Planetary Rings  

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Saturn's rings were discovered by Galileo in 1610 (although he didn't realize what they were).   (view from Cassini orbiter, not Galileo's telescope!) notice gaps and different rings

But in fact all the gas giants have rings:

Backlit picture of Jupiter from Voyager 2 notice how thin they are!

Image of Uranus & rings from Hubble Space Telescope:

Neptune's rings...
...and ring arcs

• You can see through some of them
• A solid ring would be dynamically unstable
• They rotate differentially (inner portions rotate faster than outer)

Where'd they come from?

• Rings may be leftover material from planetary formation, but how they could survive for billions of years is unclear.
• Rings may come from the tidal breakup of small moons, but the timescale for breaking up an existing moon into small ring particles is extremely long.