Henyey track

The Henyey track is an almost horizontal track of stellar evolution on the Hertzsprung-Russell diagram, which traces the path of a star, of mass greater than about 0.4 solar masses, that is in in radiative equilibrium, as it moves from its Hayashi track to the main sequence. As a star progresses along the Henyey track – named for the American astrophysicist Louis Henyey (1910–1970) – it contracts and becomes hotter, until its core has become sufficiently small and pressurized for hydrogen burning to begin.