I.1.2: Errata

In the previous post, I mistakenly stated that elements heavier than helium must be formed within a supernova.   A friend of mine was kind enough to point this out:

Are abundant supernovae actually required to produce a sufficient abundance of carbon, nitrogen, and oxygen? My impression (possibly mistaken) was that somewhat smaller stars readily produce those elements. Of course, supernovae are required to produce a host of other biologically important elements, so I'm not disputing the underlying point. Just a niggling concern about accuracy, if I were editing for publication.

My response:

You are entirely right about nucleosynthesis. I was mistaken -- stars about the size of our sun are capable of producing everything up to carbon and oxygen. Elements from nitrogen to iron are formed inside massive stars (even before they go supernova). Supernovas are only needed to (1) produce elements heavier than iron and (2) distribute the elements the star has already produced. I'll have to fix that post ... I appreciate the heads up.