Giuseppe Piazzi

Giuseppe Piazzi was an Italian Catholic priest, mathematician, and astronomer who made one of the most serendipitous discoveries in the history of astronomy. On January 1, 1801 — the first night of the 19th century — he spotted a faint object moving against the background stars from his observatory in Palermo, Sicily. Initially believing he had found a new comet, Piazzi tracked the object for several weeks before illness forced him to stop. The object turned out to be Ceres, the largest body in the asteroid belt between Mars and Jupiter, and the first asteroid ever discovered. Ceres has since been reclassified as a dwarf planet. When Ceres was lost behind the Sun, the young mathematician Carl Friedrich Gauss developed new methods of orbit calculation to predict where it would reappear — and Piazzi's discovery was recovered exactly where Gauss predicted. Piazzi also compiled a highly accurate star catalog of 7,646 stars.

• Discovered Ceres, the first asteroid (now dwarf planet), on January 1, 1801 • Compiled the Palermo star catalog with 7,646 stars • Established the Palermo Astronomical Observatory • His discovery prompted Gauss to develop new orbital calculation methods