Ulugbek, the astronomer-king

Muhammad Taragay, known as Ulugbek ("great ruler"), was born in 1394 in Sultaniyeh, in Persia, during one of his grandfather Timur’s campaigns. He grew up at Timur’s court, travelling with the army and meeting scholars from across the empire. After Timur’s death, Ulugbek’s father Shah Rukh ruled the Timurid empire from Herat, and in 1409 he made the young Ulugbek governor of Samarkand and Transoxiana.

Ulugbek ruled Samarkand for four decades, more as a scholar-king than a conqueror. He was fascinated by mathematics and astronomy, wrote poetry and history, and gathered around him the best scientists of his time.

Ulugbek built madrasahs, colleges where astronomy and mathematics were taught alongside theology:

• The Ulugbek madrasah in Bukhara, completed in 1417, bears the inscription: "Striving for knowledge is the duty of every Muslim man and woman."
• The Ulugbek madrasah in Samarkand, built in 1417–1420 on the Registan, where Ulugbek himself is said to have taught. Its portal is decorated with stars.
• A smaller madrasah in Gijduvan, near Bukhara, in 1433.

Around 1428–1429, Ulugbek built an observatory on a hill north-east of Samarkand. It was a round, three-storey building, about 30 metres high, housing an enormous instrument, a meridian arc (often described as a sextant or quadrant) with a radius of about 40 metres, partly cut into the rock. With it, astronomers could measure the positions of the sun, moon and stars with great precision.

The scientists working with Ulugbek included Qadi Zada al-Rumi, Jamshid al-Kashi and later Ali Qushji.

The main result was the Zij-i Sultani (also called the Zij of Ulugbek), a set of astronomical tables completed in 1437. It included a catalogue of 1,018 stars, the first major star catalogue since Ptolemy, and tables for calculating the movements of the planets. Ulugbek calculated the length of the sidereal year with remarkable accuracy, within about a minute of modern values, and measured the tilt of the Earth’s axis.

The Zij was copied across the Islamic world and later translated into Latin, published in Oxford in the 17th century, and admired by European astronomers.

After Shah Rukh’s death in 1447, Ulugbek became ruler of the Timurid empire, but he was a poor military leader and faced revolts. In 1449, his own son Abd al-Latif rebelled, defeated him, and had him murdered as he set off on a pilgrimage. The observatory was destroyed soon afterwards and forgotten.

In 1908, the archaeologist Vasily Vyatkin found the remains of the observatory, guided by an old document. The lower part of the great arc, cut into the rock, survives. Ulugbek’s remains were found in the Gur-Emir in 1941, showing that he had been beheaded.

The Ulugbek observatory is on the outskirts of Samarkand, near the ancient site of Afrosiyob, about 15 minutes by car from the Registan. You can see the underground section of the meridian arc and a small museum with copies of the star catalogue, instruments and portraits. Combine it with Afrosiyob and the Shah-i-Zinda. See things to do in Samarkand.

Ulugbek is honoured in Uzbekistan as a symbol of science and learning. Universities, streets and a district of Tashkent bear his name, and a statue near the observatory shows him with a book. A crater on the Moon is named after him. For visitors, his madrasahs and observatory are a reminder that Samarkand was once not only a city of conquerors but a capital of knowledge. See our Samarkand itinerary.