Charon

Moon· orbits Pluto

Charon is Pluto's largest moon — about half Pluto's size, so the two orbit a point in empty space as a 'double dwarf planet'. New Horizons revealed deep canyons and a dark reddish polar cap ('Mordor Macula').

Open in 3D viewSee Charon in the live, interactive 3D map

Key facts

Mass

1.59 × 10²¹ kg

0.0216 Moon masses

Radius

606 km

35% of our Moon's radius

Surface gravity

0.288 m/s²

3% of Earth's

Day length

6.4 days

Orbit around Pluto

6.39 Earth days

Science

Physical

Mass: 1.59 × 10²¹ kg · 0.0216 Moon masses
Radius: 606 km · 35% of our Moon's radius
Density: 1,701 kg/m³ · 1.7× water
Surface gravity: 0.288 m/s² · 3% of Earth's
Escape velocity: 591 m/s · 5% of Earth's

Orbit around Pluto

Distance from Pluto: 35,313 km
Orbital period: 6.4 days
Eccentricity: 0
Inclination: 0.00 °

Rotation

Rotation period: 6.4 days
Tidal locking: Tidally locked to its parent

Temperature

Mean: 53 K (-220 °C)

Composition

Bulk composition: A water-ice crust (with ammonia-bearing ices) over a rocky interior, and a dark, reddish, tholin-stained north pole.

Radiation & temperature

Insolation: 0.00079 S⊕ · 1/1,266 of the sunlight Earth receives
Geometric albedo: 0.38
Equilibrium temperature: 41 K (-232 °C)
Measured mean temperature: 53 K (-220 °C)
Greenhouse warming: +12 K

Discovery & history

Discovered: June 22, 1978
By: James W. Christy
Method: Photographic plates
Name: Charon, the ferryman of the dead in Greek myth — and a nod to discoverer James Christy's wife, Charlene.

James Christy spotted Charon in 1978 as a bump that kept reappearing on photographs of Pluto. Fully half Pluto's size, it is so large relative to its world that the two orbit a point in empty space between them — a genuine double system. New Horizons revealed its great reddish polar cap, nicknamed Mordor, in 2015.

Images

Charon in true colour, imaged by New Horizons — NASA / Johns Hopkins APL / SwRI (public domain) · Wikimedia Commons

Pluto and it's moon Charon Shine in False Color — NASA/GSFC · NASA Image Library

A Moon over Pluto Animation — NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute · NASA Image Library

Charon in Plutoshine — NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute · NASA Image Library

A Long-Distance Look from LORRI — NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute · NASA Image Library

A Remarkable World — NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute · NASA Image Library

Landslides on Charon — NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute · NASA Image Library

Two Faces of Pluto July 1 — NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute · NASA Image Library

Images from open archives · credit shown per image