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Rewinding a black hole - Can a spinning black hole become a star?

  1. Sep 25, 2013 #1
    "Rewinding" a black hole - Can a spinning black hole become a star?

    I couldn't fit all the important prerequisites and context in the title, so I'll set up the thought experiment here. Some of these assumptions are also questions, and might be easily refuted, thus answering the main question with a "no".

    1. We have a black hole that barely satisfies the Schwarzschild radius by the increase in gravity from the spinning mass/energy. Is this possible? Maybe the typical evolution of stars makes this an impossibility. I may have the idea of "spinning object = more gravity" all wrong or maybe it doesn't apply to "singularities" and relativistic entities. I understand that the chances of a stellar object satisfying these possibly tiny tolerances and circumstances might be astronomically low, but good thing we're dealing with astronomical numbers :D I'm looking for "possible", not "probable".

    2. Through natural processes (mass/energy gain/loss, Hawking radiation?), the spinning of the black hole slows down to the point that it doesn't satisfy the Schwarzschild radius. Imagine there's a line drawn based on how fast the object is spinning. Spinning fast enough pushes us over the line and we have a black hole. Slowing down to under the line gives us "something else". I'm seeing a delicate balance of mass and spin here that has to be just right. Again, maybe this isn't possible :/

    Is this possible? Will the black hole revert from being a singularity and become a star again (neutron?), explode like a supernova, oscillate between visible/invisible, or become something entirely different?

    We could also look at this from the other perspective, and ask if it's possible to wind something up into becoming a black hole. From what I've researched this seems to be more unlikely, similar to what happens when matter builds up on a white dwarf and results in a nova, making it impossible to gain enough mass.

    I couldn't find this question being asked anywhere and thought it was worth throwing out there. Thanks for the input!
  2. jcsd
  3. Sep 25, 2013 #2


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    Spinning black holes don't follow the Schwarzschild solution, they can be described with the Kerr metric.
    This is not true. The mass of the black hole is just determined by its total energy content. Sure, a rotating star has a bit more energy than a non-rotating star, but that effect is not significant and stars have a broad range of masses anyway.

    Which tolerances or circumstances?

    That does not make sense.

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