Moons of Saturn

The moons of Saturn are numerous and diverse, ranging from tiny moonlets only tens of meters across to the enormous Titan, which is larger than the planet Mercury.

[1][a] This number does not include the many thousands of moonlets embedded within Saturn's dense rings, nor hundreds of possible kilometer-sized distant moons that have been observed on single occasions.

[3][4][5] Seven Saturnian moons are large enough to have collapsed into a relaxed, ellipsoidal shape, though only one or two of those, Titan and possibly Rhea, are currently in hydrostatic equilibrium.

Titan is the second-largest moon in the Solar System (after Jupiter's Ganymede), with a nitrogen-rich Earth-like atmosphere and a landscape featuring river networks and hydrocarbon lakes.

[7] Iapetus has contrasting black and white hemispheres as well as an extensive ridge of equatorial mountains among the tallest in the solar system.

Saturn is expected to have around 150 irregular satellites larger than 2.8 km (1.7 mi) in diameter, plus many hundreds more that are even smaller.

The sole exception is Phoebe, the largest irregular Saturnian moon, discovered at the end of the 19th century; it is part of the Norse group but named for a Greek Titaness.

Saturn's largest moon, Titan, was discovered in 1655 by Christiaan Huygens using a 57-millimeter (2.2 in) objective lens[14] on a refracting telescope of his own design.

[29] (related image) Study of Saturn's moons has also been aided by advances in telescope instrumentation, primarily the introduction of digital charge-coupled devices which replaced photographic plates.

[13][3] In 2019, researchers Edward Ashton, Brett Gladman, and Matthew Beaudoin conducted a survey of Saturn's Hill sphere using the 3.6-meter Canada–France–Hawaii Telescope and discovered about 80 new Saturnian irregular moons.

[5] The researchers found that the Saturnian irregular moon population is more abundant at smaller sizes, suggesting that they are likely fragments from a collision that occurred a few hundred million years ago.

If this size distribution applies to even smaller diameters, Saturn would therefore intrinsically have more irregular moons than Jupiter.

[16] He proposed to name them after mythological figures associated with the Roman god of agriculture and harvest, Saturn (equated to the Greek Cronus).

[40] As Saturn devoured his children, his family could not be assembled around him, so that the choice lay among his brothers and sister, the Titans and Titanesses.

The minute interior ones seemed appropriately characterized by a return to male appellations [Enceladus and Mimas] chosen from a younger and inferior (though still superhuman) brood.

[Results of the Astronomical Observations made ... at the Cape of Good Hope, p. 415]In 1848, Lassell proposed that the eighth satellite of Saturn be named Hyperion after another Titan.

[41] All the irregular moons (except Phoebe, discovered about a century before the others) are named after Inuit, and Gallic gods, and after Norse ice giants.

[42] Some asteroids share the same names as moons of Saturn: 55 Pandora, 106 Dione, 577 Rhea, 1809 Prometheus, 1810 Epimetheus, and 4450 Pan.

Saturn's satellite system is very lopsided: one moon, Titan, comprises more than 96% of the mass in orbit around the planet.

[4] In 2007, the discovery of 150 more moonlets revealed that they (with the exception of two that have been seen outside the Encke gap) are confined to three narrow bands in the A Ring between 126,750 and 132,000 km from Saturn's center.

[4] There, "jets" of material may be due to collisions, initiated by perturbations from the nearby small moon Prometheus, of these moonlets with the core of the F Ring.

[50] One recently discovered moon, Aegaeon, resides within the bright arc of G Ring and is trapped in the 7:6 mean-motion resonance with Mimas.

[23][27] These moons probably formed as a result of accretion of the friable ring material on preexisting denser cores.

The cores with sizes from one-third to one-half the present-day moons may be themselves collisional shards formed when a parental satellite of the rings disintegrated.

A trojan body orbits at either the leading L4 or trailing L5 Lagrange point of a much larger object, such as a large moon or planet.

They are: Irregular moons are small satellites with large-radii, inclined, and frequently retrograde orbits, believed to have been acquired by the parent planet through a capture process.

[31][42] The Inuit group is further split into three distinct subgroups at different semi-major axes, and are named after their respective largest members.

[31][42] They are Aegir, Angrboda, Alvaldi, Beli, Bergelmir, Bestla, Eggther, Farbauti, Fenrir, Fornjot, Geirrod, Gerd, Greip, Gridr, Gunnlod, Hati, Hyrrokkin, Jarnsaxa, Kari, Loge, Mundilfari, Narvi, Phoebe, Skathi, Skoll, Skrymir, Surtur, Suttungr, Thiazzi, Thrymr, Ymir,[42] and 69 unnamed satellites.

The orbits and mean distances of the irregular moons are strongly variable over short timescales due to frequent planetary and solar perturbations, so the orbital elements of irregular moons listed here are averaged over a 5,000-year numerical integration by the Jet Propulsion Laboratory.

[96] In 2022, scientists of the Massachusetts Institute of Technology proposed the hypothetical former moon Chrysalis, using data from the Cassini–Huygens mission.