Convective cores - why?

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  • #1
vertices
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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?
 

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  • #2
vertices
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bump:)
 
  • #3
Ignition
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Tere is just one answer, no. The core is thermodynamic system with spherical interfasis. The core takes part in the star cicle.
 
  • #4
astrorob
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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).
 
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  • #5
vertices
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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).

yes, i see it now. thanks:)
 
  • #6
Oberst Villa
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"..stars with masses greater than 1.2M(sun) have convective cores...

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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