# Darwin / Radau equation

## Description

In astrophysics, the Darwin / Radau equation gives an approximate relation between the moment of inertia factor of a planetary body and its rotational speed and shape. The moment of inertia factor is directly related to the largest principal moment of inertia, C. It is assumed that the rotating body is in hydrostatic equilibrium and is an ellipsoid of revolution.

Related formulas## Variables

C | largest principal moment of inertia (kg*m^{2}) |

M | mass of the body (kg) |

R_{e} | mean equatorial radius of the body (m) |

η | Radau parameter (dimensionless) |