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{{#invoke:Hatnote|hatnote}} {{#invoke:Protection banner|main}} {{#invoke:Pp-move-indef|main}} {{ safesubst:#invoke:Unsubst||$N=Use mdy dates |date=__DATE__ |$B= }} {{#invoke:Infobox|infobox}}

Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond Neptune. It was the first Kuiper belt object to be discovered. It is the largest and second-most-massive known dwarf planet in the Solar System and 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, a dwarf planet in the scattered disc. Like other Kuiper belt objects, Pluto is primarily made of ice and rock<ref name="Wiley-2005" /> and is relatively small—about 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 (4.4–7.3 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. In 2014, Pluto was 32.6 AU from the Sun. Light from the Sun takes about 5.5 hours to reach Pluto at its average distance (39.4 AU).<ref name = lighttraveltime />

Pluto was discovered by Clyde Tombaugh in 1930, and was originally considered the ninth planet from the Sun. After 1992, its status as a planet fell into question following the discovery of several objects of similar size in the Kuiper belt. In 2005, Eris, which is 27% more massive than Pluto, was discovered, which led the International Astronomical Union (IAU) to define the term "planet" formally for the first time the following year.<ref name="hubblesite2007/24" /> This definition excluded Pluto and reclassified it as a member of the new "dwarf planet" category (and specifically as a plutoid).<ref name="BBC-Akwagyiram 2005-08-02" />

Pluto has five known moons: Charon (the largest, with a diameter just over half that of Pluto), Styx, Nix, Kerberos, and Hydra.<ref name="Showalter" /> Pluto and Charon are sometimes considered a binary system because the barycenter of their orbits does not lie within either body.<ref name="Olkin_2003" /> The IAU has not formalized a definition for binary dwarf planets, and Charon is officially classified as a moon of Pluto.<ref name="IAU Pluto" />

On July 14, 2015, the New Horizons spacecraft became the first spacecraft to fly by Pluto.<ref name="NYT-20150714-kc">{{#invoke:citation/CS1|citation |CitationClass=news }}</ref><ref name="AP-20150714">{{#invoke:citation/CS1|citation |CitationClass=news }}</ref><ref name="NYT-20150718">{{#invoke:citation/CS1|citation |CitationClass=news }}</ref> During its brief flyby, New Horizons made detailed measurements and observations of Pluto and its moons.<ref name="NYT-20150706">{{#invoke:citation/CS1|citation |CitationClass=news }}</ref>


Pluto sections
Intro   History    Orbit   Rotation    Geology    Mass and size    Atmosphere    Satellites   [[Pluto?section=_{{safesubst:#invoke:anchor|main}}_Origin_| {{safesubst:#invoke:anchor|main}} Origin ]]   Observation and exploration    Gallery    See also    Notes    References    External links   

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Pluto::first    Title::journal    Pluto's::planet    Charon::neptune    Center::orbit    Volume::bibcode

{{#invoke:Hatnote|hatnote}} {{#invoke:Protection banner|main}} {{#invoke:Pp-move-indef|main}} {{ safesubst:#invoke:Unsubst||$N=Use mdy dates |date=__DATE__ |$B= }} {{#invoke:Infobox|infobox}}

Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of bodies beyond Neptune. It was the first Kuiper belt object to be discovered. It is the largest and second-most-massive known dwarf planet in the Solar System and 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, a dwarf planet in the scattered disc. Like other Kuiper belt objects, Pluto is primarily made of ice and rock<ref name="Wiley-2005" /> and is relatively small—about 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 (4.4–7.3 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. In 2014, Pluto was 32.6 AU from the Sun. Light from the Sun takes about 5.5 hours to reach Pluto at its average distance (39.4 AU).<ref name = lighttraveltime />

Pluto was discovered by Clyde Tombaugh in 1930, and was originally considered the ninth planet from the Sun. After 1992, its status as a planet fell into question following the discovery of several objects of similar size in the Kuiper belt. In 2005, Eris, which is 27% more massive than Pluto, was discovered, which led the International Astronomical Union (IAU) to define the term "planet" formally for the first time the following year.<ref name="hubblesite2007/24" /> This definition excluded Pluto and reclassified it as a member of the new "dwarf planet" category (and specifically as a plutoid).<ref name="BBC-Akwagyiram 2005-08-02" />

Pluto has five known moons: Charon (the largest, with a diameter just over half that of Pluto), Styx, Nix, Kerberos, and Hydra.<ref name="Showalter" /> Pluto and Charon are sometimes considered a binary system because the barycenter of their orbits does not lie within either body.<ref name="Olkin_2003" /> The IAU has not formalized a definition for binary dwarf planets, and Charon is officially classified as a moon of Pluto.<ref name="IAU Pluto" />

On July 14, 2015, the New Horizons spacecraft became the first spacecraft to fly by Pluto.<ref name="NYT-20150714-kc">{{#invoke:citation/CS1|citation |CitationClass=news }}</ref><ref name="AP-20150714">{{#invoke:citation/CS1|citation |CitationClass=news }}</ref><ref name="NYT-20150718">{{#invoke:citation/CS1|citation |CitationClass=news }}</ref> During its brief flyby, New Horizons made detailed measurements and observations of Pluto and its moons.<ref name="NYT-20150706">{{#invoke:citation/CS1|citation |CitationClass=news }}</ref>


Pluto sections
Intro   History    Orbit   Rotation    Geology    Mass and size    Atmosphere    Satellites   [[Pluto?section=_{{safesubst:#invoke:anchor|main}}_Origin_| {{safesubst:#invoke:anchor|main}} Origin ]]   Observation and exploration    Gallery    See also    Notes    References    External links   

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