zero-age main sequence
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Related to zero-age main sequence: Helium flash
zero-age main sequence[′zir·ō ¦āj ′mān ′sē·kwəns]
The position on the Hertzsprung-Russell diagram of a star that has just reached the main sequence, when it has reached hydrostatic equilibrium and thermonuclear reactions have begun in its core, but these reactions have not had time to produce an appreciable change in composition. Abbreviated ZAMS.