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Pluto

  Pluto from New Horizons
Overview Facts and Figures Mission to Pluto Moons
This most famous 'dwarf planet' was discovered in 1930 by Clyde Tombaugh while he was working at the Lowell Observatory in Flagstaff AZ. Pluto is the largest known member of solar system bodies that comprise the Kuiper Belt.

Its elliptical orbit ranges between 30 and 49 AU from the Sun and its 248 year orbit is tilted from the ecliptic plane by about 20°. At it closest approach to the Sun, Pluto is inside the orbit of Neptune.

In 2006 , the Internation Astronomical Union reclassified Pluto from a planet to a dwarf planet. This decision was based on the distinction that the other planets have substantially cleared their orbit of other objects, where Pluto is one of many trans-neptunian objects.

The surface is thought to be a mixture of nitrogen ice, methane and carbon monoxide. The surface has a large contrast in light and dark regions. Tombaugh Regio is the light area known as the 'Heart' while the dark Cthulhu Regio is called the 'Whale.' A thin atmosphere of methane, nitrogen and carbon monoxide gas extends for over 100km from the surface.