Eris (minor-planet designation 136199 Eris) is the most massive and second-largest dwarf planet known in the Solar System. It is also the ninth-most-massive known body directly orbiting the Sun, and the largest known body in the Solar System not visited by a spacecraft. It is measured to be in diameter. Eris is 27% more massive than dwarf planet Pluto, though Pluto is slightly larger by volume. Eris's mass is about 0.27% of the Earth's mass.