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Saturn has 56 confirmed natural satellites or moons

Introduction

Saturn's rings cut across an eerie 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.

Saturn has 56 confirmed natural satellites, many of which were discovered very recently, and 3 additional un-confirmed, hypothetical moons. However, a precise number of moons can never be given, as there is no objective dividing line between the anonymous orbiting fragments that form Saturn's ring system and the larger objects that have already been named as moons.

Before the advent of telescopic photography, eight moons of Saturn were discovered by direct observation using an optical telescope:

Titan, discovered in 1655 by Christiaan Huygens;
Tethys, Dione, Rhea and Iapetus (the "Sidera Lodoicea") discovered 1671-1684 by Giovanni Domenico Cassini;
Mimas and Enceladus, discovered 1789 by William Herschel;
Hyperion, 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:

Phoebe was the first satellite discovered by telescopic photograph 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.

The study of the outer planets has since been revolutionized, first by the use of unmanned space probes, and then by advances in telescopy:

From 1980, when the first of the the Voyager space probes arrived at Saturn, to 1990, analysis of Voyager images revealed 8 more moons in the inner Saturnian system. The last discovered was Pan.
A survey starting in late 2000 found 13 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).
The Cassini mission, which arrived at Saturn in the summer of 2004, discovered three small moons in the inner Saturnian system as well as three suspected but unconfirmed moons in the F Ring. This increased the total to 37 moons, confirmed and unconfirmed.
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)..
On May 3, 2005, astronomers using the Mauna Kea Observatory announced the discovery of 12 more small outer moons.
On June 30, 2006, astronomers using the Subaru 8.2 m telescope announced the discovery of 9 more small outer moons.

The spurious satellite Chiron, "discovered" in 1861, is now known not to exist. Themis, "discovered" in 1905, also was later proven not to exist.

Table of known 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 light purple. Titan, which is planetary in size, has darker highlighting. The irregular (captured) moons are indicated in grey: light grey for prograde satellites, darker grey for retrograde satellites.

Order	Name (spheroidal moons in bold) (Pronunciation key)			Diameter (km)	Semi-major axis (km)	Orbital period (d)	Inclination (º) (to Saturn's equator)	Position	Discovered
1	XVIII	Pan		30 (35 × 35 × 23)	133,584	+0.57505	0.000º	in Encke Division	1990
2	XXXV	Daphnis		6 - 8	136,505	+0.59408	0.000º	in Keeler Gap	2005
3	XV	Atlas		31 (46 × 38 × 19)	137,670	+0.60169		outer A Ring shepherd	1980
4	XVI	Prometheus		86 (119 × 87 × 61)	139,380	+0.61299	0.000º	inner F Ring shepherd	1980
*		S/2004 S 6		~3-5	140,130	+0.61801		*Uncertain objects around the F-ring	2004
*		S/2004 S 4		~3-5	~140,100	+0.619			2004
*		S/2004 S 3		~3-5	~140,300	~ +0.62			2004
5	XVII	Pandora		81 (103 × 80 × 64)	141,720	+0.62850		outer F Ring Shepherd	1980
6	XI	Epimetheus		113 (135 × 108 × 105)	151,422	+0.69433	0.335º	co-orbitals	1980
7	X	Janus		179 (193 × 173 × 137)	151,472	+0.69466	0.165º	co-orbitals	1966
8	I	Mimas		397 (415 × 394 × 381)	185,404	+0.942422	1.566º		1789
9	XXXII	Methone		3	194,440	+1.00957			2004
10	XXXIII	Pallene		4	212,280	+1.15375			2004
11	II	Enceladus		504 (513 × 503 × 497)	237,950	+1.370218	0.010º	In the thick of E ring	1789
12	III	Tethys		1066 (1081 × 1062 × 1055)	294,619	+1.887802	0.168º		1684
12a	XIII	Telesto		24 (29 × 22 × 20)			1.158º	leading Tethys trojan	1980
12b	XIV	Calypso		21 (30 × 23 × 14)			1.473º	trailing Tethys trojan	1980
15	IV	Dione		1123 (1128 × 1122 × 1121)	377,396	+2.736915	0.002º		1684
15a	XII	Helene		33 (36 × 32 × 30)			0.212º	leading Dione trojan	1980
15b	XXXIV	Polydeuces		3.5				trailing Dione trojan	2004
18	V	Rhea		1529 (1535 × 1525 × 1526)	527,108	+4.518212	0.327º		1672
19	VI	Titan		5151	1,221,930	+15.94542	1.634º		1655
20	VII	Hyperion		292 (360 × 280 × 225)	1,481,010	+21.27661	0.568º		1848
21	VIII	Iapetus		1472 (1494 × 1498 × 1425)	3,560,820	+79.3215	7.570º		1671
22	XXIV	Kiviuq		~16	11 294 800	+448.16	49.087º	Inuit group	2000
23	XXII	Ijiraq		~12	11 355 316	+451.77	50.212º	Inuit group	2000
24	IX	Phoebe		220 (230 × 220 × 210)	12 869 700	-545.09	173.047º	Norse group	1899
25	XX	Paaliaq		~22	15 103 400	+692.98	46.151º	Inuit group	2000
26	XXVII	Skathi		~8	15 672 500	-732.52	149.084º	Norse (Skathi) Group	2000
27	XXVI	Albiorix		~32	16 266 700	+774.58	38.042º	Gallic group	2000
28	XXXVII	S/2004 S 11	-	~6	17 153 520	+838.77	40.484º	Inuit group	2004
29	XXVIII	Erriapo		~10	17 236 900	+844.89	38.109º	Gallic group	2000
30	XLVII	S/2006 S 8	-	~6	17 473 800	-862.37	155.624º	Norse group	2006
31	XXIX	Siarnaq		~40	17 776 600	+884.88	45.798º	Inuit group	2000
32		S/2004 S 13	-	~6	18 056 300	-905.85	167.379º	Norse group	2004
33		S/2006 S 4	-	~6	18 065 700	-906.56	172.666º		2006
34	XLIV	S/2004 S 19	-	~8	18 168 300	-914.29	153.272º		2006
35		S/2006 S 6	-	~6	18 556 900	-943.78	162.861º		2006
36	XXI	Tarvos		~15	18 562 800	+944.23	34.679º	Gallic group	2000
37	XXV	Mundilfari		~7	18 725 800	-956.70	169.378º	Norse group	2000
38		S/2006 S 1	-	~6	18 930 200	-972.41	154.232º		2006
39		S/2004 S 17	-	~4	19 099 200	-985.45	166.881º		2004
40	XXXVIII	S/2004 S 15	-	~6	19 104 000	-985.83	157.384º	Norse (Skathi) group	2004
41	XXXI	Narvi		~7	19 395 200	-1008.45	137.292º	Norse group	2003
42	XXIII	Suttungr		~7	19 579 000	-1022.82	174.321º		2000
43	XLIII	S/2004 S 14	-	~6	19 709 300	-1033.05	163.131º		2004
44		S/2004 S 12	-	~5	19 905 900	-1048.54	164.042º		2004
45	XL	S/2004 S 9	-	~5	19 984 800	-1054.78	158.361º	Norse (Skathi) group	2004
46	XXX	Thrymr		~7	20 278 100	-1078.09	174.524º	Norse group	2000
47	XXXVI	S/2004 S 10	-	~6	20 482 900	-1094.46	167.425º	Norse group	2004
48	XXXIX	S/2004 S 18	-	~7	20 570 000	-1101.45	147.395º	Norse (Skathi) group	2004
49		S/2004 S 7	-	~6	20 576 700	-1101.99	165.596º	Norse group	2004
50		S/2006 S 3	-	~6	21 076 300	-1142.37	150.817º		2006
51	XLI	S/2004 S 16	-	~4	21 930 644	-1212.53	162.832º		2004
52	XLVIII	S/2006 S 7	-	~6	22 288 916	-1242.36	166.918º		2006
53	XLV	S/2006 S 2	-	~7	22 321 200	-1245.06	148.384º		2006
54	XIX	Ymir		~18	22 429 673	-1254.15	172.143º		2000
55	XLVI	S/2006 S 5	-	~6	22 984 322	-1300.95	166.539º		2006
56	XLII	S/2004 S 8	-	~6	24 504 879	-1432.16	167.886º		2004

Grouping the moons

The Saturnian System (photographic montage)

Although the borders may be somewhat nebulous, Saturn's moons can be divided into eight groups.

The 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 Pan, Daphnis, Atlas, Prometheus, Pandora, S/2004 S 3, in addition to the unconfirmed moons S/2004 S 4 and S/2004 S 6.

The 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. See Epimetheus' article for a more detailed explanation of this arrangement.

The inner large moons

The innermost large moons of Saturn orbit within its tenuous E Ring. They are Mimas, Enceladus, Tethys and Dione.

Two recently discovered tiny moons also orbit within this group: Methone and Pallene. So too do the co-orbital moons that form a group of their own (see below).

The Trojan moons

Main article: Trojan moon

Trojan moons are another kind of co-orbitals. Like other co-orbitals, they are a feature unique to the Saturnian system. They are moons that orbit at exactly the same distance from Saturn as another moon, but at such a distance from the other moon that they never collide. Tethys has two tiny co-orbitals Telesto and Calypso, and Dione has also two, Helene and Polydeuces. All four of these moons orbit in the larger moons' Lagrangian points, one in each point.

The outer large moons

Saturn's largest moons all orbit beyond its E Ring and can thus be considered a distinct group. They are Rhea, Hyperion (which is relatively small and very irregular), Titan and Iapetus.

Irregular satellites

Irregular satellites of Saturn.

The Inuit group

Main article: Saturn's Inuit group of satellites

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 Kiviuq, Ijiraq, Paaliaq, Siarnaq, and S/2004 S 11.

The Norse group

Main article: Saturn's Norse group of satellites

The Norse group are 18 retrograde outer moons that are similar enough in their distance from Saturn to be considered a group. They are Phoebe, Skathi, Narvi, Mundilfari, Suttungr, Thrymr, Ymir, S/2004 S 7 through S/2004 S 10, S/2004 S 12 through S/2004 S 19, and S/2006 S 1 through S/2006 S 8. All of these moons orbit Saturn in a retrograde direction.

The Gallic group

Main article: Saturn's Gallic group of satellites

The Gallic group are three 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, Erriapo and Tarvos.

The diagram illustrates the orbits of the irregular satellites of Saturn discovered so far¹. 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 (milion 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.

Naming notes

Some asteroids share the same names as moons of Saturn: 55 Pandora, 106 Dione, 577 Rhea, 1809 Prometheus, 1810 Epimetheus, 4450 Pan. See also Name conflicts of solar system bodies.

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