The Proton-Proton Chain

The Proton-Proton Chain

. The Sun gets its energy when hydrogen nuclei are fused together to form helium nuclei within the solar core. This hydrogen burning is described by a sequence of nuclear fusion reactions called the proton-proton chain. It begins when two protons, here designated by the letter 1H, combine to form the nucleus of a deuterium atom, the deuteron that is denoted by D, together with the emission of a positron, e+, and an electron neutrino, νe. Another proton collides with the deuteron to make a nuclear isotope of helium, 3He, and then a nucleus of helium, 4He, is formed by the fusion of two 3He nuclei, returning two protons to the gas. Overall, this chain successively fuses four protons together to make one helium nucleus. Even in the hot, dense core of the Sun, only rare, fast-moving particles are able to take advantage of the tunnel effect and fuse in this way.

Copyright 2010, Professor Kenneth R. Lang, Tufts University