 Firstly, they were listed as planets, and half a century later, renamed as asteroids.Shortly after Giuseppe Piazzi's discovery of Ceres, a group of astronomers ratified the name, proposed by the discoverer, and chose the sickle as a symbol of the planet.The symbol for Pallas, the spear of Pallas Athena, was invented by Baron Franz Xaver von Zach, and introduced in his "Monatliche Correspondenz zur Beförderung der Erd- und Himmels-Kunde".