Largest moon of PlutoThe other half of a binary world
Charon
Charon is so large relative to Pluto that the two worlds orbit a centre lying in the space between them.
- Host
- Pluto
- Type
- Large icy companion
- Mean diameter
- 1,212 km
- Mean orbital radius
- 19,591 km
- Orbital period
- 6.39 days
- Surface gravity
- 0.288 m/s²
- Key feature
- Reddish north polar cap
- Explored
- New Horizons · 2015
Charon up close
NASA imagery
A shared centre
Charon is about half the diameter of Pluto. Their centre of mass lies outside Pluto, making the system behave in some respects like a double dwarf planet rather than a planet with a conventional moon.
Tidal locking is mutual: Pluto and Charon always keep the same face toward each other. Their orbital dance takes 6.39 Earth days.
A complex world
Charon's surface includes rugged ridges, smooth plains and a large dark region called Mordor Macula near the north pole. Methane escaping from Pluto may help produce the reddish material there.
New Horizons revealed tectonic scars and evidence for past geological activity. A possible ancient ocean may once have frozen beneath Charon's ice shell.
Worth knowing
Charon is named after the ferryman who carried souls to the underworld in Greek mythology.
Charon's diameter is about half of Pluto's, unusually large for a moon.
New Horizons flew past Pluto and Charon in July 2015.
Watch and explore
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Charon at 40: The Discovery of Pluto's Largest Moon NASA Video
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Research & further reading
Mission imagery and measurements are interpreted alongside orbital data. Follow the source links for the current NASA overview and precise satellite parameters.