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Convective cores - why?

  1. May 21, 2008 #1
    from Carol and Ostie (textbook):

    "stars with masses greater than 1.2M(sun) have convective cores due to the the highly temperature dependent CNO cycle."

    QUESTION:

    why does the fact the CNO cycle is sensitive to temperature mean that the core is convective?
     
  2. jcsd
  3. May 23, 2008 #2
    bump:)
     
  4. May 24, 2008 #3
    Tere is just one answer, no. The core is thermodynamic system with spherical interfasis. The core takes part in the star cicle.
     
  5. May 24, 2008 #4
    Hydrogen burning processes in large stars, as you've pointed out, is dominated by the CNO cycle. This is confined to the central regions of the star and so there's a large energy flux which naturally favours a convective central region.

    The resulting steep radiative gradient towards the centre makes the core unstable against convection (http://en.wikipedia.org/wiki/Schwarzschild_Criterion).
     
    Last edited: May 24, 2008
  6. May 24, 2008 #5
    yes, i see it now. thanks:)
     
  7. Jun 6, 2008 #6
    A factor of 1.2 is pretty close.... Suppose our sun would be just above that limit, and the increased luminosity would be compensated by a more distant earth orbit - would we notice that we have a star with a convective core ? As I understand it, there would be a turbulent flow, would these turbulences cause (high) fluctuations of the luminosity of the sun ?
     
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