Am I right to think that black holes are stars that are so dense and heavy that radiation and matter cannot leave from it's surface?
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2$\begingroup$ Probably not. A black hole isn't really a star, and it doesn't have a surface. See physics.stackexchange.com/a/557985/123208 & physics.stackexchange.com/a/7913/123208 $\endgroup$– PM 2RingCommented Feb 27 at 10:23
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1$\begingroup$ I've hidden a comment that should have been an answer, and a number of other comments discussing it. To post a brief answer, please post an answer but don't type very much in the answer box. $\endgroup$– rob ♦Commented Feb 27 at 14:45
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2 Answers
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Am I right to think that blackholes are stars ...
No. A typical definition of a star is a "luminous spheroid of plasma held together by self-gravity" (note that this definition of a star not only excludes black holes but also white dwarfs and neutron "stars" too).
It is true that some (and maybe most or even all) black holes originated as stars before they ran out of fuel and collapsed. However, there are at least two theoretical routes to forming a black hole that do not involve forming a star first - they are primordial black holes and direct collapse black holes.
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$\begingroup$ Maybe it's worth to mention that if exotic objects could be taken into consideration (such as quark "star"), then star definition exclusion list would be much longer ;-) $\endgroup$ Commented Feb 27 at 15:22
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I think you are envisioning a black hole as a traditional star that is simply invisible because all its light and heat emitted is pulled backwards and cannot escape.
This is not the case. A black hole is a region of spacetime where time and space behave differently. In a traditional black hole (barring some very modern papers), no extended matter can exist inside, because it will inexorably fall inward to the center.
