Image: Eris
A. Schaller  /  STScI
The mini-world formerly known as 2003 UB313 or Xena, shown in this artist's conception, has received an official name from the International Astronomical Union: Eris. Its moon has been named Dysnomia.
updated 9/13/2006 10:28:02 PM ET 2006-09-14T02:28:02

A distant, icy rock whose discovery shook up the solar system and led to Pluto's planetary demise has been given a name: Eris.

The christening of Eris, named after the Greek goddess of chaos and strife, was announced by the International Astronomical Union on Wednesday. Weeks earlier, the professional astronomers' group stripped Pluto of its planethood under new controversial guidelines.

Since its discovery last year, Eris ignited a debate over what constitutes a planet.

Astronomers were split over how to classify the object — which had been known as 2003 UB313, its provisional numerical designation; or as Xena, the informal code name that was chosen by its discoverers. Some argued that it should be welcomed as the 10th planet since it was larger than Pluto, but others felt Pluto was not a full-fledged planet.

After much bickering, astronomers last month voted to shrink the solar system to eight planets, downgrading Pluto to a "dwarf planet," a category that also includes Eris and the asteroid Ceres.

Eris' discoverer, Michael Brown of the California Institute of Technology, said the name was an obvious choice, calling it "too perfect to resist."

In mythology, Eris caused a quarrel among goddesses that sparked the Trojan War. In real life, Eris forced scientists to define a planet that eventually led to Pluto getting the boot. Soon after Pluto's dismissal from the club of classical planets, hundreds of scientists circulated a petition protesting the decision.

Moon also gets an official name
Eris' moon also received a formal name: Dysnomia, the daughter of Eris known as the spirit of lawlessness. Dysnomia is the object formerly known by the code name Gabrielle.

While waiting for an official designation, Brown and his colleagues reportedly used Xena as a code name because it called to mind the term "Planet X," which commonly referred to a mysterious 10th planet. The name also alluded to the title character in "Xena: Warrior Princess," a syndicated sword-and-sorcery TV series.

"It's a little sad to see Xena go away," Brown said.

In the TV show, Gabrielle was Xena's sidekick. Coincidentally, Eris was also the name of a character in "Xena: Warrior Princess."

The dwarf planet Eris, which measures about 70 miles (110 kilometers) wider than Pluto, is the farthest known object in the solar system at 9 billion miles (14 billion kilometers) away from sun. It is also the third brightest object located in the Kuiper Belt, a disc of icy debris beyond the orbit of Neptune.

This report was supplemented by information from

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