The Henyey track is a path taken by pre-main-sequence stars with masses >0.5 Solar mass in the Hertzsprung–Russell diagram after the end of Hayashi track. The astronomer Louis G. Henyey and his colleagues in the 1950s, showed that the pre-main-sequence star can remain in radiative equilibrium throughout some period of its contraction to the main sequence. The Henyey track is characterized by a slow collapse in near hydrostatic equilibrium. They are approaching the main sequence almost horizontally in the Hertzsprung–Russell diagram (i.e. the luminosity remains almost constant).