30
WE HAVE RE-OBSERVED
ALL OF THE STARS IN
PTOLEMY’S CATALOG
IMPROVED INSTRUMENTS
IN CONTEXT
KEY ASTRONOMER
Ulugh Beg (13 8 4 –14 49)BEFORE
c.130 bce Hipparchus
publishes a star catalog
giving the positions of more
than 850 stars.150 ce Ptolemy publishes
a star catalog in the
Almagest, which builds on
the work of Hipparchus and
is seen as the definitive guide
to astronomy for more than
a millennium.964 ce Abd al-Rahman al-Sufi
adds the first references to
galaxies in his star catalog.AFTER
1543 Nicolaus Copernicus
places the sun as the center
of the universe, not Earth.1577 Tycho Brahe’s star
catalog records a nova,
showing that the “fixed
stars” are not eternal
and do change.F
or more than 1,000 years,
Ptolemy’s Almagest
was the world’s standard
authority on star positions.
Translated into Arabic, Ptolemy’s
work was also influential in the
Islamic world up until the 15th
century, when the Mongol ruler
Ulugh Beg showed that a lot of
the Almagest’s data were wrong.
A grandson of the Mongol
conqueror Timur, Ulugh Beg was
just 16 years old when he became
ruler of the family’s ancestral seat
at Samarkand (in present-day
Uzbekistan) in 1409. Determinedto turn the city into a respected
place of learning, Ulugh Beg
invited scholars of many
disciplines from far and wide
to study at his new madrasa,
an educational institution.
Ulugh Beg’s own interest
was in astronomy, and it may
have been his discovery of serious
errors in the star positions of the
Almagest that inspired him to
order the building of a gigantic
observatory, the largest in the
world at the time. Located on a
hill to the north of the city, it took
five years to construct and wasUlugh Beg
The name Ulugh Beg means
“Great Leader.” The sultan–
astronomer’s birth name was
Mirza Muhammad Taraghay
bin Shahrukh. He was born
on the move, as Timur’s army
traveled through Persia.
His grandfather’s death
in 1405 brought the army to
a halt in western China. The
ensuing fight for control of his
lands was eventually won by
Ulugh Beg’s father, Shah Rukh.
In 1409, Ulugh Beg was sent
to Samarkand as his father’sregent, and by 1411, as he
turned 18, his rule over the
city was extended to include
the surrounding province.
Ulugh Beg’s flair for
mathematics and astronomy
was not matched by his
leadership skills. When Shah
Rukh died in 1447, Ulugh Beg
assumed the imperial throne,
but he did not command enough
authority to keep it. In 1449, he
was beheaded by his own son.Key work1437 Zij-i Sultani