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Black hole size

  1. Oct 27, 2011 #1
    what is the smallest possible size of a black hole?
  2. jcsd
  3. Oct 27, 2011 #2
    I'm taking it you mean the centre-singularity? I heard it could be as small as an atom, or something called planck length...

    Wondered this myself as well.
  4. Oct 27, 2011 #3


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    A black hole the mass of the sun is about 3 km in radius (Schwarzschild radius or radius of the event horizon), and the radius is directly proportional to the mass. If you can compress matter to a high enough density you can theoretically make a black hole arbitrarily small, but practically there is no known way to create black holes except in the collapse of massive stars. The smallest black hole that we know of is about 5 solar masses, so about 15 km in radius. There is a hypothesis that smaller black holes could have been created during the very early phase of the big bang, but these have never been seen.
  5. Oct 27, 2011 #4
    I have wondered in the past if there would have been black holes from the early phase of the big bang, it definitely seems possible.

    One question. Is it true that the larger stars with more mass will become smaller black holes as they will collapse further under their own pressure? Or does it not work like that? I don't know much about physics so excuse any questions that might be stupid haha
  6. Oct 27, 2011 #5


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    No. The Schwarzschild radius of a black hole is directly proportional to the mass, so the larger the mass, the larger the black hole.
  7. Oct 27, 2011 #6
    Thank you for clearing that up
  8. Oct 27, 2011 #7
    will the 15 km black hole also have 'event horizon'?
  9. Oct 27, 2011 #8

    George Jones

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    Yes. If it didn't, it wouldn't be a black hole.
  10. Oct 27, 2011 #9
    are we having proof for the existance of event horizon ? or can we explain a blackhole with out the concept of event horizon?
  11. Oct 28, 2011 #10


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    The smallest possible black hole would weigh a planck mass [which is actually pretty enormous compared to other planck units]. It's event horizon would be a planck length. It is believed such a tiny black hole would evaporate via Hawking radiation in about a planck time.
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