An Etymological Dictionary of Astronomy and Astrophysics

The transfer of photon momentum to free electrons. The acceleration by → continuum emission can be given by: a_c = (σ/m)(L/4πR²c), where σ is the → Thomson scattering  → cross section, m is the mass per free electron, L is → stellar luminosity, R is radius, and c the → speed of light. The ratio of
a_c to the → surface gravity is ≅ 2 × 10^-5L/M, with M and L in solar units. The atmosphere is is stable if a_c very smaller than g_grav. If L is above the → Eddington limit, the radiation pressure in the continuum leads to very heavy → mass loss and thus to expanding envelopes (K.S. de Boer & W. Seggewiss, 2008, Stars and Stellar Evolution, EDP Sciences).

See also: → continuum; → drive; → wind.