Helium Burning. . . and Beyond

The long description of the proton-proton and CNO cycles seems not to have gotten us very far in our solution to the fundamental question of this chapter Where did the heavy elements come from Thus far, we have been able to show only that hydrogen nuclei can fuse in the core of stars to form helium nuclei, hut there is a lot more to the story of what happens in the center of stars, a story that will eventually answer the question of the origin of the heavy elements. 

The next step in that story begins when nearly all of the hydrogen at a star s core has been exhausted, that is, has been converted to 

In the primary reaction helium burning, three alpha particles (helium nuclei) are converted to a carbon nucleus, a process sometimes referred to as the triple helium process, or triple alpha particle process  

An alert chemistry student may question the legitimacy of this equation because it suggests that three bodies (the three alpha particles) 

The reason the reaction can occur at all is that it actually consists of two steps. In the first step, two alpha particles combine to form a single beryllium-8 nucleus  

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