page_title: Moons of Pluto
section_title: Charon
hierarchical_section_title: Moons of Pluto / Charon
caption_attribution_description: English: PIA19856: A Binary Planet in Color http://photojournal.jpl.nasa.gov/catalog/PIA19856 FILE DESCRIPTION: Pluto and Charon are shown in enhanced color in this image, which is the highest-resolution color image of the pair so far returned to Earth by New Horizons. It was taken at 06:49 UT on July 14, 2015, five hours before Pluto closest approach, from a range of 150,000 miles (250,000 kilometers), with the spacecraft's Ralph instrument. The image highlights the contrasting appearance of the two worlds: Charon is mostly gray, with a dark reddish polar cap, while Pluto shows a wide variety of subtle color variations, including yellowish patches on the north polar cap and subtly contrasting colors for the two halves of Pluto's "heart", informally named Tombaugh Regio, seen in the upper right quadrant of the image. In order to fit Pluto and Charon in the same frame in their correct relative positions, the image has been rotated so the north pole on both Pluto and Charon is pointing towards the upper left. The image was made with the blue, red, and near-infrared color filters of Ralph's Multicolor Visible Imaging Camera, and shows colors that are similar, but not identical, to what would be seen with the human eye, which is sensitive to a narrower range of wavelengths. The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, designed, built, and operates the New Horizons spacecraft, and manages the mission for NASA's Science Mission Directorate. The Southwest Research Institute, based in San Antonio, leads the science team, payload operations and encounter science planning. New Horizons is part of the New Frontiers Program managed by NASA's Marshall Space Flight Center in Huntsville, Alabama.
context_page_description: The dwarf planet Pluto has five natural satellites. 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.
context_section_description: Charon is about half the diameter of Pluto and is massive enough (nearly one eighth of the mass of Pluto) that the system's barycenter lies between them, approximately 960 km above Pluto's surface. Charon and Pluto are also tidally locked, so that they always present the same face toward each other. The IAU General Assembly in August 2006 considered a proposal that Pluto and Charon be reclassified as a double planet, but the proposal was abandoned.
  It is not clear if Charon is in hydrostatic equilibrium, which the definition of 'dwarf planet' would require, though it is a perfect sphere to within current measurement uncertainty.
caption: Pluto and Charon, to scale. Photo taken by New Horizons on approach.
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