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ASTR-1010
Planetary Astronomy
Day - 31
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Course Announcements
Homework Chapter 9: Due Wednesday April 13.
Exam 3: Will be returned on Friday.
The last 1st Quarter moon observing nights are:
Tuesday (April 20) & Thursday (April 22)
8:00 pm both nights.
Exam 4 question
Looking for something different?
• ASTR-3005/3006
• ASTR-3030/3031
• Observational Astronomy
• 1 hr lecture + 1 hr lab
• Dr. Buckner
• Prereq: Astr 1010 or 1020
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Constellations and stars of
the night sky; setup, align
and use various types of
telescopes. Hands-on
use of APSU observatory.
• Methods & Instrumentation
• 2 hr lecture + 1 hr lab
• Dr. Smith
• Prereq: Phys 2020 or 2120
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Instruction on the techniques
of modern astronomy and
use of instrumentation.
Hands-on experience at
the APSU observatory.
Chapter 9
Lecture Outline
Worlds of Gas and Liquid –
The Giant Planets
The Giant Planets
• Jupiter and Saturn: mainly hydrogen and
helium.
• Uranus and Neptune: have much more
water.
• All these planets probably have a core of
dense materials.
Jupiter & Saturn
 Jupiter: NASA/JPL/University of Arizona
 Saturn: NASA and E. Karkoschka
(University of Arizona)
Uranus & Neptune
 Uranus
 Neptune: both images NASA Jet Propulsion Laboratory
(NASA-JPL)
Characteristics of the Giant
Planets
• Called giant planets because of their
mass: from 15 Earth masses
(Uranus/Neptune) to 300 (Jupiter).
• No solid surfaces: we just see the cloud
layers in the atmospheres.
• Rapid rotation.
• Strong magnetic fields.
Cloud Patterns –
Jupiter and Saturn
Jupiter
• Strong dark and light bands.
• A long-lasting giant storm (Great Red
Spot).
• Many smaller storms.
• Colors indicate complex chemistry.
Saturn
• Similar to Jupiter, but less pronounced.
Cloud Patterns –
Uranus and Neptune
Uranus/Neptune
• Almost featureless as viewed from Earth.
• More detail seen from spacecraft or
infrared observations from the Hubble
Space Telescope.
• Weak banding.
• Small, scattered bright or dark clouds.
• Transient large storms (Great Dark Spot
on Neptune).
Composition
• Mainly light elements (hydrogen/helium).
• Jupiter’s composition like that of the Sun
(71% H, 27% He).
• Biggest difference is the amount of
massive elements.
• Saturn has somewhat more than Jupiter.
• Uranus/Neptune have larger fraction of
massive elements.
Probing the Atmospheres
• Density, composition, and circulation
patterns vary with height.
• Temperature, pressure increases
downward.
• Different appearance of planets from
different heights of cloud layers.
• Example: Clouds on Jupiter.
– Ammonia (NH3) at T = 133 K.
– Ammonium hydrosulfide (NH4SH) at T = 193 K.
• Strong winds, storms, and jet streams.
Cloud Layers
Winds and Storms
• Rapid planetary rotation results in strong
Coriolis forces. This imparts a rotation to
storms.
• Most extreme winds are in Saturn’s
atmosphere (1650 km/hr).
• Alternating east/west winds make banded
clouds on Jupiter.
• Circulation pattern differs from planet to
planet in ways not understood.
Wind Speeds
Internal Heat
• All but Uranus have significant internal heat.
• Jupiter is hotter than it would be just from
sunlight.
• Jupiter radiates about 65% more energy
than it receives from the Sun.
• Heat flows from the hot interior outward.
• Heat has a big effect on the global
circulation patterns.
The Zones and Belts are
convection regions
Jupiter rotates faster at the
equator than at the poles
Polar Rotation Period
9 hr 55 min 41 sec
Equatorial Rotation Period
9 hr 50 min 28 sec