Runaway planets hurtling through universe

Posted by Emma Woollacott

Runaway planets could be hurtling through space at up to 30 million miles an hour, torn from their suns by a black hole.

Such hypervelocity planets could be produced, say astrophysicists, when a double-star system wanders too close to the supermassive black hole at the galactic center.

Strong gravitational forces would tear the stars away from each other, capturing one in orbit and flinging the other away at high speed.

"These warp-speed planets would be some of the fastest objects in our Galaxy," says astrophysicist Avi Loeb of the Harvard-Smithsonian Center for Astrophysics.

"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."

The researchers simulated what would happen if each star had a planet or two orbiting nearby. They found that the star ejected outward could carry its planets along for the ride - but the second star, as it was captured by the black hole, could have its planets torn away and flung into space.

A typical hypervelocity planet, they say, would be fired out at seven to 10 million miles per hour - but some could reach much higher speeds. Eventually, they'd escape the Milky Way altogether.

"Travel agencies advertising journeys on hypervelocity planets might appeal to particularly adventurous individuals," says Loeb.