[AGarvin]

A brief discussion was raised in a previous thread regarding the CNO cycle in stars. I've rummaged through my notes and found the exact cycles (for those interested). For those unfamiliar with the process, CNO stands for Carbon-Nitrogen-Oxygen, and it's one of two fusion cycles that power the cores of stars (the other being the proton-proton cycles). It's not a significant process in the Sun as the core is not hot enough but comes into play in larger stars.

H - Hydrogen
C - Carbon
N - Nitrogen
O - Oxygen
He - Helium
e+ - positron
nu - neutrino
g - gamma photon

The numbers represent the isotope of the element, eg, the carbon atom has 6 protons in the nucleus. If it has 6 neutrons, it's carbon-12 (6 + 6 = 12). If it has 7 neutrons, it's carbon-13.

The CNO main cycle is:

12C + 1H > 13N + g (10^6 years)
13N > 13C + e+ + nu (beta+ decay, 14 minutes)
13C + H1 > 14N + g (3x10^5 years)
14N + H1 > O15 + g (3x10^8 years)
O15 > 15N + e+ + nu (beta+ decay, 82 seconds)
*15N + H1 > 12C + 4He (10^4 years)

Times scales from Blohm-Vitense 1992.

*There's a small chance (0.0004) that instead of 15N + 1H producing 12C + 4He it will actually produce a 16O. This will trigger the CNO bi-cycle from the O16 atom:

*15N + 1H > 16O
16O + H1 > 17F
17F > 17O + e+ + g
O17 + 1H > 14N + 4He

No time scales found for the bi-cycle.

Andrew.