We once considered the Sun a planet, and it took finding Uranus to decide that moons should really be their own category of thing. These are all the places in our solar system that were once planets—but now have far more suitable names.
We know the planets close to the sun, and our closest neighbors, but few people know of the other big red hunk of matter orbiting the sun. The most distant known object in the solar system is Sedna, and astronomers hope that it's a sign of things even farther out.
The Kuiper Belt, the vast asteroid belt of ice and rock that lies beyond Neptune, is home to three objects big enough to be considered dwarf planets: Haumea, Makemake, and our old friend Pluto. And now, we might have found three more.