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Pluto
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Number
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134340
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Class
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Dwarf Planet
Double Planet Plutoid Plutino |
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Discovery date
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18.02.1930, about 23:00 UT, Flagstaff, USA (the discovery plates were taken on January 23 and 29, 1930)
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Discovery chart
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Discovery position
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17° Cancer 46' Rx
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Naming
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01.05.1930
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Orbital period
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251.1 years
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Orbit
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Aphelion
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49.892 AU
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Perihelion
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29.704 AU
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Semimajor axis
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39.798 AU
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Magnitude
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-0.7
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Diameter
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2320 km
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Inclination
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17.1
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The Pluto-Charon system is the largest of the binary systems in the solar system. Image: NASA
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Satellites
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Charon S/1978 P 1
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Discovery
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22.06.1978
Discovery of Charon is coincidentally contemporaneous with the discovery of the first centaur planet, near-homonymously-named Chiron (1977). |
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Time of announcement
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07.07.1978
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Distance between pair
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19 571 km +/- 4 km
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Orbital period
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6.387 d Like most satellites, Charon orbits in Pluto's equator. From 1985 through 1990, Pluto's equator and Charon's orbit plane were aligned with the line-of-sight from Earth, with Charon passing in front of and behind Pluto every 6.4 days. This means that from 1985 through 1990 Pluto and Charon eclipsed each other every Pluto day. Mutual Eclipses of Pluto and Charon |
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Pluto-Charon is the first known trans-neptunian binary object. Pluto and Charon have been called a double planet because Charon is larger compared to Pluto than any other moon is to a planet; indeed Charon is massive enough that, despite their proximity, Pluto orbits the system's barycenter at a point outside its surface. Charon and Pluto are also tidally locked, so that they always present the same face toward each other. |
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Hydra and Nix
S/2005 P 1 and S/2005 P 2
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Discovery
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15.06.2005 (the Hubble Space Telescope images revealing the moons were taken between May 15 and May 18, 2005)
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Time of announcement
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31.10.2005 IAU circular 8625
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Naming
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June 2006 The announcement
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Hydra and Nix are not orbiting just Pluto but the system's barycenter, which is between Pluto and Charon. They are Charon's moons as well. |
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Orbits of 4 bodies in Pluto system. P 1 is Hydra, and P 2 is Nix. Image: NASA |
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Mythology
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