The CNO cycle (carbon nitrogen oxygen) alternately called Bethe-Weizsäcker-cycle, is one of two types of fusion reactions by which stars convert hydrogen to helium, the other is the proton proton chain.

The CNO cycle, which stands for carbon-nitrogen, is one of the processes b which stars convert hydrogen to helium. This is the dominant source of energy for stars with larger mass.

It affects the internal structure of main-sequence stars because they have very high central temperatures for the extreme temperature sensitivity of the CNO cycle to fuse hydrogen into helium.

The CNO Cycle.