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The dwarf planet Pluto has five moons down to a detection limit of about 1 km in diameter. In order of distance from Pluto they are Charon, Styx, Nix, Kerberos, and Hydra. Charon, the largest of the five moons, is mutually tidally locked with Pluto, and is massive enough that Pluto–Charon is sometimes considered a double dwarf planet. ==History== The innermost and largest moon, Charon, was discovered by James Christy on 22 June 1978, nearly half a century after Pluto was discovered. This led to a substantial revision in estimates of Pluto's size, which had previously assumed that the observed mass and reflected light of the system were all attributable to Pluto alone. Two additional moons were imaged by astronomers of the Pluto Companion Search Team preparing for the ''New Horizons'' mission and working with the Hubble Space Telescope on 15 May 2005, which received the provisional designations S/2005 P 1 and S/2005 P 2. The International Astronomical Union officially named Pluto's newest moons Nix (or Pluto II, the inner of the two moons, formerly P 2) and Hydra (Pluto III, the outer moon, formerly P 1), on 21 June 2006.〔 〕 Kerberos, announced on 20 July 2011, was detected using NASA's Hubble Space Telescope during a survey searching for rings around Pluto. It was first seen in an image taken with Hubble's Wide Field Camera 3 on 28 June. It was confirmed in subsequent Hubble pictures taken on 3 and 18 July.〔 〕 Styx, announced on 7 July 2012, was discovered while looking for potential hazards for New Horizons. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Moons of Pluto」の詳細全文を読む スポンサード リンク
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