Ulugh BegBorn 22 Mar 1394; died 27 Oct 1449 at age 55.Mongol astronomer and mathematician who, although the only important Mongol scientist, was the greatest astronomer of his time. Pursuing this interest he built an observatory (begun in 1428) at Samarkand. In his observations he discovered a number of errors in the computations of the 2nd-century Alexandrian astronomer Ptolemy, whose figures were still being used. His star map of 994 stars was the first new one since Hipparchus. After Ulugh Beg was assassinated by his son, the observatory fell to ruins by 1500, rediscovered only in 1908. Written in Arabic, his work went unread by the world's next generation of astronomers. When his tables were translated into Latin in 1665, telescopic observations had surpassed them.