Brahe, Tycho de (1546–1601)
- Danish astronomer whose observations allowed Kepler to discover his laws of planetary motion. An objectionable autocrat who kept his debtors in chains, maintained a pet dwarf and wore a metal nose – having lost the original in a duel – Tycho realised the importance of detailed positional astronomy, especially painstaking observations of the positions of the planets in the sky, without which the structure of the solar system could not be elucidated. He also supported his own model of the universe, with Mercury and Venus orbiting the Sun and the Sun and the other planets orbiting the Earth, and rationed Kepler’s access to his data to try to gain his support for this model. Tycho was the last great observational astronomer of the pre-telescopic era, working on comets, which he proved to be at astronomical distances rather than in the atmosphere, and observing the supernova of 1572 in Cassiopeia as well as the Moon, about whose orbital motion he made significant discoveries.