An Etymological Dictionary of Astronomy and Astrophysics

The approximation of a stellar atmosphere with a plane parallel grey atmosphere in radiative equilibrium. It is assumed that a spectral is formed in such a way that the ratio of the line absorption coefficient to the continuous absorption coefficient is constant with depth.

See also: → Milne Universe; Arthur Stanley Eddington (1882-1944), prominent British astrophysicist; → approximation.