diproton

== English == === Etymology === From di- + proton. === Noun === diproton (plural diprotons) A hypothetical particle consisting of two protons and no neutrons; a helium-2 nucleus. Presumably an intermediate step in the fusion of hydrogen into helium. === Trivia === What happens in a star is probably something like this: protons (1H nuclei) move so fast that they come together despite their Coulomb repulsion, forming a diproton. Usually the two protons then separate. But very rarely they stay together, and one of them turns into a neutron, resulting in heavy hydrogen: deuterium.