Runaway Black Hole Escapes Its Galaxy—and It’s Leaving Baby Stars in Its Wake

A supermassive black hole that’s 10 million times the mass of the Sun is hurtling through space, leaving a trail of gas that’s spawning newborn stars in its wake. Astronomers have long theorized about runaway black holes, but none have been observed until now.

The Webb space telescope confirmed the first runaway black hole, which broke away from its home galaxy for a speedy life on the run. The black hole is one of the fastest-moving objects observed in the cosmos, traveling at a speed of 2.2 million miles per hour (1,000 kilometers per second). At that speed, it could travel from Earth to the Moon in 14 minutes, according to NASA.

Astronomers first observed a bright streak of glowing gas in 2023 using the Hubble Space Telescope, and follow-up observations with Webb confirmed it as a trail left behind by a runaway black hole. The discovery is detailed in a new study available on the pre-print server arXiv.

On the run

As it travels through space, the escaped black hole is plowing into gas ahead of it to create a massive bow shock. As the gas is heated from the motion of the black hole, it triggers the birth of new stars. The trail of newborn stars extends for 200,000 light-years behind the black hole, according to the study.

Black holes are normally housed at the center of their home galaxies. This one, however, was found approximately 230,000 light-years away from its galaxy. It must have been moving fast enough to escape the gravitational grip of its host.

So, how did the black hole make a run for it? The astronomers behind the new study believe it may have been the result of two galaxies merging together, providing a forceful kick that sent the black hole careening across the cosmos. Another possible scenario is that one of the two galaxies that merged together had a pair of binary black holes. When three black holes merge, the system becomes unstable, thereby forcing one of them out into space.

“It boggles the mind!” Pieter van Dokkum, a researcher at Yale University and lead author of the new study, told Space.com. “The forces that are needed to dislodge such a massive black hole from its home are enormous. And yet, it was predicted that such escapes should occur!”