Mirzo Ulugh Beg: the Samarkand observatory and the star table

Mirzo Ulugh Beg has remained in history as both a ruler and a scholar. But his main legacy is not a throne but a table: a catalogue in which the positions of the stars were carefully measured and recorded in an orderly way.

Key points

1. Who was he? According to Britannica, Ulugh Beg was born in 1394 and was a grandson of Amir Timur. His father Shahrukh entrusted Samarkand to him, and Ulugh Beg turned the city into a centre of science and culture (MacTutor).
2. The madrasa and the team of scholars. According to scholarly biographical sources (Dictionary of Scientific Biography), he built a madrasa in Samarkand in 1417–1420. A team of astronomers gathered around it; one of them, the mathematician Ghiyath al-Din Jamshid al-Kashi, worked on astronomical tables.
3. The observatory. The observatory was built in the 1420s; Britannica writes that construction began in 1428, while some sources give 1424. Its main instrument was a huge meridian arc, the "Fakhri sextant". According to the scholarly biographies on the MacTutor website, its radius was about 40 metres (some sources give a smaller value).
4. The "Zij-i Sultani". The result of the observatory's observations was the "Zij-i Sultani" astronomical tables; they are also known as the "Zij-i Gurgani" and, in Uzbek sources, as the "Zij-i jadidi Gurgani". Many sources, including the Stanford University project, say that it gives the positions of 1018 stars; some studies put this number at 992 or 994, the difference depending on how the stars are counted.
5. Accuracy put to the test. In a study published in 2012 in the journal Astronomy & Astrophysics, the catalogues of Ptolemy (2nd century) and Ulugh Beg were compared with modern Hipparcos data: the share of stars whose positions were off by more than 150 arcminutes came out at about 2% for Ptolemy and about 0.1% for Ulugh Beg.
6. A tragic end. Britannica writes that Ulugh Beg was killed in 1449 at the instigation of his son Abdal-Latif; the observatory was later destroyed. In 1908 the archaeologist V. L. Vyatkin found the underground part of the Fakhri sextant (MacTutor).
7. The lesson. The building was lost, the table remained. If data is collected correctly, recorded in an orderly way and copies are kept, it outlives even its author.

Example: a star table and a product master list

In Ulugh Beg's table every star has the same columns: name, coordinates, brightness. Because every row has the same structure, it is easy to find the star you need even in a table of a thousand rows.

A supermarket's product master list works on the same principle (prepared by the author, hypothetical):

If one row says "kg" and another "sack", or names are written differently, the month-end report is spoiled. Because Ulugh Beg's team put hundreds of observations into a single template, their table remained usable for centuries.