Ulugh Beg
Timurid sultan, mathematician, and astronomer who built the world's largest observatory and compiled a stellar catalog of unprecedented accuracy.
Who or what
Muhammad Taraghai ibn Shahrukh ibn Timur (1394–1449), known as Ulugh Beg, was a Timurid sultan and astronomer who ruled Samarkand.
He built the Samarkand Observatory (1420s) with a giant 40-meter sextant (the Fakhri sextant) and produced the Zij-i Sultani star catalog of 1,018 stars.
Why it mattered
Ulugh Beg was a ruler who prioritized science over conquest — his observatory was the most advanced in the world until Tycho Brahe's Uraniborg.
His star catalog was the first original catalog since Ptolemy's and remained the most accurate for over 200 years.
Key works and moments
He calculated the length of the sidereal year as 365.2570380 days (modern: 365.2563630), accurate to within one minute.
His catalog of 1,018 stars gave positions more accurate than Copernicus' later catalog.
Further detail
The Fakhri sextant had a radius of 40 meters, allowing angular measurements to a precision of a few arcseconds.
His astronomical tables included trigonometric functions, planetary positions, and precession rates.
Legacy
The Ulugh Beg catalog was used by European astronomers including John Flamsteed and Edmond Halley.
His observatory established a global standard for institutional astronomical research.
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