In the CNO cycle, how does Nitrogen-15 become Carbon-12 and Helium-4?

[AAAA]

Homework Statement

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.

Homework Equations

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.

 

[SteamKing]

Homework Statement

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.

Homework Equations

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.

There are several different CNO cycles which occur in stars of different masses. The various products in the CNO reaction chain occur at different times due to the fusion of a proton with a C or N nucleus, which then decays radioactively in one of several different ways. For more details on the various CNO cycles, see this article:

http://en.wikipedia.org/wiki/CNO_cycle

 

[Orodruin]

It is not a decay. It is a process involving an extra proton which is not visible since you did not write out the additional protons needed in any of the reactions.

 

[SteamKing]

It is not a decay. It is a process involving an extra proton which is not visible since you did not write out the additional protons needed in any of the reactions.

I think if you review the attached article in Post #2, you will see that some of the steps in the CNO cycles occur due to the spontaneous emission of positrons from unstable nuclei produced after fusion with a proton. This process occurs over a period of time (i.e., there is a measurable half-life associated with it), and it fits with the definition of radioactive decay as it is understood in non-stellar processes:

http://en.wikipedia.org/wiki/Radioactive_decay

I believe I clearly stated that this process is initiated after the various nuclei fuse with a proton, but in the interest of brevity, I chose not to reproduce the details of all of the reactions and instead referred the OP to the attached article in Post #2 for the details.