Milky Way galaxy hurls planets out into space at 30 million mph

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When galaxies wander too close to the huge black hole at the centre of our Milky Way galaxy, planets can be 'fired' off into space at up to 30 million miles per hour.

The planets are 'slingshotted' to a significant fraction of light speed by the supermassive black hole at the heart of the Milky Way, 26,000 light years from Earth.

?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.

The planets are 'fired' off into space when a double-star system wanders too close to the supermassive black hole at the galactic center.

Scientists have already seen a star being hurled out of our galaxy at 1.5 million miles per hour - and wondered what might happen if planets were attached.

The researchers simulated what would happen to each star had a planet or two orbiting nearby.

In the simulation, gravitational forces rip the stars from each other, sending one away at high speed while the other is captured into orbit around the black hole.

They found that the star ejected outward could carry its planets along for the ride - and that the other star's planets could be 'slingshotted' outwards alone.

The second star, as it's captured by the black hole, could have its planets torn away and flung into the icy blackness of interstellar space at tremendous speeds.

A typical hypervelocity planet would slingshot outward at 7 to 10 million miles per hour. However, a small fraction of them could gain much higher speeds under ideal conditions.

Current instruments can't detect a lone hypervelocity planet since they are dim, distant, and very rare. However, astronomers could spot a planet orbiting a hypervelocity star by watching for the star to dim slightly when the planet crosses its face in a transit.

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