Stop the presses: Hundreds of rogue black holes are on the loose in the Milky Way!

It’s a good thing that black holes are only dangerous if you’re within about 100 kilometres of them. And the Milky Way is a big enough place that we needn’t worry, says Kelly Holley-Bockelmann, an astronomer at Pennsylvania State University.

Her research team discovered the errant black holes – each of which is 100 to 1,000 times the mass of our sun — by studying clumps of ancient stars known as globular clusters. These are rough environments, in which black holes are constantly sinking toward the center of the cluster, occasionally meeting in a violet merger that throws one or the other of them out of the cluster at speeds up to 9 million miles per hour. Holley-Bockelmann’s computer simulations show that scientists haven’t spotted nearly as many black holes getting kicked out of globular clusters as one might expect. And so, she says, there must be extra black holes lurking there, invisibly — some of the biggest rogues ever spotted in our galaxy.