In comparison to these moons, our moon is 3,476 Km in Diameter. The Earth is 12,756 Km
in Diameter, roughly 3.7 times the size of the moon. When you consider how large our moon is
relative to the Earth, the moons of the gas giants are very small in proportion to their
host planets. In Jupiter's case, it's largest moon, Ganymede is 5262 Km in Diameter where
Jupiter itself is 143,800 Km's in Diameter. Therefore Jupiter is roughly 27.3 times Ganymede's
size! A much larger proportion than that of the Earth to its' moon.
Similarily, Pluto is
less than twice the size of it's moon Charon. Which leads you to wonder, "How close in size
do the moon and planet need to be before it becomes difficult to determine which is orbiting which?"
