Each of the four giant gas planets in the outer Solar System is orbited by rings of dust and small particles of matter. Saturn is famous for its rings.

Through a telescope, the prominent rings girdling its equator make Saturn a stunning sight. The rings, 375,000 miles across, make the planet shine brightly for astronomers. Galileo saw the rings first in 1610. Huygens recognized them as a system in 1656.

Pioneer-Saturn. The interplanetary probe Pioneer 11 flew by Jupiter in 1974 and Saturn in 1979. It sent back pictures from inside Saturn's rings.

While looking at the rings around Uranus, the interplanetary probe Voyager 2 uncovered strange incomplete-circle formations now called ring arcs. The many rings and arcs varied in depth and density.

Shattered moon. In fact, Voyager found nine rings around Uranus, but they were quite different from Jupiter and Saturn rings. Uranus' rings may be young remnants of a shattered moon. Two moons have been identified as shepherds that keep eleven large rings around Uranus from spreading into space.

Voyager found four complete rings around Neptune, but no partial ring arcs. The fine material in the rings is so diffuse they cannot be seen from Earth.

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Solar System:	The Sun
Inner System:	Mercury	Venus	Earth	Mars
Outer System:	Jupiter	Saturn	Uranus	Neptune	Pluto
Other Bodies:	Moons	Rings	Asteroids	Comets

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