sepehr-e Stömgren, kore-ye ~
Fr.: sphère de Strömgren
A theoretical sphere of → ionized hydrogen created by energetic → ultraviolet→ photons of a hot, → massive star embedded in a uniform interstellar → molecular cloud and lying at the center of the sphere. → H II region.
Named after Bengt Strömgren (1908-1987), a Danish astrophysicist, who put forward the first and simplest version of the model in 1939; → sphere.