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1995s5v.txt
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1996-01-12
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Brightness Variations in Saturn's Satellite 1995S5
This sequence of 100 sec exposures taken with HST's Wide Field and
Planetary Camera (WFPC2) in planetary mode on 10 August 1995 shows the
newly discovered object 1995S5 (red arrows) moving in its orbit around
the planet. As it moves further from Saturn, its brightness decreases
appreciably. This brightness variation is more consistent with that
expected for an elongated, opaque clump of ring material than for a
satellite, leading to the suspicion that 1995S5 is in fact a ring arc
rather than a previously undiscovered satellite. It is likely that it
lies within the narrow, braided F Ring.
In addition to 1995S5, the larger satellites Mimas and Epimetheus are
visible in each frame. Mimas is the bright object below the rings,
and is seen partly shadowed by the rings in the first frame. In
subsequent frames it is in full sunlight. Epimetheus is near the
eastern ansa of the rings, moving slowly outward. In the last frame of
the sequence tiny Pandora has emerged from Saturn's shadow about 2
arcsec from the planet's limb.
These images were obtained one to two hours before the Earth crossed
Saturn's ring plane and an 8922 A methane band filter was used to
reduce the scattered light from the planet. An average of several
other frames has been subtracted from each image to remove the light
from the edge-on rings, and so reveal any faint satellites.
Credit: Phil Nicholson (Cornell University), Mark Showalter
(NASA-Ames/Stanford) and NASA