The Henyey track is a path taken by protostars with masses >0.5 Solar mass in the Hertzsprung-Russell diagram after the end of Hayashi track. An USA astronomer Louis G. Henyey and his colleagues in the 1950s, showed that the proto-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 HR diagram (i.e. the luminosity remains almost constant).

References

• Henyey, L. G., Lelevier, R., Levée, R. D. (1955), The Early Phases of Stellar Evolution, Publications of the Astronomical Society of the Pacific, Vol. 67, No. 396, p.154-160

Stellar evolution | Hertzsprung-Russell classifications