Fastest Star Ever Being Flung Out of the Milky Way

Astronomers have discovered the fastest star ever known, dubbed US 708, hurtling through the galaxy after a massive supernova ejected it into space, and now it appears to be moving so fast that it is being flung out of the Milky Way altogether.

US 708, first discovered in 2005, wasn't always the fastest star in the galaxy. It was once a normal red giant star in a binary star system. That is, until it was stripped of all its hydrogen - leaving a helium core - by a hungry orbiting partner. Researchers believe this greedy appetite caused the partner to explode, thereby blasting away US 708.

The star, now transformed into a hypervelocity star, is traveling at about 746 miles (1,200 km) per second, fast enough to actually leave the Milky Way galaxy in about 25 million years.

"At that speed you could travel from Earth to the moon in five minutes," Eugene Magnier from the University of Hawaii, and a co-author of the paper, told Reuters.

When it does leave our galaxy, it will then transform into a white dwarf star, researchers say.

This is not the first time astronomers have found a star speeding fast enough to escape the Milky Way, but it is the first reportedly slingshot by a supernova explosion. The 20 other hypervelocity stars were likely thrown after getting too close to the supermassive black hole lurking in the center of our galaxy.

"US 708 does not come from the galactic center. We don't know any other supermassive black hole in our galaxy. One needs one of those. A smaller, stellar-mass black hole formed by the collapse of a massive star can't do the job," Stephan Geier from the European Southern Observatory, who led the study, told Discovery News.

If the new findings are confirmed, it could provide valuable insight into how supernova explosions occur, such as type I supernovae, which are used to help measure the expansion of the Universe.

The results were published in the journal Science,

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