Eris is the most-massive dwarf planet in the Solar System — roughly 27% more massive than Pluto, though slightly smaller in diameter. Its discovery in 2005 directly prompted the IAU’s 2006 reclassification: if Eris were to be called a planet, many other large KBOs would have to be too, so a new category of “dwarf planet” was created. Eris orbits the Sun in the scattered disc, ranging from 38 to 97 AU. It has one known moon, Dysnomia.