Pluto is a dwarf planet. It is the farthest away from the sun. Pluto is the second biggest dwarf planet in the solar system. and the tenth biggest dwarf planet orbiting the sun. Originally classified   as the ninth plant from the sun, Pluto is recognized as a dwarf planet. Pluto is approximately one sixth of the moon and one third of its volume. Pluto is in an inclined orbit, 4.4-7.4 billion km away from the sun. From the discovery of Pluto in 1930 until 2006, Pluto was a planet. In the late 1970’s, following the minor discovery of the plant Chiron in the outer solar system and the recognition of Pluto’s relatively low mass, its status as a major plant was questioned. In the late 20th and early 21st century, many objects similar to Pluto were discovered in the outer solar system, notably the scattered disc object Eris in 2005, which is 27% bigger the Pluto. On August 24th, 2006, the Internationale Astronomical Union defined what it means to be a ”planet” within the solar system. This definition excluded Pluto as a plant and put it in a new category ”dwarf planet” along with Eris and Ceres. After the reclassification, Pluto was added to a list of minor planets and given a number 134340. Pluto has five known moons, the largest being Charon, discovered in 1978, along with Nix and Hydra, discovered in 2005 and the provisionally found named S/2011, discovered in 2011 and S/2012, discovered in 2012. ”Vulcan” and ”Cerberus” are the names that were a popular vote, for the new moons.Pluto’s orbital period is 284 earth years. It’s orbital characteristics are substantially from those of the plants, which follow nearly circular orbits around the sun close to a flat reference plane called an ecliptic. In contrast, Pluto’s orbit is highly inclined relative to the ecliptic (over 17*) and highly elliptic. This high eccentricity means a small orbit of Pluto is closer to the sun then Neptune’s. Pluto was last closer to the sun then Neptune was February 7th, 1978 to February 11th, 1999. In long term Pluto’s orbit is in fact chaotic. While computer simulations can be used to predict its position for several million years (both forward and backward in time), after intervals longer then Lyapunov time to 10-20 million years, calculations become speculative: Pluto is sensitive to unmeasurably small details of the solar system, hard to predict  factors will gradually disturb Pluto’s orbit. Millions of years from now, Pluto may be well at aphelion, at perihelion or anywhere in between, with no way for us to predict. This dose not mean Pluto’s orbit is unstable, but, it’s potion on the orbit is unstable. Several resonances and other dynamical effects keep Pluto’s orbit stable, safe from planetary collusion and scattering. Find out more at  http://en.wikipedia.org/wiki/Pluto