MNN - Mother Nature Network

Pluto is easily the black sheep in our family of planets. Once firmly established as the ninth planet orbiting the sun, it was downgraded in 2006 and reclaimed as a dwarf planet by the International Astronomical Union (IAU). Now Pluto is just another object in the Kuiper Belt, a region extending from Neptune filled with small, icy objects orbiting the sun — but Pluto and its mysterious neighbors hold some exciting astronomical discoveries.