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Light orbiting BH

  1. Aug 4, 2004 #1

    turin

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    Homework Helper

    I just wanted a quick affirmation. Can light orbit a black hole? That is, can light remain between two well-defined distances from the event horizon (or at a single well-defined distance, which I am leaning towards) indefinitely?
     
  2. jcsd
  3. Aug 4, 2004 #2

    DW

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    For a Schwarzschild hole it can orbit at the photon sphere [tex]r_{ps}[/tex] which is at
    [tex]r_{ps} = \frac{3GM}{c^{2}}[/tex].
    It is an unstable orbit though.
     
  4. Aug 4, 2004 #3

    turin

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    Thanks, DW. That's exactly what I was looking for.
     
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