Sedna

In March 2004, a team of astronomers announced the discovery of a planet-like object, or planetoid, orbiting the Sun at an extreme distance, in the coldest known region of our solar system. Mike Brown, along with Doctors Chad Trujillo of the Gemini Observatory in Hawaii and David Rabinowitz of Yale University, New Haven, Conn., originally found the "planetoid" on November 14, 2003, using the 48-inch Samuel Oschin Telescope at Caltech's Palomar Observatory near San Diego. Within days, the object was observed by telescopes in Chile, Spain, Arizona and Hawaii, and soon after, NASA's new Spitzer Space Telescope looked for it.

The planetoid (2003 VB12), since named Sedna for an Inuit goddess who lives at the bottom of the frigid Arctic ocean, approaches the Sun only briefly during its 10,500-year solar orbit. Sedna is about one-quarter to three-eighths the size of the planet Pluto. At the farthest point in its long, elliptical orbit, Sedna is 130 billion kilometers (84 billion miles) from the Sun - that's about 86 AU, compared with the mean distances of Neptune (about 30 AU) and Pluto (about 39 AU).