Saturn's Possible New Moons

Facts

• The image above shows Epimetheus on the left and S/1995 S 3 on the right.

• Here are the provisional designations and orbital radii of some of the reported but as yet unconfirmed and unnamed moons of Saturn:

                         Distance
            Designation    (km)
            -----------  --------
            S/1981 S 7
            S/1981 S 10
            S/1981 S 11
            S/1981 S 14   200000?
            
            S/1981 S 15   174000
            S/1981 S 16   220000
            S/1981 S 17   231000
            S/1981 S 18   185000
            S/1981 S 19   186000
            
            S/1995 S 1    137450
            S/1995 S 2    139700
            S/1995 S 3    141050
            S/1995 S 4    146450
  

• The first two groups are derived from analysis of Voyager 2 data reported in IAUC 6162; the third group is from HST observations during the May 1995 ring plane crossing by Amanda S. Bosh and graduate student Andrew S. Rivkin and reported in IAUC 6192.

• Several others have also been reported (IAUC 3651, 3656 and 3660) but IAUC 6162 indicates that the new satellites previously reported should be reduced to the four in the first group above.

• It is possible that some of these are actually the same as some of the known satellites (e.g. S/1995 S 1 may be Atlas and S/1995 S 2 may be Prometheus or S/1995 S 1 may be Pan and 1995 S 2 one of the others); better orbital determinations will be needed to sort it out.

• 1993 S 3 orbits just outside the F ring and is apparently a shepherd moon. There are two other F ring shepherds ( Prometheus and Pandora), the presence of a third may account for the F ring's braided appearance.

• These moons are all very small, just a few tens of kilometers in diameter.

• These will be observed again during the next ring plane crossing in August 1995. Ring plane crossings are particularly favorable for seeing small moons since the normally bright glare of the rings is absent. 13 of Saturn's 18 known moons were discovered during ring plane crossings.

• All doubt should be laid to rest with the arrival at Saturn of the Cassini spacecraft in 2004.

Pictures

1. (above) S/1995 S 3 and Epimetheus 130k gif; 58k gif (caption)

More about new Saturnian moons

• from LANL
• press release about S/1995 S 3
• IAU Circular 6162 (Voyager)
• IAU Circular 6192 (HST)
• note from IAU Circular 6196
• Saturn Ring Plane Crossing Home Page
• Ring plane crossing info from STScI