Damn! I *Knew* he Had to be a Slytherin!
In 1604, he started to observe SN 1604, a supernova also known as Kepler's star, in the constellation Serpentarius, the 13th sign of the zodiac in which your humble correspondent was born... Lumo
Extracted from Lubosh's very nice article on the occasion of Kepler's 543rd birthday: Johannes Kepler: an anniversary
Kepler was a pivotal figure in launching the scientific revolution that mathematicized physics.