this is from S&T
A Runaway Star with a Story To Tell
Just five years ago the first
hypervelocity star was confirmed, by Warren Brown of the Harvard-Smithsonian Center for Astrophysics. Now about 16 are known. These are stars moving through space so fast, upwards of several hundred kilometers per second, that they will escape the Milky Way's gravity and forever roam the intergalactic void. Their discovery had to wait for very efficient surveys; only about one in 100 million stars is going so fast.
Several possible mechanisms can fling a star with that much speed. But the most productive of them seems to be happening at a single, very special place. If a binary star falls close enough to the supermassive black hole at the Milky Way's center, the binary can be disrupted in such a way that one star is trapped around (or in) the hole and the other is slung away with
preternatural velocity. This is thought to account for most of the escaping 16.
http://www.skyandtelescope.com/news/100993774.html