3 Juno is a main belt asteroid discovered by Karl Ludwig Harding on September 1 , 1804 . Juno was the third asteroid discovered in the Solar System and is named after Juno , the Roman goddess that is the queen of all gods . Juno was discovered on September 1 , 1804 , by German astronomer Karl L. Harding and named after the mythological figure Juno , the highest Roman goddess .