Transcript Jovian Planets

Jovian Planets
Rulers of the Solar System
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Properties
Mass
(kg)
Radius
(km)
Average
Density
(kg/m3)
# of
Moons
Mag. Rotation
field Period
(♁=1 (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
• Most of Jupiter and Saturn and about half of
Uranus and Neptune are made of Hydrogen and
Helium
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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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Magnetosphere
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Uranus’ orbit
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Composition
Size
Jupiter
Dust
Small grains
Saturn
Water ice
< house size
Uranus
Carbonaceous
Large paricles
Neptune
dark, unknown unknown, small
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
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Rings
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Ring structure
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What makes the rings?
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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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