Body diameters to scale. Positions and surface artwork are illustrative; Saturn’s rings are excluded.
A change of perspective
10.513× the diameter. See how the two worlds measure up.
Diameter is a distance across an object. Volume grows with the cube of that distance.
Choose a size to bring this comparison down to Earth.
Charon: Diameter of a sphere with Charon’s volume. JPL lists a mean radius of 606.0 km with sigma 0.5 km; doubling gives a diameter of 1,212.0 km with sigma 1.0 km. This is a mean diameter, not an equatorial, polar or longest-axis measurement.
Earth: Twice the source mean radius; body diameter only, excluding rings.
Diameter of a sphere with Charon’s volume. JPL lists a mean radius of 606.0 km with sigma 0.5 km; doubling gives a diameter of 1,212.0 km with sigma 1.0 km. This is a mean diameter, not an equatorial, polar or longest-axis measurement.
Charon, a moon of Pluto, has a mean diameter of approximately 1,212 km. The value is twice the mean radius tabulated by NASA JPL’s Planetary Satellite Physical Parameters. JPL attributes Charon’s radius to Nimmo and colleagues’ 2017 study of New Horizons images.
The quoted diameter uncertainty is ±1 km, obtained by doubling JPL’s radius sigma. The artwork is illustrative.
JPL lists the Moon with a mean radius of 1,737.4 km, giving a diameter of 3,474.8 km. Dividing 1,212 by 3,474.8 gives approximately 0.349: Charon is about 35% of the Moon’s diameter. On a model where the Moon is 10 cm across, Charon would be about 3.49 cm across. These are calculated linear-size comparisons using the JPL measurements.
Use the same measurement definition for both objects. Diameter ratios describe width; volume ratios require cubing that ratio, and mass comparisons also require density. See how sizes are compared.