Astronomers have recently uncovered strong evidence for the closest supermassive black hole to the Milky Way, located in the Large Magellanic Cloud (LMC), one of our galaxy’s nearest neighbors. This groundbreaking discovery challenges previous assumptions about the presence of such giants in nearby galaxies and has opened a new chapter in our understanding of these enigmatic cosmic objects.
The breakthrough was made possible by observing the behavior of 21 hypervelocity stars—stars traveling at such extraordinary speeds that they will escape the gravitational grip of not only the Milky Way but any nearby galaxy. These stars, once bound in binary systems, are now racing across the cosmos as a result of violent interactions with supermassive black holes. Hypervelocity stars have long been known to exist, but until now, their origins remained elusive.
To make sense of these mysterious stellar travelers, astronomers turned to data from the European Space Agency’s Gaia mission. This satellite, which has been meticulously tracking over a billion stars across the Milky Way with unparalleled precision, provided a treasure trove of information that allowed researchers to map the paths of the hypervelocity stars with remarkable accuracy. The team, led by Jesse Han of the Harvard-Smithsonian Center for Astrophysics (CfA), was able to trace the stars’ trajectories back to their points of origin.
Through this detailed analysis, the researchers made an astonishing discovery: roughly half of these hypervelocity stars were connected to the supermassive black hole at the center of our Milky Way galaxy, as expected. However, the other half appeared to have come from a different source altogether—a previously unrecognized supermassive black hole in the LMC.
The existence of this new black hole was unexpected but supported by the data. As Han remarked, “It is astounding to realize that we have another supermassive black hole just down the block, cosmically speaking. Black holes are so stealthy that this one has been practically under our noses this whole time.” The LMC is located about 163,000 light-years from the Milky Way, making it a relatively close neighbor in cosmic terms. Despite its proximity, the supermassive black hole it harbors had remained hidden until now.
The key to this discovery was the combined use of Gaia’s precise star tracking and an updated understanding of the LMC’s orbit around the Milky Way. The LMC, a satellite galaxy of the Milky Way, is in constant motion, interacting gravitationally with our galaxy. This motion has a profound effect on the stars in the LMC, particularly those near the supermassive black hole at its center. By studying the orbits of these stars and modeling their trajectories, the researchers were able to pinpoint the origin of the hypervelocity stars and identify the hidden black hole.
Kareem El-Badry, a co-author of the study from Caltech, explained, “We knew that these hypervelocity stars had existed for a while, but Gaia has given us the data we need to figure out where they actually come from. By combining these data with our new theoretical models for how these stars travel, we made this remarkable discovery.”
The formation of hypervelocity stars typically occurs in the presence of a supermassive black hole. These stars are born from the gravitational tug-of-war that happens when a binary star system comes too close to a black hole. The immense gravitational forces of the black hole tear the system apart, capturing one star into a tight orbit while sending the other speeding away at velocities that can reach millions of miles per hour. The ejected star, now a hypervelocity star, races through the galaxy, forever escaping the gravitational pull of its original home.
In the case of the LMC, the team’s theoretical models predicted that the movement of the galaxy around the Milky Way would produce a stream of hypervelocity stars. Stars ejected in the direction of the LMC’s motion would receive an additional velocity boost, further propelling them into the vastness of space. The observations confirmed this hypothesis, revealing a distinct cluster of hypervelocity stars in that direction.
The discovery of the LMC’s supermassive black hole fills a significant gap in our understanding of galactic dynamics. Prior to this study, it was believed that the only supermassive black holes capable of producing hypervelocity stars were those at the centers of galaxies like the Milky Way. However, the evidence for a second such object in a neighboring galaxy has broadened the scope of black hole research. Scott Lucchini, another co-author from CfA, noted, “The only explanation we can come up with for this data is the existence of a monster black hole in our galaxy next door. So in our cosmic neighborhood, it’s not just the Milky Way’s supermassive black hole evicting stars from its galaxy.”
Using the velocities of the hypervelocity stars, as well as the relative numbers of stars ejected by the Milky Way and the LMC, the researchers were able to estimate the mass of the black hole in the LMC. The results indicated that this black hole weighs in at about 600,000 times the mass of our Sun—significantly smaller than the Milky Way’s supermassive black hole, which has a mass of approximately 4 million solar masses. However, the LMC’s black hole is still one of the largest known in the local universe, and its discovery has important implications for the study of black holes in smaller galaxies. For comparison, there are black holes elsewhere in the universe with masses that can exceed billions of solar masses, as is the case for many supermassive black holes in the centers of large galaxies.
The implications of this discovery extend beyond just the LMC. The presence of another supermassive black hole in such a nearby galaxy raises new questions about the distribution and frequency of these objects throughout the universe. It suggests that supermassive black holes may be more common than previously thought, even in smaller galaxies, and that their influence on stellar dynamics could be more widespread than we realized.
This study, which was published in The Astrophysical Journal, represents a significant milestone in black hole research. The data, provided by the Gaia mission, has given astronomers the ability to pinpoint the exact trajectories of hypervelocity stars with an accuracy never before achieved. This achievement opens the door to further discoveries about the complex relationships between black holes and the stars in their vicinity.
The identification of the supermassive black hole in the LMC has added a new layer to our understanding of galactic evolution and the role that these enigmatic objects play in shaping the cosmos. It also raises intriguing questions about the future of the LMC and its relationship with the Milky Way. As the two galaxies continue their cosmic dance, we may see more discoveries emerge, revealing even more about the dynamic forces at play in this region of the universe.
More information: 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