62 PART 1^ |^ EXPLORING THE SKY
■ Figure 4-11
Tycho Brahe (1546–1601) was, during his lifetime, the most famous astronomer
in the world. Proud of his noble rank, he wears the elephant medal awarded
him by the king of Denmark. His artifi cial nose is suggested in this engraving.
Tycho Brahe’s model of the universe retained the fi rst principles of classical
astronomy; it was geocentric with the sun and moon revolving around Earth,
but the planets revolved around the sun. All motion was along circular paths.
SaturnJupiter
MarsVenusMercury
Moon
EarthSun■ Figure 4-12
(a) A fan hanging below a ceiling displays parallax when seen from the side.
(b) According to Aristotle, the new star of 1572 should have been located below
the sphere of the moon; consequently, reasoned Tycho, it should display paral-
lax and be seen east of its average position as it was rising and west of its aver-
age position when it was setting. Because he did not detect this daily parallax,
he concluded that the new star of 1572 had to lie on the celestial sphere.bCelestial
spher
Averageposition e Averageposition
New star setting
New star
risingageocentric universe, that meant that the new star should show par-
allax, meaning that it would appear slightly too far east as it rose
and slightly too far west as it set (■ Figure 4-12). But Tycho saw no
parallax in the position of the new star, so he concluded that it must
lie above the sphere of the moon and was probably on the starry
sphere itself. Th is contradicted Aristotle’s conception of the starry
sphere as perfect and unchanging.
No one before Tycho could have made this discovery because
no one had ever measured the positions of celestial objects so accu-
rately. Tycho had great confi dence in the precision of his measure-
ments, and he had studied astronomy thoroughly, so when he failed
to detect parallax for the new star, he knew it was important evi-
dence against the Ptolemaic theory. He announced his discovery in
a small book, De Stella Nova (Th e New Star), published in 1573.
Th e book attracted the attention of astronomers throughout
Europe, and soon Tycho’s family introduced him to the court
of the Danish King Frederik II, where he was off ered funds to
build an observatory on the island of Hveen just off the Danish
coast. To support his observatory, Tycho was given a steady
income as lord of a coastal district from which he collected rents.
(He was not a popular landlord.) On Hveen, Tycho constructedTycho Brahe
Tycho Brahe (1546–1601) was not a churchman like Copernicus
but rather a nobleman from an important family, educated at the
fi nest universities. He was well known for his vanity and his
lordly manners, and by all accounts he was a proud and haughty
nobleman. Tycho’s disposition was not improved by a dueling
injury from his university days. His nose was badly disfi gured,
and for the rest of his life he wore false noses made of gold and
silver, stuck on with wax (■ Figure 4-11).
Although Tycho offi cially studied law at the university, his real
passions were mathematics and astronomy, and early in his univer-
sity days he began measuring the positions of the planets in the
sky. In 1563, Jupiter and Saturn passed very near each other in the
sky, nearly merging into a single point on the night of August 24.
Tycho found that the Alfonsine Tables were a full month in error
and that the Prutenic Tables were in error by a number of days.
In 1572, a “new star” (now called Tycho’s supernova) appeared
in the sky, shining more brightly than Venus, and Tycho carefully
measured its position. According to classical astronomy, the new
star represented a change in the heavens and therefore had to lie
below the sphere of the moon. To Tycho, who still believed in a