 CNO cycle

The CNO cycle catalyses hydrogen fusion through carbon, nitrogen, and oxygen nuclei. Near $2\times 10^7\mathrm{K}$, its specific energy generation is approximately proportional to $\rho T^{17}$ and is therefore strongly concentrated near a star's centre.

The CNO cycle, or carbon-nitrogen-oxygen cycle, is one of the two main fusion processes that stars use to convert hydrogen into helium, the other being the proton-proton chain reaction. The CNO cycle is particularly important in stars that are more massive than the Sun, where temperatures and pressures are sufficiently high to facilitate the reaction.