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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.