Looks like the Milky Way just isn't good enough for some stars. Scientists involved in the Sloan Digital Sky Survey have discovered a new breed of "hypervelocity" solitary stars that are moving at speeds great enough to escape the Milky Way's gravitational pull.

What's puzzling, however, is the fact that none of the stars seem to have originated from the Milky Way's center.

"These new hypervelocity stars are very different from the ones that have been discovered previously," said Lauren Palladino, lead author on the study from Vanderbilt University.

"The original hypervelocity stars are large blue stars and appear to have originated from the galactic center. Our new stars are relatively small — about the size of the sun — and the surprising part is that none of them appear to come from the galactic core."

Researchers estimate that stars need a boost of over 1 million miles per hour against the motion of the Milky Way in order to escape the galaxy. Typical hypervelocity stars get this kick from the Milky Way's supermassive black hole (one that weighs in at around 4 million suns) in the middle. Binary star systems get pulled into the black hole, and as one gets eaten, the other gets flung out at tremendous speeds.

Due to the composition of the stars, the scientists have concluded that they do not originate from the center, but the puzzle still remains incomplete.

"The big question is: what boosted these stars up to such extreme velocities? We are working on that now," said Kelly Holley-Bockelmann, assistant professor of astronomy at Vanderbilt University.

You can read the full published study detailing the findings in The Astrophysical Journal.