A formula for the opacity in a star's interior. It is valid at temperatures around 104–106 K when the opacity is mostly due to absorption of photons by free electrons in the interior, and it declines as the temperature increases. For stars up to 1 solar mass the formula applies through much of the interior, but for more massive stars it is valid only in the surface layers. Kramers opacity is named after the Dutch physicist Hendrik Anthony Kramers (1894–1952).
Subjects: Astronomy and Astrophysics.