convective cores - why?


by vertices
Tags: convective, cores
vertices
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#1
May21-08, 01:13 PM
P: 230
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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vertices
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#2
May23-08, 08:32 PM
P: 230
bump:)
Ignition
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#3
May24-08, 08:39 AM
P: 55
Tere is just one answer, no. The core is thermodynamic system with spherical interfasis. The core takes part in the star cicle.

astrorob
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#4
May24-08, 08:48 AM
astrorob's Avatar
P: 141

convective cores - why?


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).
vertices
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#5
May24-08, 10:43 AM
P: 230
Quote Quote by astrorob View Post
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:)
Oberst Villa
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#6
Jun6-08, 05:33 PM
P: 145
Quote Quote by vertices View Post
"..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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