Henyey track
Encyclopedia
The Henyey track is a path taken by pre–main sequence stars with masses >0.5 Solar mass
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 in the Hertzsprung–Russell diagram
Hertzsprung–Russell diagram
The Hertzsprung–Russell diagram is a scatter graph of stars showing the relationship between the stars' absolute magnitudes or luminosities versus their spectral types or classifications and effective temperatures. Hertzsprung–Russell diagrams are not pictures or maps of the locations of the stars...

 after the end of Hayashi track
Hayashi track
The Hayashi track is a path taken by protostars in the Hertzsprung–Russell diagram after the protostellar cloud has reached approximate hydrostatic equilibrium...

. The astronomer Louis G. Henyey
Louis G. Henyey
Louis George Henyey was an American astronomer.His parents, Albert and Mary Henyey, were immigrants from Hungary...

 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
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...

 almost horizontally in the Hertzsprung–Russell diagram (i.e. the luminosity
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...

remains almost constant).
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