In 1589 Kepler entered Tubingen University. At Tubingen Kepler met perhaps the most important influence on his life, Magister Michael Maestlin, who taught mathematics and astronomy and was an accomplished and well-known astronomer himself.
In 1600, Tycho Brahe invited Kepler to work with him. As the assistant, Kepler was assigned the job of working on models of planetary motion. Upon study Brahe’s details of the Martian orbit, Kepler realized that the planet did not move at a constant speed.
In 1609 he concluded that the planets not only reside in the Copernican heliocentric, or sun centered system but that they travel in ellipses, not perfect circles around the sun.
Kepler published his first model of planetary motion in 1609 in his book, The New Astronomy. Today we know Kepler for his three laws of planetary motion, but these laws seem to have been developed almost accidentally as he searched for other , deeper patterns in the heavens.
Johannes Kepler (1571-1630)
