Tyge Ottesen Brahe (1546 - 1601)
Tycho, born Tyge Ottesen Brahe, was from a Danish noble family. Raised by his wealthy uncle, his family encouraged him to study law, though he chose instead to study astronomy. At university, he fell into an argument with a fellow student over who was the better mathematician. To settle the argument, they challenged each other to a sword duel in the dark, which resulted in Tycho losing part of his nose. For the remainder of his life, Tycho wore a brass prosthetic nose.
He developed his own model of the Solar System, known as the Tychonic System. It combined much of the geometry of the heliocentric (Copernican) system, with the philosophic benefits of the geocentric (Ptolemaic) system. Tycho said that the planets orbit the Sun, and the Moon orbits the Earth, but that the Sun also orbits the Earth. He made observations of the planets five times more accurate than any other observations at the time.
In his observations of the night sky, he discovered several "new stars". These were supernovae, in particular the supernova SN 1572 (now called Tycho's Supernova, observed in November 1572). These "new stars" did not move as much as Tycho expected them to, if they were tailless comets in the atmosphere, as was thought at the time. Instead, they must be beyond the atmosphere and more distant than the Moon. Tycho also showed that the comets themselves were not in the atmosphere, but must pass the Solar System out towards the planets.
The King of Denmark at the time granted Tycho the funding to build a research institute. He engineered many large, complex astronomical instruments, and took very precise measurements. He hired an assistant, Johannes Kepler, in 1600 until his death in 1601. Kepler used the incredibly precise data obtained at the research institute to develop his three Laws of Planetary Motion.