The
invariable plane of a
planetary system, also called
Laplace's invariable plane, is the plane passing through its
barycenter (center of mass) perpendicular to its
angular momentum vector. In the
Solar System, about 98% of this effect is contributed by the orbital angular momenta of the four
jovian planets (
Jupiter,
Saturn,
Uranus, and
Neptune). The invariable plane is within 0.5° of the orbital plane of Jupiter, and may be regarded as the weighted average of all planetary orbital and rotational planes.