Ulugh Beg Observatory: A Timurid Astronomical Research Center in Uzbekistan
Site at a Glance
- Rating
- 4.3
- Popularity
- Medium
- Country
- Uzbekistan
- Primary era
- Medieval
- Eras represented
- Medieval
- Civilizations
- Timurid
- Site type
- Civic
On this page9 sections
History
Ulugh Beg Observatory in Samarkand, Uzbekistan, was a Timurid astronomical school and research center founded by the ruler and astronomer Ulugh Beg in the first half of the 1420s. Construction was completed around 1428, although the precise year remains debated. Established during the Timurid Empire, the Central Asian dynasty founded by Amir Timur and ruled by his descendants, it is described as the last institution of its kind from the medieval Islamic period.
Foundation and scholarly community
Ulugh Beg, son of Shah Rukh and grandson of Amir Timur, became ruler of Samarkand in the fifteenth century. His abilities in mathematics and astronomy led him to invite more than 60 mathematicians and astronomers to the city, where they helped establish both the observatory and a madrasa, an institution of Islamic learning. Political, economic, military, social, and commercial factors may all have influenced the project. Ulugh Beg’s visit to the Maragha Observatory, a major medieval Islamic observatory in northwestern Iran, and differences between his observations and those of the earlier Persian astronomer al-Sufi may also have encouraged its construction.
The observatory united astronomers and mathematicians who observed the sky, calculated the positions of thousands of stars, and pursued new research. Mathematics and astronomy were taught alongside music and prosody, the study of poetic metre and rhythm. Its principal scholars included Jamshid al-Kashi, Mu’in al-Din al-Kashi, Qadi Zada Rumi, and Ali Qushji. Jamshid al-Kashi served as the first director. After his death, Qadi Zada Rumi took the position, followed by Ali Qushji after Qadi Zada’s death.
The community initially followed Ptolemaic methods closely. Ptolemy, a second-century Greco-Egyptian astronomer, had established a geocentric mathematical framework and a major star catalogue in the Almagest. The Samarkand scholars appear to have known little of work at Maragha at first, which may have given their early research a provincial character. The arrival of scholars and students from a wider range of backgrounds gradually reduced this limitation.
Teaching was largely conducted from memory by teachers who had learned from astronomers in Herat. Qadi Zada Rumi, Maulana Muhammad Khani, and Maulana Abu’l-Fath were also well versed in Islamic jurisprudence, the scholarly interpretation and application of Islamic law. A letter by Jamshid al-Kashi indicates that Ulugh Beg did not teach classes frequently. The same letter shows that astrology, which interpreted celestial movements as meaningful for events or human affairs, occupied a larger place in Samarkand’s intellectual discussions than some modern interpretations have assumed.
Observations and the Zij-i Sultani
Ulugh Beg’s principal scholarly work, the Zij-i Sultani, was written in Persian and published in 1437 after seventeen years of work. The project began in 1420, when Ulugh Beg was 26, and involved Jamshid al-Kashi, Ali Qushji, other students, and Muslim astronomers. The main observations were made with the observatory’s great quadrant.
The work listed about 1,000 stars and followed Ptolemaic astronomy without changing its planetary model. Its numerical values for stars also listed by Ptolemy were more precise, making it the first major star catalogue published after the Almagest. An eighteen-page sine table gave values to nine decimal places for each degree from 0 to 87 degrees and to eleven decimal places from 87 to 90 degrees.
The Zij-i Sultani remained influential until the nineteenth century. Hundreds of copies of the original Persian manuscript survive around the world, while translations into Arabic, Turkish, Hebrew, and other languages, together with later commentaries, carried its calculations to subsequent generations of astronomers. Ulugh Beg calculated the tropical year as 365 days, 5 hours, 49 minutes, and 15 seconds, with an error of plus 25 seconds. He also calculated the Earth’s axial tilt as 23 degrees, 30 minutes, and 17 seconds in sexagesimal notation, or 23.5047 degrees. The stated value for the tropical year was more accurate than the comparison estimate attributed to Nicolaus Copernicus, whose error was given as plus 30 seconds.
Destruction and rediscovery
The observatory’s decline followed the assassination of Ulugh Beg by his son, Abd al-Latif, around 1449. His death brought disorder to the institution, which was destroyed, and dozens of astronomers and mathematicians were driven from Samarkand.
Russian archaeologist Vassily Vyatkin rediscovered and excavated the remains in 1908. A seventeenth-century land deed for a dervish lodge, a residence and religious institution associated with Sufi practitioners, helped identify the site. An expedition led by archaeologist Vasily Shishkin completed a later phase of excavation in 1948, exposing fragments of the building and foundations reaching down to the natural rock. The site forms part of a UNESCO World Heritage property, a status recorded from 2001, and is recognized as tangible cultural heritage of Uzbekistan. The Ulugh Beg Observatory Museum was built in 1970 as a memorial to the ruler, and a museum continues to operate on the grounds.
Remains
Ulugh Beg Observatory stood on a hill approximately 21 metres above the surrounding ground. Its principal building was a three-story cylinder about 46 metres in diameter and 30 to 33 metres high, built from readily available but relatively weak brick. The design drew on the Maragha Observatory, associated with the astronomer and mathematician Nasir al-Din al-Tusi and commissioned under Hulagu Khan and Mangu Khan. The central astronomical instrument occupied the building’s middle, while the structure’s height and roof supported the practical demands of observation.
The observatory building and instruments
The Fakhrī sextant
The central instrument was the monumental Fakhrī sextant, also called a quadrant. A quadrant or sextant is a graduated instrument for measuring angular distances and the altitude of celestial bodies. With a radius of 40.04 metres, it was the largest astronomical instrument in the world at the time. Oriented precisely from north to south, its arc measured the altitude of the Sun, stars, and planets as they crossed the celestial meridian, the north-south great circle used to define their passage across the sky. These measurements supported calculations of the year’s length, planetary periods, and eclipse times.
Part of the instrument was sunk into a trench approximately 2 metres wide. This allowed it to retain its long radius without forcing the building to become dangerously tall and unstable. The divisions on the arc measured 70.2 centimetres for one degree, 11.7 millimetres for one minute, and 1 millimetre for five seconds. The surviving markings correspond closely with modern calculations.
The cylindrical structure
The arc is believed to have represented one-sixth of a circle, with an effective working range from 20 to 80 degrees. Two marble-lined barriers bounded it, and brick stairways ran alongside them. The first of the building’s three stories contained living quarters for staff. Observations were made from the second and third stories, which had numerous arches for viewing the sky.
The roof was flat and could carry additional instruments. A horizontal circle may have been used there for azimuthal observations, which measure position around the horizon. Other instruments were present but have not survived. The entrance was altered several times, chiefly for aesthetic reasons rather than to improve the accuracy of astronomical observations.
Surviving foundations and museum collections
Only the foundations and the buried section of the marble quadrant remain visible from the original observatory. Excavation exposed fragments of the building and foundations extending to the natural rock. The surviving instrument remains preserve the scale and orientation of the central measuring system, while the foundations indicate the footprint of the cylindrical structure on the raised hill.
The museum contains reproductions of Ulugh Beg’s Arabic manuscripts, star charts, and the Zij-i Sultani, together with important European printed editions of his works. Astrolabes and other instruments are also displayed. An astrolabe is a portable device used to measure the altitude of celestial objects and solve related timekeeping and positional problems. A miniature reconstruction of the observatory further represents the building and its astronomical equipment.
