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Astronomy 241: Foundations of Astrophysics I
13. Giant Planets
“Gas Giants” “Water Worlds”
Two Types of Jovian Planets
Internal Structure: Heat Sources
J. & S. put out lots of heat — not due to radioactivity since H and He isotopes are stable.
— Jupiter: left-over heat.
— Saturn: + He settling.
U. puts out very little heat —— bottled up in interior?
N. puts out more heat —— deeper convection.
Internal Structure: Magnetic Fields
J. & S. have strong fields which are well-aligned with rotation.
U. & N. have weaker fields which are highly mis-aligned.
— convection in metallic H! — local dynamo in “ocean”?
Internal Structure: Magnetic Fields
12 hours on Jupiter
Outward Appearance
Outward Appearance: Cloud Colors
50 k
m10
0 km
Dis
tanc
e be
low
clo
ud t
ops NH3
NH4SH
H2O
Outward Appearance: Belts
Convection and rapid rotation organize atmospheric motion.
Belts: sinking gas exposes red NH4SH clouds; circulates faster.
Zones: rising gas forms white
NH3 clouds; circulates slower.
Jupiter Unpeeled
Outward Appearance: Circulation Patterns
Approaching Jupiter
Outward Appearance: Great Red Spot
Outward AppearanceOutward Appearance: Great Red Spot
Jupiter's Great Red Spot Region
H
Outward Appearance: Saturn
Saturn … Four Years On
Bands like Jupiter’s, but less dramatic since atmosphere is deeper due to weaker gravity.
Outward Appearance: Uranus & Neptune
Their atmospheres are deep, methane-rich, and very cold.
• Cloud layers are too deep to be easily seen.
• Methane (CH4) absorbs red light, transmits blue.
— blue planets with subtle cloud features.
Outward Appearance: Uranus & Neptune
Great Dark Spot