Hayashi track

In astronomy, path on the Hertzsprung-Russell diagram taken by protostars as they emerge from the clouds of dust and gas out of which they were born. A protostar appears on the right (cool) side of the Hertzsprung-Russell diagram and follows a Hayashi track until it arrives on the main sequence where hydrogen burning can start. It is named after the Japanese astrophysicist Chushiro Hayashi, who studied the theory of protostars in the 1960s.