In astrophysics, the von Zeipel theorem states that the radiative flux
where the luminosity
The theorem is named after Swedish astronomer Edvard Hugo von Zeipel.
According to the theory of rotating stars, if the rotational velocity of a star depends only on the radius, it cannot simultaneously be in thermal and hydrostatic equilibrium. This is called the von Zeipel paradox. The paradox is resolved, however, if the rotational velocity also depends on height or there is a meridional circulation. A similar situation may be arisen in accretion disks.