Eris

dwarf planet · distant world · solar system

Super heavy and far away. Eris is the most massive dwarf planet we know of, even though it's smaller than Pluto. It orbits way out in the scattered disk, a region of icy bodies beyond Neptune that's so distant it takes Eris over 550 years just to circle the Sun once.

Discovered fairly recently. Scientists found Eris in January 2005 using the Palomar Observatory, making it one of the newest major planets discovered. It was named after the Greek goddess of strife and discord because of how its discovery stirred up big debates about what counts as a planet.

Bigger than Russia. Eris measures about 2,326 kilometers across, which means its entire surface area is roughly the same size as the country of Russia or South America. Even though it's smaller in volume than Pluto, Eris is actually 27% heavier, making it the real heavyweight champion of dwarf planets.

Never been visited. Eris is the largest object in our entire Solar System that no spacecraft has ever reached. It's so far away and takes so long to get there that scientists are still learning about it mainly through telescopes from Earth.

Icy and mysterious. Like other trans-Neptunian objects, Eris is made of frozen materials and rock. Its strange, stretched-out orbit brings it sometimes closer to and sometimes much farther from the Sun than other distant planets.