In this artist’s conception, a runaway planet zooms through interstellar space. New research suggests that the supermassive black hole at our galaxy’s center can fling planets outward at relativistic speeds. Eventually, such worlds will escape the Milky Way and travel through the lonely intergalactic void. In this illustration, a glowing volcano on the planet’s surface hints at active plate tectonics that may keep the planet warm.
Seven years ago, astronomers boggled when they found the first runaway star flying out of our galaxy at a speed of 1.5 million miles per hour. The discovery intrigued theorists, who wondered: If a star can get tossed outward at such an extreme velocity, could the same thing happen to planets?
New research shows that the answer is yes. Not only do runaway planets exist, but some of them zoom through space at a few percent of the speed of light — up to 30 million miles per hour.
“These warp-speed planets would be some of the fastest objects in our galaxy. If you lived on one of them, you’d be in for a wild ride from the center of the galaxy to the Universe at large,” said astrophysicist Avi Loeb of the Harvard-Smithsonian Center for Astrophysics.
“Other than subatomic particles, I don’t know of anything leaving our galaxy as fast as these runaway planets,” added lead author Idan Ginsburg of Dartmouth College.