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Saturn
| 23.04.2012, 23:40 |
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.
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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