NASA artist's concept of Eris. Image Source: Space Today Online.
We live in great times. Sometimes the incredible discoveries of our era remind me of this. It's easy to forget them because the daily tidal wave of information is so overwhelming. Today marks the sixth anniversary since the tenth planet, Eris (also known as 2003 UB313), was discovered. This frozen world, slightly smaller than our moon, is in fact larger than Pluto and has a tiny moon of its own, called Dysnomia. Wiki: "Eris was discovered by the team of Mike Brown, Chad Trujillo, and David Rabinowitz on January 5, 2005, from images taken on October 21, 2003."
Eris, Greek goddess of strife and discord. Athenian painting, ca. 575-525 BCE. Image Source: Wiki.
The planet is named after Ἔρις, the Greek goddess of strife and discord, who in the myths initiated the Trojan War. The planet's tiny moon is named after the goddess's child, Δυσνομία, "lawlessness," the demon daughter of strife.
Shortly after Eris's discovery, in September 2006, the International Astronomical Union downgraded Pluto from being considered a planet to a 'minor planet,' to share Eris's classification. The two minor planets are part of the Kuiper belt past Neptune, which will likely yield more such discoveries in the future. The belt has a 'cliff' at its edge, which may be a gap, after which there could well be another belt orbiting our sun, out past Pluto. Similar small planetary bodies in the belt include Makemake, Haumea (moons: Namaka and Hi'iaka), Sedna, Orcus (moon: Vanth), and Quaoar (moon: Weywot).
Kuiper Belt objects. Image Source: Wiki.
A video below from BBC Worldwide explains how Eris was discovered.
Video Source: BBC Worldwide via Youtube.