Eris, also 136199 Eris, is the most massive and second-largest dwarf planet known in the Sol System. Eris is a trans-Neptunian object in that its orbit is outside that of the planet Neptune.
Overview
Eris is the ninth-most-massive known body directly orbiting the Sun and the sixteenth-most massive overall in the Sol system (counting moons). It is 27% more massive than Pluto, though Pluto is slightly larger by volume.
It is a trans-Neptunian object (TNO) in the scattered disk and has a high-eccentricity orbit. Eris was discovered in January 2005 by a Palomar Observatory–based team led by Mike Brown and verified later that year. It was named in September 2006 after the Greco–Roman goddess of strife and discord. It is also the largest known object in the solar system that has not been visited by a spacecraft. Eris has been measured at 2,326 ± 12 kilometres (1,445 ± 7 mi) in diameter. Both Eris and Pluto have a surface area that is comparable to that of Russia or South America.
Moons
Eris has one known moon named Dysnomia with an estimated diameter of 700 (± 115) km and an almost circular orbit at a distance of about 37,430 km. It orbits Eris in ~15 days and 18 hours. Dysnomia was discovered in September 2005. Its initial name was S/2005 (2003 UB313) 1.
Media
Trivia
- While the dwarf planet Pluto is of similar size, it was discovered much earlier (around 1930) so was given the name "Sol IX", indicating it was the ninth planet before it was demoted. Eris might have been designated "Sol X", but that nomenclature was largely abandonded before it was discovered. Ironically, the initial project to discover Pluto was called "Planet X", but the "X" was supposed to represent the unknown and not 10.
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