Eris is a dwarf planet located in the scattered disc region of the solar system, beyond the orbit of Neptune. Discovered in 2005, it is one of the largest known dwarf planets, with a diameter of about 2,326 kilometers. Eris is primarily composed of ice and rock, and it has a highly reflective surface due to its icy composition. Eris is notable for its large moon, Dysnomia, which orbits it at a distance of about 37,000 kilometers. The discovery of Eris played a significant role in the reclassification of Pluto as a dwarf planet, sparking debates about the definition of a planet in our solar system.