metallicity

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metallicity

(met-ă-liss -ă-tee) (metal abundance) Symbol: Z . The fraction by mass of metals in a star, cluster of stars, or in some other astronomical entity. Since metals are produced by nucleosynthesis in stars, the metallicity of an object or class of objects depends on when it was formed: objects of later origin in general have a higher metallicity. Metallicity is determined by photometry or high-resolution spectroscopy, and is usually expressed relative to solar metallicity (see cosmic abundance), and as the ratio of iron to hydrogen, Fe/H. See also population I, population II.