Don't planets and moons both orbit their center of mass? The distinction only seems to make sense if the masses of the two bodies are far apart. If they have similar mass, which is the moon and which the planet?
Indeed, before the planet/dwarf planet debate, Pluto and Charon were sometimes called a “binary planet” because their center of rotation is outside the volume of either body.
Comments
Don't planets and moons both orbit their center of mass? The distinction only seems to make sense if the masses of the two bodies are far apart. If they have similar mass, which is the moon and which the planet?
Indeed, before the planet/dwarf planet debate, Pluto and Charon were sometimes called a “binary planet” because their center of rotation is outside the volume of either body.