Cool!Eris is named after the Greek goddess of strife and discord. Before it was officially named, its nickname was Xena. This nickname came from Xena: Warrior Princess, which was a popular television show around the time it was found.
Eris, the largest known dwarf planet, was first detected in data collected in October of 2003. It was not identified until January of 2005. Mike Brown and his team of astronomers discovered what was considered to be the 10th planet while doing observations at the Palomar Observatory in California. At approximately 10 billion kilometers from the Sun, it is roughly 3 times farther out than Pluto. Eris is believed to be so far out that it is even out beyond the Kuiper Belt, which is at the outer fringe of the solar system. It takes 557 Earth years for Eris to make one orbit around the Sun. It has a highly eccentric orbit around the Sun, which causes its surface temperature to vary from -217 degrees Celsius to -243 degrees Celsius. Observations of Eris have led scientists to believe that it has frozen methane on its surface.
At 2400 kilometers in diameter, Eris is slightly larger than Pluto. Its discovery was one of the reasons the International Astronomical Union felt it was necessary to definitely define what should be considered a planet. Eris does not clear out its orbit, so it did not meet one of the requirements. Consequently, it was placed in the newly created category of dwarf planet along with Pluto and Ceres, which also did not meet all of the requirements to be called a planet.
Eris has one moon that we currently know about. Its name is Dysnomia. Dysnomia was the daughter of Eris and was considered to be the cause of lawlessness in the ancient world.
Why is Eris not considered to be the tenth planet in our solar system?
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