a planet is a space object that orbits the Sun and has a nearly round shape. Its gravity must be strong enough to clear all other space objects (except satellites) out of its orbit. Dwarf planets also orbit the Sun and have a nearly round shape. But other space objects nearby are not cleared by the gravity of the dwarf planets. They are not big enough for their gravitational fields to do this. Dwarf planets are different from satellites, which orbit a planet and not the Sun.