Pluto

The best-known dwarf planet, orbiting in the Kuiper Belt beyond Neptune. Discovered in 1930 and reclassified from planet to dwarf planet in 2006. New Horizons' 2015 flyby revealed a geologically active world with nitrogen-ice glaciers, water-ice mountains and a thin nitrogen atmosphere, orbited by five moons — the largest, Charon, half Pluto's own diameter.