Runaway Planets At 30 Million Miles Per Hour Possible
March 22, 2012

Runaway Planets At 30 Million Miles Per Hour Possible

Harvard-Smithsonian Center for Astrophysics researchers have determined that some planets are flying around in space at 30 million miles per hour.

These hypervelocity planets are produced in the same way as the hypervelocity star that was found seven years ago traveling around the Milky Way Galaxy at 1.5 million miles per hour.

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

A hypervelocity star forms as a double-star system wanders too close to the supermassive black hole at the center of the galaxy.  Strong gravitational forces rip the stars apart from each other, sending one away at high speeds while the other orbits around the black hole.

The researchers in the study simulated what would happen if each of the stars had a planet or two orbiting it.

They found that the star that is ejected outward could carry its planets along for the ride, and the star sucked in to the black hole's orbit could have its planets torn away and tossed into interstellar space at tremendous speeds.

A typical hypervelocity planet would shoot outward at 7 to 10 million miles per hour, but the researchers found that a small fraction of them could gain speeds of up to 30 million miles per hour.

"Other than subatomic particles, I don't know of anything leaving our galaxy as fast as these runaway planets," lead author Idan Ginsburg of Dartmouth College said.

Astronomers do not currently have the instruments to detect a lone hypervelocity planet because they are so dim, distant and rare.  However, they do have a chance to spot a hypervelocity planet still orbiting around its hypervelocity star.

The researchers found that the chances of spotting a hypervelocity planet orbiting a star would be around 50 percent.

"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," said Ginsburg.

The researchers will be publishing their findings in the Monthly Notices of the Royal Astronomical Society.


Image Caption: 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. Credit: David A. Aguilar (CfA) [ High-res Image ]