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Jovian PlanetsJovian Planets
Rulers of the Solar System
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Properties
• Most of Jupiter and Saturn and about half of Uranus and Neptune are made of Hydrogen and Helium
Mass(kg)
Radius(km)
Average Density(kg/m3)
# of Moons
Mag. field (♁=1)
Rotation Period(days)
Surface Temp.(K)
Surface Gravity(♁=1)
Jupiter 1.9 x 1027
71,000
1330 16 14 0.41 124 2.5
Saturn 5.7 x 1026
60,000
710 18+ 0.7 0.43 97 1.1
Uranus 8.7 x 1025
26,000
1240 21 0.7 -0.69 58 0.91
Neptune
1.0 x 1026
25,000
1670 8 0.4 0.72 59 1.1
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Voyager
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Energy
• With no surface, no surface modification processes– No craters– No volcanoes– No tectonics– No erosion
• These are big planets• Big planets have lots of internal energy• With no endogenic surface processes,
where does the energy go?
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Bands &
Storms
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Bands
• Differential rotation – poles take longer to rotate than equator
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Storms
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The great red spot
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SL9
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Interiors
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ere
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Uranus’ orbit
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Planetary Rings
• All the “Jovian planets” have rings
• These are not solid, but composed of millions of tiny particles of ice and dust
• Rings have structure: gaps and spokes
Composition
Size
Jupiter Dust Small grains
Saturn Water ice < house size
Uranus Carbonaceous
Large paricles
Neptune
dark, unknown
unknown, small
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Rings
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Ring structure
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Shepard moons
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Planetary rings – Why?• Left to itself, a ring will slowly spread out due to
gravitational interactions• Rings are bounded by the stronger gravity of larger
bodies: The planet itself and some of the larger and nearby moons
• Some bounds are due to gravitational resonances, others due to the direct action of sheparding satellites
• The origin of the rings is unknown – either a failed satellite or a broken satellite
• A reason is known: the tidal stability limit at 2.5 times the radius of the body. Interior to this, 2 touching particles will be pulled apart by the planet’s gravity
• Why don’t inner planets have rings? Gravitation perturbations by the Sun will cause any small particles to spiral into the planets on a relatively short time scale.
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