Eris and Pluto dwarf planet orbits, illustration. The Sun is at centre, with the orbit of its outermost planet (Neptune, blue) shown as a red circle. Two Kuiper Belt dwarf planet orbits are also shown: Pluto (left) and Eris (upper right). A dwarf planet is an object that fails to dominate its orbit around the Sun (unlike a true planet), but which still has an independent orbit (unlike moons), and is large enough to be spherical due to gravity.