A dwarf planet is a small planetary-mass object that is in direct orbit of the Sun, smaller than any of the eight classical planets but still a world in its own right. The prototypical dwarf planet is Pluto. The interest of dwarf planets to planetary geologists is that, since they are possibly differentiated and geologically active bodies, they may display planetary geology, an expectation that was borne out by the Dawn mission to Ceres and the New Horizons mission to Pluto, both in 2015.