Protonprotonketjut
Protonprotonketjut, often abbreviated as the pp-chain, is a set of nuclear fusion reactions by which stars, including our Sun, convert hydrogen into helium. This process is the primary energy source for stars within a certain mass range. The overall reaction involves four protons (hydrogen nuclei) combining to form one helium nucleus, releasing energy in the form of gamma rays and neutrinos.
The pp-chain occurs in several steps. The most common pathway begins with two protons fusing to form
There are also less common branches of the pp-chain, such as the ppI, ppII, and ppIII chains,