In astronomy, Kepler's laws of planetary motion, published by Johannes Kepler between 1609 and 1619, describe the orbits of planets around the Sun.

Kepler's first law of planetary motion

Each planet's orbit the Sun is an ellipse. The Sun's center is always located at one focus of the orbital ellipse.

Kepler's second law of planetary motion

A planet moves in its ellipse, so the line between it and the Sun placed at a focus cover equal areas in equal times.

Kepler's third law of planetary motion

Kepler found another mathematical ratio relating the period of the planets to their distance to the Sun. This law states: "The square of the periods of the planets are proportional to the cubes of their distances from the Sun".