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[探索发现] 2015-04-10 BBC:星光七纪元-24

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This tiny companion to the bright Dog Star, was dubbed the pup. And by 1922, this new type of the star had an official classification. It was called a white dwarf. But naming it was the least of scientists’ problems. When they compared its size to its mass, something extraordinary emerged. It was denser than anything on earth, denser than anything previously imagined. They were a type of star that shouldn’t exist. The burnt down remains if one of fusion has stopped. The fuel exhausted, so how can they still shine? Mysteries, that have long intrigued professor John Aleis. Throughout their lives, stars make their energy by fusing together lighter nuclei to make heavier ones. They start off with hydrogen, then the helium, then they go on to fuse together helium to make carbon and oxygen. And as the time goes on they burn out more and more this fuel, until eventually, it’s like a car, even run out the gas. With its helium burning days at the end, the white dwarf active life is over. All it’s left with is a dead core of carbon and oxygen. It’s not really a star at all, but a cinder and an internal battle raging in the heart of the star, between gravity and fusion, now has a clear victor.
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