Eris Facts

Eris is the most recognized of the dwarf planets and is the furthest of these from the sun. It is in the Kuiper Belt and outside of Neptune’s orbit.

Eris (center) and its moon of Dysnomia

Eris Dwarf Planet Profile

Discovered By:M.E. Brown C.A. Trujillo & D.L. Rabinowitz
Discovery Date:January 5th 2005
Diameter:2,326 km
Mass:1.66 × 10^22 kg (0.23 Moons)
Orbit Distance:10,120,000,000 km (68.01 AU)
Orbit Period:560.9 years
Surface Temperature:-231°C

Named after

Named after the mythological Greek goddess of strife and discord, the name almost seems perfect due to the fact that there was a dispute over whether or not Eris qualified as a dwarf planet.

Some of the other names that scientists tossed around for Eris included Xena (from the television show about a warrior princess); Persephone, wife of the mythological Greek go Pluto/Roman Hades; and Lila.

The original designation name for Eris was 2003 UB313. The team of scientists held onto the nickname of Xena until Eris was given an officially designated name.

The 10th Planet

At one point, Pluto was considered to be the 9th planet in our solar system and Eris was going to be the 10th. Eris is large in size and was thought to be over 28% bigger than Pluto.

Dwarf Planets

In 2006, the IAU (International Astronomical Union) met and established the rules for plant classification and created a new classification of dwarf planet.

Both Pluto and Eris became dwarf planets. The New Horizons spacecraft mission flyby corrected the fact that Pluto is indeed larger than Eris, but only by around 12 miles.

Eris’s Moon

Eris has a single moon named Dysnomia that is named after the Greek mythological daughter of Eris, known as the goddess of lawlessness.

It takes Dysnomia 16 Earth days to finish a full orbit. The same team that nicknamed Eris with the name “Xena,” decided to nickname the moon with “Gabriella,” Xena’s sidekick in the television show.

Asteroid Belt

The asteroid belt is found between the orbits of Jupiter and Mars and contain thousands of small celestial objects. All of these objects in the asteroid belt could fit inside of Eris.

The size of Eris is considered to be large for the outer realm of the solar system, even though it is just 2/3 the size of our own moon.

It’s thought that Eris may have originated inside the Kuiper Belt but that during the formation of the solar system, Neptune’s gravitational pull forced Eris out into the asteroid belt.

What do we know?

Eris is quite a distance from the sun and so far that so little sunlight reaches Eris that its atmosphere often freezes.

As Eris makes its orbit closer to the sun the atmosphere begins to thaw. Scientists believe that Eris shares a lot of Pluto’s traits, including a rocky surface.

Due to Eris’ orbit, it changes in status from being the furthest outside of the Kuiper Belt and is replaced by Pluto.

Will Grundy at the Lowell Observatory called Eris the “Sputnik planet” and thought that it might be an ice lava lamp planet.

The scientists learned many lessons from Eris regarding a tiny planet so far from the sun that might have a lot of activity.

Facts about Eris

  • Eris is around three times the distance from the sun as Pluto: 14,062,199,874 km and are currently considered to be the most distant objects in the solar system that we know of so far.
  • It takes 560.9 Earth years for Eris to complete its orbit around the sun.
  • Eris has a diameter of 1,451 mi/2,336 km.
  • When Eris was first discovered its brightness was so great that scientists immediately thought Eris was bigger than Pluto.
  • We know very little about Eris’ structure or whether Eris has a magnetosphere.
  • The discovery of Eris played a big role in defining dwarf planets and later changing Pluto from a planet to a dwarf planet.
  • Scientists are using the data from the New Horizons spacecraft flyby to compare and find out information about Eris.


  • What was the nickname that scientists gave Eris before it was officially designated?
  • Which dwarf planet is bigger: Eris or Pluto?
  • What planet do scientists think share a lot of traits with Eris?
  • How many Earth years does Eris take to complete an orbit around the sun?
    560.9 Earth years
  • What is the name of Eris’ moon?
  • Where is Eris located in the outer area of the solar system?
    the Kuiper Belt