– Unknown Force Kicks Stars Out of Milky Way. Really. (TIME, Jan 10, 2014):
If you could see it from the outside, the Milky Way would look like a majestic spiral of stars and glowing gas, rotating on its axis once every 200 million years or so like a gigantic, pinwheel 100,000 light-years across. Up close, though, you’d see that each star is jostling along on its own, moving through an entirely independent orbit. It’s more like an unruly crowd, going in the same approximate direction at the same approximate speed, than a military formation marching in lockstep.
At least a few stars, however, are headed somewhere else entirely, and in a big hurry. They’re known as hypervelocity stars, and they’re going so fast that they’re on their way out of the Milky Way altogether. While the astronomers think they have an explanation for the 18 hypervelocity stars discovered since 2005, a new group of 20, just announced at a meeting of the American Astronomical Society outside of Washington, DC, seems to make no sense at all.
“What’s going on?” asks Vanderbilt University grad student Lauren Palladino, lead author of a paper in the Astrophysical Journal describing these cosmic speedsters. “We don’t know.”