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Artist's impression of Eris
Credit: European Southern Observatory (ESO)

Eris is a dwarf planet in the outer reaches of our Solar system.

It was first seen in 2005 and is around 67 astronomical units away from the Sun, that's 67 times further away from the Sun then we are on planet Earth. It is the biggest of all of the dwarf planets we currently know of - and because it's bigger then Pluto its discovery caused a debate amongst astronomers as to whether the new object would be a planet. The discussion eventually led to Pluto being de-classified as a proper planet in 2006.

Although we cannot yet be sure, we think that Eris is an icy, rocky object that is about three-quarters the size of our Moon. Like other dwarf planets, Eris's orbit is tilted by 44° to the orbits of the main planets, and takes 558 years to complete one journey around the Sun, in a very elliptical orbit.

Eris has one known moon of it's own, called Dysnomia, which is around 150km across and orbits the dwarf planet every 15.8 days.

Dwarf Planet Data Sheet show »« hide
Facts and FiguresCeresPlutoHaumeaMakemakeEris
Orbital distance (AU)12.7739.543.145.867.7
Orbital Inclination10.6°17.1°28.2°29°44°
Radius (KM)4871,1371,4367501,300
Mass (Earth Masses)20.000160.002130.00070.00070.003
Year Length (Earth Years)4.6248.5283.3309.9557
Day Length (Earth Days)0.386.390.16UnknownUnknown
Surface Gravity (g)30.0030.040.0440.050.08
Surface Temperatureabout -105°Cabout -230°Cabout -240°Cabout -243°Cabout -240°C
Number of moons03201
Notes: 1 1 AU (or Astronomical Unit) = 149,600,000 KM and is the mean distance from the Earth to the Sun
2 1 Earth Mass = 5,980,000,000,000,000,000,000,000 KG : 3 1 g = 9.8 m/s2