I'm sure we've all seen the diagrams of various layers of element fusion from hydrogen to silicon in a star that's just about to go supernova.

onion shell diagram of fusing layers (Picture from courses.lumenlearning.com)

I suspect these pictures grossly exaggerate the relative radii at which these fusing layers occur for the sake of readability. What would a more accurate to-scale picture of these fusing layers look like?

Now, I assume the answer will vary significantly based on the mass of the star, and I suspect in certain mass regimes some layers will not be fusing at all. I can think of a few other variables that may affect the answer too.

So in CYA fashion, I'll leave it up to the answerer to identify specific illustrative or interesting cases, as I'm not after a specific answer but rather a general feel for how large some of the layers are in comparison to the others.

  • $\begingroup$ While there could be well defined borders where fusion processes stop and/or transition, I would like to point out that in terms of composition/P/T.... continuity is a condition all over the star radius, for core active stars. To say that the layers are there for processes but not for a sort of "visible appearance". Just for sake of discussion. $\endgroup$ – Alchimista Sep 18 '19 at 10:39
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    $\begingroup$ Sorry, I don't know where to find the core shell sizes, but at the end of en.wikipedia.org/wiki/Type_II_supernova#Formation there's a table of the burning processes in a 25 solar mass star core that gives the mean density of each shell, and the duration of each process. The table links to the articles detailing each burning process. $\endgroup$ – PM 2Ring Oct 19 '19 at 13:07

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