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It does happen with a star but the compression of hydrogen in a star by the gravity causes fusion which keeps the star inflated so it doesn't collapse. A black hole doesn't pull in objects any more than the star it once was, it just no longer has the fusion to keep it from collapsing into a compact form. A black hole is a compressed star. If you compressed the Earth into the size of a pea, it too would be a black hole but only with the same gravity as Earth has now, it's just that you could get a lot closer the the center of the Earth.
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Space is a vacuum..there arnt many clouds of hydrogen or oxygen or any other gas just floating around in space. Thus the term vacuum. When there is gas it usually coagulates and forms a planet like Jupiter or or a sun (star). You said what prevents a star from "moving" through a cloud of gas.. Most galaxies suns and planets probably have set patters after forming much like ours...In order for what your talking about to happen our sun would have to run into another sun or planet such as Jupiter for fuel and as it stated to burn out run into another and another and another to stay burning...stars can be 20 or a hundred or more light years apart..tho they have been known to collide its probably a rare occurrence and not something that could happen to one star over and over again to where it could burn forever.
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Well what prevents the star from collapsing in on it's self is the energy being released from nuclear fusion. The intense pressure from the gravity compresses light elements like hydrogen and Helium 3 so much that fuse. Hydrogen fuses to helium 3 and so on this continues until it starts to fuse elements do not release energy when fused. They actually require energy to fuse together.
Once the star has burned through the majority of its light elements it will collapse on its self. As this collapse happens a shock wave is released out and it goes super nova (if it's large enough). As that happens some of the heavy matter collapse into a point and either forms a Pulsar or a black hole.
If a star were to drift or merge with more hydrogen it would grow. Let's say the sun merged with another star of similar size it would just become bigger and burn hotter. The bigger the star the faster the fusion happens and the shorter the life.
Did you know.. That jupitor actually creates about the same amount of heat as it recieves from the sun? This is because of the intense pressure Jupitor from the gravity. It is believed that IF Jupitor were to gain more mass its diameter would actually shrink from the increased gravity and compression of the gas.
Basically the entire reason a star doesn't collapse to infinite density is because of nuclear fusion as I said that fusion releases energy which pushes out and prevents that from happening. Once the fusion ends the star will eventually collapse into an infinite point.
Once the star has burned through the majority of its light elements it will collapse on its self. As this collapse happens a shock wave is released out and it goes super nova (if it's large enough). As that happens some of the heavy matter collapse into a point and either forms a Pulsar or a black hole.
If a star were to drift or merge with more hydrogen it would grow. Let's say the sun merged with another star of similar size it would just become bigger and burn hotter. The bigger the star the faster the fusion happens and the shorter the life.
Did you know.. That jupitor actually creates about the same amount of heat as it recieves from the sun? This is because of the intense pressure Jupitor from the gravity. It is believed that IF Jupitor were to gain more mass its diameter would actually shrink from the increased gravity and compression of the gas.
Basically the entire reason a star doesn't collapse to infinite density is because of nuclear fusion as I said that fusion releases energy which pushes out and prevents that from happening. Once the fusion ends the star will eventually collapse into an infinite point.