Superfast Planets Fly Through Space at 30 Million MPH

   on 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.

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.

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