Ulugh Beg

• 1. Introduction

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  Ulugh Beg was born on the 22nd of March 1394 in Sultaniyeh, a city his grandfather Timur was in the process of conquering. That grandfather was Timur, known to the West as Tamerlane, one of the most feared conquerors in history. To be born into that family, on the road of war, was to inherit a world in constant motion.

  By the time he was sixteen, Ulugh Beg governed Samarkand. By his mid-thirties, he was building what scholars would call one of the finest observatories in the Islamic world. And by the age of fifty-five, he was dead, killed on the orders of his own son.

  What drove a Timurid prince to spend his life mapping the stars instead of expanding an empire? How did a man who could speak five languages and calculate the length of a year to within seconds end up failing at the one thing his dynasty demanded of him? And what does it mean that his star catalogue remained the best between Ptolemy and Tycho Brahe, spanning a gap of more than a millennium?

• 2. A Conqueror's Grandson

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  Timur died in 1405, and the empire he had spent decades building needed new hands. His son Shah Rukh moved the capital from Samarkand to Herat, in modern Afghanistan. The old capital, rich and well-positioned, was handed to Shah Rukh's oldest son, Ulugh Beg, while the boy was still sixteen.

  Ulugh Beg's full name at birth was Mīrzā Muhammad Tāraghay, but the name history remembers is a title, not a given name. Ulugh Beg can be loosely translated as "Great Ruler," drawn from the Turkic words for "great" and "chief." It served as the Turkic equivalent of his grandfather's own Persian-Arabic title, Amīr-e Kabīr.

  His lineage ran through the Barlas tribe, a Turkicized Mongol group from Transoxiana, in what is now Uzbekistan. His mother Gawhar Shad was herself a daughter of the Turkic tribal aristocracy, connecting the young prince to networks of power on multiple sides. As a child he had traveled through much of the Middle East and India while Timur was still conquering, which meant his early education was not formal but geographic and vast.

  In 1411, two years after taking Samarkand, Ulugh Beg was named sovereign ruler of the whole of Mavarannahr. The ambition that would define his life, however, was not military.

• 3. The Madrasa and the Observatory

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  A visit to the Maragheh Observatory in Iran sparked Ulugh Beg's lasting interest in astronomy. That observatory was where the astronomer Nasir al-Din al-Tusi had once worked, and seeing it gave the young governor a sense of what was possible.

  Between 1417 and 1420, Ulugh Beg built a madrasa on Registan Square in Samarkand, inviting Islamic astronomers and mathematicians to teach and study there. The madrasa building still stands. Among those who came was Qadi Zada al-Rumi, who became the most notable teacher at the institution. The astronomer Jamshid al-Kashi later joined the staff as well. Ulugh Beg's most famous pupil was Ali Qushchi, who died in 1474.

  The observatory followed between 1424 and 1429. Working without telescopes, Ulugh Beg pursued accuracy through scale. The Fakhri sextant, the observatory's most important instrument, had a radius of about 36 meters. Its optical separability reached 180 seconds of arc, making it extraordinarily precise for its time. The sextant was built partly underground; the portion that survived destruction is the lower, underground section, which remains visible today.

  The purpose of the Fakhri sextant was to measure the transit altitudes of stars, specifically their maximum altitude above the horizon, which allowed astronomers to determine the declination of celestial objects. The observatory at Samarkand became the most widely known in the Islamic world. Scholars considered it not only the largest observatory in Central Asia but one of the finest anywhere in the Islamic world at that time.

• 4. Mapping the Sky

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  With the instruments at Samarkand, Ulugh Beg compiled a star catalogue of 1,018 stars, eleven fewer than in the catalogue of Ptolemy. His approach was deliberately independent. He drew on dimensions from the astronomer Abd al-Rahman al-Sufi, but subjected the positions to a fresh analysis rather than simply updating older data.

  What he found troubled him. Ptolemy's data, which had been circulating and copied for centuries, contained serious errors. Many Arabic catalogues that followed Ptolemy had simply taken his work and added the effect of precession to the longitudes, propagating those errors forward rather than correcting them.

  The result of Ulugh Beg's independent work was the Zij-i-Sultani of 1437, covering 994 stars. He redetermined the positions of 992 fixed stars from direct observation. For 27 stars that lay too far south to observe from Samarkand, he incorporated data from al-Sufi's Book of Fixed Stars, originally composed in 964. Scholars generally regard the Zij-i-Sultani as the greatest star catalogue between those of Ptolemy and Tycho Brahe.

  This catalogue reached European scholars in stages. Thomas Hyde edited it at Oxford in 1665 under a Latin title. A reprint came in 1767 by G. Sharpe. Francis Baily produced an edition in 1843 in Volume XIII of the Memoirs of the Royal Astronomical Society. Edward Ball Knobel revised it again in 1917, working from all Persian manuscripts existing in Great Britain at that time.

• 5. Measuring Time and Earth

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  In 1437, Ulugh Beg calculated the length of the sidereal year as 365 days, 6 hours, 10 minutes, and 8 seconds. This carried an error of 58 seconds. The measurement came from years of observation using a gnomon 50 meters high.

  Nicolaus Copernicus improved on this figure in 1525, shaving 28 seconds off the error by appealing to the earlier estimate of Thabit ibn Qurra, who had lived from 826 to 901 and whose figure had an error of only 2 seconds.

  For the tropical year, however, Ulugh Beg achieved something more competitive. His later measurement placed it at 365 days, 5 hours, 49 minutes, and 15 seconds, with an error of only 25 seconds. That was more accurate than Copernicus's own estimate for the tropical year, which carried an error of 30 seconds.

  He also determined the Earth's axial tilt as 23 degrees, 30 minutes, and 17 seconds in the sexagesimal system, which converts to 23.5047 degrees in decimal form.

  In mathematics, Ulugh Beg computed trigonometric tables of sine and tangent values correct to at least eight decimal places, a precision that stood well beyond what most contemporaries had achieved.

• 6. Diplomacy and Warfare

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  Once he became governor of Samarkand, Ulugh Beg pursued diplomatic ties with the Yongle emperor of the Ming dynasty. In 1416, Ming envoys Chen Cheng and Lu An presented silk and silver stuffs to Ulugh Beg on the emperor's behalf. Three years later, Ulugh Beg sent his own emissaries, Sultan-Shah and Muhammad Bakhshi, to the Ming court in Beijing.

  Those envoys, arriving in Beijing, crossed paths with Ghiyath al-Din Naqqash and other delegates representing Ulugh Beg's father Shah Rukh and other Timurid figures. The two Timurid parties stayed at separate hostelries. Ghiyath al-Din Naqqash saw the Yongle emperor riding a black horse with white feet, an animal that had been sent as a gift by Ulugh Beg.

  In 1439, the Zhengtong emperor commissioned a painting of a black horse with white feet and a white forehead, described as a gift from Ulugh Beg. Six years later, the Ming emperor expressed gratitude for tribute from Samarkand with gifts that included vessels of gold and jade, a dragon-headed spear, a horse with saddle, and embroidered silk stuffs for both Ulugh Beg and his family.

  On the battlefield, his record was less impressive. He defeated Shir Muhammad of Moghulistan in 1425, but the campaign had limited impact and Shir Muhammad remained in power. In 1427, Ulugh Beg marched against Baraq, Khan of the Golden Horde and a former protege, near the town of Sighnaq on the Syr Darya. A smaller enemy force surprised the Timurid army near a hill outside Sighnaq and defeated them soundly. The humiliation was lasting. Ulugh Beg launched no further campaigns against neighboring powers himself, and the armies he later sent northward and eastward won no significant victories.

• 7. Overthrow and Assassination

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  In 1447, Shah Rukh died, and the Timurid world fractured. Ulugh Beg traveled to Balkh, where he learned his nephew Ala al-Dawla, son of his late brother Baysunghur, had claimed rulership in Herat. Ulugh Beg marched against him, met him at Murghab, and won. He then advanced on Herat and massacred its people in 1448. But Ala al-Dawla's brother, Abul-Qasim Babur Mirza, intervened and defeated Ulugh Beg.

  Retreat to Balkh brought fresh disaster. His oldest son, Abdal-Latif Mirza, had rebelled against him there. A civil war followed. Abdal-Latif raised troops and positioned them on the banks of the Amu Darya. Ulugh Beg, hearing of unrest in Samarkand, was forced to withdraw before any engagement. Abdal-Latif followed him to Samarkand. Ulugh Beg surrendered to his own son.

  Abdal-Latif freed his father from custody and permitted him to make a pilgrimage to Mecca. He then ensured Ulugh Beg never arrived. Ulugh Beg was assassinated in 1449, along with his brother Abdal-Aziz, on his son's orders.

  Rehabilitation came from another nephew, Abdallah Mirza, who reigned in 1450-1451 and placed Ulugh Beg's remains at Timur's feet in the Gur-e-Amir mausoleum in Samarkand. Soviet archaeologists found the remains there in 1941. Soviet anthropologist Mikhail M. Gerasimov later reconstructed Ulugh Beg's face from those remains, finding features close to the Mongoloid type with slightly Europoid characteristics, distinct from his father Shah Rukh's predominantly Caucasoid appearance.

  The legacy that outlasted his dynasty began to attract new forms of recognition centuries later. In 1830, German astronomer Johann Heinrich von Madler named a lunar crater Ulugh Beigh on his map of the Moon. An asteroid, 2439 Ulugbek, was discovered on the 21st of August 1977 by N. Chernykh at Nauchnyj and named in his honor. In 2021, the dinosaur Ulughbegsaurus was named after him as well.