would prevent new stars from forming. However, this theory has been disproven by discovering young stars near Sagittarius A*. The detection of the D9 binary star suggests that not only can stars form in this region, but stellar pairs may also find a way to exist for a time.

Co-author Michal Zajaček from Masaryk University in Czechia and the University of Cologne explained: “The D9 system shows clear signs of the presence of gas and dust around the stars, indicating that it likely formed in the vicinity of Sagittarius A*.”

S cluster

The binary star was located within a dense cluster of stars and objects known as the S cluster, which orbits the supermassive black hole. Astronomers had already observed mysterious G objects—gas and dust clouds that behave like stars—within this cluster. While investigating these enigmatic G objects, the researchers detected unusual velocity variations that led to the discovery of D9.

Peißker admitted initial doubts, saying: “I thought my analysis was wrong. But the spectroscopic pattern covered about 15 years, and it became clear that this detection was indeed the first binary star observed in the S cluster.”

The discovery also provides new clues about the nature of the G objects. The team theorises that these may be binary stars in the process of merging or the remnants of stars that have already merged, offering a deeper understanding of the evolution of stars in the extreme environment around Sagittarius A*.

While much remains unknown about the precise nature of the objects orbiting Sagittarius A*, future advancements in observational technology promise to shed more light on this cosmic puzzle, the Gravity+ upgrade to the VLT Interferometer and the METIS instrument on ESO’s Extremely Large Telescope (ELT), currently under construction in Chile, will soon provide even more detailed insights into the galactic centre.

Peißker concluded: “Our discovery lets us speculate about the presence of planets. These are often found around young stars, and given the age of the D9 system, it seems plausible that planet detection in the Galactic centre could be just a matter of time.”

The study detailing the discovery of the binary system in the S cluster near Sagittarius A* was published in Nature Communications. The research team, which includes scientists from the University of Cologne, Masaryk University, and other institutions, has opened a new chapter in our understanding of stellar systems and their behaviour in the universe’s harshest environments.

This research also highlights the critical role of ESO’s observatories in advancing the cosmos study. The European Southern Observatory has long been a leader in astronomical research, enabling scientists worldwide to explore the mysteries of space. With the upcoming upgrades to its facilities, discoveries like the D9 binary star system will continue to shape our understanding of the universe.

Hero image: This image indicates the location of the newly discovered binary star D9, orbiting Sagittarius A*, the supermassive black hole at the centre of our galaxy. The cut-out shows the binary system detected by the SINFONI spectrograph on ESO’s Very Large Telescope. While the two stars cannot be discerned separately in this image, the binary nature of D9 was revealed by the spectra captured by SINFONI over several years. Credit: ESO/F. Peißker et al., S. Guisard