Ring system in the context of "Shepherd moon"

Quaoar (minor-planet designation: 50000 Quaoar) is a ringed dwarf planet in the Kuiper belt, a band of icy planetesimals beyond Neptune. It has a slightly ellipsoidal shape with an average diameter of 1,100 km (680 mi), about half the size of the dwarf planet Pluto. The object was discovered by American astronomers Chad Trujillo and Michael Brown at Palomar Observatory on 4 June 2002. Quaoar has a reddish surface made of crystalline water ice, tholins, and traces of frozen methane.

Quaoar has two thin rings orbiting outside its Roche limit, which defied initial theoretical expectations that rings outside the Roche limit should be unstable. Quaoar has one moon named Weywot and another unnamed moon that has not yet been confirmed. It is believed that Quaoar's elongated shape, gravitational influence of its moons, and extremely cold temperature help keep its rings stable.

Saturn has the most extensive and complex ring system of any planet in the Solar System. The rings consist of particles in orbit around the planet and are made almost entirely of water ice, with a trace component of rocky material. Particles range from micrometers to meters in size. There is no consensus as to when the rings formed: while investigations using theoretical models suggested they formed early in the Solar System's existence, newer data from Cassini suggests a more recent date of formation.

Though light reflected from the rings increases Saturn's apparent brightness, they are not themselves visible from Earth with the naked eye. In 1610, the year after his first observations with a telescope, Galileo Galilei became the first person to observe Saturn's rings, though he could not see them well enough to discern their true nature. In 1655, Christiaan Huygens was the first person to describe them as a disk surrounding Saturn. The concept that Saturn's rings are made up of a series of tiny ringlets can be traced to Pierre-Simon Laplace.

Quaoar (minor-planet designation: 50000 Quaoar) is a ringed dwarf planet in the Kuiper belt, a band of icy planetesimals beyond Neptune. It has a slightly ellipsoidal shape with an average diameter of 1,100 km (680 mi), about half the size of the dwarf planet Pluto. The object was discovered by American astronomers Chad Trujillo and Michael Brown at Palomar Observatory on 4 June 2002. Quaoar has a reddish surface made of crystalline water ice, tholins, and traces of frozen methane.

Quaoar has two thin rings orbiting outside its Roche limit, which defies theoretical expectations that rings outside the Roche limit should be unstable. Quaoar has one moon named Weywot and another unnamed moon that has not yet been confirmed. It is believed that Quaoar's elongated shape, gravitational influence of its moons, and extremely cold temperature help keep its rings stable.

2060 Chiron is a ringed small Solar System body in the outer Solar System, orbiting the Sun between Saturn and Uranus. Discovered in 1977 by Charles Kowal, it was the first-identified member of a new class of objects now known as centaurs—bodies orbiting between the asteroid belt and the Kuiper belt. Chiron is named after the centaur Chiron in Greek mythology.

Although it was initially called an asteroid and classified only as a minor planet with the designation "2060 Chiron", in 1989 it was found to exhibit behavior typical of a comet. Today it is classified as both a minor planet and a comet, and is accordingly also known by the cometary designation 95P/Chiron. More recently, a series of occultation events through the 2010s and early 2020s revealed that Chiron hosts rings, making it one of four minor planets known to have rings (the three others being 10199 Chariklo, Haumea, and Quaoar) and the only known comet to do so.

10199 Chariklo /ˈkærəkloʊ/ is a ringed asteroid or centaur in the outer Solar System. It is the largest known centaur, with a diameter of about 250 km (160 mi). It orbits the Sun between Saturn and Uranus with an orbital period of 62.5 years. It was discovered on 15 February 1997 by the University of Arizona's Spacewatch project at Kitt Peak National Observatory. Chariklo has a dark, reddish surface composed of water ice, silicate minerals, amorphous carbon, and various complex organic compounds (also known as tholins).

Chariklo's ring system consists of two narrow rings of icy particles in orbit around the object. The rings of Chariklo were discovered in 2013, when astronomers observed Chariklo occulting or passing in front of a star. Chariklo was the first minor planet discovered to have rings, and as of 2025, it is one of the four minor planets known to have rings (the three others being 2060 Chiron, Haumea, and Quaoar). It is unknown what keeps Chariklo's rings stable, as it has been predicted that they should decay within a few million years. Astronomers have hypothesized that Chariklo's rings might be maintained by the gravitational influence of yet-undiscovered shepherd moons orbiting Chariklo. The origin of Chariklo's rings is uncertain, with various possible explanations including ejection of surface material via outgassing or tidal disruption of a moon around Chariklo.

José Luis Ortiz Moreno (born 1967) is a Spanish astronomer, and former vice director of Technology at the Instituto de Astrofísica de Andalucía (IAA), Spain. He leads a team working on minor planets at the Sierra Nevada Observatory in Granada, Spain, and was involved in the 2017 discovery of a ring system around the dwarf planet Haumea. The main-belt asteroid 4436 Ortizmoreno was named in his honor.