PIAZZI , GIUSEPPE

Born at Ponte in Valtellina, Italy, Piazzi was a monk who originally taught philosophy but later in life developed an interest in astronomy. He became professor of mathematics at Palermo, Sicily, setting up an observatory there in 1787. He was a careful observer, publishing a catalog of 7646 stars in 1814. In his work he had found that proper motion was not the rarity assumed by some but the property of most stars and he found that 61 Cygni had a very large proper motion of 5.2''. His most dramatic discovery was that of the minor planet Ceres in 1801. He named it after the goddess of agriculture, once widely worshipped in Sicily. Although Piazzi lost the planet, its position was precisely predicted by Karl Gauss after a staggering feat of calculation based on three observations of Piazzi. Three more similar bodies were quickly found. He had a dispute with William Herschel over their nature. Piazzi proposed that they shoud be called ‘planetoids’ but Herschel's alternative suggestion of ‘asteroid’ has proved more acceptable until quite recently.