thumb|upright=1.5|The [[natural satellite|moons Prometheus (right) and Pandora (left) orbit just inside and outside, respectively, the F ring of Saturn, but only Prometheus is thought to function as a shepherd moon.]]

A ring system is a disc or torus orbiting an astronomical object that is composed of numerous solid bodies such as dust particles, meteoroids, minor planets, moonlets, or stellar objects.

Ring systems are best known as planetary rings, common components of satellite systems around giant planets such as the rings of Saturn, or circumplanetary disks. But they can also be galactic rings and circumstellar discs, belts of minor planets, such as the asteroid belt or Kuiper belt, or rings of interplanetary dust, such as around the Sun at distances of Mercury, Venus, and Earth, in mean motion resonance with these planets.

Jupiter

Jupiter's ring system was the third to be discovered, when it was first observed by the Voyager 1 probe in 1979,

Hypothetical future ring systems

Mars

Mars may develop dusty rings in about 50 million years when its moon Phobos, slowly spiraling inward, crashes in to the planet. The resulting temporary ring system might eventually clump back into a new moon, a cycle that could have repeated several times in Martian history, as suggested by studies of the Borealis Basin and Deimos's orbit.

Rings systems of minor planets and moons

Reports in March 2008 suggested that Saturn's moon Rhea may have its own tenuous ring system, which would make it the only moon known to have a ring system.

Both rings display unusual properties. The outer ring orbits at a distance of , approximately 7.5 times the radius of Quaoar and more than double the distance of its Roche limit. The inner ring orbits at a distance of , approximately 4.6 times the radius of Quaoar and also beyond its Roche limit.

Visual comparison

thumb|400px|left|A [[Galileo spacecraft|Galileo image of Jupiter's main ring.]]

thumb|left|250px|A [[Voyager 2 image of Uranus's rings.]]

thumb|320px|A pair of [[Voyager 2 images of Neptune's rings.]]

See also

  • Shepherd moon
  • Circumplanetary disk
  • Circumstellar disc
  • Accretion disk
  • Lists of astronomical objects

References

</references>

  • USGS/IAU Ring and Ring Gap Nomenclature
  • Everything a Curious Mind Should Know About Planetary Ring Systems with Dr Mark Showalter, Bridging the Gaps: A Portal for Curious Minds
  • Physical Chemistry of Evolution of Planetary Systems
  • Gladyshev G. P. Thermodynamics and Macrokinetics of Natural Hierarchical Processes, p.&nbsp;217. Nauka, Moscow, 1988 (in Russian).