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Statue of "Mirzo Ulugbek" in Riga, Latvia.

Ulugh Beg (Chaghatay/Persian: الغ‌بیگ‎ - also Uluğ Bey, Ulugh Bek and Ulug Bek) (1393 or 1394 in Sultaniyeh (Persia) – October 27, 1449) was a Timurid ruler as well as an astronomer, mathematician and sultan. His commonly known name is not truly a personal name, but rather a moniker, which can be loosely translated as "Great Ruler" or "Patriarch Ruler" and was the Turkic equivalent of Timur's Perso-Arabic title Amīr-e Kabīr^[1]. His real name was Mīrzā Mohammad Taragai bin Shāhrukh. Ulugh Beg was also notable for his work in astronomy-related mathematics, such as trigonometry and spherical geometry.

He was the grandson of the conqueror Timur (Tamerlane) (1336-1405) and oldest son of Shah Rukh, both of whom came from the Mongol Barlas tribe of Transoxiana (then Persia, now Uzbekistan). His mother was the Persian noble Goharshad. Like his grandfather Timur, he was also the ancestor of Babur, founder of Mughal Dynasty. Ulugh Beg was born in Sultaniyeh in Iran. As a child he wandered through a substantial chunk of the Middle East and India as his grandfather expanded his conquests in those areas. With Timur's death, however, and the accession of Ulugh's father to much of the Timurid Empire, he settled in Samarkand which had been Timur's capital. After Shah Rukh moved the capital to Herat (in modern Afghanistan), sixteen-year-old Ulugh Beg became the shah's governor in Samarkand in 1409. In 1411 he became a sovereign of the whole Mavarannahr khanate.

The teenaged ruler set out to turn the city into an intellectual center for the empire. In 1417-1420 he built a madrasa ("university" or "institute") on Registan Square in Samarkand, and invited numerous Islamic astronomers and mathematicians to study there. Ulugh Beg's most famous pupil in mathematics was Ghiyath al-Kashi (circa 1370 - 1429).

His own particular interests concentrated on astronomy, and in 1428 he built an enormous observatory, called the Gurkhani Zij, similar to Tycho Brahe's later Uraniborg. Lacking telescopes to work with, he increased his accuracy by increasing the length of his sextant; the so-called Fakhri Sextant had a radius of circa 36 meters (118 feet) and the optical separability of 180" (seconds of arc). Using it he compiled the 1437 Zij-i Sultani of 994 stars, generally considered the greatest of star catalogues between those of Ptolemy and Brahe. The serious errors which he found in the Arabian star catalogues (the authors had simply copied from Ptolemy, adding the effect of precession to the longitudes) induced him to redetermine the positions of 992 fixed stars, to which he added 27 stars from Al Sufi's catalogue from 964, which were too far south for observation from Samarkand. This catalogue, the first original one since Ptolemy, was edited by Thomas Hyde at Oxford in 1665 under the tile Tabulae longitudinis et latitudinis stellarum fixarum ex observatione Ulugbeighi by G. Sharpe in 1767, and in 1843 by Francis Baily in vol. xiii. of the Memoirs of the Royal Astronomical Society.

In 1437 Ulugh Beg determined the length of the sidereal year as 365.2570370...^d = 365^d 6^h 10^m 8^s (an error +58^s). In his measurements within many years he used a 50 m high gnomon. This value was improved by 28^s 88 years later in 1525 by Nicolaus Copernicus (1473-1543), who appealed to the estimation of Thabit ibn Qurra (826-901), which was accurate to +2^s.

Ulugh Beg, here depicted on a Soviet stamp, was one of Islam's greatest astronomers during the Middle Ages.

Unfortunately Ulugh's scientific prowess was not matched by his administrative skills. He lost some battles to rival kingdoms, and in 1448 massacred the people of Herat after defeating Mirza Ala-u-dowleh, son of Bai sunqur. Within two years he was beheaded by his own eldest son, 'Abd al-Latif while on his way to Mecca. Eventually he was rehabilitated by his relative Babur, founder of the Mughal Empire, who placed Ulugh Beg's remains in the tomb of Timur in Samarkand, found by archeologists in 1941.

In honour of his achievements the Ulugh Beigh crater on the Moon was named after him by the German astronomer Johann Heinrich von Mädler in his 1830 map of the Moon.

• Muslim scholars

• The observatory and memorial museum of Ulugbek
• Bukhara Ulugbek Madrasah
• Registan the heart of ancient Samarkand.
• Biography by School of Mathematics and Statistics University of St Andrews, Scotland
• Legacy of Ulug Beg

1. ^ B.F. Manz, "Tīmūr Lang", in Encyclopaedia of Islam, Online Edition, 2006

• 1839. L. P. E. A. Sedillot (1808-1875). Tables astronomiques d’Oloug Beg, commentees et publiees avec le texte en regard, TomeI, 1 fascicule, Paris. A very rare work, but referenced in the Bibliographie generale de l’astronomie jusqu’en 1880, by J.
• 1847. L. P. E. A. Sedillot (1808-1875). Prolegomenes des Tablesastronomiques d’Oloug Beg, publiees avec Notes et Variantes, et precedes d’une Introduction. Paris: F. Didot.
• 1853. L. P. E. A. Sedillot (1808-1875). Prolegomenes des Tablesastronomiques d’Oloug Beg, traduction et commentaire. Paris.
• Le Prince Savant annexe les étoiles, Frédérique Beaupertuis-Bressand, in Samarcande 1400-1500, La cité-oasis de Tamerlan : coeur d'un Empire et d'une Renaissance, book directed by Vincent Fourniau, éditions Autrement, 1995, ISSN 1157 - 4488.
• L'âge d'or de l'astronomie ottomane, Antoine Gautier, in L'Astronomie, (Monthly magazine created by Camille Flammarion in 1882), December 2005, volume 119.
• This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.