Astronomy Picture of the Day
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December 23, 1995
Prometheus, Pandora and Saturn's F Ring
The third and fourth innermost moons of
Saturn were unexpectedly discovered
to be gravitational "shepherds." The inner moon
Prometheus and the outer moon
Pandora use their gravitational attraction to define
Saturn's outermost ring. Were any of the smaller
chunks of ice and rock that compose Saturn's F Ring to stray, the ring
particle would be gravitationally pulled back into place by one of these
passing moons. This complex interaction creates a ring structure with two
narrow braids and several unusual knots.
Tomorrow's picture: Uranus' Moon Miranda
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