Tycho Brahe (info • help) (born Tyge Ottesen Brahe, 14 December 1546 – 24 October 1601) was an astronomer from Denmark. He built a large observatory called Uraniborg on a place called Hven in Denmark. He discovered that the universe besides the solar system was always changing when he studied a supernova and a comet. Johannes Kepler was his assistant. Tycho made very careful observations of the planets. When Tycho died in 1601, Kepler continued Tycho's work.