1. The problem statement, all variables and given/known data I understand the rest of the cycle, the way my textbook has it, which is: 12C→13N→13C→14N→15O→15N→12C+4He The portion in bold is what I don't understand. 2. Relevant equations 3. The attempt at a solution I do understand that when the mass number increases (like from Carbon-13 to Nitrogen-14), that a hydrogen nucleus is fused(?) together with the Carbon-12 nucleus, and the Nitrogen-14 nucleus and energy (in the form of gamma rays?) are emitted. What I don't understand is how Nitrogen-15 can decay(?) into Carbon-12 and a Helium-4 nucleus. I was thinking that this was a form of alpha decay, the emitting of the Helium nucleus. However, if that is the case, I don't see how Carbon-12 is also formed. Any help is appreciated, thanks :) Sorry if what I wrote down is hard to follow.