This Star Orbits Our Galaxy’s Heart at a Record-Breaking Speed—and Could Help Uncover Secrets About the Behemoth Black Hole There

The speedster travels at up to 56 million miles per hour, or about 8 percent the speed of light. It also gets very close to the supermassive black hole at the center of the Milky Way

Margherita Bassi | Daily Correspondent

August 28, 2026 11:45 a.m.

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At the center of our Milky Way galaxy, some 27,000 light-years from Earth, sits a supermassive black hole called Sagittarius A*. Astronomers have long suspected that it’s spinning, but they’ve never been able to confirm it.

Now, however, they have identified a stellar research assistant: A speedy star that periodically gets up close and personal with Sagittarius A*. During its closest approach to the supermassive object, the star, dubbed S301, should be affected by the black hole’s rotation, allowing scientists to measure the spin directly for the first time. The findings were published August 19 in the journal Nature.

“The star which we have discovered has such a great potential, and we’re really all excited about it,” study co-author Stefan Gillessen, an astronomer at the Max Planck Institute for Extraterrestrial Physics in Germany, tells Science News’ Mara Johnson-Groh.

Gillessen and his colleagues detected S301 with the European Southern Observatory’s Very Large Telescope Interferometer in Chile. It combines light from several telescopes to observe extremely faint astronomical objects. They spied the star near Sagittarius A* in spring 2023 and collected follow-up measurements over the next couple of years. That data was also combined with archival observations dating back to 2017.

Analyses revealed that S301 has an elongated, oval-shaped orbit, with the black hole at one far end. Along that path, the star reaches a top speed of about 56 million miles per hour—roughly 8 percent the speed of light —and is the fastest star ever recorded in the Milky Way.

As it approaches Sagittarius A*, “the star comes in in one direction, getting faster and faster and faster, then gets a very sharp turn around the black hole,” Gillessen tells Ari Daniel for NPR’s “All Things Considered.” Then “it flies back out again and decelerates until it’s at its farthest point. Once you know the orbit, it’s pretty much like the Swiss railway system. Things are there precisely on time.”

It takes just 8.7 years to complete a loop around Sagittarius A*, and at its closest point, the two objects are separated by merely 12 times the distance between Earth and the sun.

S301’s routine proximity to the supermassive black hole makes it the first known star that could be used to measure Sagittarius A*’s rotation directly. It can do that because Einstein’s general theory of relativity posits that a rotating black hole also twists space-time, which should change the orbits of nearby stars.

“The ⁠star gets pushed ​onto a slightly different orbit each time it passes the black hole,” Gillessen tells Reuters’ Will Dunham. Observing that change over the next decade should allow the team to determine the black hole’s spin, a measurement that’s “unheard of, so far.”

“Without this star, we would need to measure the motion of other stars for several more decades to get anywhere close to measuring the spin of the black hole,” study co-author Juan Osorno, an astronomer at the Paris Observatory, says in a statement.

Such a direct measurement would bolster Einstein’s theory. It would also provide a huge asset in learning about the Milky Way’s history, Ziri Younsi, an astrophysicist at University College London who did not participate in the study, tells the Guardian’s Hannah Devlin. S301 “is incredibly important as a discovery.”

Where did this supremely helpful star come from? It was probably part of a two-star system, according to the researchers. But after getting too close to Sagittarius A*, the pair may have been ripped apart by the black hole’s gravity. Sagittarius A* kept S301 close by and banished the other star, likely flinging it beyond the galaxy.

Margherita Bassi is a freelance journalist and trilingual storyteller. Her work has appeared in publications including BBC Travel, Discover magazine, Live Science, Atlas Obscura and Hidden Compass.