Friedrich Bessel

Friedrich Wilhelm Bessel was born on 22 July 1784 in Germany and trained himself across astronomy, mathematics, physics, and geodesy. He became the first astronomer to determine reliable stellar distance using parallax — a geometric feat that had eluded predecessors for generations. Along the way he systematically studied a class of mathematical functions so fundamental they now carry his name: Bessel functions. He died on 17 March 1846, having opened the door to measuring the true scale of the cosmos.