Introduction to the Gas Giant Planets

Outside of the inner rocky worlds, and beyond the orbit of the asteroids lies the domain of the gas giant planets. This is actually a bit of a misleading title page. These four giant planets, Jupiter, Saturn, Uranus, and Neptune are of two varieties. Jupiter and Saturn are composed almost entirely of gas, with hydrogen and helium being the most common element. In fact, the relative ratio of hydrogen to helium in Jupiter and Saturn are almost the same as the Sun. The only thing preventing either of them from becoming stars is an insufficient amount of mass. Uranus and Neptune have a significant amount of gas, but are primarily liquid, with hydrogen, helium, and methane gases in the exterior. Their magnetic fields of all four of these planets are immense compared to Earth, and in some cases trap so much radiation that human presence near them is impossible. We glory in the beauty of our Moon, but out there, the gas giant planets all have many moons. Neptune has the least natural satellites (13) and Jupiter the most (63). And if that were not enough to make your evenings romantic, should you somehow be able to live out there, each of the gas giant planets has a system of rings. Yes ... those of Saturn are the most beautiful, but the other three worlds have ring systems as well. Jupiter is the largest and most massive of the gas giants and its red spot and colored weather bands are quite distinctive. Saturn's rings are unlike any other planet, and would barely fit between Earth and its Moon. One of Saturn's many moons, Titan, is extremely interesting because it has a thick atmosphere with constituents somewhat similar to the hypothetical early Earth. Uranus is interesting in that it is tipped on its side, with the rings and moons all spinning around it in a top-bottom fashion instead of left right manner. Nothing compares to the blue beauty of Neptune, and its largest moon Triton, is the coldest object in the Solar System.





5th from Sun

6th from Sun

7th from Sun

8th from Sun

At the end of this Gas Planet section of the course is a recount of the Voyager Mission that gave us many of the wonderful images we still enjoy today, as well as a great deal of scientific information and surprises. This recount appeared in my copy of "The Planetary Report," Volume XXII Sep/Oct, 2002. You will be asked to go to that page, instead of watching the in class video, "And Then There Was Voyager," and later respond to a short Voyager Quiz and Commentary. Note ... you will find the connection to the Voyager Quiz in the Neptune page.

You are encouraged to begin this section of the Planet Unit at Jupiter, and then move steadily outward. If you ever get lost, you can always return to this Introductory page, or the Planet Introduction, or even the Syllabus, but why do that when so much awaits you at Jupiter.

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