The researchers created simulations that examined what would happen if each star had at least one planet orbiting nearby. They found that up to 10 percent of planets tightly orbiting one of the stars could stay bound as the star is flung outward. The other star that is captured by the black hole could also have its planet ripped away from it, and this planet would then be pitched into interstellar space at intensely fast speeds as well.
"We were trying to predict, if you have planets around each of the stars in the binary system, what fraction of the planets might go along with the hypervelocity star for the ride," Loeb told SPACE.com. "What we found is that some of them get expelled at high speeds, up to a few percent of the speed of light. Some of the planets get ripped apart from the host stars and get sent out at high speeds, and they also become hypervelocity planets this way."
These planets would travel through space at unparalleled velocities, the researchers said.
A typical runaway planet would likely dash outward at 7 to 10 million mph (11.3 to 16.1 million kph), but given the right circumstances, a small fraction could have their speeds boosted to up to 30 million mph (48.3 million kph).
"It's like a pinball machine," Loeb said. "Things are kicking around, and if things happen to move in just the right way, a planet could get kicked out at a much higher speed than other planets."
Eventually, these hypervelocity planets will escape the Milky Way and travel through interstellar space on a wild ride, he added.