Топик: Saturn

Much like its neighbor Jupiter, the sixth planet from the sun has a  rocky core and a gaseous surface. But Saturn is chiefly known for its  intricate series of rings that encircle it. The mile-thick rings are made of  countless orbiting ice particles, from less than an inch to several feet in  size.

Up close, it's clear that Saturn has more rings than we can count. But  though you can't see all of them from Earth, you can spot three of them  with a good telescope,.  

The two outermost rings are separated by a dark band called the  Cassini Division, named for the astronomer who discovered it in 1675. The  Cassini division isn't empty, but it has less material in it. The middle ring  is the brightest, and just inside it is a fuzzy one that can be difficult to  spot.

Saturn has 18 known satellites, made mostly of ice and rock. The  largest, Titan, orbits Saturn every 16 days and is visible through a  good-sized amateur telescope. Titan, which is larger than the planet  Mercury, has a thick atmosphere that obscures its surface. Though  researchers aren't sure how many moons Saturn has, the total is likely at  least 20, and may be much higher.

Historical notes 

When Galileo Galilei first studied Saturn in the early 1600s, he  thought it was an object with three parts. Not knowing he was seeing a  planet with rings, the stumped astronomer entered a small drawing -- a  symbol with one large circle and two smaller ones -- in his notebook, as a  noun in a sentence describing his discovery. Debate raged for more than  40 years about these "ears," until Christiaan Huygens proposed that they  were rings. Giovanni Domenico Cassini later discovered a gap between the  rings, which gained his name, and he also proposed that the rings were  not solid objects, but rather made of small particles.

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