Pluto is an example of a celestial body that is classified as a PLANET and an ORB. It is the second-most-massive known dwarf PLANET in the Solar System and the tenth-most-massive body observed directly orbiting the Sun. Pluto was discovered in 1930 and was originally classified as the ninth PLANET from the Sun. However, in 2006 it was reclassified as a dwarf PLANET due to its size and irregular orbit. It is composed primarily of rock and ice and is one of the five recognized dwarf planets in the Solar System.