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It says:
No. In principle, there can be overlaps, see Supernova. The onion burning progenitors burn carbon and helium simultaneously. Said: Rursus ( ☻) 11:25, 24 October 2008 (UTC)
I guess the point is that when helium density drops sufficiently, helium fusion no longer produces enough energy in the core to prevent the core from contracting significantly. I also assume that the core becomes gradually more compact and hotter as the helium gets used up, and the helium fusion will proceed faster. The inert products of the helium burning must also build up in the core: whilst the core is not hot enough to fuse these they will not contribute to the gas pressure keeping the core from contracting.
So I would conclude that the final stage of helium buring before the core contracts and ignites carbon fusion would proceed much faster as fusion is very sensitive to increases in temperature. It might be a close thing as to whether the helium in the core runs out before or after the carbon fusion begins, and might depend on the mass, metallicity and other properties of the star. Perhaps the article would be correct if the statement Carbon burning starts when helium burning ends were changed to something like Carbon burning starts when the amount of helium in the core drops below a level where helium fusion alone produces sufficient energy to maintain the star in hydrostatic equilibirum but this seems a bit of a mouthful... Puzl bustr ( talk) 18:10, 24 September 2009 (UTC)
Added a term for the energy produced for the Mg-23 process, calculated from the masses of the terms in AMU. Puzl bustr ( talk) 14:03, 25 September 2009 (UTC)
Added a reference for the nuclear equations Puzl bustr ( talk) 20:29, 9 October 2009 (UTC)
What we like to do for the OP's point is make a distinction between hydrostatic and explosive carbon burning. In the former case, the the quoted text purported to be wrong is correct. This is also a useful way to keep the article from having too many qualifiers. In this sense, after a general description which applies to all types of carbon burning, the major sections should be quiescent and explosive (or hydrostatic and non-equilibrium...whichever terms you prefer). DAID ( talk) 18:04, 18 November 2009 (UTC)
I re-wrote the section to remove an erroneous (for masses below 10 solar) reference to red supergiant stars and instead mention Asymptotic Giant Branch stars. I used the Ostlie reference to expand the discussion of carbon fusion and explain the basic variations depending on the mass of the star. Hope this is enough to reduce the warnings on the page. Puzl bustr ( talk) 12:03, 17 October 2009 (UTC)
I added these references as open-access ones. Also added a section on neutrino losses with the Clayton ref. Puzl bustr ( talk) 21:11, 19 October 2009 (UTC)
This
level-5 vital article is rated C-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | |||||||||||||||||||||
|
It says:
No. In principle, there can be overlaps, see Supernova. The onion burning progenitors burn carbon and helium simultaneously. Said: Rursus ( ☻) 11:25, 24 October 2008 (UTC)
I guess the point is that when helium density drops sufficiently, helium fusion no longer produces enough energy in the core to prevent the core from contracting significantly. I also assume that the core becomes gradually more compact and hotter as the helium gets used up, and the helium fusion will proceed faster. The inert products of the helium burning must also build up in the core: whilst the core is not hot enough to fuse these they will not contribute to the gas pressure keeping the core from contracting.
So I would conclude that the final stage of helium buring before the core contracts and ignites carbon fusion would proceed much faster as fusion is very sensitive to increases in temperature. It might be a close thing as to whether the helium in the core runs out before or after the carbon fusion begins, and might depend on the mass, metallicity and other properties of the star. Perhaps the article would be correct if the statement Carbon burning starts when helium burning ends were changed to something like Carbon burning starts when the amount of helium in the core drops below a level where helium fusion alone produces sufficient energy to maintain the star in hydrostatic equilibirum but this seems a bit of a mouthful... Puzl bustr ( talk) 18:10, 24 September 2009 (UTC)
Added a term for the energy produced for the Mg-23 process, calculated from the masses of the terms in AMU. Puzl bustr ( talk) 14:03, 25 September 2009 (UTC)
Added a reference for the nuclear equations Puzl bustr ( talk) 20:29, 9 October 2009 (UTC)
What we like to do for the OP's point is make a distinction between hydrostatic and explosive carbon burning. In the former case, the the quoted text purported to be wrong is correct. This is also a useful way to keep the article from having too many qualifiers. In this sense, after a general description which applies to all types of carbon burning, the major sections should be quiescent and explosive (or hydrostatic and non-equilibrium...whichever terms you prefer). DAID ( talk) 18:04, 18 November 2009 (UTC)
I re-wrote the section to remove an erroneous (for masses below 10 solar) reference to red supergiant stars and instead mention Asymptotic Giant Branch stars. I used the Ostlie reference to expand the discussion of carbon fusion and explain the basic variations depending on the mass of the star. Hope this is enough to reduce the warnings on the page. Puzl bustr ( talk) 12:03, 17 October 2009 (UTC)
I added these references as open-access ones. Also added a section on neutrino losses with the Clayton ref. Puzl bustr ( talk) 21:11, 19 October 2009 (UTC)