Hayashi limit

English

Etymology

Named after Japanese astrophysicist Chushiro Hayashi (25 Jul 1920–28 Feb 2010).

Noun

Hayashi limit (plural Hayashi limits)

1. (astrophysics) A theoretical maximum radius of a star of given mass; the radius at which the inward force of gravity exactly balances the outward pressure of the gas of the star.

   When a star is fully within hydrostatic equilibrium—a condition where the inward force of gravity is matched by the outward pressure of the gas—the star can not exceed the radius defined by the Hayashi limit.^[Wikipedia]

   • 1977, Rudolf Kippenhahn, Walter Strohmeyer, The Interaction of Variable Stars with Their Environment, Remeis-Sternwarte, page 69:

     However, the approximate locations of the Hayashi limits point to remarkably low masses for the three T Tauri stars investigated here. It should be noted, that the Hayashi limits are valid only for stars in hydrostatic equilibrium.

   • 2006, Peter Eggleton, Evolutionary Processes in Binary and Multiple Stars, Cambridge University Press, page 75:

     Since the Hayashi limit approaches close to the main sequence at about 1 M⊙, the 'Hertzsprung gap' between the terminal main sequence and the Hayashi limit is much less marked than at high masses.

   • 2009, Donald Gerard Luttermoser, Beverly Joy Smith, Robert E. Stencel, editors, The Biggest, Baddest, Coolest Stars: Proceedings of a Workshop, Astronomical Society of the Pacific, page 33:

     The latest-type RSGs^{[Red Supergiants]} in the Magellanic Clouds are cooler than the current evolutionary tracks allow, occupying the region to the right of the Hayashi limit where stars are no longer in hydrostatic equilibrium.

Related terms

• Hayashi boundary
• Hayashi track

Translations

theoretical upper limit of the radius of a hydrostatically stable star

• French: limite de Hayashi f
• German: Hayashi-Limit n
• Italian: limite di Hayashi m

Further reading

• Hayashi track § Forbidden zone on Wikipedia.Wikipedia
• Eddington luminosity on Wikipedia.Wikipedia