A1 10 Gas Giants

The Gas Giants
LACC §10.1, 10.2, 10.3
• Understand what conditions and processes shaped
the gas giant planets
• Understand what gives each planet it’s color:
Jupiter--orange and brown belts, Saturn--yellow,
Uranus and Neptune--blue (green)
• Know the oddities of each planet

An attempt to answer the “big question”: what is out
there?

Thursday, March 18, 2010 1

Condensation then Accretion
Near the sun, i.e. within
the frost line,
temperatures where
higher (>150 K, -190°F).
Volatile materials,
hydrogen compounds,
remained gaseous and
did not condense:
• water (H2O)
• ammonia (HN3)
• methane (CH4)
http://csep10.phys.utk.edu/astr161/lect/solarsys/scale.html

Gas Giants: Mass & Size

Jupiter’s mass is
less than 1/1000th
the sun’s

http://csep10.phys.utk.edu/astr161/lect/solarsys/scale.html

http://solarsystem.nasa.gov/planets/proﬁle.cfm?Object=Neptune&Display=Gallery

Gas Giants: the
Sun in the Sky
The sun is about 0.5° across as it appears from Earth

0.10°, 1/5th 0.06°, 1/8th 0.03°, 1/17th 0.02°, 1/25th
3.7% as bright 1.1% as bright 0.3% as bright 0.1% as bright

(These planets are not to scale.)


Gas Giants: Interiors

http://solarsystem.nasa.gov/multimedia/gallery.cfm?Page=29

Jupiter: Interior -250°F

80°F

19000°F

44500°F

71500°F

http://physics.uoregon.edu/~jimbrau/BrauImNew/Chap11/FG11_10.jpg

Uranus: Interior Our knowledge of the
internal structure of
Uranus is inferred
from the planet's
radius, mass, period of
rotation, the shape of
its gravitational ﬁeld
and the behavior of
hydrogen, helium, and
water at high
pressure. Its internal
structure is similar to
that of Neptune
except for the fact
that it is less active in
terms of atmospheric
dynamics and interior
heat ﬂow.
http://www.trinity.wa.edu.au/intranet/subjects/astronomy/My%20Webs/Yr%208%20Astro/Uranus.htm


Gas Giants: Atmospheres
Jupiter Uranus

•
Hydrogen: 86.1%
•
Hydrogen: 83%

•
Helium: 13.6%
•
Helium: 15%

•
Methane: 0.1%
•
Methane: 2%

•
Ammonia: 0.02% Neptune

•
Water Vapor: 0.2% ?
•
Hydrogen: 85%
Saturn
•
Helium: 13%

•
Hydrogen: 92.4%
•
Methane: 2%

•
Helium: 7.4%

•
Methane: 0.2% (Percent by volume)

•
Ammonia: 0.02%

•
Water Vapor: 0.4% ?
http://www.astro.washington.edu/users/larson/Astro150b/Lectures/JupSatUraNep/
jupsaturanept.html#atmospheres


Gas Giants: Clouds
Different compounds
form clouds at different
temperatures. From
warmest to coolest:
• H2O 32°F
• (NH4)SH -100°F
• NH3 -190°F
• CH4 -325°F

http://astronomyonline.org/SolarSystem/NeptuneIntroduction.asp

Gas Giants: Clouds

http://lasp.colorado.edu/~bagenal/3720/CLASS17/17GiantPlanets1.html


Jupiter: Between Cloud Layers

http://apod.nasa.gov/apod/ap000429.html


Jupiter: Orange and White
Explanation: What makes the colors in
Jupiter's clouds? With a mean temperature of
120 degrees Kelvin (-153 degrees Celsius)
and a composition dominated by Hydrogen
(about 90%), and Helium (about 10%) with a
smattering of hydrogen compounds like
methane and ammonia, astronomers have
been hard pressed to explain the blue, orange
and brown cloud bands and the salmon
colored "red" spot. Trouble is -- at the cool
cloud temperatures Jupiter's atmospheric
constituents should be colorless! Some
suggest that more colorful hydrogen
compounds well up from warmer regions in
the atmosphere, tinting the cloud tops.
Alternatively, compounds of trace elements
like sulfur may color the clouds. The colors
do indicate the clouds' altitudes, blue is
lowest through red as highest. The dark
colored bands are called belts and the light
colored ones zones. In addition to the belts
and zones, the Voyager missions revealed the
presence of intricate vortices visible, for
example, in this 1979 image from the
Voyager I ﬂyby. Centuries of visual
http://ciclops.org/view.php?id=110&js=1 observations of Jupiter have revealed that the
colors of its clouds are ever changing.

Jupiter: Belts and Zones

Jupiter's thick atmosphere is
striped by wind-driven cloud
bands that remain ﬁxed in
latitude - dark ... belts [and]
light ... zones. At Jupiter's
belt-zone boundaries the
shearing wind velocities can
reach nearly 300 miles per
hour.

http://zebu.uoregon.edu/~imamura/121/lecture-13/
http://apod.nasa.gov/apod/ap970310.html
jupiter_atmosphere.html


Jupiter: Great Red Spot
The Great Red Spot
is a cold, high
pressure area 2-3
times wider than
planet Earth. Its outer
edge rotates in a
counter clockwise
direction about once
every six days.
Jupiter's own rapid
rotation period is a
brief 10 hours.

http://apod.nasa.gov/apod/ap960803.html http://apod.nasa.gov/apod/ap960802.html


Saturn: Pale Yellow
The total thickness of the three cloud layers in Saturn's atmosphere is roughly 200 km, compared with about
80 km on Jupiter, and each layer is itself somewhat thicker than its counterpart on Jupiter. The reason for this
difference is Saturn's weaker gravity. http://saturn.jpl.nasa.gov/multimedia/
images/image-details.cfm?
imageID=506

At the haze level, Jupiter's gravitational ﬁeld is nearly two and a half times stronger than Saturn's, so Jupiter's
atmosphere is pulled much more powerfully toward the center of the planet. Thus Jupiter's atmosphere is
compressed more than Saturn's, and the clouds are squeezed more closely together. The colors of Saturn's
cloud layers, as well as the planet's overall butterscotch hue, are due to the same basic cloud chemistry as on
Jupiter. However, because Saturn's clouds are thicker, there are few holes and gaps in the top layer, so we
rarely glimpse the more colorful levels below. Instead, we see only different levels in the topmost layer,
which accounts for Saturn's rather uniform appearance.
http://lasp.colorado.edu/~bagenal/3720/CLASS17/17GiantPlanets1.html


Uranus: Pale Blue
The picture is a composite of images taken through blue, green and orange ﬁlters.
The darker shadings at the upper right of the disk correspond to the day-night
boundary on the planet.

Beyond this The blue-green
boundary lies the color results from
hidden northern the absorption of
hemisphere of red light by
Uranus, which methane gas in
currently remains in Uranus' deep, cold
total darkness as the and remarkably
planet rotates. clear atmosphere.
http://www.spaceimages.com/urintrcoph.html


Uranus: Rotational Axis = 98°

• On Jupiter, the angle between incoming sunlight and the planet's axis of
rotation is always about 90°. Consequently, Jupiter has no seasons!
• On Uranus, the angle between incoming sunlight and the planet's axis of
rotation changes from 0° to 180° and back over the course of the planet's
(84 yr!) orbit about the Sun. Consequently, Uranus has extreme seasons!

http://www.ifa.hawaii.edu/~barnes/ast110_06/quizzes/disc02.html


Neptune: Pale Blue
http://www.wired.com/science/discoveries/news/2008/09/
dayintech_0923

...like in the case of
Uranus the color is
due to methane. The
surface of Neptune
appears darker
than that of Uranus
due to dimmer
illumination (greater
distance from the
Sun).

http://
curious.astro.cornell.edu/
question.php?number=236


Neptune: Unlike Jupiter's Great Red Spot,
the Great Dark Spot of Neptune
is thought to be a hole in the
Great Dark Spot methane cloud deck of Neptune.
The white clouds shown in the
picture are above the "hole". In
many images of Neptune, the
Great Dark Spot can be seen to
change size and shape.

The Great Red Spot of Jupiter is
thought to be a hurricane which
has been raging on Jupiter for at
least 400 years. The Great Dark
Spot, seen here by Voyager in
1989, disappeared in 1994, and
was replaced very soon by a
similar "Spot" in a similar place,
but in the northern hemisphere
instead of in the southern
hemisphere.
http://www.windows.ucar.edu/tour/link=/neptune/atmosphere/N_clouds_GDS.html&edu=high


The Gas Giants
LACC §10.1, 10.2, 10.3
the gas giant planets: condensation beyond the frost
line.
• Understand what gives each planet it’s color:
Jupiter--Sulfur chemistry w/ (NH4)SH clouds,
Saturn--Ammonia, NH3 cloud tops, Uranus and
Neptune--Methane, CH4, cloud tops
• Know the oddities of each planet: Jupiter’s great red
spot, Saturn’s low density, Uranus is on its side,
Neptune is more massive than Uranus yet smaller.
An attempt to answer the “big question”: what is out
there?

LACC Ch 10: Franknoi, Morrison, and
Wolff, Voyages Through the Universe,
3rd ed.

• Ch. 10, pp. 240-241: 2, 4.

• Ch 10: Tutorial Quiz accessible from: http://
www.brookscole.com/cgi-brookscole/course_products_bc.pl?
ﬁd=M20b&product_isbn_issn=9780495017899&discipline_number=19
Must Know: 5, 8, 9, 10, 11, 12, 13, 14, 18, 20
Important: 7, 15, 17, 19

Due beginning of next class period.
Be thinking about your Solar System Project.


Rings of the Gas Giants
LACC §11.1, 11.4

the gas giant planets’ ring systems
• Know the ring systems in some detail
• Know why some rings are bright and some rings are
dark
An attempt to answer the “big questions”: what is out
there? Are we alone?


Ring Systems

http://www.jb.man.ac.uk/distance/strobel/solarsys/solsysb.htm

Ring Systems
Moons of Saturn:
Moons of Jupiter:
1.Atlas
1.Metis
2.1980S27
2.Adrastea
3.1980S26
3.Amalthea
4.Janus
4.Thebe
5.Epimetheus
5.Io
6.Mimas
6.Europa
7.Enceladus
7.Ganymede
8.Telesto
8.Callisto
9.Tethys
9.Leda
10.Calypso
10.Himalia
11.Dione
11.Lysithea
12.1980S6
12.Elara
13.Rhea
13.Ananke
14.Titan
14.Carme
15.Hyperion
15.Pasiphae
16.Iapetus
16.Sinope
17.Phoebe

http://www.astro.rug.nl/%7Eetolstoy/ACTUEELONDERZOEK/JAAR2000/moons/aoz.html


Jupiter’s Ring
Jupiter's intricate, swirling
ring system is formed by
dust kicked up as
interplanetary
meteoroids smash into
the giant planet's four
small inner moons,
according to... NASA's
Galileo spacecraft.
http://www2.jpl.nasa.gov/galileo/
status980915.html

http://pds.jpl.nasa.gov/planets/captions/jupiter/jupring.htm

Saturn’s Rings
Most of the rings are only a few tens of meters
thick with a total mass equivalent to a medium
sized moon. The rings are made out of particles
ranging from microscopic dust to barnyard
sized boulders with perhaps a few kilometer-
sized objects as well. ...the rings are
composed mostly of ice crystals with some
impurities.

Scientists once thought that the rings were
formed at the same time, as the planets when
they coalescing out of swirling clouds of
interstellar gas 4.8 billion years ago. Under this
model, remnants of material within the Roche
limit could not condense and would become
rings. However, in recent years this idea seems
to be ﬂawed. The rings appear to be young,
perhaps only hundreds of millions of years
old. One of the clues to this theory is that the
rings are bright. As Saturn travels though space,
the rings accumulate dust particles that have
been darkened from solar radiation. If the rings
were old, they should appear dark. Another
theory suggests that perhaps a comet few too
close to Saturn and tidal forces broke it into
pieces.... Perhaps one of Saturn's moons was
struck by an asteroid smashing it into the bits
and pieces that form the rings.

http://www.solarviews.com/eng/
http://pds.jpl.nasa.gov/planets/captions/saturn/2moons.htm saturnrings.htm

Saturn’s Rings

http://science.nasa.gov/headlines/y2002/12feb_rings.htm


Saturn’s Rings
This image shows Saturn's rings and the shadow of nearby Mimas.
They are now nearly edge-on toward the Sun, and long moon
shadows drape across them. Scientists are now studying the
clumpy, disturbed ring material, stretching up to two miles above
the ring plane - contrasted with an estimated normal ring
thickness of only six feet

http://www.dailymail.co.uk/sciencetech/article-1172205/Saturn-
close-Sensational-cosmic-images-bring-ringed-planet-life.html


Saturn’s Rings:
Shepherd Moons

This composite of two images shows Pan, left, and Prometheus, right, in
nearby rings. Pan is trailed by a series of edge waves in the outer boundary
of the gap. Prometheus just touches the inner edge of Saturn's F ring, and is
followed by a series of dark channels
http://www.dailymail.co.uk/sciencetech/article-1172205/Saturn-
close-Sensational-cosmic-images-bring-ringed-planet-life.html


Saturn’s Rings: New
Ring Discovered in
Infrared
This diagram highlights a slice of Saturn's
largest ring. The ring (red band in inset photo)
was discovered by NASA's Spitzer Space
Telescope, which detected infrared light, or
heat, from the dusty ring material. Spitzer
viewed the ring edge-on from its Earth-trailing
orbit around the sun.

The ring has a diameter equivalent to 300
Saturns lined up side to side. And it's thick too
-- about 20 Saturns could ﬁt into its vertical
height. The ring is tilted about 27 degrees from
Saturn's main ring plane.
http://gallery.spitzer.caltech.edu/Imagegallery/image.php?image_name=ssc2009-19a


http://gallery.spitzer.caltech.edu/Imagegallery/image.php?image_name=ssc2009-19b


Saturn’s Rings: New Ring
Discovered in Infrared
Saturn's newest halo is tilted at about 27 degrees from the main ring
plane and encompasses the orbit of the moon Phoebe. Both the ring
and Phoebe orbit in the opposite direction of Saturn's other rings
and most of its moons, including Titan and Iapetus.

Why did it take so long to ﬁnd something so big? The answer is that
the ring is very tenuous, made up of a sparse collection of ice and
dust particles. If you could transport yourself to the ring, you
wouldn't even know you were there because the particles are so far
apart. There's not a lot of sunlight out at Saturn, so this small density
of particles doesn't reﬂect much visible light. Spitzer was able to spot
the band because it sees infrared light, or heat radiation, from
objects. Even though the ring material is very cold, it still gives off
heat that can Spitzer can see.
http://gallery.spitzer.caltech.edu/Imagegallery/image.php?image_name=ssc2009-19b


Uranus’s Ring(s)
Radio measurements showed
the outermost ring, the epsilon,
to be composed mostly of ice
boulders several feet across.
However, a very tenuous
distribution of ﬁne dust also
seems to be spread throughout
the ring system.

The particles that make up the
rings may be remnants of a
moon that was broken by a
high-velocity impact or torn up
by gravitational effects.
http://www.nineplanets.org/uranus.html

http://pds.jpl.nasa.gov/planets/captions/neptune/neprings.htm

Shepherd Moons
Shepherd moons work in pairs on the inner and outer edge of rings to
gravitational push and pull (accelerate and de-accelerate) ring particles.
The result is to conﬁne the ring particles to within the shepherd moons
orbits.

http://pds.jpl.nasa.gov/planets/captions/neptune/neprings.htm


Neptune’s (Rings)
None of Neptune’s rings were detected from scattering effects on Voyager’s radio signal
propagating through the rings, which indicates that they are nearly devoid of particles in the
centimetre size range or larger. The fact that the rings were most visible in Voyager images when
backlit by sunlight implies that they are largely populated by dust-sized particles,
which scatter light forward much better than back toward the Sun and Earth.Their chemical
makeup is not known, but, like the rings of Uranus, the surfaces of Neptune’s ring particles (and
possibly the particles in their entirety) may be composed of radiation-darkened methane
ices.

The present rings are narrow, and scientists have found it difficult to explain how the orbits of
the known moons can effectively confine the natural radial spreading of the rings. This has led
many to speculate that Neptune’s present rings may be much younger than the planet
itself, perhaps substantially less than a million years. The present ring system may
be markedly different from any that existed a million years ago. It is even possible that the next
spacecraft to visit Neptune’s rings will find a system greatly evolved from the one Voyager 2
imaged in 1989.
http://www.britannica.com/EBchecked/topic/409330/Neptune/54304/The-ring-system


Neptune’s (Rings)
None of Neptune’s rings were detected from scattering effects on Voyager’s
radio signal propagating through the rings, which indicates that they are
nearly devoid of particles in the centimetre size range or larger. The fact
that the rings were most visible in Voyager images when backlit by sunlight
implies that they are largely populated by dust-sized particles,
which scatter light forward much better than back toward the Sun and
Earth.Their chemical makeup is not known, but, like the rings of Uranus, the
surfaces of Neptune’s ring particles (and possibly the particles in their
entirety) may be composed of radiation-darkened methane ices.
The present rings are narrow, and scientists have found it difficult to explain
how the orbits of the known moons can effectively confine the natural
radial spreading of the rings. This has led many to speculate that Neptune’s
present rings may be much younger than the planet itself,
perhaps substantially less than a million years. The present ring
system may be markedly different from any that existed a million years ago.
It is even possible that the next spacecraft to visit Neptune’s rings will find a
system greatly evolved from the one Voyager 2 imaged in 1989.
http://www.britannica.com/EBchecked/topic/409330/Neptune/54304/The-ring-system


Rhea’s (Rings!? 6 March ‘08)

http://planetary.org/news/2008/0306_A_Ringed_Moon_of_Saturn_Cassini.html

Ring Systems
Ring systems are not stable; they evolve and change over
time. Unless something replenishes them or keeps them
from dissipating, they will not last longer than a few 100
millions years; one of Neptune’s might not last a century.
They generally form inside a planet’s Roche limit. Object’s
that come closer than this distance to a planet tend to be
ripped apart by tidal forces. Since the gas giants have
strong gravitational ﬁelds, they have strong tidal forces.
Shepherding moons are moons that keep a ring system
nice an tidy, by not letting material drift out of a ring and/or
into gaps.


Rings of the Gas Giants
LACC §11.1, 11.4
the gas giant planets’ ring systems: Roche limit,
shepherding moons
• Know the ring systems in some detail: Jupiter (dust
from moons?), Saturn (recent break up of icy
object?), Uranus (break up of a moon?), Neptune
(unknown)
• Know why some rings are bright and some rings are
dark: Bright = icy and young, Dark = dusty and old
An attempt to answer the “big questions”: what is out
there? Are we alone?

HW Ch 11: Franknoi, Morrison, and
Wolff, Voyages Through the Universe,
3rd ed.

• Ch 11, pp. 263-264: 9.

• Ch 11: Tutorial Quiz accessible from: http://
www.brookscole.com/cgi-brookscole/course_products_bc.pl?
ﬁd=M20b&product_isbn_issn=9780495017899&discipline_number=19
Must Know: 2, 3, 5, 6, 7, 9, 10, 12, 13, 15, 19, 20
Important: 1, 4, 8, 11, 17, 18

Due at the beginning of next class period.
Be working your Solar System project.


A1 10 Gas Giants

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