Short answers, pulled from the story.
Ulugh Beg, born Mīrzā Muhammad Tāraghay on the 22nd of March 1394, was a Timurid sultan, astronomer, and mathematician. He is recognized by many scholars as the most important observational astronomer of the 15th century, chiefly for building the Ulugh Beg Observatory in Samarkand and compiling the Zij-i-Sultani star catalogue in 1437.
Ulugh Beg built his observatory in Samarkand between 1424 and 1429. Its most important instrument was the Fakhri sextant, with a radius of about 36 meters, used to measure the transit altitudes of stars. Scholars considered it one of the finest observatories in the Islamic world and the largest in Central Asia.
Ulugh Beg's Zij-i-Sultani of 1437 catalogued 994 stars and is generally regarded as the greatest star catalogue between those of Ptolemy and Tycho Brahe. He independently redetermined the positions of 992 fixed stars, correcting errors that had been carried forward in Arabian catalogues for centuries.
Ulugh Beg was assassinated in 1449 on the orders of his own son, Abdal-Latif Mirza, after being defeated in a succession conflict and surrendering to him. His brother Abdal-Aziz was killed at the same time. Ulugh Beg had been allowed to depart on a pilgrimage to Mecca but was killed before reaching his destination.
In 1437, Ulugh Beg calculated the sidereal year as 365 days, 6 hours, 10 minutes, and 8 seconds, with an error of 58 seconds. He also measured the tropical year as 365 days, 5 hours, 49 minutes, and 15 seconds, an error of 25 seconds, which was more accurate than Copernicus's later estimate.
Ulugh Beg was the grandson of Timur, also known as Tamerlane, through his father Shah Rukh. Both Timur and Shah Rukh came from the Barlas tribe, a Turkicized Mongol group from Transoxiana. Ulugh Beg's title, meaning "Great Ruler," was the Turkic equivalent of Timur's own Persian-Arabic title Amīr-e Kabīr.