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Astronomy 2021: Closer to Home – The Solar System
“Uncle Bob”

Saturn

credit: NASA/JPL-Caltech/Space Science Institute. September 15, 2016.

In 1610 Galileo Galilei, through a four-foot telescope with two 2” lenses, thought he saw that Saturn had two very close moons that would come and go. He was observing the rings that can appear and disappear depending on their tilt toward us. I can give some direct testimony: I saw one of his telescopes and his notes on exhibit at the Franklin in Philadelphia some years ago. I’ll never forget the experience.

Author Sailko. Wiki Commons license.

Saturn has many rings and with a good backyard scope one can see the Cassini division, a gap that divides the two main groups of rings. Let’s focus on some of the lesser known facts about the planet proper. STORMS, for example. Saturn is second only to Neptune in having winds measuring over 500 miles per second. When a storm does pop up out of the gaseous atmosphere it can be violent and persist for a long time.

credit: NASA/JPL-Caltech/Space Science Institute.
Here is a storm which over several months has caught its tail.

Saturn orbits the Sun in about 30 years time, but it has a very short day of only 10 hours. Saturn’s surface color, creamier than bright white Jupiter, is caused by ammonia crystals refracting the sunlight … and Saturn floats! Or … it would if we could find a big enough bathtub. Its density is only 70% that of water.

One of Saturn’s more curious surface features is a hexagonal storm surrounding the north pole. It’s size, at 8600 miles along each side, is enormous. Earth’s sihlouette would not span a single side. The hex rotates at a different rate than the surface clouds, seemingly tied to inner structures. The shape is said to form due to differences in the rotation rates of the various fluids, and this phenomenon has been simulated in the lab.

Probing below Saturn’s surface, instruments have determined a thick layer of gas and way, way down, a solid core. On the way down however one would encounter strange chemistry. Under all of the massive weight of merely the gas, the temperature and pressure prevent hydrogen nuclei from organizing electrons into gas molecules. The electrons sort of drift along, much like in a sample of metal. The material in this layer is referred to as metallic hydrogen, but I like the term “shiny hydrogen.” I wonder if we’ll ever get a picture?

More on the innards.

While we wait for that picture, please enjoy the Saturn segment of “The Planets” composed by Gustav Holst, accompanied by eye-catching illustrations.

See an album of Cassini spacecraft Saturn images.

Next month: Jupiter

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