Superfast Planets Fly Through Space at 30 Million MPH

By Amir Khan | March 23 2012 3:52 PM

Planets get flung across the galaxy at mind-boggling speeds of up to 30 million mph (48 million km/h) after encountering black holes, according to new research.

David A. Aguilar

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.

Sponsorship Link

When solar systems with two stars come too close to a black hole, the gravitational force drags one star into orbit around the black hole and sends the other outward at superfast speeds.

Seven years ago, astrophysicists first spotted a star exiting the Milky Way at 1.5 million miles per hour (2.5 million km/h).

Researchers simulated a hypervelocity star to see what would happen to any planets in its orbit and found that orbiting planets may go along for the ride.

These warp-speed planets would be some of the fastest objects in our galaxy. Avi Loeb, study coauthor and astrophysicist at the Harvard-Smithsonian Center for Astrophysics, said in a statement. 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.

Most planets would be expelled at 7 to 10 million miles per hour (11 to 16 million km/h), according to the models, but a fraction under ideal circumstances could accelerate to speeds that clock at 4 percent of the speed of light, the authors wrote.

Other than subatomic particles, I don't know of anything leaving our galaxy as fast as these runaway planets, Idan Ginsburg, study coauthor and astrophysicist at Dartmouth College, said in a statement.

Technological limitations mean astromoners can't detect hypervelocity planets that are dim, distant and rare, but researchers said they might be able to spot a hypervelocity planet by looking for a dark spot that would occur when the planet crosses the star's face.

If a star does have a hypervelocity planet orbiting it, the chances of seeing the planet would be almost 50 percent because it would be in a very tight orbit, researchers said.

With one-in-two odds of seeing a transit, if a hypervelocity star had a planet, it makes a lot of sense to watch for them, Loeb said.

The journal Monthly Notices of the Royal Astronomical Society published the paper on March 14.