Pluto, our lonely (dwarf) planet. Discovered in 1930 by Clyde Tombaugh, Pluto is located in the Kuiper Belt, a region of icy bodies beyond Neptune. It has a very long orbit that takes about 248 years to complete one revolution around the Sun. Pluto is very small, smaller than Earth's Moon. Its surface is composed of a mixture of ice and water, featuring mountains, plains, and possibly even subsurface oceans.