The credit for discovering and proving that planets move in elliptical orbits goes to Johannes Kepler. He published his groundbreaking laws of planetary motion in the early 17th century, based on the meticulous observations of his mentor, Tycho Brahe.

While Nicolaus Copernicus had proposed a heliocentric model of the solar system, he still believed that planets moved in perfect circles. Kepler's work revolutionized our understanding of planetary motion by showing that the orbits were actually ellipses, with the Sun at one focus of the ellipse.