Omar Khayyam was an 11th century Persian astronomer, mathematician, and poet. He is best known for his collection of poems, The Rubaiyat of Omar Khayyam, which has been translated into many languages. He also wrote treatises on mathematics and astronomy, including a work on the solar calendar. Khayyam's contributions to astronomy include the discovery of the Jalali calendar, which is still used in Iran today. He also developed a method for determining the positions of the planets and stars. Khayyam's work had a lasting impact on Islamic science and culture.