Hayashi track

The evolutionary track on the Hertzsprung-Russell diagram of a protostar, before it becomes a main-sequence star. The track shows the changes in luminosity and surface temperature that occur in the early phases of a star's life. The exact position of the track on the diagram depends on the star's mass. Hayashi tracks are named after the Japanese astrophysicist, Chushiro Hayashi, who pioneered the theoretical work in the 1960s.