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Thread: How big would John Mitchell's dark star have to be?

  1. #1
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    How big would John Mitchell's dark star have to be?

    That is, a normal star that is large enough to gravitationally attract light. Is there an absolute limit to how large stars can get?
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  2. #2
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    He was apparently thinking of an object at least as dense as the Sun, but with 500 times the diameter. That works out about right; such an object would have a mass of at least 125 million solar masses, which would have a Schwarzschild radius of 370 million kilometers, which is indeed a little more than 500 times the Sun's radius of 700,000 km.

    The largest stars we know of are about 130 solar masses; we think there may be limits on the possibility of larger stars forming. But of course there are indeed supermassive black holes as big or bigger than what Mitchell was envisioning.
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  3. #3
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    M87* (I think the asterisk means "black hole") is about 6.5 billion solar masses.
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  4. #4
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    Quote Originally Posted by Roger E. Moore View Post
    M87* (I think the asterisk means "black hole") is about 6.5 billion solar masses.
    Andromeda would be a closer example (pun intended). It's BH is about 230 million solar masses and you only need about 125 million solar masses for a BH (EH) radius of 370 million km.
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