Black hole 'evicted' star from Milky Way

July 23, 2010 at 8:50 PM
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CAMBRIDGE, Mass., July 23 (UPI) -- A "hypervelocity" star speeding out of our galaxy was sent on its way by a violent encounter with a black hole at the heart of the Milky Way, scientists say.

The hypervelocity star is one of the fastest ever detected, heading out of our galaxy at a speed of 1.6 million mph, a Space Telescope Science Institute release said Thursday.

The star was the lone survivor of a trio of stars that wandered too close to the black hole, which captured one and threw the other two out of the Milky Way with such violence they coalesced into a single super-hot blue star, scientists say.

About 16 hypervelocity stars have been discovered since 2005 and most are thought to be exiles from the heart of our galaxy. But scientists used the Hubble space telescope for the first direct observation linking a fast-flying star to a galactic center origin, the release said.

"Using Hubble, we can for the first time trace back to where the star comes from by measuring the star's direction of motion on the sky. Its motion points directly from the Milky Way center," astronomer Warren Brown of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., says.

"These exiled stars are rare in the Milky Way's population of 100 billion stars," Brown said. "For every 100 million stars in the galaxy lurks one hypervelocity star."

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