In astrophysics the term nonmetal refers to hydrogen and helium. All chemical elements in a star that are heavier than helium are counted as metals. In this sense, the first four "metals" collecting in stellar cores through nucleosynthesis are carbon, nitrogen, oxygen, and neon, all of which are strictly nonmetals in chemistry. A star fuses lighter atoms, mostly hydrogen, and helium, into heavier atoms over its lifetime. Used in that sense, the metallicity of an astronomical object is the proportion of its matter made up of heavier chemical elements.[1][2]

References

  1. ↑ Martin, John C. "What we learn from a star's metal content". John C. Martin's Homepage. Retrieved March 25, 2021.
  2. ↑ Martin, John C.; Morrison, Heather L. (May 18, 1998) [1998]. "A new analysis of RR Lyrae kinematics in the solar neighborhood". The Astronomical Journal (published October 1, 1998). 116 (4): 1724–1735. arXiv:astro-ph/9806258. Bibcode:1998AJ....116.1724M. doi:10.1086/300568. S2CID 18530430 – via IOPscience.


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