Does Kepler’s third law work on all celestial bodies?
In its original form, Kepler’s third law was developed to describe planetary orbits, that is, the orbits of planets such as earth, mercury, and venus around the sun. Today though, we know that Kepler’s third law applies to all systems with radial force that obey the inverse-square law. Comets, exoplanets (planets that orbit around other stars), moons and even satellites are subject to the forces described in Kepler’s law.