A dwarf planet that ignited the fiercest row in decades among the world's astronomers has been appropriately named Eris, after the goddess of discord who sparked the Trojan War. The object, previous known as 2003 UB313, was spotted in January 2005 by a team of Californian astronomers, whose leader, Michael Brown, proposed the name, the Paris-based International Astronomical Union (IAU) said in a press release on Friday.
About the same size as Pluto and likewise inhabiting the Kuiper Belt, a region beyond the orbit of Neptune, 2003 UB313 staked a claim on being the Solar System's 10th planet.
But that claim was rejected by the IAU last month, which ruled that large objects in this region were "dwarf planets" that were too small to be considered fully-fledged planets.
That definition meant that little Pluto lost its 76-year status as the ninth and outermost planet of the Solar System -- a decision that outraged a large number of astronomers, who are campaigning furiously for a review.
Pluto and Eris, together with the large asteroid Ceres, are the forerunners of IAU's new "dwarf planet" category, whose numbers are expectedly to grow rapidly as astronomers, using bigger and better telescopes, identify more and more objects in the Kuiper Belt.
In Greek legends, Eris stirs up jealousy and envy to cause fighting and anger among men.
At the wedding of Peleus and Thetis, the parents of the Greek hero Achilles, all the gods with the exception of Eris were invited.
Enraged at her exclusion, she spitefully caused a quarrel among the goddesses that led to the Trojan War.
Her name is pronounced "ee-ris", the IAU said, adding without apparent irony that the monicker was accepted "almost unanimously" by two committees that oversee the nomenclature of heavenly objects.
Under the IAU listing, Eris is officially designated (136199) Eris. It has a moon, (136199) Eris I, which has been named Dysnomia. In Greek mythology, Eris had two daughters, Dysnomia, a willful spirit of lawlessness, and Eunomia, a peaceable character who puts an end to strife.
Until Eris was officially named, 2003 UB313 was dubbed Xena, after TV's warrior princess, of which Brown is a fan.
According to measurements by the orbiting Hubble telescope, Eris has a diameter of 2,400 kilometers (1,500 miles), making it slightly larger than Pluto.
Campaigners for Pluto say the IAU ruling, made by a vote at a conference in Prague, was unscientific and undemocratic.
Pluto's status had long been contested by astronomers who said its tiny size, odd orbit and orbital plane precluded it from joining the other acknowledged planets.
They also argued that, if Pluto was accepted, the way was open for a vast expansion of the planetary list as more Kuiper Belt objects were uncovered, and this would be confusing for the public.
By the new IAU yardstick, a planet has "cleared the neighbourhood around its orbit" -- in other words, it is massive enough to wield a gravity that clears rocks and other debris on its orbital path.
The eight planets recognised by the IAU are Mercury, Earth, Venus, Mars, Jupiter, Saturn, Uranus and Neptune.
