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Lecture 18

AS101 Lecture 18

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Wilfrid Laurier University
Patrick Mc Graw

Lecture 18 4/10/2013 12:54:00 PM Jovian Planets and their moons, Part I Common characteristics of Jovian Planets:  Larger than terrestrial planets.  Contain a lot more hydrogen and helium, and hydrogen-containing compounds like water, ammonia, methane (a.k.a. “ices”)  Multiple satellites (some with atmospheres/oceans.)  All have rings made up of icy/rocky debris. (Saturn's are the most prominent.)  In summary, you could almost say that it's as if each one of the Jovian planets forms its own miniature solar system. Jupiter:  Distance from Sun: 5.2 au  Orbital period: 11.86 years  Rotation period: 10 hours  Surface temp (top of cloud layer): -108 C  90%hydrogen, 10% helium, less than 1% other stuff.  Moons of Jupiter: other moons: o Many smaller objects (less than a few hundred km across) orbit Jupiter. o Closer than the Galilean four include Amalthea, Metis, Adrastea, Thebe.  Internal structure: o Metallic Hydrogen: Under high pressures, hydrogen becomes an electrical conductor and behaves like a liquid metal. o Liquid metal creates an extremely strong magnetic field compared to Earth. Jovian weather: Belt and Zone Circulation:  Belts: darker bands of lower pressure.  Zones: lighter bands of higher pressure.  Patterns of wind can be understood based on the interaction of convection and the planet's rotation, much as on Earth.  Convection: a pattern of circulation in which a fluid (or gas) heated from below rises, then loses some of its heat and sinks. Earths and jupiters weather: similarities:  Wind patterns created by the combination of convection, pressure differences and the planet's rotation.  Winds spiral around high and low pressure areas due to the Coriolis effect.  Large-scale bands parallel to latitude lines, smaller systems within the global pattern. Earths and jupiters weather: Differences:  Jupiter rotates faster, so the effect of rotation is stronger.  Jupiter is more symmetrical: no continents, oceans, mountain ranges to break up the pattern. (And weaker seasonal changes.)  Main energy source on Earth is heat from the sun. On Jupiter, weather patterns are mostly driven by heat escaping from the planet's interior. Jupiters hot interior:  Infrared observations show both Jupiter and Saturn emit noticeably more energy than they absorb from the sun.  Both are gradually cooling off--- still losing the heat they gained in the process of forming.  Estimated temp. at Jupiter's core: 25,000 K.  Not hot enough to start a fusion reaction and become a star, but not far from the borderline. Saturn:  Distance from Sun: 9.6 au  Orbital period: 29.5 years  Rotation period: 10.6 hours  Surface temperature: - 139 C  Composition: about 96% hydrogen, 3% helium. (less helium than Jupiter or the Sun...)  Moons: o More than 62 known moons o Largest moon, Titan, is larger than Mercury. o Titan is the only moon in the solar system with a significant atmosphere Jupiter and Saturn are real giants:  Together, Jupiter and Saturn add up to 92% of the total planetary mass in the solar system. Jupiter and Saturn:  Similarities: o Similar size and composition o Prob
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