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IAUC 3497: SATURN

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IAUC number 

                                                  Circular No. 3497
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM     Telephone 617-864-5758


SATURN
     The Space Telescope Wide Field/Planetary Camera Team reports
recent CCD observations that show a local maximum in the density of
the E ring at the orbital distance of Saturn II (Enceladus).  A
simple model was used to correct the observed brightness profile to
a true radial distribution of the material.  This implies that
Enceladus is the source of at least the E-ring particles.  The Team
suggests that a recent impact event seems the most likely cause for
material to be ejected from the satellite.  The observations contain
data that may lead to an estimate of the age of the ring.

     A. Dollfus, Observatoire de Meudon, communicates the following
detailed measurements (in the ring plane, + = east, - = west of
the center of Saturn) of his original 1966 discovery and of the 1980
observations reported on IAUC 3474:

1966 S 2, m ~ 14.  1966 Dec. 15.765 UT, +21".94; 15.778, +21".99;
   15.784, +21".64; 15.816, +20".23; 15.820, +19".44; 15.830, +18".96;
   15.845, (+16".98); 15.860, (+15".65).

1980 S 1 (= 1966 S 2?), m ~ 14.  1980 Mar. 23.889 UT, +23".39;
   23.904, +23".83; 23.907, +24".26; 23.915, +24".48; 23.918, +24".59;
   23.931, +24".48; 23.935, +24".48; 23.956, +23".61; 23.960, +23".06;
   23.971, +21".36; 23.974, +21".64; 23.987, +20".33; 23.990, +19".89.

1980 S 19 = 1980 S 3, m ~ 15.  Mar. 23.886 UT, -24".96; 23.889,
   -24".86; 23.904, -24".26; 23.907, (-24".48); 23.915, -23".61;
   23.931, -22".79; 23.935, -22".79.

1980 S 20, m ~ 15-16, not seen detached from ring lineament.  Mar.
   20.899 UT, +18".90; 20.908, +20".12; 20.915, +21".89; 20.925,
   +21".72; 20.928, +21".66.

1980 S 21, m ~ 15-16, dubious because of possible interaction with
   a dust particle on the lens.  Mar. 22.973 UT, -22".44; 22.974,
   -22".00; 22.977, -21".72; 22.983, -21".67; 22.988, (-21".79).

He confirms that his new 1966 measurements are consistent with a
maximum elongation of 2.53 Rs and with the revolution period of
0.69465 day given on IAUC 3483.  Agreement with other 1966 observations
is as shown by orbit 16 of Aksnes and Franklin (1978, Icarus
36, 107).  The Flagstaff-Tucson observations of 1966 Dec. 18.061-18.069
UT probably refer to 1980 S 3.  The motion of 1980 S 20 (if
real) is compatible with a third object in the 1966 S 2/1980 S 3
orbit.  1980 S 22, m ~ 17, is now felt to be extremely questionable.


1980 August 4                  (3497)              Brian G. Marsden

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