Stellar metallicity

Stellar metallicity is the abundance of elements heavier than helium in a star relative to hydrogen. It traces the chemical enrichment of the gas from which the star formed.

Metallicity: In astronomy, metallicity is the abundance of elements heavier than helium in an object, usually relative to hydrogen. Stellar metallicity is the stellar form of this broader abundance measure.
Galactic archaeology: The reconstruction of a galaxy’s formation history from the ages, motions, and chemical compositions of its stars. Stellar metallicities preserve clues about when and where stars formed.
Big Bang nucleosynthesis: The formation of the lightest atomic nuclei during the first minutes of the universe. It left primordial gas with almost no elements heavier than helium.
Alpha enhancement: An elevated abundance of alpha-capture elements relative to iron compared with the Sun. Two stars with equal iron metallicity can differ substantially in alpha-element abundance.
Non-LTE effects: Departures from local thermodynamic equilibrium that alter the populations of atomic energy levels. They can bias abundances inferred when spectral lines are modeled under LTE assumptions.
Abundance notation: A logarithmic system expresses elemental abundances relative to hydrogen and often to the Sun. Astronomers report stellar iron abundance as [Fe/H] using this notation.
Metallicity distribution function: A statistical distribution describing the metallicities of stars in a population or region. Its shape records chemical enrichment across a stellar population.
Stellar nucleosynthesis: The production of atomic nuclei through reactions inside stars. Stars create many of the heavy elements measured in later generations.
Carbon-enhanced metal-poor star: A metal-poor star whose carbon abundance is unusually high relative to iron. Its composition shows how a low overall metallicity can conceal strong element-specific enrichment.
3D stellar atmosphere modeling: Numerical modeling of stellar atmospheres that resolves three-dimensional structure and convective motion. It can change predicted line strengths and revise inferred stellar abundances.

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