Strömgren integral

The Strömgren integral is a concept used in the field of astrophysics, particularly in the study of ionized regions around stars, known as H II regions. It was introduced by the Swedish astronomer Bertil Strömgren in the 1930s. The Strömgren integral refers specifically to the calculation of the ionization balance in a gas that is exposed to a source of ionizing radiation, such as a hot, massive star.