whose accurate observations of the planets enabled German astronomer
and mathematician Johannes Kepler to prove that planets orbit the
Sun in ellipses. Brahe's discovery and report of the 1572 supernova
brought him recognition, and his observations of the comet of 1577
proved that it moved in an orbit among the planets, thus disproving
the Greek view that comets were in the Earth's atmosphere.
Brahe was a colourful figure who wore a silver nose after his own
was cut off in a duel, and who took an interest in alchemy. In 1576
Frederick II of Denmark gave him the island of Hven, where he set
up an observatory. Brahe was the greatest observer in the days before
telescopes, making the most accurate measurements of the positions
of stars and planets. He moved to Prague as imperial mathematician
in 1599, where he was joined by Kepler, who inherited his observations
when he died.
Brahe was born in Skåne (then under Danish rule). He studied
at Copenhagen and in Germany at Wittenberg and Rostock.
Observing the 1577 comet, he came to the conclusion that its orbit
must be elongated, which conflicted with the belief in planetary spheres.
Brahe, the last great astronomer to reject the heliocentric theory
of Copernicus, tried to compromise, suggesting that, with the exception
of the Earth, all the planets revolved around the Sun.
He prepared tables of the motion of the Sun and determined the length
of a year to within less than a second, necessitating the calendar
reform of 1582.