Planet Sedna

On March 15, 2004, a team of astronomers (including Mike Brown, Chad Trujillo, and David Rabinowitz) announced the NASA-sponsored discovery of a very large planetary body (originally designated 2003 VB12) in one of the most distant planetary orbits yet discovered within the Solar System. Confirmed by the Spitzer (infrared) Space Telescope and tentatively named Sedna after the Inuit Goddess of the Sea (from which all creatures of the very cold Arctic sea were created),

Sedna is currently located around 90 AUs from our Sun, Sol -- an orbital distance that is roughly three times farther out than that of Pluto or Neptune -- but will eventually move as much as 10 times farther away (around 990 AUs) in a 12,260-year orbit around Sol; it's orbital semi-major axis is around 532 AUs with an extremely high eccentricity of 0.857.

Based on its current distance, brightness, and presumed albedo or ability to reflect light, Sedna has been estimated to have more than half the diameter of Pluto and may be larger than any other planetary body found since Pluto -- at 730 to 1,470 miles or 1,180 to 2,360 kilometers (km) across, compared to Pluto's diameter of around 1,440 miles or 2,320 km.