Proton capture

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Proton capture is a nuclear reaction where a nucleus grabs one or more protons and becomes heavier. Protons are positively charged, so they repel the nucleus and it’s harder for a proton to join than for a neutron. This process helps make proton-rich isotopes in the universe. In stars it can happen in two ways: quickly (the rp-process) or more slowly (the p-process). It also plays a role in the CNO cycle that powers hydrogen burning in stars. Proton capture can destroy lithium in stars by turning it into helium.