When the object did not appear where it should on January 2, Piazzi began to doubt his observations until the thought occurred to him that perhaps he was seeing a "new star *." It wasn't until the third of January when his "suspicion was converted into certainty, being assured it was not a fixed star." Finally, on the fourth night of his observations, he had "the satisfaction to see it had moved at the same rate as on the preceding days."
Although he was certain he had discovered a new planet, Piazzi announced it as a newly discovered comet. He wasn't able to observe it much longer, as its orbit carried it into the glare of the sun. Later, using mathematician Carl Friedrich Gauss's newly developed method of orbit calculation, astronomers were able to locate it again. Combined with the the Titius-Bode law which predicted a planet should be located in that area, the new object was declared a new planet. Piazzi named it "Ceres Ferdinandea," after the Roman and Sicilian goddess of grain and King Ferdinand IV of Naples and Sicily.
In fairly short order, over the next few years, three other objects were discovered in a roughly similar orbit; Pallas in 1802, Juno in 1804 and Vesta in 1807. In fact, by the end of the century, several hundred had been found. By that time, it Ceres's designation had been changed from planet to a new term, asteroid.
A few facts about Ceres; It has a diameter of 960 x 932 with a mass of 8.7e20 kg. Its rotation period is 9.075 hours with an orbital period of 4.60 years at a distance of 2.767AU.
* planet