# Kelper 3rd law

Kepler’s 3rd Law: P^2 = a^3

Kepler’s 3rd law is a mathematical formula. It means that if you know the period of a planet’s orbit (P = how long it takes the planet to go around the Sun), then you can determine that planet’s distance from the Sun (a = the semimajor axis of the planet’s orbit).

It also tells us that planets that are far away from the Sun have longer periods than those close to the Sun. They move more slowly around the Sun.