Which astronomer formulated the three laws of planetary motion in the early 17th century?

Johannes Kepler formulated the three laws of planetary motion in the early 17th century.

Kepler published his first two laws in 1609 in Astronomia nova, based largely on the exceptionally precise observations of the Danish astronomer Tycho Brahe. The first law states that planets move in ellipses with the Sun at one focus, replacing the older assumption that their paths had to be perfect circles.

His second law says that a line joining a planet and the Sun sweeps out equal areas in equal times. This means a planet moves faster when it is closer to the Sun and slower when it is farther away. Kepler published his third law in 1619, showing that a planet’s orbital period is related mathematically to the size of its orbit.

These laws described planetary motion without explaining its underlying cause. Isaac Newton later used them, together with his laws of motion and universal gravitation, to develop a broader physical explanation.