# circular orbit

A circular orbit is any orbit that has an eccentricity of zero
– an ideal condition that is seldom if ever actually achieved. The
velocity *v* needed to maintain such an orbit, known as the circular
velocity, is given by *v* = √{*G*(*M* + *m*)/*R*},
where *m* and *M* are the masses of the orbiting object and the
central body, respectively, *R* is the radius of the orbit, and *G* is the gravitational constant.