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Lecture 21
Outline For Rest of Semester
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Oct. 29th Chapter 9 (Earth)
Nov 3rd and 5th Chapter 9 and Chapter 10 (Earth and Moon)
Nov. 10th and 12th Mars, Venus, and Mercury
Nov. 17th and 19th Jupiter and Saturn
Nov 24th Uranus and Neptune
Nov 26th Thanksgiving
Dec. 1st - Exam 3
Dec. 3rd – Pluto, and the Kuiper Belt
Dec. 8th and 10th – Chapter 7 and 8 (Comparative Planetology I and II)
Tuesday December 15th (7:30 am – 10:15 am) Final Exam
No Reading days are scheduled this semester
Exam Period begins at 7:30 a.m. on Monday, December 14 and ends on
December 21
Outline
• Jupiter and Saturn
– Orbit
– Surface
– Atmosphere
– Rings
– Moons
Questions
•
•
•
•
On posting “(with answers)” notes
NASA finding water on the moon
Why so many questions?
I have not had a chance to post Quiz
solutions in ppt recently
• #18 “made no sense”
#18 Mars’ Atmosphere
• Why does Earth have oxygen in its
atmosphere while Mars does not?
Venus Greenhouse
• The so-called greenhouse effect, which
produces very high temperatures on the
surface of Venus, is …
The absorption of CO2 gas by the planet’s
atmosphere of infrared radiation emitted
by its surface.
Mercury Elongation
Outline
• Jupiter and Saturn
– Orbit
– Surface
– Atmosphere
– Rings
– Moons
It is difficult to see!
http://homepage.ntlworld.com/mjpowell/Astro/Naked-Eye-Planets/Naked-Eye-Planets.htm
• Why is the ecliptic at an angle with respect
to the horizon?
Typo?
• More than 1200 Earth’s would fit inside
Jupiter
• Jupiter is 11 times larger in diameter than
Earth
Typo? No!
• More than 1200 Earth’s would fit inside
Jupiter
• Jupiter is 11 times larger in diameter than
Earth
V ~ R3 ~ D3 = (pi/6)D3
VEarth ~ D3Earth
VJupiter ~ (11*DEarth)3 ~ (11)3 D3Earth~ 1300 D3Earth
Inferior planets
superior planets
A planet’s
synodic period
is measured
with respect to
the Earth and
the Sun (for
example, from
one opposition
to the next)
Periods
•
•
•
•
Rotational
Orbital
Sidereal
Synodic
Measured with respect
to something that is not
rotating or orbiting
Orbit
• http://learning.nd.edu/orbital/orbitals.swf
Extra-credit in-class Quiz
Use cell phone if
• If you have free text plan and
• Don’t mind receiving ads
otherwise
Use notecard and hand in at end of class
Register for quiz 2
Text to 41411:
Replace with
your GMU
email name
astr111 2 rweigel
You will receive either one or two
texts in response
Question
• Which is longer, Jupiter’s synodic or
orbital period?
• Which is longer, Jupiter’s synodic or
Saturn’s synodic period?
• Guess Jupiter’s and Saturn’s synodic
period.
• Which is longer, Jupiter’s synodic or orbital
period?
• Which is longer, Jupiter’s synodic or
Saturn’s synodic period?
• Guess Jupiter’s and Saturn’s synodic
period.
2 1 a Synodic, Jupiter’s, longer than Earth’s
2 1 b Synodic, Saturn’s, longer than Earth’s
2 1 c Synodic, Saturn’s, shorter than Earth’s
2 1 d Synodic,Jupiter’s, shorter than Earth’s
2 1 e Orbital, Jupiter’s, longer than Earth’s
2 1 f Orbital, Jupiter’s, longer than Earth’s
2 1 g Orbital, Saturn’s, longer than Earth’s
2 1 h Orbital, Saturn’s, longer than Earth’s
Question
Time to repeat
from Earth’s
perspective
• Which is longer, Jupiter’s synodic or
orbital period? orbital
• Which is longer, Jupiter’s synodic or
Saturn’s synodic period? Jupiter’s
• Guess Jupiter’s and Saturn’s synodic
period. A little longer than Earth’s
orbital period.
Kepler’s Third Law
P2 = a3
P = planet’s sidereal period, in years
a = planet’s semimajor axis, in AU
Long orbital periods of Jupiter and
Saturn cause favorable viewing times
to shift
What is wrong with either of these
tables?
What is wrong with either of these
tables?
Correct
The best time to observe Saturn from Earth is when it
is
22
22
22
22
22
A. at opposition and it is midnight at your location
on Earth.
B. at opposition and it is sunset or sunrise at your
location on Earth.
C. at conjunction and it is midnight at your location
on Earth.
D. at conjunction and it is sunset or sunrise at your
location on Earth.
E. at opposition and it is just before sunrise at your
location on Earth.
The best time to observe Saturn from Earth is when it
is
A. at opposition and it is midnight at your location
on Earth.
B. at opposition and it is sunset or sunrise at your
location on Earth.
C. at conjunction and it is midnight at your location
on Earth.
D. at conjunction and it is sunset or sunrise at your
location on Earth.
E. at opposition and it is just before sunrise at your
location on Earth.
Outline
• Jupiter and Saturn
– Orbit
– Surface
– Atmosphere
– Rings
– Moons
What happens to ornaments when
hoop is spun?
hoop
hoop
23A
22B
22C
22D
How to get Oblate
hoop
The farther away from the axis, the more “thrown out” it gets.
Extra-credit in-class Quiz
Use cell phone if
• If you have free text plan and
• Don’t mind receiving ads
otherwise
Use notecard and hand in at end of class
All questions (correct or incorrect) worth
20 points (about two quiz questions).
Register for quiz 3
Text to 41411:
astr111 3 rweigel
Replace with
your GMU
email name
NOT G
NUMBER!
You will receive either one or two
texts in response
Both have arms attached
to ears and shoulders.
When they spin, which
pair of arms swings out
the most? Least?
W
X
3 1 a. X Most, Y Least
3 1 b. Y Least, X Most
3 1 c. W Most, Y Least
3 1 d. X,Y,Z Most, W Least
3 1 e. W Most, X, Y, Z Least
W
Y
X Z
Y
Z
Both have arms attached
to ears and shoulders.
When they spin, which
pair of arms swings out
the most? Least?
W
X
3 1 a. X Most, Y Least
3 1 b. Y Least, X Most
3 1 c. W Most, Y Least
3 1 d. X,Y,Z Most, W Least
3 1 e. W Most, X, Y, Z Least
W
Y
X Z
Y
Z
The farther away from the axis, the more “thrown out” it gets.
Both have arms attached
to ears and shoulders.
When they spin, which
pair of arms swings out
the most? Least?
All red arms are same distance from spin axis.
Black arms are closer.
Red arms swing out most.
Black arms wing out least.
The oblateness of Jupiter and
Saturn reveals their rocky cores
• Jupiter probably has a
rocky core several times
more massive than the
Earth
• The core is surrounded
by a layer of liquid “ices”
(water, ammonia,
methane, and
associated compounds)
The oblateness of Jupiter and
Saturn reveals their rocky cores
• On top of this is a layer of
helium and liquid metallic
hydrogen and an outermost
layer composed primarily of
ordinary hydrogen and
helium
• Saturn’s internal structure is
similar to that of Jupiter, but
its core makes up a larger
fraction of its volume and its
liquid metallic hydrogen
mantle is shallower than that
of Jupiter
Metallic hydrogen inside Jupiter and Saturn
endows the planets with strong magnetic
fields
• Jupiter and Saturn have strong magnetic fields created by
currents in the metallic hydrogen layer
• Jupiter’s huge magnetosphere contains a vast current sheet of
electrically charged particles
• Saturn’s magnetic field and magnetosphere are much less
extensive than Jupiter’s
Jupiter and Saturn have extensive
magnetospheres
• The Jovian magnetosphere encloses a low-density plasma of charged
particles
• The magnetosphere exists in a delicate balance between pressures from the
plasma and from the solar wind
• When this balance is disturbed, the size of the magnetosphere fluctuates
drastically
Synchrotron Radiation
Charged particles in the densest portions of
Jupiter’s magnetosphere emit synchrotron
radiation at radio wavelengths
Golf!
Outline
• Jupiter and Saturn
– Orbit
– Surface
– Atmosphere
– Rings
– Moons
Atmospheres
• gravity and escape velocity
Atmospheres
• gravity and escape velocity
Atmospheres
• The visible “surfaces” of
Jupiter and Saturn are
actually the tops of their
clouds
Atmospheres
• The rapid rotation of the
planets twists the clouds
into dark belts and light
zones that run parallel to
the equator
The chemical composition of
Jupiter and Saturn is difficult to
measure. Why?
Atmospheres
• The outer layers of both
planets’ atmospheres
show differential rotation
– The equatorial regions
rotate slightly faster than
the polar regions
Atmospheres
• For both Jupiter and
Saturn, the polar rotation
rate is nearly the same
as the internal rotation
rate
Spacecraft images show
remarkable activity
in the clouds of Jupiter and
Saturn
Video
• Chapter 14 videos
• http://bcs.whfreeman.com/universe7e
Storms
• Both Jupiter and Saturn
emit more energy than
they receive from the Sun
• Presumably both planets
are still cooling
• The colored ovals visible
in the Jovian atmosphere
represent gigantic storms
• Some, such as the Great
Red Spot, are quite
stable and persist for
many years
Storms in Saturn’s atmosphere seem to
be shorter-lived
The internal heat of Jupiter and
Saturn has a major effect on the
planets’ atmospheres
• Explain how Infrared and Visible (indicated
on the previous slide) relate to the
blackbody curves we studied.
• X-Ray image at airport
http://static.howstuffworks.com/gif/airport-security-xray2.jpg
A space probe has explored
Jupiter’s deep atmosphere
• There are presumed to be three cloud
layers in the atmospheres of Jupiter and
Saturn
• The reasons for the distinctive colors of
these different layers are not yet known
• The cloud layers in Saturn’s atmosphere
are spread out over a greater range of
altitude than those of Jupiter, giving Saturn
a more washed-out appearance
Spacecraft images show
remarkable activity
in the clouds of Jupiter and
Saturn
In the news: Hurricane on Saturn?
•
http://saturn.jpl.nasa.gov/multimedia/videos/video-details.cfm?videoID=136
• http://www.youtube.com/watch?v=dnF6PV
SSSag
– Hurricane-like vortex at Saturn's south pole,
where the vertical structure of the clouds is
highlighted by shadows. Such a storm, with a
well-developed eye ringed by towering clouds,
is a phenomenon never before seen on
another planet.
Both Jupiter and Saturn emit more
energy than they receive from the
Sun. What does this tell us?
Jupiter radiates more energy into space than
it receives from the Sun. What is the primary
source of the excess energy that Jupiter
radiates?
3 2 A. Decay of radioactive materials in Jupiter's
3 2 B.
3 2 C.
3 2 D.
3 2 E.
core
Tidal forces from Jupiter's moons
Jupiter is still contracting, and the
contraction releases energy
Jupiter's rotation is slowing down
dramatically, and this slowdown releases
energy
All of the above are the energy sources
Jupiter radiates more energy into space than it
receives from the Sun. What is the primary source
of the excess energy that Jupiter radiates?
3 2 A. Decay of radioactive materials in Jupiter's
3 2 B.
3 2 C.
3 2 D.
3 2 E.
core
Tidal forces from Jupiter's moons
Jupiter is still contracting, and the
contraction releases energy
Jupiter's rotation is slowing down
dramatically, and this slowdown releases
energy
All of the above are the energy sources
What can you
say about these
planets?
•
33a
33b
33c
33d
If both these planets formed at the
same time, which would be expected
to be warmer? Which would be
expected to have more tectonic
activity?
Planet #1, Planet #1
Planet #1, Planet #2
Planet #2, Planet #2
Planet #2, Planet #1
•
33a
33b
33c
33d
If both these planets formed at the
same time, which would be expected
to be warmer? Which would be
expected to have more tectonic
activity?
Planet #1, Planet #1
Planet #1, Planet #2
Planet #2, Planet #2
Planet #2, Planet #1
If Jupiter and Saturn formed at the
same time, which should be emitting
more heat?
• Saturn’s atmosphere contains
less helium than Jupiter’s
atmosphere
• This lower abundance may be the
result of helium raining downward
into the planet
• Helium “rainfall” may also account
for Saturn’s surprisingly strong
heat output
Outline
• Jupiter and Saturn
– Orbit
– Surface
– Atmosphere
– Rings
– Moons
• Link
Something is Fishy
• How can a planet be solid?
• Pebbles, snowballs and boulder size
• How was this determined?
• Videos 12.8-12.10
Earth-based observations reveal three
broad rings encircling Saturn
• Saturn is circled by a system of thin, broad rings lying in the plane of the
planet’s equator
• This system is tilted away from the plane of Saturn’s orbit, which causes the
rings to be seen at various angles by an Earth-based observer over the
course of a Saturnian year
Saturn’s rings are composed of
numerous icy fragments, while Jupiter’s
rings are made of small
rocky particles
• The principal rings of Saturn are composed of numerous
particles of ice and ice-coated rock ranging in size from a
few micrometers to about 10 m
• Jupiter’s faint rings are composed of a relatively small
amount of small, dark, rocky particles that reflect very
little light
• Most of its rings exist inside the Roche limit of Saturn, where disruptive tidal
forces are stronger than the gravitational forces attracting the ring particles
to each other
• Each of Saturn’s major rings is composed of a great many narrow ringlets
Saturn’s rings consist of thousands
of narrow,
closely spaced ringlets
Saturn’s inner satellites affect the
appearance
and structure of its rings
The faint F ring, which is just outside the A ring, is kept narrow
by the gravitational pull of shepherd satellites
Outline
• Jupiter and Saturn
– Orbit
– Surface
– Atmosphere
– Rings
– Moons
Preview
• Already discussed influence on Saturn’s
rings.
• Jupiter’s moons are even more interesting