Download Planetary Rings - Physics and Astronomy

Chapter 8
Moons, Rings,
and Plutoids
Copyright © 2010 Pearson Education, Inc.
Copyright © 2010 Pearson Education, Inc.
Chapter 8
Moons, Rings, and Plutoids
Copyright © 2010 Pearson Education, Inc.
Units of Chapter 8
The Galilean Moons of Jupiter
The Large Moons of Saturn and Neptune
The Medium-Sized Jovian Moons
Planetary Rings
Beyond Neptune
Plutoids and the Kuiper Belt
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Question 1
As their distance from
Jupiter increases, the
four Galilean satellites
show a consistent
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a) increase in density.
b) increase in size.
c) decrease in cratering.
d) decrease in density.
e) amount of cratering.
Question 1
As their distance from
Jupiter increases, the
four Galilean satellites
show a consistent
a) increase in density.
b) increase in size.
c) decrease in cratering.
d) decrease in density.
e) amount of cratering.
Like a miniature version of our solar
system, Jupiter’s four large moons
show a decrease in density as distance
increases. Io is most dense of the four;
Callisto is least dense.
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The Galilean Moons of Jupiter
All four Jovian planets have extensive moon
systems, and more are continually being
discovered.
The Galilean moons of Jupiter are those observed
by Galileo: Io, Europa, Ganymede, and Callisto.
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The Galilean Moons of Jupiter
This image shows Jupiter with two of its Galilean
moons.
Galilean Moons
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The Galilean Moons of Jupiter
The Galilean
moons and their
orbits
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The Galilean Moons of Jupiter
Their interiors
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The Galilean Moons of Jupiter
Io is the densest of Jupiter’s moons, and the
most geologically active object in the solar
system.
• It has many active volcanoes, some quite
large.
• Io can change surface features in a few
weeks.
• Io has no craters; they fill in too fast – Io has
the youngest surface of any solar system
object.
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Question 3
What is thought
to cause Io’s
volcanism?
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a) Jupiter’s magnetosphere
b) Jupiter’s rapid rotation
c) tidal stress from Jupiter and Europa
d) radioactive decay from its core
e) Io’s large mass and tectonic activity
Question 3
What is thought
to cause Io’s
volcanism?
a) Jupiter’s magnetosphere
b) Jupiter’s rapid rotation
c) tidal stress from Jupiter and Europa
d) radioactive decay from its core
e) Io’s large mass and tectonic activity
Io is constantly
“squeezed” by its huge
neighbor as well as by
companion moons,
heating its interior.
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The Galilean Moons of Jupiter
Io Cutaway
Io is very close to Jupiter, and
also experiences gravitational
forces from Europa. The tidal
forces are huge, and provide
the energy for the volcanoes.
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Question 2
The surface of which
jovian moon most
resembles the pack ice of
the Arctic Ocean?
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a) Europa
b) Io
c) Amalthea
d) Ganymede
e) Callisto
Question 2
The surface of which
jovian moon most
resembles the pack ice of
the Arctic Ocean?
a) Europa
b) Io
c) Amalthea
d) Ganymede
e) Callisto
Ice-filled
surface
cracks
indicate an
ocean may
lie below.
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The Galilean Moons of Jupiter
Europa has no craters;
surface is water ice, possibly
with liquid water below.
Tidal forces stress and crack
ice; water flows, keeping
surface relatively flat.
Galileo’s View
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The Galilean Moons of Jupiter
Ganymede is the largest
moon in the solar
system – larger than
Pluto and Mercury.
It has a history similar
to Earth’s Moon, but
with water ice instead
of lunar rock.
Galileo’s View
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The Galilean Moons of Jupiter
Callisto is similar to Ganymede; no evidence
of plate activity.
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The Large Moons of Saturn and
Neptune
Titan has been known for many years to have an
atmosphere thicker and denser than Earth’s;
mostly nitrogen and argon.
Makes surface
impossible to see; the
picture at right was
taken from only 4000 km
away.
Saturn Moon
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The Large Moons of Saturn and
Neptune
Infrared image of Titan,
showing detail, and
possible icy volcano
Few craters, consistent
with active surface
Complex
chemical
interactions in
atmosphere
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The Large Moons of Saturn and
Neptune
The Huygens
lander took
these images
of the surface
of Titan.
Huygens Probe
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The Large Moons of Saturn and
Neptune
Trace chemicals in
Titan’s atmosphere
make it chemically
complex.
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The Large Moons of Saturn and
Neptune
Triton is in a retrograde orbit;
its surface has few craters,
indicating an active surface.
Nitrogen geysers
have been observed
on Triton,
contributing to the
surface features.
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The Medium-Sized Jovian Moons
Densities of these moons suggest that they are
rock and water ice.
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The Medium-Sized Jovian Moons
Moons of Saturn, in natural color
Note the similarities,
as well as
the large
crater on
Mimas.
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The Medium-Sized Jovian Moons
Moons of
Uranus and
Neptune
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The Medium-Sized Jovian Moons
Miranda shows evidence
of a violent past, although
the origin of the surface
features is unknown.
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Question 8
Which moon in the
solar system shows a
dense atmosphere?
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a) our Moon
b) Phobos
c) Europa
d) Titan
e) Triton
Question 8
Which moon in the
solar system shows a
dense atmosphere?
a) our Moon
b) Phobos
c) Europa
d) Titan
e) Triton
The Huygens probe, deployed by
the Cassini spacecraft in 2005,
showed that Titan’s atmosphere
has a complex organic chemistry.
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Planetary Rings
The ring system
of Saturn is
large and
complex, and
easily seen from
Earth. The other
Jovian planets
have ring
systems as well.
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Question 13
Which of these
moons are most
exciting to
exobiologists?
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a) Io and Enceladus
b) Titan and Europa
c) Titan and Triton
d) Europa and Miranda
e) Phobos and Deimos
Question 13
Which of these
moons are most
exciting to
exobiologists?
a) Io and Enceladus
b) Titan and Europa
c) Titan and Triton
d) Europa and Miranda
e) Phobos and Deimos
Titan shows
evidence of
channels under
its dense
atmosphere.
Europa has indications of
liquid water beneath the ice.
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Planetary Rings
The rings are not solid; they are composed of
small rocky and icy particles.
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Planetary Rings
Our view of Saturn’s
rings changes as the
planets move in their
orbits.
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Question 7
Why are the
rings of Saturn
so bright?
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a) They are made of frozen metallic hydrogen.
b) They contain glassy beads expelled by
volcanoes on Enceladus.
c) They contain shiny bits of iron.
d) Titan and other moons reflect additional
glow onto the rings.
e) They are made of relatively new ice.
Question 7
Why are the
rings of Saturn
so bright?
a) They are made of frozen metallic hydrogen.
b) They contain glassy beads expelled by
volcanoes on Enceladus.
c) They contain shiny bits of iron.
d) Titan and other moons reflect an additional
glow onto the rings.
e) They are made of relatively new ice.
Saturn’s rings are perhaps
only 50 million years old,
the result of a small moon
coming within the planet’s
Roche limit.
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Planetary Rings
The Roche limit
is where the
tidal forces of
the planet are
too strong for a
moon to
survive; this is
where rings are
formed.
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Question 5
The Roche
limit is defined
as the critical
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a) distance from a planet, inside of which a
moon can be tidally destroyed.
b) density that a moon can have and be solid.
c) distance from a planet that a moon can
experience synchronous rotation.
d) mass a moon can have and still be
classified as a moon.
Question 5
The Roche
limit is defined
as the critical
a) distance from a planet, inside of which a
moon can be tidally destroyed.
b) density that a moon can have and be solid.
c) distance from a planet that a moon can
experience synchronous rotation.
d) mass a moon can have and still be
classified as a moon.
Saturn’s rings, as well as those
of the other jovian planets, lie
within its planet’s Roche limit.
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Planetary Rings
All observed ring systems are within this limit.
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Planetary Rings
Voyager probes showed Saturn’s rings to be
much more complex than originally thought.
Ring Crossing
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Earth is shown
on the same
scale as the
rings.
Planetary Rings
“Shepherd” moons
define the edges of
some of the rings.
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Cassini Spacecraft
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Question 6
Shepherd
satellites are
defined as
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a) satellites in the coma of a comet.
b) moons that confine a narrow ring.
c) a type of moon that orbits another moon.
d) moons that share an orbit of another,
larger moon.
e) moons that orbit inside a system of rings.
Question 6
Shepherd
satellites are
defined as
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a) satellites in the coma of a comet.
b) moons that confine a narrow ring.
c) a type of moon that orbits another moon.
d) moons that share an orbit of another,
larger moon.
e) moons that orbit inside a system of rings.
Planetary Rings
Jupiter has been found to have a small, thin ring.
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Question 4
How was the
ring of Jupiter
discovered?
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a) by optical telescopic observers from Earth
b) by Voyager I as it passed Jupiter
c) by an occultation of a star
d) by radar imaging using the Arecibo dish
e) with the Hubble Space Telescope’s superior
resolution
Question 4
How was the
ring of Jupiter
discovered?
a) by optical telescopic observers from Earth
b) by Voyager I as it passed Jupiter
c) by an occultation of a star
d) by radar imaging using the Arecibo dish
e) with the Hubble Space Telescope’s superior
resolution
Jupiter’s ring is
composed of dark, dusty
particles that were first
seen when Voyager was
past the planet, looking
back toward the Sun.
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Planetary Rings
The rings of
Uranus are more
complex.
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Planetary Rings
Two shepherd
moons keep the
epsilon ring
from diffusing.
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Planetary Rings
Neptune has five rings, three narrow and two
wide.
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Question 10
The rings of
Neptune
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a) were confirmed by Voyager 2 in 1989.
b) appear both narrow and diffuse.
c) all lie within Neptune’s Roche limit.
d) often appear as clumpy ring arcs, rather than
complete and symmetrical rings.
e) All of these are correct.
Question 10
The rings of
Neptune
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a) were confirmed by Voyager 2 in 1989.
b) appear both narrow and diffuse.
c) all lie within Neptune’s Roche limit.
d) often appear as clumpy ring arcs, rather than
complete and symmetrical rings.
e) All of these are correct.
Beyond Neptune
Pluto was discovered
in 1930. It was
thought to be needed
to explain
irregularities in the
orbits of Uranus and
Neptune, but it turned
out that there were no
such irregularities.
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Beyond Neptune
Pluto’s moon, Charon, was discovered in 1978.
It is orbitally locked to Pluto, and about a sixth
as large.
Pluto also has two smaller
moons, Nix and Hydra,
discovered in 2005.
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Question 12
Many astronomers
believe Pluto is
perhaps best
classified as
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a) a cold terrestrial planet.
b) a small jovian planet.
c) a large Kuiper belt object.
d) a wandering moon.
e) a captured comet.
Question 12
Many astronomers
believe Pluto is
perhaps best
classified as
a) a cold terrestrial planet.
b) a small jovian planet.
c) a large Kuiper belt object.
d) a wandering moon.
e) a captured comet.
Several other large
Kuiper belt objects
have been discovered,
including the largest
known, called Eris.
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Beyond Neptune
Charon’s orbit is at a large angle to the plane of
Pluto’s orbit.
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Astronomy for $100
What is a celestial body that
(a) is in orbit around the Sun
(b) has sufficient mass for its self-gravity to overcome
rigid body forces so that it assumes a hydrostatic
equilibrium (nearly round) shape
(c) has cleared the neighborhood around its orbit
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What is a planet?
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Plutoids and the Kuiper Belt
The first Kuiper belt
objects were observed
in the 1990s, and more
than 700 are now
known. Some of them
are comparable in size
to Pluto.
These images show
Eris and its moon
Dysnomia.
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Plutoids and the Kuiper Belt
This figure shows several of the largest known
trans-Neptunian objects, now collectively called
plutoids.
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