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Formation of a black hole

  1. Jan 12, 2010 #1
    Hi,

    I'm trying to understand how exactly a black hole fits into the evolution of red supergiants, especially in terms of a timeline. I understand that when the core of the star collapses, it reaches a point where the neutron pressure overcomes it's gravitational force and this deceleration (and bounce back) of matter causes the shock wave that creates a type II supernova.
    However, does this only apply to cores less than the chandrasekhar limit which form neutron stars or also to those above that limit which form black holes? I can't see how a supernova could be caused when there isn't enough neutron pressure to halt the core collapse and therefore cause the shock wave. So my question is basically, would there be a supernova when (just before) a black hole is created?

    I'm pretty sure I'm missing something here but I can't seem to find what it is...
     
  2. jcsd
  3. Jan 12, 2010 #2

    mgb_phys

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    You can still have an outgoing shock wave even if you don't form a neutron star surface.
    The outer envelope of the star expands to form the supernova driven by the energy given off by the collapsing core - it doesn't really matter what the core ends up becoming.
     
  4. Jan 12, 2010 #3
    Oh, I read (on wikipedia and some books) that a shock wave causes the supernova, and that this shock wave is caused by the bounce back of matter. I guess you would get a lot of energy converted from gravitational potential as the core collapses?
     
  5. Jan 12, 2010 #4

    mgb_phys

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    Yes it's not a shockwave bouncing off the neutron star surface, its an outgoing shockwave driven by the gravitational energy of the core collapse
     
  6. Jan 12, 2010 #5
    Ok, that makes sense. Another simple question. Would a collapsing core become a neutron star first, or would it become a black hole in one fluid movement? Thanks for your help!
     
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