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Astronomy 04
The Solar System
Chapter 23: “Jupiter & Saturn”
Chapter 24: “Uranus, Neptune”
Reminder: Test 3 Review will be this Fri 6/13. Test 3 will be Mon 6/16.
Extra Credit Deadline is Mon 6/23 (Last Day of Classes)
A Comparison of Mercury Venus & Mars
Mercury
Venus
Mars
Small
No atmosphere
No Clouds
Hot and Cold
Slow Rotation
No Mag Field
Craters
Few Smooth Plains
Caloris Basin
Geo Dead
Earth-sized
Thick CO2 atmosphere
Sulfuric Acid Clouds
Hottest Planet (900F)
Slow Reverse Rotation
Weak Mag Field
Large craters only
Lowland lava plains
Dormant Volcanoes
Continental Areas
Geo Alive
Small
Thin CO2 atmosphere
Water Ice Clouds
Cold
24-Hour Day
Weak Mag Field
Craters
Lowland lava plains
Extinct Volcanoes
Continental Areas
Vallis Marineris Canyon
Dry Riverbeds
Two Small Moons
Geo Dead
Jupiter is :
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The largest of the planets in
our Solar System.
Its radius is 11.3 Earth radii.
Its mass is 317 Earth
masses.
It is composed mostly of
hydrogen (90%) and helium
(9%) and traces of
everything else.
Jupiter's mean density is 1.3
gm/cc, close to that of
water.
History of Exploration by
Unmanned Spacecraft
Pioneers 10 & 11 - Launched
in 1972-73.
Explored asteroid belt.
 Flew past and
photographed Jupiter
and (Pioneer 11) Saturn.
 Probed Jupiter’s intense
radiation belts.

Voyager 1 & 2 - Launched
in 1977

Photographed Jupiter,
Saturn and (Voyager 2)
Uranus and Neptune.

Made possible by rare,
once in 175-year,
alignment of planets.
Galileo Spacecraft:

Released probe into
Jupiter’s atmosphere.
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Impact Jupiter after
successful orbital mission.
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Photographed Jupiter and its
Satellites.
Cassini Spacecraft:
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The Cassini Spacecraft has
been in orbit about Saturn
for the past two years.
Basic Characteristics:
1) Large size but low density
Jupiter:
318X mass of Earth
Density 1.3 g/cm3.
Saturn:
95X mass of Earth
Density 0.7 g/cm3.
Uranus &
Neptune
15X mass of Earth
Density 1.6 g/cm3.
Basic Characteristics:
2) Composition & Chemistry
Hydrogen (H)
Helium (He)
Methane (CH4)
Sulfur
Ammonia (NH3)
Acetylene (C2H2)
Ethane (C2H6)
Basic Characteristics:
3) Equatorial cloud belts:
Jupiter & Saturn:
 Clouds of
ammonia and
sulfur
compounds.
Uranus:
 No visible clouds.
Neptune:
 Clouds of
methane crystals.
Jupiter
Basic Characteristics:
4) Fast rotation
Jupiter in 9 hours
56 minutes
Saturn in 10 hours
40 minutes.

Rapid rotation
causes distention
at the equator so
that equatorial
diameter is
greater then polar
diameter.
Ju[iter
Jupiter
Chapter
24: “Jupiter & Saturn”
Jupiter
Jupiter
Jupiter
Saturn
Uranus
Neptune
The equatorial belts are bands of clouds moving
with velocities up to 400 miles/hr. Wind direction
alternates from one band to another.
The light colored zones are regions of upward
moving convective currents. The darker belts are
made of downward sinking material. The two are
therefore always found next to each other.
The boundaries between the bands display
complex turbulence and vortex phenomenon.
Wind velocities in the atmospheres of the Gas
Giant plants increase from Jupiter to Neptune.
Winds in the atmosphere of Neptune were
recorded at over 1300 mph.
Jupiter has a giant, strong magnetic field and
trapped radiation belts.
Jupiter is a strong emitter of synchrotron
radiation (radio waves) caused by electrons
accelerating along the planet’s magnetic lines
of force.
Jupiter radiates more energy than it receives
from the Sun. This heat is generated from
slow contraction.
Jupiter’s Great Red
Spot is almost 20,000
miles long. It is a
massive high pressure
system which rotates
in 6 days.
Without surface friction
to slow their speed,
storms last for
hundreds of years or
longer.
Moons of Jupiter
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61+ Moons and a Faint Ring
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Galilean Satellites:
Ganymede & Callisto – Larger than Mercury
Io & Europa are about the size of our Moon
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Many of other Moons may be captured Asteroids
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Callisto is the outermost of
Galilean moons at a distance
of 1.2 million miles.
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It is in synchronous
revolution around Jupiter
every 17 days.
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The moon has a heavily
cratered surface that has
seen little change over the
last 4.4 billion years.
CALLISTO
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Callisto froze solid before
the process of differentiation
occurred. It is a geologically
dead world.
CALLISTO
Closeup of Callisto
GANYMEDE
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Ganymede is the largest moon
in the Solar System.
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Parts of its surface are very old
like Callisto but others are
relatively young, perhaps a
billion years old.
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Ganymede may have a rocky,
metallic core.
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Tidal forces may occasionally
heat the interior and cause
water to erupt and resurface
portions of the moon.
Closeup of Ganymede
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Europa is predominantly a rocky
world with an ice-covered surface
that is crisscrossed with cracks
and low ridges.
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Few craters are evident.
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The ice appears to be the frozen
surface of a great water ocean that
has broken up and refrozen many
times.
EUROPA
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Tidal forces may generate enough
heat to keep water in the liquid
state not too far beneath the
surface layer of ice.
EUROPA
Closeup of Europa
IO
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Io is a close twin our Moon
with about the same size and
density.
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Io has active volcanoes on
its surface. Volcanoes emit
hot rocky lava, sulfur and
sulfur dioxide.
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The sulfur and sulfur
dioxide recondense in the
cold and snow down upon
Io’s surface.
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IO
Io is constantly resurfacing
itself.
Closeup of Io
Today we will see the Sky Skan Full Dome Presentation
… “Saturn: Jewel of the Heavens”
Reminders:
Extra Credit Deadline is this Fri 6/22
Your final exam is Wed 6/27 at 7:00 a.m.
Cloud belts of Saturn as viewed by Cassini spacecraft
Photograph of “dragon storm” in Saturn’s
atmosphere (Cassini spacecraft)
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All four giant planets have
rings.
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Saturn’s Rings are ice
particles spread out into
several vast flat rings.
Uranus and Neptune’s rings
are composed of dark
particles confined to a few
narrow rings.
Jupiter’s ring is composed
of dust particles.
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Io
Saturn’s Rings as viewed by the Cassini spacecraft
Electrically charged clouds of dust particles
floating above Saturn rings (Cassini
spacecraft)
Moons of Saturn
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31+ Moons and Massive Ring System
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Titan is most significant satellite and the only moon with a
significant atmosphere
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Ring material size of ping-pong, tennis and basketballs.
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Saturn’s Titan is about the
size of Jupiter’s Ganymede
and is about half ice and
half rock.
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It is the only moon to have a
substantial atmosphere.
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The atmospheric surface
pressure is 1.6 times that of
Earth.
Io
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Titan’s atmosphere is
composed mostly of
methane. Nitrogen and
hydrocarbon compounds are
also present.
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Methane clouds composed
of shroud the surface. The
surface is probably covered
with methane ice and
perhaps methane oceans.
Io
False color image of Titan by Cassini revealing surface features
Surface of Titan in color as viewed by
the Huygens probe
Clouds over Titan’s south pole
Uranus
Rings
of Uranus
Neptune has a storm
similar to the great
Red Spot called the
Great Dark Spot.
Moons of Uranus
 26+ Moons and 11 Dark Rings
 Miranda – A Moon that may have broken up and then
reassembled.
Moons of Neptune
 13+ Moons
 Triton – A large satellite in retrograde orbit
Miranda
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Triton is the largest moon
of Neptune.
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It has the coldest
temperature of any object
unmanned spacecraft have
visited – 35-40 degrees
above Absolute Zero.
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Triton is so cold that N and
CH4 are frozen on its
surface.
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The moon is 75% rock and
25% water ice. Io