Hartmann, Dieter H. Department of Physics and Astronomy, Clemson University, Clemson, South Carolina.
Meyer, Bradley S. Department of Physics and Astronomy, Clemson University, Clemson, South Carolina.
Last reviewed:August 2021
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- Evidence of nucleosynthesis
- Hydrogen burning
- Helium burning
- Carbon burning
- Oxygen burning
- Silicon burning
- The s-process
- The r-process
- The p-process
- The ν-process
- The LiBeB process
- Related Primary Literature
- Additional Reading
The formation of nuclides present in the universe by various nuclear reactions. Theories of the origin of the chemical elements involve synthesis with charged and neutral particles (neutrons, protons, neutrinos, photons) and other nuclear building blocks of matter, such as alpha particles. The theory of nucleosynthesis comprises a dozen distinct processes, including big bang nucleosynthesis, cosmic-ray spallation in the interstellar medium, and static or explosive burning in various stellar environments (hydrogen-, helium-, carbon-, oxygen-, and silicon-burning, and the, s-, r-, p-, γ-, and ν-processes) (Fig. 1). Acceptable theories must lead to an understanding of the cosmic abundances observed in the solar system, stars, and the interstellar medium. The curve of these abundances is shown in Fig. 2. Hydrogen and helium constitute about 98% of the total element content by mass and more than 99.8% by number of atoms. There is a rapid decrease with increasing nuclear mass number A, although the abundance of iron-group elements like iron and nickel are remarkably large. The processes of nucleosynthesis described in this article attempt to explain the observed pattern. See also: Alpha particle; Atom; Chemical element; Cosmic abundance of elements; Interstellar matter; Matter; Neutron; Nuclide; Periodic table; Proton; Star
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