It was discovered on January 1 , 1801 , by Giuseppe Piazzi , and is named after the Roman goddess Ceresâ '' the goddess of growing plants , the harvest , and of motherly love . It was discovered on 1 January 1801 by Giuseppe Piazzi , and for half a century it was classified as the eighth planet . It is named after Ceres , the Roman goddess of growing plants , the harvest , and motherly love .