 Johann <unk> Bode , in 1772 , first suggested that an <unk> planet could exist between the orbits of Mars and Jupiter . Kepler had already noticed the gap between Mars and Jupiter in 1596 . Bode based his idea on the Titius – Bode law — a now @-@ discredited hypothesis Johann Daniel Titius first proposed in 1766 — observing that there was a regular pattern in the semi @-@ major axes of the orbits of known planets , marred only by the large gap between Mars and Jupiter . The pattern predicted that the missing planet ought to have an orbit with a semi @-@ major axis near 2 @.@ 8 astronomical units ( AU ) . William Herschel 's discovery of <unk> in <unk> near the predicted distance for the next body beyond Saturn increased faith in the law of Titius and Bode , and in 1800 , a group headed by Franz <unk> von Zach , editor of the <unk> <unk> , sent requests to twenty @-@ four experienced astronomers ( dubbed the " celestial police " ) , asking that they combine their efforts and begin a methodical search for the expected planet . Although they did not discover Ceres , they later found several large asteroids . 
