Brightness variations in Saturn's satellite 1995S5

This sequence of 100 sec exposures taken with HST's Wide Field andPlanetary Camera (WFPC2) in planetary mode on 10 August 1995 shows thenewly discovered object 1995S5 (red arrows) moving in its orbit aroundthe planet. As it moves further from Saturn, its brightness decreasesappreciably. This brightness variation is more consistent with thatexpected for an elongated, opaque clump of ring material than for asatellite, leading to the suspicion that 1995S5 is in fact a ring arcrather than a previously undiscovered satellite. It is likely that itlies within the narrow, braided F Ring.

In addition to 1995S5, the larger satellites Mimas and Epimetheus arevisible in each frame. Mimas is the bright object below the rings,and is seen partly shadowed by the rings in the first frame. Insubsequent frames it is in full sunlight. Epimetheus is near theeastern ansa of the rings, moving slowly outward. In the last frame ofthe sequence tiny Pandora has emerged from Saturn's shadow about 2arcsec from the planet's limb.