Astronomers believe that it was created when objects in the Kuiper belt were `` scattered '' by the gravity of the outer planets ; mainly Neptune . Unlike most objects in the Solar System which move in a round and flat path , the scattered disc is much more erratic . The MPC also makes a clear distinction between the Kuiper belt and the scattered disc ; separating those objects in stable orbits ( the Kuiper belt ) from those in scattered orbits ( the scattered disc and the centaurs ) .