Proton-Proton Chain Reaction

Discovered by: Arthur Eddington in the 1920s.

What is it? The fusion reaction whereby hydrogen nucleii combine to produce helium nucleii in stars.

Why is it important? The primary source of solar energy, and similar size stars, is the fusion of hydrogen to form helium (the proton-proton chain reaction), which occurs at a solar-core temperature of 14 million kelvin. The net result is the fusion of four protons into one alpha particle, with the release of two positrons and two neutrinos (which changes two of the protons into neutrons), and energy.