Astronomers have uncovered compelling evidence of the closest supermassive black hole outside of our own Milky Way galaxy. Nestled within the Large Magellanic Cloud (LMC), one of our nearest galactic neighbors, this stealthy giant had long eluded detection. Thanks to high-precision mapping and advanced modeling, researchers have traced its telltale signs through an unusual cast of hypervelocity stars.
The breakthrough came as scientists meticulously tracked the movement of 21 hypervelocity stars on the Milky Way’s fringes. These stars, traveling at astonishing speeds, are destined to escape the gravitational pull of the Milky Way and any nearby galaxy. Researchers determined their points of origin by analyzing their trajectories—much like forensic experts tracing the path of a bullet.
They found it remarkable: roughly half of these hypervelocity stars had been hurled from the Milky Way’s supermassive black hole, Sagittarius A*. However, the remaining stars pointed to an unexpected source—a previously unknown supermassive black hole in the LMC.
“It’s astounding to realize that we have another supermassive black hole just down the block, cosmically speaking,” said Jesse Han of the Center for Astrophysics | Harvard & Smithsonian (CfA), who led the study. “Black holes are so stealthy that this one has been practically under our noses the whole time.”
The discovery was made possible by data from the European Space Agency’s Gaia mission, a satellite mapping over a billion stars with stunning accuracy. Combined with a deeper understanding of the LMC’s orbit around the Milky Way, this data enabled researchers to create new theoretical models tracking how hypervelocity stars are launched.
Our galaxy is being slowly pulled by neighboring galaxy
Hypervelocity stars are formed when a double-star system strays too close to a supermassive black hole. The immense gravitational forces tear the pair apart, capturing one star while flinging the other out of the galaxy at millions of miles per hour. “By combining Gaia’s data with our models, we identified a cluster of hypervelocity stars that could only have originated from a supermassive black hole in the LMC,” explained co-author Kareem El-Badry of Caltech.
The team’s research calculated the LMC black hole’s mass to be about 600,000 times that of our Sun. Though massive, it pales in comparison to Sagittarius A*, the Milky Way’s supermassive black hole, which is about 4 million solar masses. By contrast, some supermassive black holes elsewhere in the universe exceed billions of solar masses.
Labeled artist’s impression of a hypervelocity star ejected from the Large Magellanic Cloud (shown on right). When a binary star system ventures too close to a supermassive black hole, the intense gravitational forces tear the pair apart. One star is captured into a tight orbit around the black hole, while the other is flung outward at extreme velocities—often exceeding millions of miles per hour—becoming a hypervelocity star. The inset illustration depicts this process: the original binary’s orbital path is shown as interwoven lines, with one star being captured by the black hole (near center of inset) while the other is ejected into space (lower right). Credit: CfA/Melissa Weiss
A key part of the study involved predicting that the LMC black hole would eject hypervelocity stars in a specific pattern based on its motion relative to the Milky Way. Sure enough, researchers discovered a cluster of these speedy stars exactly where their models had suggested.
This discovery adds a new chapter to our understanding of black holes and raises exciting questions about the dynamics between galaxies in close proximity. “The only explanation for this data is the existence of a monster black hole in our galactic backyard,” said co-author Scott Lucchini, also of CfA. “It’s not just the Milky Way’s supermassive black hole evicting stars—our neighbor’s black hole is doing the same.”
With their findings accepted for publication in The Astrophysical Journal, the researchers have laid the groundwork for further exploration of this cosmic colossus. As astronomers refine their models and improve observations, we may soon learn even more about the hidden forces shaping our galactic neighborhood.
Journal Reference
Jiwon Jesse Han et al., Hypervelocity Stars Trace a Supermassive Black Hole in the Large Magellanic Cloud, The Astrophysical Journal (2025). On arXiv: DOI: 10.48550/arxiv.2502.00102