Brahe , Tycho

(1546–1601) Danish astronomer

Tycho, whose father Otto was the governor of Helsingborg castle, was born in Knudstrup, Denmark. Kidnapped by and brought up by his uncle Jörgen, an admiral in the Danish navy, he was sent to Leipzig University in 1562 to study law. However, his interest in astronomy had already been kindled. He witnessed a partial solar eclipse in 1560 in Copenhagen whose predictability so impressed him that he began a serious study of Ptolemy's Almagest. He was allowed to continue with the formal study of astronomy and began a tour of the universities of northern Europe. It was while at Rostock in 1566 that, according to tradition, he became involved in a dispute with another young Danish nobleman over who was the better mathematician. The dispute led to a duel in which Tycho lost part of his nose. This he replaced with a mixture of gold, silver, and wax; the nose is clearly visible in contemporary engravings.

Tycho became aware that the successful solar-eclipse prediction of 1560 was not a typical index of the state of 16th-century astronomy. For instance, a conjunction of Jupiter and Saturn predicted by current tables was wrong by ten days. Tycho therefore began his long apprenticeship, traveling through northern Europe meeting the astronomers, instrument makers, and patrons who would support him later on.

His international reputation was made with the dramatic events that centered upon the nova of 1572 – ever since known asTycho's star. Not since the days of Hipparchus (second centurybc) had a new star visible to the naked eye appeared in the sky. InDe nova stella (1573; On the New Star), Tycho was able to demonstrate that the new star showed no parallax and therefore truly belonged to the sphere of the fixed stars. This was important cosmologically because according to Aristotle no change could take place in the heavens, which were supposed to be eternal and incorruptible; change could take place only in the sublunary sphere. By demonstrating that the new star of 1572 and the great comet of 1577 were changes in the heavens, Tycho was providing new evidence against the traditional Aristotelian cosmology.

In order to induce him to stay in Denmark, Tycho's monarch, Frederick II, offered him the island of Hven and unlimited funds to build an observatory there at Uraniborg. Tycho moved there in 1577, building an observatory/castle stocked with the best instruments then in existence, and constructing enormous quadrants and sextants. He became the greatest observational astronomer of the pretelescopic age. Before Tycho, astronomers tended to work with observations many centuries old. Copernicus would be more likely to use the tables of Ptolemy (second centuryad) than to make his own observations. When modern tables, such as the Prutenic Tables of Erasmus Reinhold, were constructed, although based on the Copernican system, they were scarcely more reliable. Tycho changed all this. Twenty years' careful observation using accurate instruments enabled him to determine the positions of 777 stars with unparalleled accuracy. He did not, however, accept the Copernican heliocentric system. Instead he proposed a compromise between that and the Ptolemaic, suggesting that the Earth remains at the center, immobile; the Sun and Moon move round the Earth; and all other bodies move round the Sun. His system received hardly any support.

After the death of Frederick II in 1588, Tycho quarreled with his successor, Christian IV, on his coming of age. The last recorded observation made at Hven was on 15 March, 1596. Tycho set off once more on his travels, this time encumbered by his enormous instruments. Eventually he found a new patron, one even stranger than himself, the mad Holy Roman Emperor Rudolph II. Tycho was made Imperial Mathematician in 1599, given yet another castle at Benatek outside Prague, and, more important, given the young Johannes Kepler as an assistant. Although the relationship was a stormy one, both benefited enormously. Tycho died suddenly in 1601 after a short illness leaving Kepler to publish Tycho's Rudolphine Tables posthumously in 1627. His last words were: “Let me not seemed to have lived in vain.” That such a fear was groundless is witnessed on the title page of Kepler's great work, Astronomia nova: “Founded on observations of the noble Tycho Brahe.”