Friedrich Wilhelm Bessel was a German astronomer and mathematician born on July 22, 1784. He is best known for his work in stellar parallax, which provided the first accurate measurement of the distance to a star, specifically 61 Cygni. This groundbreaking achievement helped establish the scale of the universe. Bessel also made significant contributions to the field of mathematics, particularly in the study of Bessel functions, which are important in various applications, including engineering and physics. He passed away on March 17, 1846, leaving a lasting legacy in both astronomy and mathematics.