# Orbital Period of a Comet

Given the minimum and maximum distance of the orbit of a comet in an elliptical orbit, you can use Kepler’s Third Law and the definition of the semi-major axis of an ellipse to calculate its orbital period

*P* is the orbital period of the comet,

is the mathematical constant pi,

*a* is the semi-major axis of the comet’s orbit,

*G* is the gravitational constant,

*M* is the mass of the Sun, and

*m* is the mass of the comet.