Tycho Brahe

Tycho Brahe, who came from the nobility, was intended by his family for a career as a lawyer and diplomat. He eventually became an astronomer. His scientific interests included Alchemy and he was a convinced believer in Astrology (celestial influences were believed to play a part in alchemical processes).

On 11 November 1572, he emerged into the dark of the early evening, after a long stint of alchemical experimentation, and his first glance at the sky showed him an extra star in the constellation of Cassiopeia, almost directly overhead. He instantly summoned his chemical assistant to confirm that the star really was there. He was not the first to see the new star (a supernova) but his observations of it (published in 1574) did much to prove beyond reasonable doubt that the star really belonged to the firmament and was not merely a local phenomenon in the sublunary world (as comets were generally believed to be). The star is now usually known as 'Tycho's supernova'. It turned Tycho's interest back to astronomy.

With financial help from the King of Denmark, he went on to set up a purpose-built observatory, on the island of Hveen in Copenhagen Sound. The observatory, called Uraniborg, was equipped with exceptionally large and accurate instruments (and with an alchemical laboratory in its basement). At Uraniborg Tycho made twenty years' worth of astronomical observations. After quarrelling with the new King, Tycho closed down his observatory and sought a place for himself and his instruments at various courts.

In 1599 he was appointed Imperial Mathematician to the Holy Roman Emperor, Rudolph II, in Prague. Johannes Kepler (1571 -1630) joined him as an assistant, to help with mathematical calculations. Tycho intended that this work should prove the truth of his cosmological model, in which the Earth (with the Moon in orbit around it) was at rest in the centre of the Universe and the Sun went round the Earth (all other planets being in orbit about the Sun and thus carried round with it).

When Tycho died, Kepler succeeded him as Imperial Mathematician. Tycho's observations of planetary positions, which were made using instruments with open sights (a telescope was not used for astronomy until about 1609), were much more accurate than any made by his predecessors. They allowed Kepler, who (unlike Tycho) was a convinced follower of Copernicus, to deduce his three laws of planetary motion (1609, 1619) and to construct astronomical tables, the Rudolphine Tables (Ulm, 1627), whose enduring accuracy did much to persuade astronomers of the correctness of the Copernican theory. However, until at least the mid-seventeenth century, Tycho's model of the planetary system was that favoured by most astronomers. It had the advantage of avoiding the problems introduced by ascribing motion to the Earth.

Article by: J. V. Field, London