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Tycho published his observations and his interpretation that the new star was truly
a star and that the heavens had changed. Modern astronomers would agree with
this; in their terminology the star was an exploding supernova.
People
Tycho Brahe (1546-1601)
The astronomer/astrologer and alchemist Tycho Brahe, the survivor of a pair of twins, was
born into a noble family in Denmark. He was educated by his uncle and later at the University
of Copenhagen. An eclipse in 1560, and the fact that it had been predicted, inspired him to
turn to astronomy. At the age of 17 he observed: ”What's needed is a long term project with
the aim of mapping the heavens conducted from a single location over a period of several
years.” These words consequently mapped out his future scientific work. After a student-related
squabble, Tycho lost part of his nose in a duel and for the rest of his life he wore a replace-
ment nose allegedly of gold (post mortem examination of his remains in 1901 suggests that
it was really of copper). He traveled throughout Europe until in 1571 he set up an observatory
in Copenhagen. In 1572, he observed the supernova of 1572 and was financed by the King to
establish an Observatory at Uraniborg. He moved to Prague in 1599 where his patron was
Rudolf II, the Holy Roman Emperor. He developed a model of the solar system, which had
the Sun orbiting the Earth while the other planets (except the Earth) orbited the Sun. It was a
half-way house between the Ptolemaic Theory that all the planets and the Sun orbit the Earth
and the Copernican Theory that all the planets orbit the Sun, and only the Moon orbits the
Earth. He died in 1601, after straining his bladder by retaining urine for the duration of a
banquet out of a mistaken sense of propriety. However, some claim he died from mercury
poisoning, whether self-administered as medicine or accidentally ingested during astrological
experiments. Some say it was administered with the intention to murder but that is never
going to be certain. His records of the motion of the planet Mars were passed on to his pupil
Kepler, who used them to discover the laws of planetary motion.
The topic attracted the attention of King Frederick II of Denmark and Norway. He
financed Tycho to build next to Uraniborg, an observatory containing underground
chambers with more stable foundations and temperatures for the instruments,
which Brahe called Stjerneborg (“Star Castle”). Tycho occupied the complex until
1597 when Frederick's successor, Christian IV, came to the throne. Tycho then
moved to Prague where he had the support of Emperor Rudolf II. The observatory
was destroyed after he left and all that remains today are the ground works, fitted
with a modern roof as a vistors' center.
At the Uraniborg observatory, Tycho had installed astronomical instruments he had
made himself - not telescopes because they had yet to be invented, but sighting instru-
ments that measured the positions of stars and planets. He created these instruments to
take what were then the most accurate measurements of the stars and the positions of
the planets, ultimately determining their positions to a fraction of an arc minute. His
pupil Johannes Kepler (1571-1630) used Tycho's measurements to establish the plan-
etary laws of motion. The measurements were also useful in further investigation of
the accuracy of these laws and determining any departures from them, if Brahe's meas-
urements could be linked to observations being carried out later, in Paris.
Picard gathered the data to do this, using the eclipses of Jupiter as clocks that he
observed from Hven and also at Paris. Each eclipse progressed over many minutes,
but there were two principal opportunities to make a decisive observation of the
timing to an accuracy of seconds. The satellite gradually approaches the column of
shadow behind Jupiter, its approaching side touches the edge of the shadow (first
