Saturn's New Moons

1995s3

 

Many new Saturnian moons are now confirmed; the pre-2000 reports are probably in error. More recent discoveries can be seen here. And more discoveries are expected from Cassini, now in orbit around Saturn.


Cassini

Oct 2000 Announcement

  • Gladman's page
  • McMaster announcement
  • The satellites are temporarily designated
              S/2000 S 1
              S/2000 S 2
              S/2000 S 3
              S/2000 S 4
              S/2000 S 5
              S/2000 S 6
    
    if confirmed they will be assigned permanent names.

Dec 2000 Announcement

  • Gladman et al have found six more:
              S/2000 S 7
              S/2000 S 8
              S/2000 S 9
              S/2000 S 10
              S/2000 S 11
              S/2000 S 12
  • preliminary orbits of these satellites

pre-2000 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
    
              S/1995 S 5    140060
              S/1995 S 6    139910
              S/1995 S 7    139440
    
    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; the fourth group is from HST observations by P. D. Nicholson et al during the August 1995 ring plane crossing as reported in IAUC 6243.

  • 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 S/1995 S 2 one of the others); better orbital determinations will be needed to sort it out. IAUC 6243 confirms the probable identification of S/1995 S 2.

  • The orbit of S/1995 S 7 is "indistinguishable" from that of S/1995 S 2 (= Prometheus) but S/1995 S 7 trails behind by 15 degrees.

  • S/1995 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.

  • IAUC 6243 indicates that S/1995 S 5 and S/1995 S 6 may be just clumps or arcs of ring material rather than true satellites.

  • These objects, if they are real, are all very small, just a few tens of kilometers in diameter.

  • 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.

  • It now appears that none of these are real. They are most likely just short-lived clumps of material.

  • 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 47k jpg; 180k gif (caption)
  2. Pandora and S/1995 S 6 from ESO 61k gif (caption)
  3. HST view of the motions of Saturn's inner satellites 307k gif (caption)

More about new Saturnian moons


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Bill Arnett; last updated: 2005 May 11

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