Which astronomer published the laws of planetary motion in his 1609 and 1619 works?

Johannes Kepler published the laws of planetary motion in works released in 1609 and 1619.

Kepler’s first two laws appeared in Astronomia nova, published in 1609. They established that planets travel in elliptical orbits with the Sun at one focus and that a planet sweeps out equal areas in equal times. His third law appeared in Harmonices Mundi in 1619 and relates a planet’s orbital period to its average distance from the Sun.

Kepler developed these laws using exceptionally precise observations made by Tycho Brahe, especially observations of Mars. The data forced Kepler to abandon the long-standing assumption that celestial orbits had to be perfect circles.

His work transformed the Copernican model into a predictive mathematical system. Isaac Newton later showed that Kepler’s laws follow from universal gravitation. Kepler therefore connected observational astronomy with the physical laws that explain planetary motion.