Supermassive Black Hole Likely Lurking in Milky Way's Nearest Neighbor

Astronomers have found what appears to be the closest supermassive black hole outside of our own Milky Way galaxy. This giant black hole is in the Large Magellanic Cloud, the closest satellite galaxy to our own.

To make this discovery, researchers traced the paths of 21 stars on the outskirts of the Milky Way using data from the European Space Agency's Gaia mission. These "hypervelocity" stars are traveling so fast that they will escape the gravitational clutches of the Milky Way or any nearby galaxy.

Like forensic experts recreating the paths of bullets, the researchers were able to determine where these hypervelocity stars came from. They found that about half are linked to the supermassive black hole at the center of the Milky Way. However, the other half originated from somewhere else: a previously unknown giant black hole in the Large Magellanic Cloud, which lies about 160,000 light-years away.

"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," says Kareem El-Badry, assistant professor of astronomy at Caltech and the second author of a new study about the results appearing in The Astrophysical Journal. El-Badry is an experienced black hole hunter who previously discovered the nearest known stellar-mass black hole to Earth, lying 1,600 light-years away.

"By combining these data with our new theoretical models for how these stars travel, we made this remarkable discovery," he says.

Jesse Han of the Center for Astrophysics | Harvard & Smithsonian (CfA), who led the new study, says, "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."

Read the full story from CfA here.

A paper describing these results has been accepted for publication in The Astrophysical Journal and is available here.