Roger Moore on Nostr: I'm not sure, but I'd guess it has to do with the CNO cycle. In the CNO cycle, carbon ...

I'm not sure, but I'd guess it has to do with the CNO cycle. In the CNO cycle, carbon and nitrogen absorb protons to transmute into nitrogen or oxygen. Some of those nuclei are unstable and undergo reverse beta decay, so 13N > 13C and 15O > 15N. The key is that going to the unstable nuclei is less favorable than going to stable ones. So 14N + 1H > 15O is slow compared to 15N + 1H > 12C + 4He. The net result is stars have a lot more 14N than 15N.