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Astronomy 1010
Planetary Astronomy
Fall_2015
Day-34
Course Announcements
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SW-chapter 9 due: Wed. Nov. 18
SW-chapter 10 due: Mon. Nov. 23
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I will collect the L-T books on Monday, Nov. 23,
though I will take them at any time now.
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1st Quarter Obs. (last one of semester): Thurs. Nov. 19
Reports Due: Monday Nov. 23 – AT CLASS TIME!
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 Jupiter and Saturn
were known to the
ancients.
 Uranus was too faint
to be discerned from
the other stars.
 Discovered in 1781
by Herschel by
accident (at first
thought it was a
comet).
 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.
 No solid surfaces: We just see the cloud layers
in the atmospheres.
More Giant Characteristics
 We see atmospheres (some very cloudy,
some not), not surfaces.
 They are less dense than the terrestrial
planets; in fact, Saturn would float in a
large enough tub of water.
 Jupiter’s chemistry is like the Sun: mostly
hydrogen and helium.
 Saturn has some more heavy elements,
but is like Jupiter; Uranus and Neptune
have much more heavy elements.
 Planetary diameters are found by observing
how long it takes for a planet to pass over a
star: stellar occultation.
 Planetary masses are found by observing the
motions of a planet’s moons and effects of
gravity.
i_Clicker Question
Jovian Planets: Jovian Transit
Jovian Planets: Jupiter Formation
 All giants have rapid
rotation and therefore
different amounts of
oblateness.
 They also have different
obliquities.
• Jupiter: 3°.
• Uranus: 98°, which results in
extreme seasons.
i_Clicker Question
Jovian Planets: Oblateness
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Strong dark and light bands.
A long-lasting giant storm (Great Red Spot).
Many smaller storms.
Colors indicate complex chemistry.
 Saturn has a similar band structure
to Jupiter, but less pronounced.
 It has violent storms and a feature similar to
Earth’s jet stream.