Ulugh Beg (1394–1449)

Mongol mathematician and astronomer, ruler of Samarkand from 1409 and of the Mongol Empire from 1447. He built an observatory from which he made very accurate observations of the Sun and planets. He published a set of astronomical tables, called the Zij of Ulugh Beg.

Ulugh Beg was born at Sulaniyya in central Asia and brought up at the court of his grandfather Tamerlane. At the age of 15 Ulugh Beg became ruler of the city of Samarkand and the province of Maverannakhr. In 1447 he succeeded his father, Shahrukh, to the throne, but was assassinated two years later in a coup by his son.

In 1420 Ulugh Beg founded an institution of higher learning, or ‘madrasa’, in Samarkand. It specialized in astronomy and higher mathematics. Four years later he built a three-storey observatory and a sextant. By observing the altitude of the Sun at noon every day, he was able to deduce the Sun's meridianal height, its distance from the zenith, and the inclination of the ecliptic.

The Zij of Ulugh Beg and his school is written in Tajik. It consists of a theoretical section and tables of calendar calculations, of trigonometry, and of the positions of planets, as well as a star catalogue of 1,018 stars. This includes 992 stars whose positions Ulugh Beg redetermined with unusual precision.