Virial Theorem relates the total kinetic energy of a self-gravitating body due to the motion of its constituent parts, T, to the gravitational potential energy, U, of the body.
$$2T+U=0$$
The general equation for the virial theorem is,
$$\\langle T\\rangle=-\\frac{1}{2}\\sum_{k=1}^{N} \\langle F_{k} \\cdot r_{k}\\rangle$$