An Etymological Dictionary of Astronomy and Astrophysics

A general equation applicable to a gravitationally → bound system of equal mass objects (stars, galaxies, etc.), which is stable against → dynamical disruption.
It states that in such a system the average → gravitational potential energy (W_vir) is twice the average → kinetic energy (K_vir) of the system: W_vir = -2K_vir. This general proposition, first derived by Rudolf Clausius (1822-1888),
has important applications in a variety of fields ranging from statistical mechanics to astrophysics. See also → virialization, → virial equilibrium, → virialized.

See also: → virial; → theorem.