What is the Roche limit?
The closer you are to a planet, the stronger is its gravitational pull on you. For a large moon, this means that the side closest to the planet is being pulled substantially more forcefully than the side facing away from the planet. Within a certain distance from the planet, that difference can be enough to pull the moon apart. The Roche limit is the minimum distance that a moon (or other large object) can be from a planet without being torn to bits. (For smaller objects, the difference in gravitational pull from one side to the other isn’t enough to pull it apart.) If the planet and the orbiting body have the same density, that distance is about 2.5 times the radius of the planet.
