Often equipped with a graduated scale, it can be used to measure right ascension. On the traveller's sundial shown above, it is the inner ring. The most prominent and most famous planetary rings in the Solar System are those around Saturn, but the other three giant planets ( Jupiter, Uranus, and Neptune) also have ring systems. There are also dust rings around the Sun at the distances of Mercury, Venus, and Earth, in mean motion resonance with these planets. [1] [2] [3] Recent evidence suggests that ring systems may also be found around other types of astronomical objects, including minor planets, moons, brown dwarfs, and other stars. Fainter planetary rings can form as a result of meteoroid impacts with moons orbiting around the planet or, in case of Saturn's E-ring, the ejecta of cryovolcanic material. [5] [6] a b Smith, Bradford A.; Soderblom, Laurence A.; Johnson, Torrence V.; Ingersoll, Andrew P.; Collins, Stewart A.; Shoemaker, Eugene M.; Hunt, G. E.; Masursky, Harold; Carr, Michael H. (1979-06-01). "The Jupiter System Through the Eyes of Voyager 1". Science. 204 (4396): 951–972. Bibcode: 1979Sci...204..951S. doi: 10.1126/science.204.4396.951. ISSN 0036-8075. PMID 17800430. S2CID 33147728. Gáspár, András; Rieke, George H. (April 20, 2020). "New HST data and modeling reveal a massive planetesimal collision around Fomalhaut". PNAS. 117 (18): 9712–9722. arXiv: 2004.08736. Bibcode: 2020PNAS..117.9712G. doi: 10.1073/pnas.1912506117. PMC 7211925. PMID 32312810. S2CID 215827666.

Another Centaur named Chiron was announced to have a possible ring system in 2015. Ringed Centaurs may be common, although their distances from Earth makes them a challenge to study.To solve this problem, we use the “small-angle formula” to relate angular and linear diameters in the sky. For angles in the sky that are small, the formula is usually written as This ring is also often marked with the zodiac signs and twenty-five stars, similar to the astrolabe. Tiscareno, Matthew S.; Burns, Joseph A.; Cuzzi, Jeffrey N.; Hedman, Matthew M. (2010). "Cassini imaging search rules out rings around Rhea". Geophysical Research Letters. 37 (14): L14205. arXiv: 1008.1764. Bibcode: 2010GeoRL..3714205T. doi: 10.1029/2010GL043663. S2CID 59458559.

A ring is a collection of vast numbers of particles, each like a tiny moon obeying Kepler’s laws as it follows its own orbit around the planet. Thus, the inner particles revolve faster than those farther out, and the ring as a whole does not rotate as a solid body. In fact, it is better not to think of a ring rotating at all, but rather to consider the revolution (or motion in orbit) of its individual moonlets. In 2023, it was discovered that the dwarf planet and Kuiper belt object Quaoar has a widely-separated ring. [31] [32] The ring is at a distance over seven times the radius of Quaoar, more than double the previously understood theoretical maximum within the Roche limit. [31] Rings around exoplanets [ edit ] Ring formation around extrasolar planet Ring systems of planets [ edit ] The ring orbiting Saturn consists mostly of chunks of ice and dust. The small dark spot on Saturn is the shadow from Saturn's moon Enceladus.Gratton, R.; etal. (June 2020). "Searching for the near-infrared counterpart of Proxima c using multi-epoch high-contrast SPHERE data at VLT". Astronomy & Astrophysics. 638: A120. arXiv: 2004.06685. Bibcode: 2020A&A...638A.120G. doi: 10.1051/0004-6361/202037594. S2CID 215754278. Fixed astronomical rings are mounted on a plinth, like armillary spheres, and can be used as sundials.