Wheeling Around the Solar System a century later, a shy mathematician named Johannes Kepler asked if there might be a key to the orbit of planets in the data of Tycho Brahe. Kepler worked with great diligence, and discovered that the planets orbit the Sun on elliptical orbits ("Kepler and Mars--Understanding How Planets Moved"). Although Kepler could not say WHY the planets orbited the Sun, he did develop mathematical descriptions for HOW they orbited.