Eris is a dwarf planet residing in the Kuiper Belt in the outer edges of the Solar System.
Named after the Greek goddess of strife and discord, Eris is roughly the same size as Pluto, 1445 miles in diameter (2,326 kilometers), though about 27% greater mass, making it the most massive dwarf planet in the Solar System. Eris is the 9th most massive object orbiting our Sun, though 16th overall when factoring in the seven larger Moons. It is located at a distance of 96 AU, nearly three times the distance of Pluto from the Sun.

At the time of its discovery on October 21, 2003 at the Palomar Observatory, NASA considered it the 10th planet of our Solar System, which lead the International Astronomical Union to redefine the term ‘planet’ and incorporating the dwarf planet designation. A dwarf planet is a planetary sized object that is neither an actual planet nor a natural satellite, but something in the middle. Pluto, Ceres, Makemake, and Hasmea were designated as such, though potentially thousands more are predicted to existe beyond Neptune within the Kuiper Belt. Just when you thought our Solar System wasn’t all that interesting… plot twist, there’s entire worlds out there!

Eris harbors a single moon called Dysnomia (another nod to Greek mythology), named after the lawless and anarchistic daughter of Eris. What’s with the edgy designations here, astronomers? Dysnomia was discovered on September 10, 2005 by a team led by Michael Brown at the W.M. Keck Observatory.