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 2,326 Â± 12 kilometers (1,445.3 Â± 7.5 mi) in diameter. Eris is 27% more massive than dwarf planet Pluto, though Pluto is slightly larger by volume. Eris' mass is about 0.27% of the Earth's mass. Eris was discovered in January 2005 by a Palomar Observatory-based team led by Mike Brown, and its identity was verified later that year.