Nucleosynthesis triple-alpha process

Primary nucleosynthesis Some astronomical evidence suggests that 13C nucleosynthesis has a primary component that is, a production rate in stars that does not rely on the prior presence of carbon in the interstellar gas from which the stars formed (see below). This is attested to by nitrogen also having a primary component (see 14N). This can occur in a red AGB star, which is creating new 12C by the triple-alpha process in a helium-burning shell beneath its H-containing envelope. Such stars undergo... 

Schematic diagram illustrating the triple alpha process that occurs during stellar nucleosynthesis. [Attributed to Borb, reproduced from https //en.

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