Nucleosynthesis is the production of atomic nuclei through nuclear reactions. It includes Big Bang nucleosynthesis, stellar nucleosynthesis and production in explosive or compact-remnant environments. Making nuclei and delivering them to the interstellar medium are separate steps in chemical enrichment.
Stellar nucleosynthesis encompasses nuclear production during stellar evolution and explosions, including hydrogen burning, core helium burning, advanced burning and neutron-capture processes. Stellar mass, composition, mixing and mass loss govern which nuclei form and which eventually escape. Slow neutron-capture process and rapid neutron-capture process build many nuclei beyond the iron group.
Two alpha captures and an intervening beta-plus decay turn each nitrogen-14 nucleus into neon-22, incorporating eight baryons from helium and converting one proton to a neutron. With no loss or dilution and nuclear mass defects neglected, a nitrogen-14 mass fraction therefore yields neon-22 mass fraction , not . In otherwise symmetric carbon-oxygen matter this gives the displayed electron fraction in stellar matter. A final neon mass fraction and a pre-helium-burning metallicity must not silently be treated as identical.
Hot explosive material can use photodisintegration on pre-existing heavy seed nuclei through neutron, proton and alpha emission. This gamma process supplies some proton-rich isotopes that the principal neutron-capture paths bypass. It is a particular mechanism, rather than a synonym for every proposed proton-rich nucleosynthetic process.
At sufficiently large neutron density, successive neutron captures outrun relevant beta decays and produce very neutron-rich nuclei. Decay toward stability afterward yields many heavy isotopes, including some actinides. Neutron-rich ejecta from neutron star mergers provide an established site; particular magnetically driven collapse outflows are additional candidates. This does not imply that every ordinary core-collapse supernova produces a complete heavy-element pattern.
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Nucleosynthesis is the process by which elements are formed through nuclear reactions, primarily in stars and during cosmic events. It encompasses several distinct processes, each contributing to the formation of different elements in the universe. Here are the main types of nucleosynthesis: 1. **Big Bang Nucleosynthesis**: This occurred within the first few minutes after the Big Bang, when the universe was hot and dense.