Johannes Kepler formulated the three laws of planetary motion, publishing the first two in 1609 and the third in 1619.
Kepler used the exceptionally precise observational data collected by Danish astronomer Tycho Brahe. His first law established that planets move in elliptical orbits with the Sun at one focus, replacing the long-standing assumption that celestial motion had to be made from perfect circles. His second law states that a line from a planet to the Sun sweeps out equal areas in equal times.
The third law relates a planet's orbital period to its average distance from the Sun. Kepler's work supported the Sun-centered model associated with Nicolaus Copernicus and later provided a foundation for Isaac Newton's theory of universal gravitation. Galileo's telescopic observations supported heliocentrism, but Galileo did not formulate Kepler's three laws. Kepler also made major contributions to optics and helped establish modern mathematical astronomy.