Download Jupiter

Jupiter
Notes compiled by
Paul Woodward
Department of Astronomy
We will spend the next few days on the outer, gaseous planets,
focusing first on Jupiter, then on Jupiter’s moons and Saturn. We
will not spend time on Uranus and Neptune.
1
Today, we will mainly discuss Jupiter.
Its orbit, and its place in our solar system, are shown on the next
two slides.
It is a little more than 5 times further from the sun than is the earth.
Its orbit, like the earth’s, lies pretty much in the ecliptic plane.
Jupiter rotates in the same sense as its orbital motion, as does the
earth, and its rotational axis is essentially perpendicular to the
plane of its orbit.
This pperpendicular
p
orientation of the rotation axis of Jupiter
p
means
that Jupiter does not have seasons, like we do on earth (because the
earth’s rotation axis is tilted relative to its orbital plane, the ecliptic
plane).
2
The following tables give comparisons of some of the physical
properties of the planets.
The most important columns of these tables to see for the moment
are those that compare the sizes and material compositions of the
planets.
planets
These data show that Jupiter, Saturn, Uranus, and Neptune are
fundamentally different sorts of planets from the inner
(“terrestrial”) planets, Mercury, Venus, earth, and Mars. They are
in fact gaseous giants.
3
The following table compares the four outer gaseous giant planets.
From this table it is clear that
1. Jupiter and Saturn are much larger than Uranus and Neptune.
2 Uranus and Neptune contain much more heavy elements along
2.
with their primary constituents, hydrogen and helium. (The
average density of Jupiter is made larger than that of Uranus
because its huge gravity has compressed the hydrogen and
helium.)
4
Jupiter is the third brightest object in the sky (other than the sun),
after the Moon and Venus.
Galileo discovered the 4 large satellites of Jupiter, the “Galilean
moons,” with his telescope. This apparent planetary system in
miniature, where the 4 moons obviously revolved about Jupiter
and not about the earth, contributed to the demise of the Ptolemaic
system of the cosmos, in which the earth was at the center.
The moons of Jupiter, whose orbital radii and periods can be
determined through observation from the earth, can be used to
“weigh” Jupiter.
This procedure reveals that the average density of Jupiter is much
lower than that of the earth.
Because of its huge size, even a small telescope can resolve the
disk of the planet to measure its size. Through large telescopes we
can even see the weather on Jupiter.
5
Jupiter with its four Galilean satellites
6
60-inch photograph of Jupiter
Caltech & Carnegie Institute
Through a 120-inch telescope, we can see quite a bit of
atmospheric detail in the disk of Jupiter.
7
Lick Observatory, 1927
Jupiter, observed in 6 wavelength bands: UV, v, green, yellow, red, IR
The following 3 slides show the level of detail a student, Rolf
Karlstad, was able to obtain by compositing images taken at 1/60
sec with a video camera through his small telescope.
8
Considering
the size of
the
telescope,
this image of
Jupiter is
amazingly
good.
good
It was
obtained by
compositing
over a
thousand
individual
1/60 sec
exposures,
exposures
after each
was aligned
with the
others. This
is manual
adaptive
optics.
Jupiter and more than
one of its moons are
both visible here.
9
Here we see Jupiter, 3 of its moons, and the shadow of a moon on the planet.
Through a 200-inch telescope, we can see even more atmospheric
detail in the disk of Jupiter, and can clearly see shadows cast by
Jupiter’s moons.
10
Jupiter
viewed
through the
200-inch
Palomar
telescope.
l
Ganymede
and its
shadow are
visible, as
is also the
Great Red
Spot.
Jupiter
viewed
through the
200-inch
Palomar
telescope.
l
Ganymede
and its
shadow are
visible.
However,
the Great
Red Spot
does not
stand out in
this red
light photo.
11
The following image of Jupiter was also made from earth, but now
through the Hubble Space Telescope, orbiting above the earth’s
atmosphere.
Hubble Space
Telescope image
of Jupiter,
2/13/95
12
Determination of the average density of Jupiter from the
characteristics of the orbits of its moons indicates that Jupiter must
be largely composed of gas rather than of rock, like the terrestrial
planets.
We can use Newton
Newton’ss law of gravitation and our knowledge of the
behavior of materials under pressure to get a good idea of the
interior structure of Jupiter, even though we are unable to observe
the interior directly.
If we know the “equation of state” – the pressure a gas exerts at
any given density and temperature – then we can build a model of
a planet
l t like
lik JJupiter
it as a spherical
h i l object
bj t supported
t d against
i t its
it own
gravity by the pressure its gaseous components exert.
Assuming a cold interior (cold in that we believe there are no
nuclear reactions going on, as there are in the sun) allows us to
build an approximate spherical model of Jupiter, because the
behavior of most constituents at zero temperature is believed to be
known from theory.
Even if we did not have this theory available, we could use
information about the density and temperature of various materials
at high pressures that we can obtain on the earth. We can obtain
these measurements, for example, by driving the materials to high
pressures by subjecting them to shock waves from high explosives.
Our knowledge
g of material pproperties
p
is therefore gained
g
from a
combination of theoretical calculation and from laboratory
experiments.
This knowledge tells us how much pressure a given mix of
materials will exert when compressed to a particular density and
maintained at a particular temperature.
13
At relatively low temperatures, the pressure is determined mainly
by the density of the material and does not depend much at all
upon the particular value of the temperature.
From Newton’s law of gravitation, we can determine the
gravitational force at any particular distance from the center of a
spherical planet, even at a distance that is inside the planet.
This gravitational force must be balanced by the pressure of the
material making up the planet at that radius (i.e. at that distance
from the center of the planet).
Balancing the gravitational and pressure forces at each distance
from the planet’s center, and using our knowledge of the material
density we require to generate the pressure, we can build a model
to tell us how the density of the material must vary with distance
from the center of the planet.
We do this on a computer, and it takes about one second.
For each material composition we choose for our model of the
planet, and for each planet mass we might obtain from
“weighing” the planet by observing the orbital motion of its
moons, we get a run of density with radius.
The density is largest in the planet’s core, and we find that at a
large enough distance from the core the density becomes zero.
This is the surface of our model planet.
Therefore:
1. given a material composition,
2 given
2.
i
a mass for
f the
h planet,
l
and,
d off course,
3. given the assumption that the temperature is everywhere in the
range of cold values for which the pressure is insensitive to
temperature,
we can compute a radius for the model of the planet.
14
The result of such model building is the set of mass-radius curves
on the next slide.
Points J, S, U, and N on this plot indicate the observed data for the
planets Jupiter, Saturn, Uranus, and Neptune.
The point J, representing Jupiter, lies very close to the mass-radius
relations for cold planets constructed from pure hydrogen (the
top curve) and for hydrogen-helium mixture (next curve down,
labeled x=0.25) with 25% helium by mass.
We may therefore conclude that Jupiter is largely hydrogen and
helium,, not onlyy near its surface but in the interior as well.
We also note that the point S, representing Saturn, lies right on the
curve for cold planets consisting of hydrogen-helium mixtures
with 25% helium by mass.
Mass-radius curves for
objects of various compositions at zero temperature.
Curve labeled X = 0.25 is
for an approximately solar
mixture of hydrogen and
helium Points JJ, S
helium.
S, U
U, and
N represent the outer
planets. Radius is in units
of hundredths of a solar
radius (1 R~= 6.96×105 km)
and mass is in units of solar
masses (1 M = 1.99×1011 g).
Jupiter
p
and Saturn are
clearly composed
predominantly of hydrogen
and helium; Uranus and
Neptune must have a large
complement of heavier
elements.
(from Encyclopedia of the Solar System)
15
It is interesting to note that the figure indicates that if Jupiter were
much more massive, it would actually be smaller!
This strange result can be true because the gases that make up
planets like Jupiter are compressible, just like the pillows in the
illustration from your text book that appears on the next slide.
slide
16
Jupiter has enormous pressures in its interior which compress
hydrogen into a liquid metallic state.
No one has observed liquid metallic hydrogen in the laboratory.
Instead, we believe it exists under the conditions in Jupiter’s
interior as a result of theoretical calculations done on
computers.
Liquid metals should not be unfamiliar to you. Mercury is a metal
that is a liquid at room temperature.
17
The “phase diagram” on the next slide divides a pressuretemperature plane into regions in which hydrogen is either
liquid or solid, molecular or metallic.
The interiors of models of the outer planets trace lines in this phase
diagram, where progressing along one of these lines
corresponds
d to
t moving
i in
i or outt in
i radius
di within
ithi the
th planet.
l t
Uranus and Neptune do not reach the metallic region of this phase
diagram, but both Jupiter and Saturn do.
The shaded area, which is crossed by the line representing the
Saturn interior model, indicates a region of pressure and
temperature in which it is believed that any helium mixed in
with the hydrogen would naturally separate out.
It is believed that such separation of helium from hydrogen is
happening inside Saturn, with the helium falling toward the
center of the planet, and releasing gravitational potential
energy in the form of heat as it does so.
(from Encyclopedia of the Solar System)
18
(from Encyclopedia of the Solar System)
To get a better idea of the interior structure of giant planets like
Jupiter, we can take advantage of their rapid rotation.
If Jupiter were not rotating, its gravity would force it to assume a
spherical shape.
A spherical planet exerts a gravitational force on a satellite just as
if all its mass were concentrated at a single point at its center
(don’t worry why this is true, but it is).
The orbit of a satellite can then tell us the mass of the planet, but it
cannot tell us anything about the distribution of the mass with
radius within the planet.
p
Through the centrifugal force, rapid rotation causes a fluid planet
like Jupiter or Saturn to become distorted.
Then the gravitational forces felt by a spacecraft orbiting the planet
can reveal details of the internal distribution of mass in the planet.
19
Figure 11.3 (a) Gravity alone makes a planet spherical, but rapid
rotation flattens out the spherical shape by flinging material near
the equator outward. (b) Saturn is clearly not spherical.
Jupiter is not actually a perfectly spherical object, as we have
assumed in building our model of its interior.
It is not spherical because it is rotating rapidly, and the centrifugal
force acts to fling the material near Jupiter’s equator outward,
giving the planet a slightly oblate aspect.
This phenomenon is more noticeable for Saturn, which is roughly
the same radius as Jupiter and spinning at about the same rate,
but which has only about a third of Jupiter’s mass.
Thus the centrifugal acceleration outward of the material near
Saturn’s equator is about the same as for Jupiter, but the
ggravitational
av tat o a acceleration
acce e at o inward
wa d iss only
o y about a third
t d as large.
a ge.
The result is that Saturn is significantly more visibly oblate than
Jupiter.
20
To study the atmospheres of the giant planets, it is most useful to
go there and look at them close up.
The Voyager spacecraft returned to earth stunning views of the
dynamics of Jupiter’s atmosphere.
Voyager-2 was able to execute a 4-planet fly-by, called by NASA
a Grand Tour of the outer solar system.
21
Two Voyager spacecraft were launched in the 1970s to visit the
outer planets.
Voyager-2 took advantage of a special alignment of these planets
in order to visit all four.
22
Voyager-1 image of Jupiter from 47 million km.
Ganymede is at the right center, and Europa is at the top right.
Jupiter as observed by the Cassini space probe in “true color.”
In the intervening 20 years, the image improved quite a bit.
23
Jupiter as observed by the Cassini space probe in “true color.”
In the intervening 20 years, the image improved quite a bit.
The Galileo probe not only orbited Jupiter, it also descended into
its atmosphere to a depth where the pressure was 20 times that of
the earth’s atmosphere at sea level. At that point communication
with the probe was lost.
As one descends through the atmosphere of Jupiter from the top of
the troposphere (see graph on next slide), the temperature
increases.
The outermost cloud layer is composed of ammonia, which
condenses only at very low temperatures.
At ggreater depth
p one encounters clouds of ammonium
hydrosulfide, and finally, at still greater depths, clouds of water.
24
25
Models for the temperature structure show the Jovian atmosphere
getting hotter with depth, even though sunlight does not penetrate
much below the clouds.
Jupiter was quite hot when it formed, since the kinetic energy of
motion of the bodies that collided with it to build it up to its
presentt size
i was converted
t d into
i t heat.
h t
That kinetic energy of motion also included gravitational potential
energy that had been converted into kinetic energy before the
objects collided with the early Jupiter.
Models predict that such a hot Jupiter would, over the course of
4 5 billion years (the approximate age of the solar system),
4.5
system) have
gradually cooled to its present temperature by emitting heat into
space.
Early on, as Jupiter cooled it contracted, liberating more
gravitational energy and generating additional heat. But now
Jupiter cools at essentially constant radius.
Thus heat is constantly rising from Jupiter’s core through the
interior to the surface, where it is radiated into space.
This heat transport occurs by convection.
Gas heated by contact with the warm interior becomes buoyant
(j like
(just
lik a hot
h air
i balloon)
b ll
) andd rises
i through
h
h the
h atmosphere,
h
carrying the heat with it.
Gas that has given up part of its heat by radiating it into space near
the “surface” of the planet is cooled, is compressed by the warmer
surrounding gas, becomes denser, and sinks.
This convection drives powerful winds on Jupiter.
Jupiter
Because Jupiter is rapidly rotating, the wind currents are quite
complex and are organized near the surface into horizontal bands.
On both Jupiter and Saturn, the atmosphere near the equator
rotates faster than the planet generally.
26
The next slide illustrates the sort of convection in horizontal bands
near the surface of Jupiter that we think is going on there.
In the horizontal bands of rising air, white ammonia clouds are
formed as the temperature drops due to the expansion of the gas as
the pressure drops
drops.
These white ammonia clouds therefore mark bands of rising gas.
When the gas, having given off some of its heat in the form of
radiation into space, begins to descend again, there are no longer
ammonia clouds.
The horizontal
Th
h i t l bands
b d off descending
d
di gas are therefore
th f
clear,
l
so that
th t
we can see through them to the warmer ammonium hydrosulfide
clouds below.
On the next slide, an image of Jupiter in visible light, on the left, is
compared to one in infrared light, on the right.
The infrared image is brightest where the gas is warmest. You can
see that the bright infrared bands are the bands where there are no
white ammonia clouds. These, we believe, are the bands of
descending gas.
Note that the Great Red Spot is dark in the infrared image.
image
27
Fig. 11.7
Air Flow on Jupiter
The motions of the gas in the atmosphere of Jupiter are also strongly
constrained by the rapid rotation of the planet, which gives rise to the
Coriolis effect.
The Coriolis effect, together with unequal rates of heating by sunlight at
different latitudes, causes a phenomenon called meridional circulation.
This circulation tends to even out the heat deposited
p
byy the sun byy settingg
up a convection flow.
On a slowly rotating planet like Venus, the meridional circulation is very
simple, on a more rapidly rotating planet like the earth it is more complex,
and on a very rapidly rotating planet like Jupiter we get the many
horizontal bands that are the most striking aspect of the planet.
Because Jupiter, unlike Earth or Venus, has heat coming up from its interior
via
i convection,
ti whether
h th the
th sun is
i heating
h ti the
th outer
t atmosphere
t
h or not,
t the
th
cause of the meridional circulation bands is more complex. Nevertheless, it
is the Coriolis force, which expresses the principle of the conservation of
angular momentum, that constrains the gas to circulate in horizontal bands.
28
You can observe the coriolis effect on a merry-go-round.
The ball rolled inward veers to the right so that its angular momentum is conserved. It
must spin faster than the inner part of the merry-go-round because its angular
momentum is higher.
The ball rolled outward from the center also veers to the right to conserve its angular
momentum. It has a lower angular momentum than the outer part of the merry-goround, and so must spin more slowly.
29
30
On a rapidly
rotating
planet like
the earth, the
Coriolis
effect causes
each of the 2
large
circulation
cells of a
slowly
rotating
planet to split
into 3 cells.
Here the
resulting
surface wind
patterns are
s ow .
shown.
These motions
combine with
the circular
flows around
low pressure
regions shown
earlier to give
the overall
winds.
31
Fig. 11.7
Air Flow on Jupiter
Comparison of a 5 µm image (left) from Palomar on 1/10/79
with a Voyager-1 image recorded 1 hour later.
The Great Red Spot is revealed as a cold region surrounded by warm areas at 5 µm.
32
Figure 11.8: This photograph shows Jupiter’s Great Red Spot, a
huge high-pressure storm that is large enough to swallow two or
three Earths. The smaller photo (right) of the Great Red Spot is
overlaid with a weather map of the region.
Zonal (east-west) wind
velocity for the giant
planets as a function of
latitude. There are gaps
where we lack contrasts
suitable for tracking winds
or where the atmosphere
was in
i darkness
d k
((on th
the
night side or shadowed by
Saturn’s rings).
From P. Gierasch and B.
Conrath (1993),
J. Geophys. Res. 98, 54595469.
(from Encyclopedia of the Solar System)
33
The persistence of features of Jupiter’s weather can be seen in the
next two slides.
The Great Red Spot has been observed for 3 centuries, in fact,
since the invention of the telescope.
Some of the smaller white ovals have been fairly continuously
observed for decades.
From these slides, clearly the smaller features are transient, but the
general positions of the belts and zones are quite steady.
Two very similar views of Jupiter, from 46.3 and 40 million km,
and on 5/9/79 (left) and on 1/24/79 (right).
Note the persistence of the Great Red Spot and individual bands.
34
Cylindrical projections of the atmospheric features of Jupiter
as observed by Voyager-1 (top) from 400º longitude to 0º
and by Voyager-2 (bottom).
Cylindrical projections of the atmospheric features of Jupiter
as observed by the Cassini space probe in ultraviolet light (top)
& “true” color 20 years after the Voyager missions.
35
Cassini animation of Jovian weather.
A number of images follow which show some of the great wealth
of weather phenomena on Jupiter.
The short animated sequences produced by NASA from the
Voyager data give life to these scenes.
36
Voyager-1 image 2/13/79 of Jupiter from 20 million km.
Great Red Spot is seen with Io, and Europa is to the right.
Galileo image of
Jupiter
with Great Red Spot.
37
Cassini image of
Jupiter
with Io in the
foreground.
Cassini image of Jupiter, 12/31/00, in true color on the left and in false color on the right.
Color on the right denotes the height of the clouds.
Red regions are deep water clouds.
Bright blue regions are high haze (as for the region of the Great Red Spot).
White spots are energetic lightning storms high in the atmosphere.
The darkest blue regions are very deep hot spots from which thermal emission escapes freely.
38
Cassini image of Jupiter in infrared light of 727 nanometers,
which is only moderately absorbed by atmospheric methane.
The Voyager spacecraft produced gorgeous close-ups of Jupiter’s
Great Red Spot.
39
Figure 11.8: This photograph shows Jupiter’s Great Red Spot, a
huge high-pressure storm that is large enough to swallow two or
three Earths. The smaller photo (right) of the Great Red Spot is
overlaid with a weather map of the region.
Voyager-2 image of Jupiter’s Great Red Spot, 7/3/79
40
Galileo image of Jupiter’s Great Red Spot.
More recently, the Galileo spacecraft produced very high
resolution images of atmospheric phenomena on Jupiter,
including, of course, the Great Red Spot.
The image on the next slide was made by combining images take through 3
infrared filters:
1.
886 nm, where methane strongly absorbs, is shown as red. Due to this
absorption, only high clouds can reflect light in this wavelength.
2.
Reflected light at 732 nm, where methane absorbs less strongly, is shown in
green.
3.
Reflected light at 757 nm, where there are essentially no absorbers in the
Jovian atmosphere, is shown in blue. This light is reflected from the
deepest clouds.
Thus blue or black areas of the next slide are deep clouds; pink areas are high,
thin hazes; white areas are high, thick clouds.
This Galileo mosaic was taken on June 26, 1996, and it has been map-projected
onto a uniform longitude-latitude grid.
41
A false color mosaic of Jupiter’s Great Red Spot from the Galileo
spacecraft, made from images through 3 infrared filters.
A “true” color mosaic of Jupiter’s Great Red Spot from the Galileo
spacecraft, made from images through near infrared & violet filters.
42
True and false color mosaics of the turbulent region west of Jupiter's Great Red
Spot. The Great Red Spot is on the planetary limb on the right hand side of
each mosaic. The region west (left) of the Great Red Spot is characterized
by large, turbulent structures that rapidly change in appearance. The
turbulence results from the collision of a westward jet that is deflected
northward by the Great Red Spot into a higher latitude eastward jet. The
large eddies nearest to the Great Red Spot are bright, suggesting that
convection and cloud formation are active there.
The first mosaic combines the violet (410 nanometers) and near infrared
continuum (756 nanometers) filter images to create a mosaic similar to how
Jupiter would appear to human eyes. Differences in coloration are due to
the composition and abundance of trace chemicals in Jupiter's atmosphere.
The second mosaic uses the Galileo imaging camera's three near-infrared
(invisible) wavelengths (756 nanometers, 727 nanometers, and 889
nanometers displayed in red, green, and blue) to show variations in cloud
height and thickness. Light blue clouds are high and thin, reddish clouds are
deep, and white clouds are high and thick. Purple most likely represents a
high haze overlying a clear deep atmosphere. Galileo is the first spacecraft
to distinguish cloud layers on Jupiter.
The mosaic is centered at 16.5 degrees south planetocentric
latitude and 85 degrees west longitude. The north-south
dimension of the Great Red Spot is approximately 11,000
kilometers. The smallest resolved features are tens of
kilometers in size. North is at the top of the picture. The
images used were taken on June 26, 1997 at a range of 1.2
million kilometers (1.05 million miles) by the Solid State
Imaging (SSI) system on NASA's Galileo spacecraft.
43
A “true” color
image of
turbulence near
Jupiter’s Great
Red Spot from
the Galileo
spacecraft,
made using
near infrared &
violet filters.
A false color
image of
turbulence near
Jupiter’s Great
Red Spot from
the Galileo
spacecraft,
made using 3
near infrared
filters.
44
Galileo spacecraft image in infrared light at 727 nm (moderately absorbed by atmospheric
methane) shows features of Jupiter’s main visible cloud deck and upper tropospheric haze.
Higher features are brighter than lower features. The oval vortices in the upper half of this
image are 2 of the 3 long-lived White Ovals that formed to the south of the Great Red Spot
in the 1930s and, like the GRS, rotate in a counterclockwise sense. The east-to-west
dimension of the left-most White Oval is 9000 km (the diameter of the earth is 12,756 km).
The White Ovals drift in longitude relative to one another. At this time, on February 19,
1997, the two ovals are restricting the balloon shaped oval between them.
Jupiter's white oval storms before (top) and after (bottom) their historic merger in
February 1998. The three classic white ovals which formed in the 1930's have
occupied the band from 31 to 35 degrees south planetocentric latitude ever since.
The top panel shows two of the ovals with a pear-shaped region between them.
Winds around the white ovals are counterclockwise (anticyclonic), indicating they
are high-pressure systems. Winds around the pear-shaped region are clockwise
(cyclonic) indicating that it is a low-pressure region.
(cyclonic),
region The two white ovals were
named BC (right)and DE (left) shortly after they formed. The lower panel shows
the merged oval, named BE. The pear-shaped cyclonic region is absent. The
merger took place in February 1998 when Jupiter was behind the Sun and could
not be seen from Earth.
The top and bottom panels show the features in the same viewing geometry.
One might expect the area of the merged feature to equal the sum of the areas of
the original features,
features but the oval might have lost some material during the merger
or it might have stretched out in the vertical direction. Vertical stretching causes
the ovals to spin faster, similar to what happens when figure skaters spin and pull
their arms closer to their bodies. The images allow determination of both the areas
of the storms and the related winds; this will help distinguish among the
mechanisms involved.
45
The top mosaic combines images obtained using the Galileo imaging camera's
three near-infrared filters (756, 727, and 889 nanometers displayed in red, green,
and blue respectively) to show variations in cloud height and thickness. Light blue
clouds are high and thin, reddish cloudsare deep, and white clouds are high and
thick. The clouds and haze over the white ovals are high, extending into Jupiter's
stratosphere. There is a lack of high haze over the cylonic pear-shaped feature
between the ovals.
ovals Dark purple most likely represents a high haze overlying a
clear deep atmosphere. Galileo is the first spacecraft to distinguish cloud layers on
Jupiter. The bottom mosaic uses images obtained with the camera's 756
nanometer filter only.
North is at the top of these mosaics. The smallest resolved features are tens of
kilometers in size. The top images were taken on February 19, 1997, while the
bottom images were taken on September 25, 1998, all at ranges of about 1 million
kilometers (620,000
(620 000 miles) by the Solid State Imaging (CCD) system on NASA
NASA'ss
Galileo spacecraft.
46
A mosaic
image of
Jupiter’s
southern
hemisphere
from the
Galileo
spacecraft,
made using a
near infrared
filter.
A mosaic
image of
Jupiter’s
northern
hemisphere
from the
Galileo
spacecraft,
made using a
near infrared
filter.
47
A mosaic
image of
Jupiter’s
northern
hemisphere
from the
Galileo
spacecraft,
made using
near infrared
continuum and
violet filters to
approximate
“true” color.
The atmospheric flow near the poles seems to be considerably less
complex, presumably because of the much smaller rotation speed
of the gas there. (Remember that the rotation speed right at either
pole is, of course, zero.)
48
Polar view of the northern hemisphere of Jupiter -- Voyager-1
Polar view of the southern hemisphere of Jupiter -- Voyager-1
49
Jupiter turns out to have a ring.
But we will leave discussion of rings around planets to the lecture
on Saturn.
Voyager-1 image of Jupiter,
with line drawn to indicate the position of its ring.
50
Voyager-2 image of
Jupiter’s ring system
(orange lines).
Color composite, taken from 1.45
million km.
Multiple images on the limb are the
result of long exposure through
orange and violet filters.
Voyager-2 image of
Jupiter’s ring from 1.5 million km
51
Cassini movie of 2 small moons
orbiting within Jupiter’s ring.
52