Eris (dwarf planet)

Eris (symbol 16px|⯰) is a dwarf planet and a trans-Neptunian object (TNO).Formal designation: 136199 Eris; Provisional designation: 2003 UB313. It is the second-largest known dwarf planet in the Solar System. Eris is slightly smaller than Pluto, but it has more mass than Pluto, making it the most massive dwarf planet. 

It is a "scattered disc object" in the Kuiper belt, further out than Pluto. It is also called a plutoid because the IAU decided to rename all trans-Neptunian dwarf planet as plutoids. Eris orbits the sun once every 557 Earth years. It has an elliptical orbit, inclined at an angle of 44° between the plane of the orbit of the planet and the ecliptic, the plane containing Earth's orbital path.

When it was first discovered, scientists nicknamed Eris by the name “Xena”.  

Eris has one smaller moon, called Dysnomia, that is the second largest moon of a dwarf planet. 

Discovery
136199 Eris was discovered by Michael E. Brown, Chad Trujillo and David Rabinowitz on January 5, 2005, when they were having a close look at some images of the outer Solar System taken in 2003.

Naming
136199 Eris was originally called Xena, after the main character of the television series Xena: Warrior Princess.  Due to complications, it was officially named 136199 Eris on September 13, 2006. Eris is named after the goddess of strife, discord, ⁣ contention and rivalry in Greek mythology.

Moon of 136199 Eris
136199 Eris has one moon called Dysnomia.Also with the provisional designation: 2003 UB313. It was discovered on September 10, 2005. Dysnomia was originally nicknamed Gabrielle, after a character from the television series Xena: Warrior Princess, like 136199 Eris. However, like 136199 Eris, it was renamed to Dysnomia due to complications. Dysnomia was named after the daughter of 136199 Eris, in Greek mythology. Dysnomia is the goddess (or spirit) of lawlessness and poor civil constitution.

Classification
Media reports have argued that 136199 Eris is the tenth planet, along with astronomers and NASA scientists.  However, the definition of a planet was changed in August 2006. Under the new specifications, 136199 Eris, along with 134340 Pluto, was lowered in status to a dwarf planet.

Future
Scientists continue to find out more about Eris and its moon, and look for more moons and possible rings. Because Eris is so far away, it would take 24.5 years to visit Eris with a space probe. McGranaghan, R.; Sagan, B.; Dove, G.; Tullos, A.; Lyne, J. E.; Emery, J. P. (2011). "A Survey of Mission Opportunities to Trans-Neptunian Objects". Journal of the British Interplanetary Society. 64: 296–303. Bibcode:2011JBIS...64..296M

 References and notes

Related pages
 Dwarf planet
 Pluto

 Other websites 

Eris