The mass of the supermassive black hole in the center of the Large Magellanic Cloud, a small satellite galaxy of the Milky Way, is about 600,000 solar masses.
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 thousands of kilometers per second — 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). Image credit: CfA / Melissa Weiss.
“The halo of our Milky Way Galaxy contains a small number of stars that are traveling faster than the local escape velocity on trajectories that will carry them into intergalactic space,” said Dr. Jesse Han from the Harvard & Smithsonian’s Center for Astrophysics and colleagues.
“One mechanism for producing such hypervelocity stars is the Hills mechanism: when a close binary star strays near a supermassive black hole, one star can be captured, while the other is ejected at velocities that can reach over 1,000 km per second.”
In their new study, the astronomers traced the paths with ultra-fine precision of 21 hypervelocity stars in the Milky Way’s outer halo.
They confidently classified 16 of these stars and found that 7 of them were consistent with originating from the center of the Milky Way.
However, the other 9 stars were consistent with originating from the center of the Large Magellanic Cloud, which is located around 160,000 light-years away from us.
“It is astounding to realize that we have another supermassive black hole just down the block, cosmically speaking,” Dr. Han said.
“Black holes are so stealthy that this one has been practically under our noses this whole time.”
The researchers found the Large Magellanic Cloud’s black hole by using data from ESA’s Gaia mission.
They also used an improved understanding of the dwarf galaxy’s orbit around the Milky Way recently obtained by other astronomers.
“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,” said Dr. Kareem El-Badry, an astronomer at Caltech.
“By combining these data with our new theoretical models for how these stars travel, we made this remarkable discovery.”
“The only explanation we can come up with for these data is the existence of a monster black hole in our galaxy next door,” said Dr. Scott Lucchini, an astronomer at the Harvard & Smithsonian’s Center for Astrophysics.
“So in our cosmic neighborhood it’s not just the Milky Way’s supermassive black hole evicting stars from its galaxy.”
A paper reporting this discovery will be published in the Astrophysical Journal.
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Jiwon Jesse Han et al. 2025. Hypervelocity Stars Trace a Supermassive Black Hole in the Large Magellanic Cloud. ApJ, in press; arXiv: 2502.00102
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