A Planetary Ring System is a disc or ring of dust, asteroids, moonlets, and other solid material that specifically orbits a planet. Similar ring systems can be found orbiting other astronomical objects, such as moons and even some stars.
Planetary rings, once thought unique to the planet Saturn, are now known to exist around all large planets. These rings are not solid objects, but composed of countless particles with sizes from specks of dust to small moons.
All rings lie predominantly within their planet's Roche limit, where tidal forces would destroy a self-gravitating fluid body. They are also within the planet’s magnetosphere, and in the case of Uranus, they are within the upper reaches of the planetary atmosphere.
For each planet, the rings are quite different. Jupiter's ring is thin and composed of dust-like small particles. Saturn's rings are broad, bright, and opaque. Uranus has narrow, dark rings among broad lanes of dust that are invisible from Earth. Neptune's rings include incomplete arcs restricted to a small range of their circumference.
The ringed planets are not just objects of beauty, but complicated physical systems that provide a local laboratory and analogy for other cosmic systems like galaxies and planet-forming disks.
- Gaps within a planetary ring can be flown through while in supercruise without causing an emergency drop.