The lonely rock at the edge of the solar system that caused Pluto's downfall has been dubbed Eris after the Greek goddess of strife, astronomers said on Thursday.

"Eris caused strife and discord by causing quarrels among people and that's what this one has done too," said Mike Brown, the California Institute of Technology researcher who discovered the object in 2005.

Brown's discovery, larger and farther from the Sun than Pluto, set off a heated debate about what should be considered a planet. The 2,500 members of the International Astronomers Union decided last month to downgrade Pluto to a "dwarf planet," leaving only eight full planets in the solar system. Many scientists have refused to accept the change.

Eris, pronounced EE-ris, is considered a dwarf planet as well. The most distant known solar system object from the Sun, it takes 557 years to complete an orbit. Unlike Pluto, its orbit does not cross paths with Neptune, the most distant full-sized planet.

Dignified celestial body
The body was dubbed UB313 after it was discovered. Brown nicknamed it Xena, after the television warrior princess, but said he didn't consider that to be an appropriate formal name for a celestial body. "Then the next one would be Spock or something, and that wouldn't be quite so dignified," Brown said in a telephone interview.

The astronomers' union accepted Eris on Wednesday. The group also accepted Brown's proposed name for Eris's moon, Dysnomia. Dysnomia is Eris' daughter in Greek mythology, and the word means "lawlessness" in Greek. "It sounds like a disease. But in any case we all liked it," said Ted Bowell, an astronomer at Lowell Observatory in Arizona who heads the division of the astronomers' union that deals with planets.

In Greek mythology, Eris started the Trojan war after she was excluded from a wedding on Mount Olympus, home of the gods.

To get revenge for the snub, she tossed an apple inscribed "to the most beautiful one" into the party, causing a squabble among the goddesses.

Paris, the prince of Troy, was forced to settle the dispute by picking one goddess as most beautiful, earning the spite of the others and the ultimate defeat of his city in the Trojan war. Brown said he plans to study Eris and Dysnomia further to figure out the dwarf planet's mass and density.