Mystery of speeding star unravelled

Carnegie astronomers have determined a mystery star, speeding away from the Milky Way at 1.6 million miles per hour is from our neighboring galaxy.  

The Carnegie Institution for Science team said the star, dubbed HE 0437-5439, is about nine times the mass of our Sun, about 35 million years old, and is one of ten so-called hypervelocity stars so far found speeding away from the Milky Way, researchers said. 

But this one is different, researchers said:  “Their type, speed, and age make them consistent with having been ejected from the center of our galaxy, where we know there is a super-massive black hole. This star, discovered in 2005, initially appeared to have an elemental makeup like our Sun’s, suggesting that it, too, came from the center of our galaxy. But that didn’t make sense because it would have taken 100 million years to get to its location, and HE 0437-5439 is only 35 million years old.” 

Recent observations say the start was ejected from our neighboring galaxy, called Large Magellanic Cloud by a yet-to-be-observed massive black hole.

The Carnegie astronomers were able to measure the relative abundances of certain elements for the first time in any hypervelocity star. The relative abundance of key elements tells them where a star originated, the group said. Based on the speed of the star’s rotation measured by the discoverers, and confirmed by this team, the astronomers believe that the star was originally part of a binary system. The binary could have passed close to a black hole 1,000 the mass of the Sun. As one star was pulled into the black hole, the other was whipped into frenzy and flung out of the galaxy.  

NASA’s Chandra X-ray Observatory grabbed a picture of one of the hypervelocity stars screaming out of the galaxy at 3 million miles per hour.  At this rate, the star, called RX J0822-4300, is destined to escape from the Milky Way after millions of years, even though it has only traveled about 20 light years so far. 

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