Four New Saturn Satellites Discovered
IAU Circular 6192
Congratulation to Amanda Bosh and Andrew Rivkin who have announced
their discovery of four new possible satellites of Saturn in IAU
Circular 6192 (see below). The new satellites were detected using the
Hubble Space Telescope's Wide Field Planetary Camera II during the May 22
Saturn ring plane crossing.
The new moons have diameters ranging from 19 to 34 miles. One of the moons,
tentatively named 1995 S3, is apparently a shepherd moon for the F ring
since it orbits just outside of the ring. There are already two known moon
shepherds for the F Ring, Prometheus and Pandora, and the discovery of
a third shepherding moon may account for the unusual braiding observed
in Voyager images of the F Ring.
HST's Planned WF/PC Observations of the May Ring Plane Crossing
Hubble Image of a New Saturn Moon
Ron Baalke
Note: Permission has been obtained from Brian Marsden to place
this IAU Circular on this home page. For more information on IAU
Circulars, see the
Central Bureau for Astronomical Telegrams home page,
and also look at
CBAT's Circular Distribution Policy.
IAU Circular 6192
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
Phone 617-495-7244/7440/7444 (for emergency use only)
SATELLITES OF SATURN
A. S. Bosh, Lowell Observatory; and A. S. Rivkin, Lowell
Observatory and Lunar and Planetary Laboratory, report: "We have
discovered four probable satellites of Saturn, from twenty-seven
400-s images taken in the 890-nm methane band with the HST Wide
Field Planetary Camera 2 during an 11-hr span at the May 22 ring-
plane crossing. For each satellite, we give below the orbital
radius; the angular distance from Saturn at May 22.48584 UT
(negative values indicating that the satellite is west of Saturn);
the longitude at the same epoch (measured from the sub-earth
point); the approximate V magnitude at opposition; and the number
of images in which the satellite was detected: S/1995 S 1, 137450
+/- 200 km, -16".4, +120 deg, 17.2, 15; S/1995 S 2, 139700 +/-
300 km, -18".0, +69 deg, 16.3, 12; S/1995 S 3, 141050 +/- 100 km,
-10".5, +33 deg, 17.5, 14; S/1995 S 4, 146450 +/- 450 km, +14".2,
-44 deg, 18.3, 11. S/1995 S 1, S 2, and S 3 were identified in
each frame in which they were not close to Saturn or a bright
satellite. S/1995 S 4 was not identified in seven frames in which
it should have been visible, all before ring-plane crossing, when
the background noise was higher. Satellite positions were fitted
to a circular orbit in the plane of the rings, including terms
arising from Saturn's nonspherical gravity field. Maximum
residuals were in all cases < 0".5, and for S/1995 S 2 and S 3 were
no greater than 0".15, which is approximately the centering error.
All known satellites are accounted for except Saturn XVIII (Pan),
XV (Atlas), and XVI (Prometheus), which may be visible but are
still uncertain; the possibility exists that S/1995 S 1 is Atlas
and that S/1995 S 2 is Prometheus, although they would be 26 and 21
deg from their respective predicted positions. We see no
satellites outside the rings (the distance of which from Saturn at
the times of observation was > 20") with opposition V mag equal to
or brighter than 19, i.e., that of Saturn XIV (Calypso)."
1995 July 26 (6192) Daniel W. E. Green
Saturn Ring Plane Crossing Home Page
Please direct questions and comments about this Home Page to
Ron Baalke
ron@jpl.nasa.gov
