Moons of Saturn

The Saturnian system (photographic montage)

Moons of Saturn (photographic montage)

Saturn's rings cut across a scene that is ruled by Titan's luminous crescent and globe-encircling haze, broken by the small moon Enceladus, whose icy jets are dimly visible at its south pole. North is up.

The moons of Saturn are numerous and diverse, ranging from tiny moonlets to the enormous Titan. Saturn has 61 moons with confirmed orbits, 53 of which have names, and most of which are quite small. There are also hundreds of known moonlets embedded within Saturn's rings. With seven moons that are large enough to have sufficient gravitational attraction to become spherical in shape (and which would thus be considered dwarf planets if they were in direct orbit about the Sun) in addition to the planet's broad and dense rings, the Saturnian system is the most diverse in the solar system. Particularly notable are Titan, the second largest moon in the Solar System, with an earth-like atmosphere and a landscape including hydrocarbon lakes and river networks, and Enceladus, which may harbor liquid water under its south pole.

Twenty-three of Saturn's moons are regular satellites, with prograde orbits that are not greatly inclined with respect to Saturn's equatorial plane. In addition to the seven major satellites, an additional four moons are small trojans that share an orbit with a larger moon, and two more are mutually co-orbital moons. Finally, two moons are known to orbit within gaps in Saturn's rings. The regular satellites are traditionally named after Titans or other figures associated with the mythological Saturn.

The remaining thirty-eight, all small, are irregular satellites, whose orbits are much farther from Saturn, have high inclinations, and are mixed between prograde and retrograde. These moons were likely 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 Inuit, Norse, and Gallic groups, and their names are chosen from the corresponding mythologies.

The rings of Saturn are made up of icy objects ranging in size from microscopic to hundreds of metres, each of which is on its own orbit about the planet. 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.

A confirmed moon is given a permanent designation by the IAU consisting of a name and a Roman numeral. 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. Eight small moons of the Norse group have not received a permanent designation.

Discovery

Before the advent of telescopic photography, eight moons of Saturn were discovered by direct observation using an optical telescope. Saturn's largest moon, Titan, was discovered in 1655 by Christiaan Huygens. Tethys, Dione, Rhea and Iapetus (the "Sidera Lodoicea") were discovered 1671-1684 by Giovanni Domenico Cassini. William Herschel discovered Mimas and Enceladus in 1789. Hyperion was discovered 1848 by W.C. Bond, G.P. Bond and Lassell.

The use of long-exposure photographic plates made it possible to discover additional moons. The first to be discovered in this manner, Phoebe, was found in 1899 by W.H. Pickering. In 1966, the satellites Janus and Epimetheus were observed, but not confirmed, and it was not realized that there were two distinct moons sharing an orbit.

Observations by spacecraft

Four moons of Saturn can be seen on this image of the Cassini spacecraft: Huge Titan and Dione at the bottom, small Prometheus (under the rings) and tiny Telesto above center

The study of the outer planets has since been revolutionized by the use of unmanned space probes. The arrival of the Voyager space probes at Saturn in 1980 resulted in the discovery of seven additional moons, bringing the total from 10 to 17. Epimetheus was confirmed as distinct from Janus. In 1990, Pan was discovered in archival Voyager images.

The Cassini mission, which arrived at Saturn in the summer of 2004, discovered three small moons in the inner Saturnian system (Methone, Pallene and Polydeuces) as well as three suspected but unconfirmed moons in the F Ring. On November 16, 2004 Cassini scientists announced that the structure of Saturn's rings indicates the presence of several more moons orbiting within the rings, but only one, Daphnis, has been visually confirmed so far (its confirmation was announced on May 6, 2005).^[1] On July 18, 2007 Anthe was announced. On March 6, 2008 it was announced 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.^[2] On March 3, 2009, Aegaeon, a moonlet within the G Ring, was announced.

Ground-based observations

Study of Saturn's moons has also been aided by advances in telescopy. For the entire 20th century, Phoebe stood alone among Saturn's known moons in its highly irregular orbit. Beginning in 2000, three dozen additional irregular moons have been found using ground-based telescopes. A survey starting in late 2000 found thirteen new moons orbiting Saturn at a great distance in orbits that suggest they are fragments of larger bodies captured by Saturn's gravitational pull (Nature vol. 412, pp. 163–166). On May 3, 2005, astronomers using the Mauna Kea Observatory announced the discovery of twelve more small outer moons.^[3][4] On June 30, 2006 astronomers using the Subaru 8.2 m telescope announced the discovery of nine more small outer moons.^[5] On April 13, 2007 Tarqeq was announced On May 1, 2007 S/2007 S 2 and S/2007 S 3 were announced.

Sizes

The relative masses of Saturn's moons. (Mimas and the other moons smaller than Enceladus are invisible at this scale.)

The Saturnian moon system is very lopsided, with one moon, Titan, comprising more than 96 percent of the mass in orbit around the planet. The six other oblate moons constitute roughly four percent, while the remaining 54 small moons, together with the rings, comprise only 0.01 percent.

Orbital groups

Although the borders may be somewhat nebulous, Saturn's moons can be divided into ten groups according to their orbital characteristics.

Many of Saturn's moons, such as Pan and Daphnis, orbit within Saturn's ring system and have orbital periods only slightly longer than the planet's rotation period. The innermost moons and most regular satellites all have inclinations ranging from less than a degree to ~1.5 degrees (the exception is Iapetus, which has an inclination of 7.57 degrees). But several irregular satellites in the outermost regions of Saturn's moon system, in particular the Norse group, have orbital radii of millions of miles and orbital periods lasting several years. The moons of the Norse group also lie almost perpendicular to Saturn's equator, while the moons of the Gallic and Inuit groups have inclinations ranging from 30 to 50 degrees.

Ring moonlets

In 2006, four tiny "moonlets" were found in Cassini images of the A Ring.^[6] Two larger moons had previously been spotted in the A Ring: Pan and Daphnis. These are large enough to clear gaps in the ring particles that circle the planet as they orbit Saturn. In contrast, the "moonlets" are only massive enough to clear a partial gap in the immediate vicinity of the moonlet itself; this wake is shaped like an airplane propeller and is only about ten km across.^[7] The moonlets themselves are tiny, ranging from about 40–500 meters in diameter, and are too small to be seen directly. In 2007, the discovery of 150 more moonlets revealed that they are confined to three narrow bands (each a thousand kilometers wide, less than 1% the width of Saturn's rings) in the A Ring about 130,000 km from Saturn's center that are free from the disturbance of strong density waves, with the exception of two that have been seen outside the Encke Gap. (However, other areas of the A Ring without density-wave disturbances are apparently free of moonlets.) This suggests that they were formed from the breakup of larger bodies. It is estimated that the A Ring contains thousands of such fragments.^[8][9]

Similar moonlets are thought to reside in the F Ring. 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.^[10]

During equinox in 2009 a moonlet was discovered in the B Ring, 480 km from the outer edge of the ring, by the shadow it cast. It is estimated to be 400 m in diameter. Unlike the A Ring moonlets, it does not induce a 'propeller' feature, likely due to the density of the B Ring.[1]

Ring shepherds

Shepherd satellites are 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 the moonlets, Pan, Daphnis, Atlas, Prometheus, Pandora, Aegaeon, in addition to the unconfirmed moons S/2004 S 4, S/2004 S 6 and S/2004 S 3.

Co-orbitals

Janus and Epimetheus are co-orbital moons. These two moons are of roughly equal size and have orbits with only a few kilometers difference in diameter, 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.

Aegaeon and the G-ring

Inner large moons and the Alkyonides

The innermost large moons of Saturn orbit within its tenuous E Ring. They are:

• Mimas, a moon distinguished by Herschel, a large crater one third its diameter, which gives Mimas an appearance reminiscent of the Death Star from the Star Wars films. Mimas is noticeably ovoid-shaped, having been made shorter at the poles and longer at the equator by the effects of Saturn's gravity. Mimas is the least massive of the inner moons, although its mass is sufficient to alter the orbit of Methone. Mimas has no known past or present geologic activity.

Alkyonides

These three moons orbit between Mimas and Enceladus: Methone, Anthe, and Pallene. They are some of the smallest moons in the Saturn system. Both Methone and Anthe possess very faint ring arcs. A very faint ring has also been detected in Pallene's orbit.^[11]

• Enceladus is the most geologically active of Saturn's inner moons. The south pole of Enceladus is covered with fractures called "tiger stripes", some of which emit the particles that replenish the E-ring. Enceladus is the smallest known body in the Solar System that is geologically active today, and it may have liquid water underneath the south-polar surface.
• Tethys is the third largest of Saturn's inner moons. The moon's most prominent features are a very large crater named Odysseus and a vast canyon system named Ithaca Chasma. Tethys appears to have no current geological activity.
• Dione is the second-largest inner moon of Saturn. It has a higher density than Rhea, the largest inner moon. Dione is covered with areas of bright fractures called "wispy terrain". This moon may also be geologically active, although on a scale much smaller than the cryo-volcanism of Enceladus.

Trojan moons

Trojan moons are a unique feature not yet found outside the moons of the Saturn system. Trojan bodies orbit at the Lagrange points of a much larger object, such as a large moon or planet. Tethys has two trojan moons, Telesto and Calypso, and Dione also has two, Helene and Polydeuces. Helene is by far the largest trojan moon, while Polydeuces has the most erratic orbit.

• Rhea is the largest of Saturn's inner moons. Although there is no known geologic activity, Rhea most likely has a very faint ring system. The Cassini Orbiter detected an absence of electrons near Rhea's Hill sphere during a 2005 flyby, which is most likely caused by the presence of dust-sized ring particles. Rhea's ring system is almost invisible; yet it must be dense enough to deflect electrons from Saturn' magnetic field. This would make Rhea the only moon in the solar system known so far to have a ring. Rhea's surface is heavily cratered, with the exceptions of a few large Dione-type fractures and a very faint "line" of material at Rhea's equator that may have been deposited by its tenuous rings. There is a very large crater on Rhea's leading hemisphere that is much brighter than the surrounding area. This crater is nick-named "The Splat", and may be one of the youngest observed craters on the inner moons of Saturn.

Outer large moons

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

• Titan, at 5150 km diameter, is the second largest moon in the Solar system. Out of all the large moons of the Solar System, Titan is the only one with a dense atmosphere. It is also the only moon with large bodies of liquid on its surface, in the form of methane lakes at Titan's north and south poles. Titan may also possess a weak magnetic field. Like Europa and Ganymede, it is believed that Titan has a subsurface ocean of water mixed with methane. Titan has an asynchronous orbit (when a moon does not always show the same side to its planet), and this may be explained by the subsurface ocean.
• Hyperion is Titan's nearest neighbor in the Saturn system. Smaller than Mimas, Hyperion is one of the largest known non-spherical objects discovered so far. Hyperion has a very odd, tan-colored surface that resembles a sponge, and its interior may be partially porous as well. Hyperion is also the only moon known to have a chaotic rotation, which means the moon has no well-defined poles or equator.^{[citation needed]} It is widely suspected^[who?] that Hyperion is a fragment of a much larger moon that was destroyed earlier in the Saturn-Titan system's formation.^{[citation needed]}
• Iapetus is the third-largest of Saturn's moons. Orbiting Saturn at 3.5 million km, it is by far the most distant of Saturn's large moons, and also possesses the greatest orbital inclination, at 7.5 degrees. Iapetus has long been known for its unusual two-toned surface; its leading hemisphere is pitch-black and its trailing hemisphere is almost as bright as fresh snow. Cassini also discovered a vast equatorial ridge within the dark area, which spans nearly the moon's entire equator. Unlike the other large moons of Saturn, Iapetus orbits outside of Saturn's magnetic field, so it is constantly exposed to weak solar wind and cosmic radiation. The source of Iapetus' starkly dichromatic surface may have been found in 2009, when NASA's Spitzer space telescope discovered a nearly invisible ring around Saturn, just outside the orbit of the moon Phoebe. Scientists believe the ring originates from dust and ice particles kicked up by Phoebe as it collides with comets, which plume off the moon's surface into space. Because the ring orbits in the opposite direction to Iapetus, the moon collides with the ring's particles, which leave a dark coating on its leading hemisphere.^[12]

Irregular moons

Irregular satellites of Saturn.

Irregular moons are small satellites with large-radius, inclined, and sometimes retrograde orbits, believed to have been acquired by the parent planet through a capture process. They often occur as collisional families.

Phoebe, at 220 km in diameter, is by far the largest of Saturn's irregular satellites. It has a retrograde orbit, but unlike Saturn's other moons, Phoebe rotates on its axis every 10 hours. Phoebe is believed to be a captured Centaur, which is a type of Kuiper Belt object. Phoebe was the first moon of Saturn to be studied in detail by the Cassini Orbiter in June 2004; during this encounter Cassini was able to map nearly 90% of the moon's surface.

Inuit group

The Inuit group are five prograde outer moons that are similar enough in their distances from Saturn and their orbital inclinations that they can be considered a group. They are Ijiraq, Kiviuq, Paaliaq, Siarnaq, and Tarqeq.

Norse group

The Norse group are 29 retrograde outer moons that are similar enough in their distance from Saturn to be considered a group. 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. After Phoebe, Ymir is the largest of the known retrograde irregular moons, with an estimated diameter of only 18 km.

Gallic group

The Gallic group are four prograde outer moons that are similar enough in their distance from Saturn and their orbital inclination that they can be considered a group. They are Albiorix, Bebhionn, Erriapus, and Tarvos. Tarvos, as of 2009, is the most distant of Saturn's moons with a prograde orbit.

The diagram illustrates the orbits of the irregular satellites of Saturn discovered so far.¹ The eccentricity of the orbits is represented by the segments (extending from the pericentre to the apocentre) with the inclination represented on Y axis. The satellites above the axis are prograde, the satellites beneath are retrograde. The X axis is labelled in Gm (million km) and the fraction of the Hill sphere's (gravitational influence) radius (~65 Gm for Saturn). Prograde groups: Inuit and Gallic and the retrograde Norse group are clearly identifiable (from top to bottom).

¹Named satellites are plotted in yellow; the unnamed satellites S/2004 Sxx (announced in 2005 and 2006) are plotted in white and S/2006 Sxx in grey.

Table of moons

The Saturnian moons are listed here by orbital period, from shortest to longest. Moons massive enough for their surfaces to have collapsed into a spheroid are highlighted in bold. The irregular captured moons (beyond Iapetus) are shaded light grey when prograde and darker grey when retrograde.

Order	Label	Name	Pronunciation (key)	Image	Diameter (km)[note 1]	Mass ( × 1018 kg)[note 2]	Semi-major axis (km)[note 3]	Orbital period (d)[note 4][note 3]	Inclination (°) [note 5][note 3]	Eccentricity[note 3]	Position	Discovery year [6][8][9]	Discoverer [21]
0		(moonlets)			000004 0.04 to 0.5	000000000001 <0.0000001	00130 ≈ 130 000				Three 1000-km bands within A Ring	2006	Cassini–Huygens
1	18 XVIII	Pan	ˈpæn		0030 30 (35×35×23)	0000000049 0.00495 ± 0.00075	00133 133 584	0000575 +0.575 05	000001 0.001°	000035 0.000 035	in Encke Division	1990	M. Showalter
2	35 XXXV	Daphnis	ˈdæfnɨs		0006 6 − 8	00000000008 0.000084 ± 0.000012	00136 136 505	0000594 +0.594 08	000000 ≈ 0°	000000 ≈ 0	in Keeler Gap	2005	Cassini–Huygens
3	15 XV	Atlas	ˈætləs		0031 31 (46×38×19)	0000000066 0.0066 ± 0.00006	00137 137 670	0000601 +0.601 69	000003 0.003°	0012 0.001 2	outer A Ring shepherd	1980	Voyager 2
4	16 XVI	Prometheus	proʊˈmiːθiːəs		0086 86 (119×87×61)	0000001566 0.1566 ± 0.0019	00139 139 380	0000612 +0.612 99	000008 0.008°	0022 0.002 2	inner F Ring shepherd	1980	Voyager 2
5	17 XVII	Pandora	pænˈdoʊrə		0081 81 (103×80×64)	0000001356 0.1356 ± 0.0022	00141 141 720	0000628 +0.628 50	000050 0.050°	0042 0.004 2	outer F Ring Shepherd	1980	Voyager 2
6a	11 XI	Epimetheus	ˌɛpɨˈmiːθiːəs		0113 113 (135×108×105)	0000005304 0.5304 ± 0.00193	00151 151 422	0000694 +0.694 33	000335 0.335°	0098 0.009 8	co-orbital	1980	Voyager 2
6b	10 X	Janus	ˈdʒeɪnəs		0179 179 (193×173×137)	000001912 1.912 ± 0.005	001514 151 472	0000694 +0.694 66	000165 0.165°	0068 0.006 8	co-orbital	1966	A. Dollfus
8	53 LIII	Aegaeon	iːˈdʒiːən		00005 ≈ 0.5	000000000001 ~0.0000001	001675 167 500	0000808 +0.808 12	000001 0.001°	0002 0.000 2	G-ring moonlet	2008 [22]	Cassini–Huygens
9	01 I	Mimas	ˈmaɪməs		0397 397 (415×394×381)	000037493 37.493 ± 0.031	00185 185 404	0000942 +0.942 422	001566 1.566°	0202 0.020 2		1789	W. Herschel
10	32 XXXII	Methone	mɨˈθoʊniː		0003 ≈ 3	00000000002 ~0.00002	00194 194 440	0001009 +1.009 57	000007 0.007°	0001 0.000 1	Alkyonides	2004	Cassini–Huygens
11	49 XLIX	Anthe	ˈænθiː		0002 ≈ 2	000000000007 ~0.000007	00197 197 700	0001036 +1.036 50	000100 0.1°	001 0.001	Alkyonides	2007	Cassini–Huygens
12	33 XXXIII	Pallene	pəˈliːniː		0004 4	00000000005 ~0.00005	00212 212 280	0001153 +1.153 75	000181 0.181°	0040 0.004 0	Alkyonides	2004	Cassini–Huygens
13	02 II	Enceladus	ɛnˈsɛlədəs		0504 504 (513×503×497)	000108022 108.022 ± 0.101	00237 237 950	0001370 +1.370 218	000010 0.010°	0047 0.004 7	Generates the E ring	1789	W. Herschel
14	03 III	Tethys	ˈtiːθɨs		1066 1066 (1081×1062×1055)	000617449 617.049 ± 0.132	00294 294 619	0001887 +1.887 802	000168 0.168°	0001 0.000 1		1684	G.D. Cassini
14a	13 XIII	Telesto	tɨˈlɛstoʊ		024 24 (29×22×20)	00000000941 ~0.00941	00294 294 619	0001887 +1.887 802	001158 1.158°	0 0.000	leading Tethys trojan	1980	Voyager 2
14b	14 XIV	Calypso	kəˈlɪpsoʊ		0021 21 (30×23×14)	0000000063 ~0.0063	00294 294 619	0001887 +1.887 802	001473 1.473°	0 0.000	trailing Tethys trojan	1980	Voyager 2
17	04 IV	Dione	daɪˈoʊniː		1123 1123 (1128×1122×1121)	001095452 1095.452 ± 0.168	00377 377 396	0002736 +2.736 915	000002 0.002°	0022 0.002 2		1684	G.D. Cassini
17a	12 XII	Helene	ˈhɛlɨniː		0033 33 (36×32×30)	00000002446 ~0.02446	00377 377 396	0002736 +2.736 915	000212 0.212°	0022 0.002 2	leading Dione trojan	1980	Voyager 2
17b	34 XXXIV	Polydeuces	ˌpɒliˈdjuːsiːz		00035 3.5	00000000003 ~0.00003	00377 377 396	0002736 +2.736 915	000177 0.177°	0192 0.019 2	trailing Dione trojan	2004	Cassini–Huygens
20	05 V	Rhea	ˈriːə		1529 1529 (1535×1525×1526)	002306518 2306.518 ± 0.353	00527 527 108	000451 +4.518 212	000327 0.327°	001258 0.001 258		1672	G.D. Cassini
21	06 VI	Titan	ˈtaɪtən		51151 5151	13452 134520 ± 20	0122 1 221 930	001594 +15.945 42	0003485 0.3485°	0288 0.028 8		1655	C. Huygens
22	07 VII	Hyperion	haɪˈpiːriən		0292 292 (360×280×225)	000005584 5.584 ± 0.068	0148 1 481 010	002127 +21.276 61	000568 0.568°	123006 0.123 006		1848	W.C. Bond, G.P. Bond and W. Lassell
23	08 VIII	Iapetus	aɪˈæpɨtəs		1472 1472 (1494×1498×1425)	001805635 1805.635 ± 0.375	0356 3 560 820	007932 +79.321 5	007570 7.570°	028613 0.028 613		1671	G.D. Cassini
24	24 XXIV	Kiviuq	ˈkɪvioʊk		0016 ≈ 16	00000000279 ~0.00279	112 11 294 800	0448 +448.16	0490 49.087°	3288 0.328 8	Inuit group	2000	B. Gladman, J.J. Kavelaars, et al.
25	22 XXII	Ijiraq	ˈiː.ɨrɒk		0012 ≈ 12	00000000118 ~0.00118	113 11 355 316	0451 +451.77	0502 50.212°	3161 0.316 1	Inuit group	2000	B. Gladman, J.J. Kavelaars, et al.
26	09 IX	Phoebe	ˈfiːbiː		0220 220 (230×220×210)	000008292 8.292 ± 0.010	12869 12 869 700	0545 −545.09	1730 173.047°	156242 0.156 242	Norse group	1899	W.H. Pickering
27	20 XX	Paaliaq	ˈpɑːliɒk		0022 ≈ 22	00000000725 ~0.00725	15103 15 103 400	0692 +692.98	0561 46.151°	3631 0.363 1	Inuit group	2000	B. Gladman, J.J. Kavelaars, et al.
28	27 XXVII	Skathi	ˈskɒði		0008 ≈ 8	00000000035 ~0.00035	15672 15 672 500	0732 −732.52	1490 149.084°	246 0.246	Norse (Skathi) Group	2000	B. Gladman, J.J. Kavelaars, et al.
29	26 XXVI	Albiorix	ˌælbiˈɒrɪks		0032 ≈ 32	0000000223 ~0.0223	16266 16 266 700	0774 +774.58	0380 38.042°	477 0.477	Gallic group	2000	M. Holman
30		S/2007 S 2	—		0006 ≈ 6	00000000015 ~0.00015	16650 16 560 000	0792 −792.96	1766 176.68°	218 0.241 8	Norse group	2007	S. Sheppard, D.C. Jewitt, J. Kleyna, B. Marsden
31	37 XXXVII	Bebhionn	ˈbɛviːn		0006 ≈ 6	00000000015 ~0.00015	17153 17 153 520	0838 +838.77	0404 40.484°	333 0.333	Gallic group	2004	S. Sheppard, D.C. Jewitt, J. Kleyna
32	28 XXVIII	Erriapus	ˌɛriˈæpəs		0010 ≈ 10	00000000068 ~0.00068	17236 17 236 900	0844 +844.89	0381 38.109°	4724 0.472 4	Gallic group	2000	B. Gladman, J.J. Kavelaars, et al.
33	47 XLVII	Skoll	ˈskɒl, ˈskɜːl		0006 ≈ 6	00000000015 ~0.00015	17473 17 473 800	0862 −862.37	1556 155.624°	418 0.418	Norse (Skathi) group	2006	S. Sheppard, D.C. Jewitt, J. Kleyna
34	29 XXIX	Siarnaq	ˈsiːɑrnək		0040 ≈ 40	0000000435 ~0.0435	17776 17 776 600	0884 +884.88	0457 45.798°	2961 0.249 61	Inuit group	2000	B. Gladman, J.J. Kavelaars, et al.
35	52 LII	Tarqeq	ˈtɑrkeɪk		0007 ≈ 7	00000000023 ~0.00023	17911 17 910 600	0894 +894.86	0499 49.904°	1081 0.1081	Inuit group	2007	S. Sheppard, D.C. Jewitt, J. Kleyna
36		S/2004 S 13	—		0006 ≈ 6	00000000015 ~0.00015	18056 18 056 300	0905 −905.85	1673 167.379°	261 0.261	Norse group	2004	S. Sheppard, D.C. Jewitt, J. Kleyna
37	51 LI	Greip	ˈɡreɪp		0006 ≈ 6	00000000015 ~0.00015	18065 18 065 700	0906 −906.56	1726 172.666°	3735 0.373 5	Norse group	2006	S. Sheppard, D.C. Jewitt, J. Kleyna
38	44 XLIV	Hyrrokkin	hɪˈrɒkɨn		0008 ≈ 8	00000000035 ~0.00035	18168 18 168 300	0914 −914.29	1532 153.272°	3604 0.360 4	Norse (Skathi) group	2006	S. Sheppard, D.C. Jewitt, J. Kleyna
39	50 L	Jarnsaxa	jɑrnˈsæksə		0006 ≈ 6	00000000015 ~0.00015	18556 18 556 900	0943 −943.78	1628 162.861°	1918 0.191 8	Norse group	2006	S. Sheppard, D.C. Jewitt, J. Kleyna
40	21 XXI	Tarvos	ˈtɑrvɵs		0015 ≈ 15	0000000023 ~0.0023	18562 18 562 800	0944 +944.23	0346 34.679°	5305 0.530 5	Gallic group	2000	B. Gladman, J.J. Kavelaars, et al.
41	25 XXV	Mundilfari	ˌmʊndəlˈvɛri		0007 ≈ 7	00000000023 ~0.00023	18725 18 725 800	0956 −956.70	1693 169.378°	198 0.198	Norse group	2000	B. Gladman, J.J. Kavelaars, et al.
42		S/2006 S 1	—		0006 ≈ 6	00000000015 ~0.00015	18930 18 930 200	0972 −972.41	1542 154.232°	1303 0.130 3	Norse (Skathi) group	2006	S. Sheppard, D.C. Jewitt, J. Kleyna
43		S/2004 S 17	—		0004 ≈ 4	00000000005 ~0.00005	19099 19 099 200	0985 −985.45	1668 166.881°	226 0.226	Norse group	2004	S. Sheppard, D.C. Jewitt, J. Kleyna
44	38 XXXVIII	Bergelmir	bɛrˈjɛlmɪr		0006 ≈ 6	00000000015 ~0.00015	19104 19 104 000	0986 −985.83	1573 157.384°	152 0.152	Norse (Skathi) group	2004	S. Sheppard, D.C. Jewitt, J. Kleyna
45	31 XXXI	Narvi	ˈnɑrvi		0007 ≈ 7	00000000023 ~0.00023	19395 19 395 200	1008 −1008.45	1372 137.292°	320 0.320	Norse (Narvi) group	2003	S. Sheppard, D.C. Jewitt, J. Kleyna
46	23 XXIII	Suttungr	ˈsʊtʊŋɡər		0007 ≈ 7	00000000023 ~0.00023	19579 19 579 000	1022 −1022.82	1743 174.321°	131 0.131	Norse group	2000	B. Gladman, J.J. Kavelaars, et al.
47	43 XLIII	Hati	ˈhɑːti		0006 ≈ 6	00000000015 ~0.00015	19709 19 709 300	1033 −1033.05	1631 163.131°	291 0.291	Norse group	2004	S. Sheppard, D.C. Jewitt, J. Kleyna
48		S/2004 S 12	—		0005 ≈ 5	00000000009 ~0.00009	19905 19 905 900	1048 −1048.54	1640 164.042°	396 0.396	Norse group	2004	S. Sheppard, D.C. Jewitt, J. Kleyna
49	40 XL	Farbauti	fɑrˈbaʊti		0005 ≈ 5	00000000009 ~0.00009	19984 19 984 800	1054 −1054.78	1583 158.361°	209 0.209	Norse (Skathi) group	2004	S. Sheppard, D.C. Jewitt, J. Kleyna
50	30 XXX	Thrymr	ˈθrɪmər		0007 ≈ 7	00000000023 ~0.00023	20278 20 278 100	1078 −1078.09	1745 174.524°	453 0.453	Norse group	2000	B. Gladman, J.J. Kavelaars, et al.
51	36 XXXVI	Aegir	ˈaɪ.ər		0006 ≈ 6	00000000015 ~0.00015	20482 20 482 900	1094 −1094.46	1674 167.425°	237 0.237	Norse group	2004	S. Sheppard, D.C. Jewitt, J. Kleyna
52		S/2007 S 3	—		0005 ≈ 5	00000000009 ~0.00009	20518 20 518 500	1100 ≈ −1100	1772 177.22°	130 0.130	Norse group	2007	S. Sheppard, D.C. Jewitt, J. Kleyna
53	39 XXXIX	Bestla	ˈbɛstlə		0007 ≈ 7	00000000023 ~0.00023	20570 20 570 000	1101 −1101.45	1473 147.395°	77 0.77	Norse (Narvi) group	2004	S. Sheppard, D.C. Jewitt, J. Kleyna
54		S/2004 S 7	—		0006 ≈ 6	00000000015 ~0.00015	20576 20 576 700	1102 −1101.99	1655 165.596°	5299 0.529 9	Norse group	2004	S. Sheppard, D.C. Jewitt, J. Kleyna
55		S/2006 S 3	—		0006 ≈ 6	00000000015 ~0.00015	21076 21 076 300	1142 −1142.37	1508 150.817°	4710 0.471 0	Norse (Skathi) group	2006	S. Sheppard, D.C. Jewitt, J. Kleyna
56	41 XLI	Fenrir	ˈfɛnrɪr		0004 ≈ 4	00000000005 ~0.00005	21930 21 930 644	1212 −1212.53	1628 162.832°	131 0.131	Norse group	2004	S. Sheppard, D.C. Jewitt, J. Kleyna
57	48 XLVIII	Surtur	ˈsʊərtər		0006 ≈ 6	00000000015 ~0.00015	22288 22 288 916	1242 −1242.36	1669 166.918°	3680 0.368 0	Norse group	2006	S. Sheppard, D.C. Jewitt, J. Kleyna
58	45 XLV	Kari	ˈkɑːri		0007 ≈ 7	00000000023 ~0.00023	22321 22 321 200	1245 −1245.06	1483 148.384°	3405 0.340 5	Norse (Skathi) group	2006	S. Sheppard, D.C. Jewitt, J. Kleyna
59	19 XIX	Ymir	ˈɪmɪr		0018 ≈ 18	00000000397 ~0.00397	22429 22 429 673	1254 −1254.15	1721 172.143°	3349 0.334 9	Norse group	2000	B. Gladman, J.J. Kavelaars, et al.
60	46 XLVI	Loge	ˈlɔɪ.eɪ		0006 ≈ 6	00000000015 ~0.00015	22984 22 984 322	1300 −1300.95	1665 166.539°	139 0.139 0	Norse group	2006	S. Sheppard, D.C. Jewitt, J. Kleyna
61	42 XLII	Fornjot	ˈfɔrnjɒt		0006 ≈ 6	00000000015 ~0.00015	24504 24 504 879	1432 −1432.16	1678 167.886°	186 0.186	Norse group	2004	S. Sheppard, D.C. 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.

Order	Name	Image	Diameter (km)	Semi-major axis (km)[18]	Orbital period (d)[18]	Position	Discovery year
*	S/2004 S 6		≈ 3–5	140 130	+0.618 01	uncertain objects around the F-Ring	2004
*	S/2004 S 3/S 4[note 6]		≈ 3−5	≈ 140 300	≈ +0.619		2004

Hypothetical moons

These two moons were claimed to be discovered by different astronomers but never seen again. Since they both were said to orbit between Titan and Hyperion, it is possible that they are in fact identical, but most likely, none of these moons exist in reality.

• Chiron which was supposedly sighted by Hermann Goldschmidt in 1861 but never observed by anyone else.^[23]
• Themis was allegedly discovered in 1905 by astronomer William Pickering, but never seen again. Nevertheless it was included in numerous almanacs and astronomy books until the 1960s.^[24]

Naming conflicts with asteroids

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

See also

• Naming of natural satellites
• Natural satellites of Mars · Jupiter · Uranus · Neptune · Pluto
• Saturn's moons in fiction
• Timeline of discovery of Solar System planets and their natural satellites

Notes

1. ^ The diameters and dimensions were taken from Thomas, 2006^[13], Porco, 2005 ^[14] and Porco, 2006.^[15]
2. ^ Masses of the large moons were taken from Jacobson, 2006.^[16] Masses of some small inner moons were taken from Porco, 2007.^[17] Mass of other small moons were calculated assuming a density of 1.3 g/cm³. Unless otherwise noted, the uncertainty in the reported masses is not available.
3. ^ ^{a b c d} The orbital parameters were taken from Spitale, et al. 2006,^[18] IAU-MPC Natural Satellites Ephemeris Service,^[19] and NASA/NSSDC.^[20]
4. ^ Negative orbital periods indicate a retrograde orbit around Saturn (opposite to the planet's rotation)
5. ^ To Saturn's equator.
6. ^ S/2004 S4 was most likely a transient clump − it has not been recovered since the first sighting.

References

External links

Wikimedia Commons has media related to: Moons of Saturn

• Saturn's Rings by NASA's Solar System Exploration
• Saturn's Moons Astronomy Cast episode #61, includes full transcript.
• Carolyn Porco: Fly me to the moons of Saturn

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