page_title: Pluto
hierarchical_section_title: Pluto
caption_attribution_description: English: Three years after NASA's New Horizons spacecraft gave mankind our first close-up views of Pluto and its largest moon, Charon, scientists are still revealing the wonders of these incredible worlds in the outer Solar System. Marking the anniversary of New Horizons' historic flight through the Pluto system on July 14, 2015, mission scientists released the highest-resolution color images of Pluto and Charon. These natural-color images result from refined calibration of data gathered by New Horizons' color Multispectral Visible Imaging Camera (MVIC). The processing creates images that would approximate the colors that the human eye would perceive, bringing them closer to “true color” than the images released near the encounter. This image was taken as New Horizons zipped toward Pluto and its moons on July 14, 2015, from a range of 22,025 miles (35,445) kilometers. This single color MVIC scan includes no data from other New Horizons imagers or instruments added. The striking features on Pluto are clearly visible, including the bright expanse of Pluto's icy, nitrogen-and-methane rich "heart," Sputnik Planitia.
context_page_description: Pluto is an icy dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It was the first and the largest Kuiper belt object to be discovered.
  Pluto was discovered by Clyde Tombaugh in 1930 and declared to be the ninth planet from the Sun. After 1992, its status as a planet was questioned following the discovery of several objects of similar size in the Kuiper belt. In 2005, Eris, a dwarf planet in the scattered disc which is 27% more massive than Pluto, was discovered. This led the International Astronomical Union to define the term "planet" formally in 2006, during their 26th General Assembly. That definition excluded Pluto and reclassified it as a dwarf planet.
  It is the ninth-largest and tenth-most-massive known object directly orbiting the Sun. It is the largest known trans-Neptunian object by volume but is less massive than Eris. Like other Kuiper belt objects, Pluto is primarily made of ice and rock and is relatively small—one-sixth the mass of the Moon and one-third its volume. It has a moderately eccentric and inclined orbit during which it ranges from 30 to 49 astronomical units or AU from the Sun.
context_section_description: Pluto (minor planet designation: 134340 Pluto) is an icy dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It was the first and the largest Kuiper belt object to be discovered.
  Pluto was discovered by Clyde Tombaugh in 1930 and declared to be the ninth planet from the Sun. After 1992, its status as a planet was questioned following the discovery of several objects of similar size in the Kuiper belt. In 2005, Eris, a dwarf planet in the scattered disc which is 27% more massive than Pluto, was discovered. This led the International Astronomical Union (IAU) to define the term "planet" formally in 2006, during their 26th General Assembly. That definition excluded Pluto and reclassified it as a dwarf planet.
  It is the ninth-largest and tenth-most-massive known object directly orbiting the Sun. It is the largest known trans-Neptunian object by volume but is less massive than Eris. Like other Kuiper belt objects, Pluto is primarily made of ice and rock and is relatively small—one-sixth the mass of the Moon and one-third its volume. It has a moderately eccentric and inclined orbit during which it ranges from 30 to 49 astronomical units or AU (4.4–7.4 billion km) from the Sun. This means that Pluto periodically comes closer to the Sun than Neptune, but a stable orbital resonance with Neptune prevents them from colliding.  Light from the Sun takes 5.5 hours to reach Pluto at its average distance (39.5 AU).
  Pluto has five known moons: Charon (the largest, with a diameter just over half that of Pluto), Styx, Nix, Kerberos, and Hydra. Pluto and Charon are sometimes considered a binary system because the barycenter of their orbits does not lie within either body.
  The New Horizons spacecraft performed a flyby of Pluto on July 14, 2015, becoming the first ever, and to date only, spacecraft to do so. During its brief flyby, New Horizons made detailed measurements and observations of Pluto and its moons. In September 2016, astronomers announced that the reddish-brown cap of the north pole of Charon is composed of tholins, organic macromolecules that may be ingredients for the emergence of life, and produced from methane, nitrogen and other gases released from the atmosphere of Pluto and transferred 19,000 km (12,000 mi) to the orbiting moon.
caption: Northern hemisphere of Pluto in true color, taken by NASA's New Horizons probe in 2015[a]
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