A nearly vertical path of stellar evolution on the Hertzsprung-Russell diagram down which an infant star progresses on its way to the main sequence. While on the Hayashi track, a star is largely or completely in convective equilibrium; as it progresses, its luminosity, initially very high, decreases rapidly with contraction, but its surface temperature remains almost the same. The sequence runs in reverse for stars leaving the main sequence to become giants. The track is named after Chushiro Hayashi.
