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Hertzsprung-Russell Diagram



Zero-age Main Sequence: The position, on the main sequence of a Hertzsprung-Russell diagram, reached by stars after they have passed through their T Tauri phase. It corresponds to a star with 75% hydrogen, 23% helium and 2% metals in its core. Nuclear fusion then gradually changes this ratio and the star evolves across the main sequence.

See also: Star.

Subjects: Physics