The method he developed to calculate the orbit of a comet he discovered in 1796 (now designated C/1796 F1) became standard in the nineteenth century. He later suggested that comets’ tails are somehow expelled from their heads by the Sun, thereby anticipating the discovery of radiation pressure. In 1802, a year to the day after its discovery, Olbers recovered the asteroid Ceres in the position predicted by C. F. Gauss. Olbers subsequently discovered Pallas (1802) and Vesta (1807). In 1823 he first pointed out what has come to be called Olbers’ paradox.