Star Found Leaving The Milky Way At 2.7 Million Miles Per Hour

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.

One theory is that US 708 had a close encounter with a much more massive object, which sent it zipping through space. Another hypothesis explains that a shockwave from a nearby supernova could have sent it on its way. If the supernova was a Type Ia, which are believed to occur in close binary systems where the gas is stripped from a donor star onto a white dwarf star, that would be a reasonable explanation.

Scientists hope to further study US 708 to figure out the origins of HVSs.

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