the Solar System is the plane passing through its center of mass perpendicular to its angular momentum vector. Earth's orbit, and hence, the ecliptic, is inclined a little more than 1° to the invariable plane, Jupiter's orbit is within a little more than ½° of it, and Mercury, the planet with the highest inclination, lies around 6°. Because of this, most Solar System bodies appear very close to the ecliptic in the sky.

The invariable plane is defined