Stars aren’t often able to drift out of the Milky Way galaxy that we call home, primarily because the speed at which a star would drift is not great enough to rest it from the gravitational grip of our enormous galaxy. But astronomers recently spotted a star, named US 708, rocketing out of the galaxy at an impressive 4.3 million kilometers per hour, or 2.7 million miles per hour. It was likely given its speed by a nearby supernova.
Stars have been observed obtaining the needed velocity to release itself from the grip of the galaxy’s gravity, but this is so far the fastest ever observed. It is also the only known compact helium star to achieve hypervelocity star (HVS) status.
New measurements published in Science cast significant doubt on the previously favored theory for where HVSs get their incredible speeds.
“According to the widely accepted theory for the acceleration of hypervelocity stars, a close binary is disrupted by the supermassive black hole (SMBH) in the center of our Galaxy, and one component is ejected as a HVS,” the authors note.