proton-proton chain

[ proh-ton-proh-ton ]

noun

, Physics, Astronomy.

1. a series of thermonuclear reactions, responsible for the energy production in stars like the sun, in which the nuclei of hydrogen atoms are transformed into helium nuclei by sequential addition of single hydrogen nuclei.

proton-proton chain

1. A set of thermonuclear reactions in which hydrogen nuclei (protons) fuse to form deuterium; these then fuse to form light helium isotopes, releasing more hydrogen nuclei that undergo further fusion with each other and with other nuclei. The main product of the proton-proton chain is He 4, the most common isotope of helium. The proton-proton chain releases large amounts of energy and involves the conversion of protons into neutrons, positrons, and electron neutrinos. The proton-proton chain is the main reaction in most main-sequence stars, including the Sun.
2. See also carbon cycle