The Irregular Satellites of Saturn / Les Satellites Irreguliers de Saturne 

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Information on the irregular satellite system of Saturn

In 1898, William Pickering discovered the first irregular satellite of Saturn, known as Phoebe.
In 2000 many new satellites were discovered by an international collaboration of astronomers.
The links below provide additional information on these new saturnian satellites.
NEW! UPDATE (January 2003) : Between August and December 2002 all 12 of the new satellites which received designations in 2000 have been recovered by our team at a variety of telescopes around the world. As a result, all satellites have now been observed at 3 oppositions. Only minor modifications of their orbits have occurred as a result of these tracking observations (see orbital information links at the bottom of this page). These twelve satellites have now reached a stage of orbital precision to receive full (Roman numeral) designations by the International Astronomical Union.

Old (discovery) PRESS RELEASE, July 9 2001 / Communique de press, 9 juillet 2001

CONTACTS (telephone, fax, e-mail)


As of Jan 30/2003, 12 new saturnian satellites have been discovered and announced (see IAU telegrams below).
These satellites all belong to the `irregular' class, meaning that thier orbits are highly inclined with respect to the planet's equator (and ring plane), and may be significantly non-circular.
Independent orbital determinations (B. Marsden, MPC; R. Jacobson, JPL; B. Gray, Project Pluto) have shown that the new satellites split into three or four `groups'. The first group contains 4 retrograde orbits like those of Phoebe, one other satellite is isolated on a retrograde orbit, while the 7 others form two new prograde cluster (that is, which go around the planet in the same sense that it spins).
The situation of Saturn thus seems to resemble that of Jupiter, which also has retrograde and prograde satellites, concentrated into clusters.
Technical astrometric and orbital information is available at the bottom of this page


IAU Circular 7512 (Oct 26, 2000) (Discovery of S 1 and S 2)
IAU Circular 7513 (Oct 26, 2000) (Discovery of S 3, and S 4)
IAU Circular 7521 (Nov 18, 2000) (Discovery of S 5 and S 6)
IAU Circular 7538 (Dec 7, 2000) (Discovery of S 7, S 8, and S 9)
IAU Circular 7539 (Dec 7, 2000) (Discovery of S 10)
IAU Circular 7545 (Dec 19, 2000) (Discovery of S 11)
IAU Circular 7548 (Dec 23, 2000) (Discovery of S 12)


Animation of S/2000 S 2.
Animation of S/2000 S 4.
Discovery Image of S/2000 S 1 / Image de découverte de S/2000 S 1
Discovery Image of S/2000 S 2 / Image de découverte de S/2000 S 2
Offset plot (postscript file) of saturnian irregulars.
Photo (tif file) of 4 team members (Gladman/Petit/Holman/Kavelaars, L to R)

Press releases / Communiques de presse (Oct 2000)

In 1997 a group of astronomers reported the discovery of the first two known irregular moons of the giant planet Uranus and in 1999 they added to that total with the discovery of three additional satellites. Beginning October 26/2000 the most recent discovery was announced. This time the focus of the search was Saturn, revealing four new irregular moons of that planet, which has since grown to twelve announced satellites in 2000. Prior to this search Saturn was thought to have only one satellite of this class (Phoebe). The newly-discovered satellites are small (less than 50 km across) and likely icy moons, the remnants of a capture event long ago. The satellites orbit Saturn at distances of roughly 10-20 million kilometers from planet.
Coupled with their 1999 discoveries, this group is responsible for the discovery of 17 irregular satellites, and since 1997 they have more than doubled the number of known irregular satellites in the Solar System. Continued observations of the Uranian system over the past two years is beginning to reveal the secret pasts of those irregulars. These new discoveries around Saturn will provide additional information about the processes at work during the formation of the gas giant planets.

Observatoire de la Cote d'Azur. Press Release (Oct. 26/00). Texte en francais (French release)
ESO Press office web page for ESO press release (26 Oct 2000).
McMaster University press release (26 Oct 2000).
Cornell University press release (26 Oct 2000).

Saturn (Nine Planets database)
Phoebe Saturn's previous irregular moon (Nine Planets database)
The Uranian Irregulars home page, describing the previous discoveries of that planet's irregular moons. (Un lien francais aussi)


orbit projection NEW! Astrometric information on the saturnian irregulars.

Orbital information on the saturnian irregulars.

            IMAGE at right: View of current orbits, given current estimages. Courtesy B. Gray at Project Pluto. Full Resolution GIF image available.

Page maintained by: Brett Gladman (OCA). URL: