Johannes Kepler

Considered a pioneer in astronomy, Johannes Kepler is best known for his three laws of planetary motion. The first and most famous law states that planets orbit in ellipses, not in circles, as was the common belief at the time. Kepler worked as an assistant to the Danish astronomer Tycho Brahe until Brahe's death in 1601. Kepler's first two laws were based on Brahe's precise measurements of Mars' orbit.

Image credits: main image, Tony Persiani.