Tycho Brahe

Tycho Brahe was a Danish nobleman and astronomer whose observations of the stars and planets, made without a telescope, were far more accurate than any before him. From his island observatory of Uraniborg he showed that the heavens could change, contradicting the ancient view inherited from Aristotle, and his records later allowed Johannes Kepler to work out the laws of planetary motion. He is often described as the greatest astronomer of the age before the telescope.

Tyge Ottesen Brahe was born on 14 December 1546 at Knutstorp Castle in Scania, then part of the Danish kingdom and Swedish only since 1658. His family belonged to the highest Danish nobility. At the age of two he was taken to be raised by his childless uncle Jørgen Brahe, who made him his heir.

He entered the University of Copenhagen in 1559, aged 12, to study law, but a solar eclipse in August 1560, predicted a day out, convinced him that astronomy needed better measurements. At Leipzig in 1563 he noticed that both the Copernican and the Ptolemaic tables wrongly predicted a conjunction of Jupiter and Saturn. He began keeping systematic records of his observations. At Rostock in December 1566 he lost the bridge of his nose in a duel with a cousin over mathematics, and wore a metal replacement for the rest of his life.

Back in Denmark, Tycho chose science over a career at court. His partner, Kirsten Jørgensdatter, was a commoner, so they never formally married. On 11 November 1572 he saw a brilliant new star in Cassiopeia. Finding that it showed no daily parallax, he concluded it lay far beyond the Moon, among the fixed stars. His short book De nova stella (1573) challenged the belief that the heavens were unchanging and made his name across Europe. He showed in the same way that the Great Comet of 1577 moved far beyond the Moon.

To keep him in Denmark, King Frederick II granted Tycho the island of Hven in the Sound, between Zealand and Scania, and funds to build an observatory. Construction of Uraniborg, named after the muse of astronomy, began in 1576, and in 1584 he added Stjerneborg, a partly underground observatory that kept his instruments steady. Almost 100 students and craftsmen worked there over two decades, among them his sister Sophie. Royal support was lavish, at one point about 1% of the crown's annual revenue.

His great quadrants and sextants measured positions to around one arcminute, several times better than any contemporary, and he produced the first tables to correct for atmospheric refraction. He also proposed his own Tychonic system, in which the Sun and Moon circled a motionless Earth while the other planets circled the Sun, keeping some advantages of Nicolaus Copernicus's model without a moving Earth.

After Frederick died in 1588, Tycho's influence declined under the regency for the young Christian IV, and he quarrelled with powerful enemies at court. In 1597 he left Hven, completing a catalogue of 1,000 stars shortly before. After stays near Hamburg and in Wittenberg, in 1599 he entered the service of Emperor Rudolf II of the Holy Roman Empire and moved to Prague. There he hired the young Kepler as his assistant, though Kepler, a convinced Copernican, rejected Tycho's model.

In October 1601 Tycho fell ill after a banquet, apparently with a bladder or kidney complaint, and died eleven days later, on 24 October, aged 54. Rumours that he had been poisoned with mercury were tested on his exhumed remains in 2010, and researchers concluded that the levels found ruled out murder.

Kepler used Tycho's observations of Mars to deduce his laws of planetary motion and to complete the Rudolphine Tables in 1627. Tycho's planetary system remained popular in the 17th century, especially among Jesuit astronomers, but it was his insistence on precise, repeated measurement that made him a founder of the Scientific Revolution.

Our 1600 map shows Denmark–Norway, including Scania and Hven, at the end of Tycho's life, and the Holy Roman Empire where he spent his final years.