An Etymological Dictionary of Astronomy and Astrophysics

The exponent appearing in the power law that describes the → effective temperature of a → rotating star as a function of the → effective gravity, as deduced from the → von Zeipel theorem or law. Generalizing this law, the effective temperature is usually expressed as T_eff∝ g_eff^β, where β is the gravity darkening exponent with a value of 0.25. It has, however, been shown that the relation between the effective temperature and gravity is not exactly a power law. Moreover, the value of β = 0.25 is appropriate only in the limit of slow rotators and is
smaller for fast rotating stars (Espinosa Lara & Rieutord, 2011, A&A 533, A43).

See also: → gravity; → darkening; → exponent.