Celestial Objects
Pluto
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A dwarf planet in the Kuiper Belt, discovered by Clyde Tombaugh. Pluto was classified as the solar system's ninth planet from 1930 until 2006, when the International Astronomical Union adopted a new formal definition of "planet" that Pluto does not meet, reclassifying it as a dwarf planet; the decision remains debated among some astronomers and the public.
Facts
Diameter (km) Orbital Distance39.5 AU average (about 5.91 billion km) from the Sun, on an eccentric orbit 1 Discovery Year Disputed
Object TypeDwarf planet (IAU classification, 2006); planet (1930-2006 classification) 1 Classified as the ninth planet 1930-2006; reclassified as a dwarf planet by the IAU's 2006 definition, a decision some astronomers and the New Horizons mission team have publicly disputed on scientific grounds. Cross-Tradition Connections
Associated With
Ceres, Celestial Objects Why this is disputed. Both bodies were reclassified as dwarf planets under the IAU's 2006 dynamical definition of planet, a classification a minority of planetary scientists dispute in favor of a geophysical definition; see the recorded dissent on Ceres's object-type.
Performed the first close flyby of Pluto, in July 2015.
Pluto was the mission's primary flyby target, reached on 14 July 2015.
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