Saturn
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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