An Etymological Dictionary of Astronomy and Astrophysics
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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).

→ continuum; → drive; → wind.