PHY 1060 Lecture Notes - Lecture 5: Occultation, Jet Stream, Great Dark Spot
Module5: The Giant Planets
Chapter 10: Worlds of Gas and Liquid
• Jupiter, Saturn Uranus and Neptune are the giant planets
o Jupiter and Saturn: mainly hydrogen and helium
▪ 5.2 AU from Sun and 9.6 AU from Sun
▪ Called gas giants
o Uranus and Neptune: smaller, have much more water, water ice, and other ices
▪ 19.2 AU from Sun, and 30.0 AU from Sun
▪ Called ice giants
• Jupiter and Saturn were known to the ancients
o Uranus was too faint to be discerned from the other stars
o Discovered in 1781 by Herschel by accident (at first though it was a comet)
▪ Deviated from predicted orbit
▪ Something could have been pulling it
o Neptune was found because Uranus was straying from its predicted orbit
▪ Gravity of Neptune was tugging on Uranus
▪ Found in 1846 by Galle after being mathematically predicted by Le
Verrier and Adams
• Called giant planets because of their mass—from 14.5 Earth masses (Uranus) to 318
(Jupiter)—and also, their physical size
o No solid surfaces: we just see the cloud layers in the atmospheres
• Planetary diameters are found by observing how long it takes for a planet to pass over a
star: stellar occultation
o Planetary masses are found by observing the motions of a planet’s moons and
effects of gravity
• We see atmospheres (some very cloudy, some not), not surfaces
o They are less dense than the terrestrial planets; in fact, Saturn would float in a
large enough tub of water
o Jupiter’s chemistry is like the Sun: mostly hydrogen and helium
o Saturn has some more heavy elements, but is like Jupiter; Uranus and Neptune
have much more heavy elements
• All giants have rapid rotation and therefor different amounts of oblateness (flatness)
o They also have obliquities (axis tilt measurements)
▪ Jupiter: 3 deg
▪ Uranus: 98 deg (results in exteme seasons)
• Appears to be rotating clockwise
• May have been knocked over by collision early on
• Jupiter cloud patterns:
o Strong dark and light bands
o A long-lasting giant storm (great red spot)
▪ Two earths could fit side by side
o Many smaller storms
o Colors indicate complex chemistry
▪ Compounds of hydrogen
• Saturn cloud patterns:
o Saturn has a similar band structure to Jupiter, but less pronounced
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