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Pluto
Pluto is a dwarf planet in the Kuiper belt, which is at the outer edges of the solar system. With a diameter of 2300 km, Pluto is the second-largest dwarf planet after Eris (2600-km diameter). The smallest dwarf planet is Ceres (950-km diameter), which is an asteroid between the orbits of Mars and Jupiter.
This is the most detailed view to date of the entire surface of Pluto, as constructed from multiple NASA Hubble Space Telescope photographs taken from 2002 to 2003. Hubble's view isn't sharp enough to see craters or mountains, if they exist on the surface, but it reveals a complex-looking and variegated world with white, dark-orange, and charcoal-black terrain. The overall color is believed to be a result of ultraviolet radiation from the distant Sun breaking up methane that is present on Pluto's surface, leaving behind a dark, molasses-colored, carbon-rich residue.
The center image (180°) has a mysterious bright spot that is unusually rich in carbon monoxide frost. This region will be photographed in the highest possible detail when NASA's New Horizons probe flies by Pluto in 2015.
The original Hubble images are a few pixels wide, but through a technique called dithering, multiple, slightly offset pictures can be combined to synthesize a higher-resolution view than could be seen in a single exposure. The final images shown here took 20 computers operating continuously four years to generate.