Friedrich Bessel was a German mathematician and astronomer born on July 22, 1784. He is best known for his work in the field of astrometry, which involves measuring the positions and movements of celestial bodies. Bessel was the first to successfully measure the parallax of a star, specifically 61 Cygni, which provided evidence for the vast distances between stars. In addition to his contributions to astronomy, Bessel made significant advancements in mathematics, particularly in the development of Bessel functions. These functions are important in various fields, including engineering and physics, as they appear in solutions to problems involving wave propagation and heat conduction. Bessel passed away on March 17, 1846.