Question

Imagine a moon orbiting outside the ring system of a jovian planet. How can such a moon open a gap in the rings without leaving its own orbit?

a) The tidal gravity of the moon will destroy ring particles at certain distances from the planet.
b) Ring particles in orbital resonance with the moon will be nudged out of their orbits.
c) The gravity of the moon will distort the entire ring system, making the orbits of ring particles eccentric and causing them to crash into one another.
d) Any ring particle whose orbital period is half that of the moon will be slowly pushed toward the planet and eventually collide with it.
e) This is not possible--only moons that orbit inside the ring system can open gaps in the rings.

Answer 1

A moon can open a gap in the rings of a jovian planet due to gravitational resonances that alter the orbits of ring particles, as seen in Saturn's Cassini Division. Tidal forces from the planet also contribute to the ring structure.

Step-by-step explanation:

A moon orbiting outside the ring system of a jovian planet can open a gap in the rings due to gravitational resonances with the ring particles. When the orbital period of the moon and the ring particles are in a simple ratio, like 1:2 or 2:3, the repeated gravitational tugs of the moon on the particles can push them into new orbits, thereby creating gaps. This phenomenon is observed in the Cassini Division of Saturn's rings, where the moon Mimas caused particles to be nudged into different orbits, leading to the formation of a gap.

Tidal forces exerted by the planet can also affect the structure of a ring system. Close to the planet, these forces can tear apart bodies or prevent loose particles from coalescing, influencing the formation and maintenance of rings. Interactions between rings and moons are crucial for the existence of the rings themselves; without the gravitational effects of moons, rings would likely spread and dissipate.