Moons of Saturn

Artist's concepts of the Saturnian ring–moon system

Saturn, its rings and major icy moons—from Mimas to Rhea
Images of several moons of Saturn. From left to right: Mimas, Enceladus, Tethys, Dione, Rhea; Titan in the background; Iapetus (top) and irregularly shaped Hyperion (bottom). Some small moons are also shown. All to scale.

The moons of Saturn are numerous and diverse, ranging from tiny moonlets less than 1 kilometre across, to the enormous Titan, which is larger than the planet Mercury. Saturn has 62 moons with confirmed orbits, fifty-three of which have names, and only thirteen of which have diameters larger than 50 kilometres.[1][2][3] Saturn has seven moons that are large enough to become spherical, and dense rings with complex orbital motions of their own. Particularly notable among Saturn's moons are Titan, the second largest moon in the Solar System, with a nitrogen-rich Earth-like atmosphere and a landscape including hydrocarbon lakes and dry river networks, and Enceladus, which emits jets of gas and dust and may harbor liquid water under its south pole region.

Twenty-four of Saturn's moons are regular satellites; they have prograde orbits not greatly inclined to Saturn's equatorial plane. They include the seven major satellites, four small moons which exist in a Trojan orbit with larger moons, two mutually co-orbital moons and two moons which act as shepherds of Saturn's F Ring. Two other known regular satellites orbit within gaps in Saturn's rings. The relatively large Hyperion is locked in a resonance with Titan. The remaining regular moons orbit near the outer edge of the A Ring, within G Ring and between the major moons Mimas and Enceladus. The regular satellites are traditionally named after Titans and Titanesses or other figures associated with the mythological Saturn.

The remaining thirty-eight, all small except one, are irregular satellites, whose orbits are much farther from Saturn, have high inclinations, and are mixed between prograde and retrograde. These moons are probably captured minor planets, or debris from the breakup of such bodies after they were captured, creating collisional families. The irregular satellites have been classified by their orbital characteristics into the Inuit, Norse, and Gallic groups, and their names are chosen from the corresponding mythologies. The largest of the irregular moons is Phoebe, the ninth moon of Saturn, and was discovered at the end of the 19th century.

The rings of Saturn are made up of objects ranging in size from microscopic to hundreds of meters, each of which is on its own orbit about the planet.[4] Thus a precise number of Saturnian moons cannot be given, as there is no objective boundary between the countless small anonymous objects that form Saturn's ring system and the larger objects that have been named as moons. At least 150 moonlets embedded in the rings have been detected by the disturbance they create in the surrounding ring material, though this is thought to be only a small sample of the total population of such objects.[5]

Contents

Discovery and naming

Early observations

Before the advent of telescopic photography, eight moons of Saturn were discovered by direct observation using optical telescopes. Saturn's largest moon, Titan, was discovered in 1655 by Christiaan Huygens using a 57-millimeter (2.2 in) objective lens[6] on a refracting telescope of his own design.[7] Tethys, Dione, Rhea and Iapetus (the "Sidera Lodoicea") were discovered in 1671–1672 by Giovanni Domenico Cassini.[8] Mimas and Enceladus were discovered in 1789 by William Herschel.[8] Hyperion was discovered in 1848 by W.C. Bond, G.P. Bond[9] and William Lassell.[10]

The use of long-exposure photographic plates made possible the discovery of additional moons. The first to be discovered in this manner, Phoebe, was found in 1899 by W.H. Pickering.[11] In 1966 the tenth satellite of Saturn was discovered by Audouin Dollfus, when the rings were observed edge-on near an equinox.[12] It was later named Janus. A few years later it was realized that all observations of 1966 could only be explained if another satellite had been present and that it had an orbit similar to that of Janus.[12] This object is now known as Epimetheus, the eleventh moon of Saturn. It shares the same orbit with Janus—the only known example of co-orbitals in the Solar System.[13] In 1980 three additional Saturnian moons were discovered from the ground and later confirmed by the Voyager probes. They are trojan moons of Dione (Helene) and Tethys (Telesto and Calypso).[13]

Observations by spacecraft

Four moons of Saturn can be seen on this image by the Cassini spacecraft: Huge Titan and Dione at the bottom, small Prometheus (under the rings) and tiny Telesto above center.
Five moons in another Cassini image: Rhea bisected in the foreground, Mimas behind it, bright Enceladus above and beyond the rings, Pandora eclipsed by the F Ring, and Janus off to the left.

The study of the outer planets has since been revolutionized by the use of unmanned space probes. The arrival of the Voyager spacecraft at Saturn in 1980–1981 resulted in the discovery of three additional moons—Atlas, Prometheus and Pandora, bringing the total to 17.[13] In addition, Epimetheus was confirmed as distinct from Janus. In 1990, Pan was discovered in archival Voyager images.[13]

The Cassini mission, which arrived at Saturn in the summer of 2004, initially discovered three small inner moons including Methone and Pallene between Mimas and Enceladus as well as the second Lagrangian moon of Dione—Polydeuces. It also observed three suspected but unconfirmed moons in the F Ring.[14] In November 2004 Cassini scientists announced that the structure of Saturn's rings indicates the presence of several more moons orbiting within the rings, although only one, Daphnis, has been visually confirmed so far (in 2005).[15] In 2007 Anthe was announced.[16] In 2008 it was reported that Cassini observations of a depletion of energetic electrons in Saturn's magnetosphere near Rhea might be the signature of a tenuous ring system around Saturn's second largest moon.[17] In March 2009, Aegaeon, a moonlet within the G Ring, was announced.[18] In July of the same year, S/2009 S 1, the first moonlet within the B Ring, was observed.[3]

Outer moons

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. For the entire 20th century, Phoebe stood alone among Saturn's known moons with its highly irregular orbit. Beginning in 2000, however, three dozen additional irregular moons have been discovered using ground-based telescopes.[19] A survey starting in late 2000 and conducted using three medium-size telescopes found thirteen new moons orbiting Saturn at a great distance, in eccentric orbits, which are highly inclined to both the equator of Saturn and the ecliptic.[20] They are probably fragments of larger bodies captured by Saturn's gravitational pull.[19][20] In 2005, astronomers using the Mauna Kea Observatory announced the discovery of twelve more small outer moons.[21][22] In 2006, astronomers using the Subaru 8.2 m telescope reported the discovery of further nine irregular moons.[23] In April 2007, Tarqeq (S/2007 S 1) was announced. In May of the same year S/2007 S 2 and S/2007 S 3 were reported.[24]

Naming

The modern names for Saturnian moons were suggested by John Herschel in 1847.[8] He proposed to name them after mythological figures associated with the Roman god of agriculture and harvest, Saturn (equated to the Greek Kronos).[8] In particular, the then known seven satellites were named after Titans and Titanesses—brothers and sisters of Saturn.[11] In 1848 Lassell proposed that the eighth satellite of Saturn was named Hyperion after another Titan.[10] When in the 20th century the names of Titans were exhausted, the moons were named after different characters of the Greco-Roman mythology or giants from other mythologies.[25] All the irregular moons (except Phoebe) are named after Inuit and Gallic gods and after Norse ice giants.[26]

Some asteroids share the same names as moons of Saturn: 55 Pandora, 106 Dione, 577 Rhea, 1809 Prometheus, 1810 Epimetheus, and 4450 Pan. In addition, two more asteroids previously shared the names of Saturnian moons until spelling differences were made permanent by the International Astronomical Union (IAU): Calypso and asteroid 53 Kalypso; and Helene and asteroid 101 Helena.

Sizes

The Saturnian moon system is very lopsided: one moon, Titan, comprises more than 96% of the mass in orbit around the planet. The six other ellipsoidal moons constitute roughly 4%, while the remaining 54 small moons, together with the rings, comprise only 0.04%.[note 1]

Saturn's major satellites, compared to Earth's Moon
Name
Diameter
(km)[27]
Mass
(kg)[28]
Orbital radius
(km)[29]
Orbital period
(days)[29]
Mimas 396
(12% Moon)
0.4×1020
(0.05% Moon)
185,000
(50% Moon)
0.9
(3% Moon)
Enceladus 504
(14% Moon)
1.1×1020
(0.2% Moon)
238,000
(60% Moon)
1.4
(5% Moon)
Tethys 1,062
(30% Moon)
6.2×1020
(0.8% Moon)
295,000
(80% Moon)
1.9
(7% Moon)
Dione 1,123
(32% Moon)
11×1020
(1.5% Moon)
377,000
(100% Moon)
2.7
(10% Moon)
Rhea 1,527
(44% Moon)
23×1020
(3% Moon)
527,000
(140% Moon)
4.5
(20% Moon)
Titan 5,150
(148% Moon)
(75% Mars)
1,350×1020
(180% Moon)
1,222,000
(320% Moon)
16
(60% Moon)
Iapetus 1,470
(42% Moon)
18×1020
(2.5% Moon)
3,560,000
(930% Moon)
79
(290% Moon)

Orbital groups

Although the boundaries may be somewhat vague, Saturn's moons can be divided into ten groups according to their orbital characteristics. Many of them, such as Pan and Daphnis, orbit within Saturn's ring system and have orbital periods only slightly longer than the planet's rotation period.[30] The innermost moons and most regular satellites all have mean orbital inclinations ranging from less than a degree to about 1.5 degrees (except Iapetus, which has an inclination of 7.57 degrees) and small orbital eccentricities.[31] On the other hand, irregular satellites in the outermost regions of Saturn's moon system, in particular the Norse group, have orbital radii of millions of kilometers and orbital periods lasting several years. The moons of the Norse group also orbit in the opposite direction to Saturn's rotation.[26]

Ring moonlets

During late July 2009, a moonlet was discovered in the B Ring,[3] 480 km from the outer edge of the ring, by the shadow it cast. It is estimated to be 300 m in diameter. Unlike the A Ring moonlets (see below), it does not induce a 'propeller' feature, probably due to the density of the B Ring.[32]

In 2006, four tiny moonlets were found in Cassini images of the A Ring.[33] Before this discovery only two larger moons had been known within gaps in the A Ring: Pan and Daphnis. These are large enough to clear continuous gaps in the ring.[33] In contrast, a moonlet is only massive enough to clear two small—about 10 km across—partial gaps in the immediate vicinity of the moonlet itself creating a structure shaped like an airplane propeller.[34] The moonlets themselves are tiny, ranging from about 40 to 500 meters in diameter, and are too small to be seen directly.[5] 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. Each band is about a thousand kilometers wide, which is less than 1% the width of Saturn's rings.[5] This region is relatively free from the disturbances related to resonances with larger satellites,[5] although other areas of the A Ring without disturbances are apparently free of moonlets. The moonlets were probably formed from the breakup of a larger satellite.[34] It is estimated that the A Ring contains 7,000–8,000 propellers larger than 0.8 km in size and millions larger than 0.25 km.[5]

Similar moonlets may reside in the F Ring.[5] 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. One of the largest F-Ring moonlets may be the as-yet unconfirmed object S/2004 S 6. The F Ring also contains transient "fans" which are thought to result from even smaller moonlets, about 1 km in diameter, orbiting near the F Ring core.[35]

One of the recently discovered moons, Aegaeon, resides within the bright arc of G Ring and is trapped in the 7:6 mean motion resonance with Mimas.[18] This means that it makes exactly seven revolutions around Saturn while Mimas makes exactly six. The moon is the largest among the population of bodies that are sources of dust in this ring.[36]

Ring shepherds

Shepherd satellites are small moons that orbit within, or just beyond, a planet's ring system. They have the effect of sculpting the rings: giving them sharp edges, and creating gaps between them. Saturn's shepherd moons are Pan (Encke gap), Daphnis (Keeler gap), Atlas (A Ring), Prometheus (F Ring) and Pandora (F Ring).[14][18] These moons together with co-orbitals (see below) 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.[30]

Co-orbitals

Janus and Epimetheus are called co-orbital moons.[13] They are of roughly equal size, with Janus being slightly larger than Epimetheus.[30] Janus and Epimetheus have orbits with only a few kilometers difference in semi-major axis, close enough that they would collide if they attempted to pass each other. Instead of colliding, however, their gravitational interaction causes them to swap orbits every four years.[37]

Inner large moons

The innermost large moons of Saturn orbit within its tenuous E Ring, along with three smaller moons of the Alkyoniods group.

Alkyonides

Three small moons orbit between Mimas and Enceladus: Methone, Anthe, and Pallene. Named after the Alkyonides of Greek mythology, they are some of the smallest moons in the Saturn system. All Alkyonides possess very faint ring arcs along their orbits.[44]

Trojan moons

Trojan moons are a unique feature not found outside the Saturnian system. 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. Tethys has two Trojan moons, Telesto (leading) and Calypso (trailing), and Dione also has two, Helene (leading) and Polydeuces (trailing).[14] Helene is by far the largest Trojan moon,[38] while Polydeuces is the smallest and has the most chaotic orbit.[37]

Outer large moons

These moons all orbit beyond the E Ring. They are:-

Irregular moons

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. They often occur as collisional families or groups.[19] The precise size as well as albedo of the irregular moons are not known for sure because the moons are very small to be resolved by a telescope, although the latter is usually assumed to be quite low—around 6% (albedo of Phoebe) or less.[20] The irregulars generally have featureless visible and near infrared spectra dominated by water absorption bands.[19] They are neutral or moderately red in color—similar to C-type, P-type, or D-type asteroids,[26] though they are much less red than Kuiper Belt objects.[19][note 3]

Inuit group

The Inuit group includes five prograde outer moons that are similar enough in their distances from the planet (186–297 radii of Saturn), their orbital inclinations (45–50°) and their colors that they can be considered a group.[20][26] The moons are Ijiraq, Kiviuq, Paaliaq, Siarnaq, and Tarqeq.[26] The largest among them is Siarnaq with an estimated size of about 40 km.

Gallic group

The Gallic group are four prograde outer moons that are similar enough in their distance from the planet (207–302 radii of Saturn), their orbital inclination (35–40°) and their color that they can be considered a group.[20][26] They are Albiorix, Bebhionn, Erriapus, and Tarvos.[26] Tarvos, as of 2009, is the most distant of Saturn's moons with a prograde orbit. The largest among these moons is Albiorix with an estimated size of about 32 km.

Norse group

The Norse (or Phoebe) group consists of 29 retrograde outer moons.[20][26] They are Aegir, Bergelmir, Bestla, Farbauti, Fenrir, Fornjot, Greip, Hati, Hyrrokkin, Jarnsaxa, Kari, Loge, Mundilfari, Narvi, Phoebe, Skathi, Skoll, Surtur, Suttungr, Thrymr, Ymir, S/2004 S 7, S/2004 S 12, S/2004 S 13, S/2004 S 17, S/2006 S 1, S/2006 S 3, S/2007 S 2, and S/2007 S 3.[26] After Phoebe, Ymir is the largest of the known retrograde irregular moons, with an estimated diameter of only 18 km. The Norse group may itself consist of several smaller subgroups.[26]

Tables of moons

Confirmed moons

The Saturnian moons are listed here by orbital period (or semi-major axis), from shortest to longest. Moons massive enough for their surfaces to have collapsed into a spheroid are highlighted in bold, while the irregular moons are listed in red, orange and gray background.
Key

Major icy moons

Titan

Inuit group

Gallic group

Norse group


Order
Label
[note 4]
Name
Pronunciation (key) Image Diameter (km)[note 5]
Mass
(×1015 kg) [note 6]
Semi-major axis (km) [note 7]
Orbital period (d)[note 7][note 8]
Inclination [note 7][note 9]
Eccentricity
Position Discovery
year
[25]
Discoverer
[25]
0 S/2009 S/2009 S 1 ≈ 0.3 <0.0001 ≈ 117,000 ≈ 0.47 ≈ 0° ≈ 0 outer B Ring 2009 Cassini–Huygens[3]
0 (moonlets) 0.04 to 0.4 (Earhart) <0.0001 ≈ 130,000 ≈ 0.55 ≈ 0° ≈ 0 Three 1000 km bands within A Ring 2006 Cassini–Huygens
1 XVIII Pan Pan ˈpæn 28.2 ± 2.6
(34×31×20)
4.95±0.75 133,584 +0.57505 0.001° 0.000035 in Encke Division 1990 M. Showalter
2 XXXV Daphnis Daphnis ˈdæfnɨs 7.6 ± 1.6
(9×8×6)
0.084±0.012 136,505 +0.59408 ≈ 0° ≈ 0 in Keeler Gap 2005 Cassini–Huygens
3 XV Atlas Atlas ˈætləs 30.2 ± 1.8
(41×35×19)
6.6 ± 0.045 137,670 +0.60169 0.003° 0.0012 outer A Ring shepherd 1980 Voyager 2
4 XVI Prometheus Prometheus proʊˈmiːθiːəs 86.2 ± 5.4
(136×79×59)
159.5 ± 1.5 139,380 +0.61299 0.008° 0.0022 inner F Ring shepherd 1980 Voyager 2
5 XVII Pandora Pandora pænˈdɔərə 81.4 ± 3.0
(104×81×64)
137.1 ± 1.9 141,720 +0.62850 0.050° 0.0042 outer F Ring Shepherd 1980 Voyager 2
6a XI Epimetheus Epimetheus ˌɛpɨˈmiːθiːəs 116.2 ± 3.6
(130×114×106)
526.6±0.6 151,422 +0.69433 0.335° 0.0098 co-orbital with Janus 1977 J. Fountain, and S. Larson
6b X Janus Janus ˈdʒeɪnəs 179.0 ± 2.8
(203×185×153)
1,897.5 ± 0.6 151,472 +0.69466 0.165° 0.0068 co-orbital with Epimetheus 1966 A. Dollfus
8 LIII Aegaeon Aegaeon iːˈdʒiːən ≈ 0.5 ~0.0001 167,500 +0.80812 0.001° 0.0002 G Ring moonlet 2008 Cassini–Huygens
9 I MimasMimas ˈmaɪməs 396.4 ± 0.8
(416×393×381)
37,493 ± 31 185,404 +0.942422 1.566° 0.0202   1789 W. Herschel
10 XXXII Methone Methone mɨˈθoʊniː 3.2 ± 1.2 ~0.02 194,440 +1.00957 0.007° 0.0001 Alkyonides 2004 Cassini–Huygens
11 XLIX Anthe Anthe ˈænθiː ≈ 1 ~0.007 197,700 +1.03650 0.1° 0.001 Alkyonides 2007 Cassini–Huygens
12 XXXIII Pallene Pallene pəˈliːniː 5.0 ± 1.2
(6×6×4)
~0.05 212,280 +1.15375 0.181° 0.0040 Alkyonides 2004 Cassini–Huygens
13 II EnceladusEnceladus ɛnˈsɛlədəs 504.2 ± 0.4
(513×503×497)
108,022 ± 101 237,950 +1.370218 0.010° 0.0047 Generates the E ring 1789 W. Herschel
14 III TethysTethys ˈtiːθɨs 1,062 ± 1.2
(1077×1057×1053)
617,049 ± 132 294,619 +1.887802 0.168° 0.0001   1684 G. Cassini
14a XIII Telesto Telesto tɨˈlɛstoʊ 24.8 ± 0.8
(33×24×20)
~9.41 294,619 +1.887802 1.158° 0.000 leading Tethys Trojan 1980 B. Smith, H. Reitsema, S. Larson, and J. Fountain
14b XIV Calypso Calypso kəˈlɪpsoʊ 21.4 ± 1.4
(30×23×14)
~6.3 294,619 +1.887802 1.473° 0.000 trailing Tethys Trojan 1980 D. Pascu, P. Seidelmann, W. Baum, and D. Currie
17 IV DioneDione daɪˈoʊniː 1,122.8 ± 0.8
(1128×1123×1119)
1,095,452 ± 168 377,396 +2.736915 0.002° 0.0022   1684 G. Cassini
17a XII Helene Helene ˈhɛlɨniː 35.2 ± 0.8
(43×38×26)
~24.46 377,396 +2.736915 0.212° 0.0022 leading Dione Trojan 1980 P. Laques and J. Lecacheux
17b XXXIV Polydeuces Polydeuces ˌpɒliˈdjuːsiːz 2.6 ± 0.8
(3×2×1)
~0.03 377,396 +2.736915 0.177° 0.0192 trailing Dione Trojan 2004 Cassini–Huygens
20 V RheaRhea ˈriːə 1,527.0 ± 1.2
(1530×1526×1525)
2,306,518 ± 353 527,108 +4.518212 0.327° 0.001258   1672 G. Cassini
21 VI TitanTitan ˈtaɪtən 5,151 134,520,000
± 20,000
1,221,930 +15.94542 0.3485° 0.0288   1655 C. Huygens
22 VII HyperionHyperion haɪˈpɪəriən 270 ± 8
(360×266×205)
5,620 ± 50 1,481,010 +21.27661 0.568° 0.123006 in 4:3 resonance with Titan 1848 W. Bond
G. Bond
W. Lassell
23 VIII IapetusIapetus aɪˈæpɨtəs 1,468.6 ± 5.6
(1491×1491×1424)
1,805,635 ± 375 3,560,820 +79.3215 7.570° 0.028613   1671 G. Cassini
24 XXIV KiviuqKiviuq ˈkɪviək ≈ 16 ~2.79 11,294,800 +448.16 49.087° 0.3288 Inuit group 2000 B. Gladman, J. Kavelaars, et al.
25 XXII IjiraqIjiraq ˈiː.ɨrɒk ≈ 12 ~1.18 11,355,316 +451.77 50.212° 0.3161 Inuit group 2000 B. Gladman, J. Kavelaars, et al.
26 IX Phoebe ♣†Phoebe ˈfiːbiː 213.0 ± 1.4
(219×217×204)
8,292 ± 10 12,869,700 −545.09 173.047° 0.156242 Norse group 1899 W. Pickering
27 XX PaaliaqPaaliaq ˈpɑːliɒk ≈ 22 ~7.25 15,103,400 +692.98 46.151° 0.3631 Inuit group 2000 B. Gladman, J. Kavelaars, et al.
28 XXVII SkathiSkathi ˈskɒði ≈ 8 ~0.35 15,672,500 −732.52 149.084° 0.246 Norse (Skathi) Group 2000 B. Gladman, J. Kavelaars, et al.
29 XXVI AlbiorixAlbiorix ˌælbiˈɒrɪks ≈ 32 ~22.3 16,266,700 +774.58 38.042° 0.477 Gallic group 2000 M. Holman
30   S/2007AS/2007 S 2 ≈ 6 ~0.15 16,560,000 −792.96 176.68° 0.2418 Norse group 2007 S. Sheppard, D. Jewitt, J. Kleyna, B. Marsden
31 XXXVII BebhionnBebhionn bɛˈviːn, ˈvɪvi.ɒn ≈ 6 ~0.15 17,153,520 +838.77 40.484° 0.333 Gallic group 2004 S. Sheppard, D. Jewitt, J. Kleyna
32 XXVIII ErriapusErriapus ˌɛriˈæpəs ≈ 10 ~0.68 17,236,900 +844.89 38.109° 0.4724 Gallic group 2000 B. Gladman, J. Kavelaars, et al.
33 XLVII SkollSkoll ˈskɒl, ˈskɜːl ≈ 6 ~0.15 17,473,800 −862.37 155.624° 0.418 Norse (Skathi) group 2006 S. Sheppard, D. Jewitt, J. Kleyna
34 XXIX SiarnaqSiarnaq ˈsiːɑrnək ≈ 40 ~43.5 17,776,600 +884.88 45.798° 0.24961 Inuit group 2000 B. Gladman, J. Kavelaars, et al.
35 LII TarqeqTarqeq ˈtɑrkeɪk ≈ 7 ~0.23 17,910,600 +894.86 49.904° 0.1081 Inuit group 2007 S. Sheppard, D. Jewitt, J. Kleyna
36   S/2004BS/2004 S 13 ≈ 6 ~0.15 18,056,300 −905.85 167.379° 0.261 Norse group 2004 S. Sheppard, D. Jewitt, J. Kleyna
37 LI GreipGreip ˈɡreɪp ≈ 6 ~0.15 18,065,700 −906.56 172.666° 0.3735 Norse group 2006 S. Sheppard, D. Jewitt, J. Kleyna
38 XLIV HyrrokkinHyrrokkin hɪˈrɒkɨn ≈ 8 ~0.35 18,168,300 −914.29 153.272° 0.3604 Norse (Skathi) group 2006 S. Sheppard, D. Jewitt, J. Kleyna
39 L JarnsaxaJarnsaxa jɑrnˈsæksə ≈ 6 ~0.15 18,556,900 −943.78 162.861° 0.1918 Norse group 2006 S. Sheppard, D. Jewitt, J. Kleyna
40 XXI TarvosTarvos ˈtɑrvɵs ≈ 15 ~2.3 18,562,800 +944.23 34.679° 0.5305 Gallic group 2000 B. Gladman, J. Kavelaars, et al.
41 XXV MundilfariMundilfari ˌmʊndəlˈvɛri ≈ 7 ~0.23 18,725,800 −956.70 169.378° 0.198 Norse group 2000 B. Gladman, J. Kavelaars, et al.
42   S/2006S/2006 S 1 ≈ 6 ~0.15 18,930,200 −972.41 154.232° 0.1303 Norse (Skathi) group 2006 S. Sheppard, D.C. Jewitt, J. Kleyna
43   S/2004CS/2004 S 17 ≈ 4 ~0.05 19,099,200 −985.45 166.881° 0.226 Norse group 2004 S. Sheppard, D. Jewitt, J. Kleyna
44 XXXVIII BergelmirBergelmir bɛərˈjɛlmɪər ≈ 6 ~0.15 19,104,000 −985.83 157.384° 0.152 Norse (Skathi) group 2004 S. Sheppard, D. Jewitt, J. Kleyna
45 XXXI NarviNarvi ˈnɑrvi ≈ 7 ~0.23 19,395,200 −1,008.45 137.292° 0.320 Norse (Narvi) group 2003 S. Sheppard, D. Jewitt, J. Kleyna
46 XXIII SuttungrSuttungr ˈsʊtʊŋɡər ≈ 7 ~0.23 19,579,000 −1,022.82 174.321° 0.131 Norse group 2000 B. Gladman, J. Kavelaars, et al.
47 XLIII HatiHati ˈhɑːti ≈ 6 ~0.15 19,709,300 −1,033.05 163.131° 0.291 Norse group 2004 S. Sheppard, D. Jewitt, J. Kleyna
48   S/2004AS/2004 S 12 ≈ 5 ~0.09 19,905,900 −1,048.54 164.042° 0.396 Norse group 2004 S. Sheppard, D. Jewitt, J. Kleyna
49 XL FarbautiFarbauti fɑrˈbaʊti ≈ 5 ~0.09 19,984,800 −1,054.78 158.361° 0.209 Norse (Skathi) group 2004 S. Sheppard, D. Jewitt, J. Kleyna
50 XXX ThrymrThrymr ˈθrɪmər ≈ 7 ~0.23 20,278,100 −1,078.09 174.524° 0.453 Norse group 2000 B. Gladman, J. Kavelaars, et al.
51 XXXVI AegirAegir ˈaɪ.ɪər ≈ 6 ~0.15 20,482,900 −1,094.46 167.425° 0.237 Norse group 2004 S. Sheppard, D. Jewitt, J. Kleyna
52   S/2007BS/2007 S 3 ≈ 5 ~0.09 20,518,500 ≈ −1,100 177.22° 0.130 Norse group 2007 S. Sheppard, D. Jewitt, J. Kleyna
53 XXXIX BestlaBestla ˈbɛstlə ≈ 7 ~0.23 20,570,000 −1,101.45 147.395° 0.77 Norse (Narvi) group 2004 S. Sheppard, D. Jewitt, J. Kleyna
54   S/2007CS/2004 S 7 ≈ 6 ~0.15 20,576,700 −1,101.99 165.596° 0.5299 Norse group 2004 S. Sheppard, D. Jewitt, J. Kleyna
55   S/2006S/2006 S 3 ≈ 6 ~0.15 21,076,300 −1,142.37 150.817° 0.4710 Norse (Skathi) group 2006 S. Sheppard, D. Jewitt, J. Kleyna
56 XLI FenrirFenrir ˈfɛnrɪər ≈ 4 ~0.05 21,930,644 −1,212.53 162.832° 0.131 Norse group 2004 S. Sheppard, D. Jewitt, J. Kleyna
57 XLVIII SurturSurtur ˈsɜrtər ≈ 6 ~0.15 22,288,916 −1,242.36 166.918° 0.3680 Norse group 2006 S. Sheppard, D. Jewitt, J. Kleyna
58 XLV KariKari ˈkɑri ≈ 7 ~0.23 22,321,200 −1,245.06 148.384° 0.3405 Norse (Skathi) group 2006 S. Sheppard, D. Jewitt, J. Kleyna
59 XIX YmirYmir ˈɪmɪər ≈ 18 ~3.97 22,429,673 −1,254.15 172.143° 0.3349 Norse group 2000 B. Gladman, J. Kavelaars, et al.
60 XLVI LogeLoge ˈlɔɪ.eɪ ≈ 6 ~0.15 22,984,322 −1,300.95 166.539° 0.1390 Norse group 2006 S. Sheppard, D. Jewitt, J. Kleyna
61 XLII FornjotFornjot ˈfɔrnjɒt ≈ 6 ~0.15 24,504,879 −1,432.16 167.886° 0.186 Norse group 2004 S. Sheppard, D. Jewitt, J. Kleyna

Unconfirmed moons

The following objects (observed by Cassini) have not been confirmed as solid bodies. It is not yet clear if these are real satellites or merely persistent clumps within the F Ring.[14]

Name Image Diameter (km) Semi-major
axis (km)[37]
Orbital
period (d)[37]
Position Discovery year
S/2004 S 6 ≈ 3–5 ≈ 140,130 +0.61801 uncertain objects around the F Ring 2004
S/2004 S 3/S 4[note 10] ≈ 3−5 ≈ 140,300 ≈ +0.619 2004

Hypothetical moons

Two moons were claimed to be discovered by different astronomers but never seen again. Both moons were said to orbit between Titan and Hyperion.[63]

Notes

  1. ^ The mass of the rings is about the mass of Mimas,[4] while the combined mass of Janus, Hyperion and Phoebe—the most massive of the remaining moons—is about one-third of that. The total mass of the rings and small moons is around 5.5 × 1019 kg.
  2. ^ Inktomi was once known as "The Splat".[49]
  3. ^ The photometric color may be used as a proxy for the chemical composition of satellites' surfaces.
  4. ^ A confirmed moon is given a permanent designation by the IAU consisting of a name and a Roman numeral.[25] The nine moons that were known before 1900 (of which Phoebe is the only irregular) are numbered in order of their distance from Saturn; the rest are numbered in the order by which they received their permanent designations. Nine small moons of the Norse group and S/2009 S 1 have not yet received a permanent designation.
  5. ^ The diameters and dimensions of the inner moons from Pan through Janus, Methone, Pallene, Telepso, Calypso, Helene, Hyperion and Phoebe were taken from Thomas 2010, Table 3.[27] Diameters and dimensions of Mimas, Enceladus, Tethys, Dione, Rhea and Iapetus are from Thomas 2010, Table 1.[27] The approximate sizes of other satellites are from the website of Scott Sheppard.[31]
  6. ^ Masses of the large moons were taken from Jacobson, 2006.[28] Masses of Pan, Daphnis, Atlas, Prometheus, Pandora, Epimethius, Janus, Hyperion and Phoebe were taken from Thomas, 2010, Table 3.[27] Masses of other small moons were calculated assuming a density of 1.3 g/cm3.
  7. ^ a b c The orbital parameters were taken from Spitale, et al. 2006,[37] IAU-MPC Natural Satellites Ephemeris Service,[62] and NASA/NSSDC.[29]
  8. ^ Negative orbital periods indicate a retrograde orbit around Saturn (opposite to the planet's rotation).
  9. ^ To Saturn's equator
  10. ^ S/2004 S4 was most likely a transient clump—it has not been recovered since the first sighting.[14]

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