Images: Astronomers see three new planets

The designated dozen would include Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. The three newcomers would be Ceres, the largest known asteroid which orbits between Mars and Jupiter; Charon, which has been considered Pluto's moon; and the recently discovered 2003 UB313, an object nicknamed Xena that was discovered in 2005 orbiting far beyond Pluto in the outer solar system.

This is an artist's montage of an "expanded" solar system.