Solar System/Eris

Eris (pronounced EAR-us or AIR-us) is  the largest known dwarf planet in the solar system, with a diameter of about 2500 kilometers and a mass that is 27% greater than Pluto's. It was first spotted in January 2005. Eris's orbit is beyond the Kuiper belt.

Classification
Since Eris orbits beyond the orbit of Neptune, it is a trans-Neptunian object. Since it is a trans-Neptunian dwarf planet, it is a plutoid.

Orbit
It takes Eris 557 years to orbit the sun. The orbit is highly elliptical, with an aphelion 97.5 AU from the Sun but a perihelion only 37.9 AU from the Sun. Its orbit is tilted by 44° relative to Earth's orbit.

Physical characteristics
Methane is known to be present on Eris.

Satellite
Eris has only one known moon, Dysnomia, which has an estimated diameter of between 100 and 250 kilometers.