Jupiter ... the king of the planets

Introduction to Jupiter

Here is the largest planet in the Solar System, with more mass than all of the other planets and moons combined. In fact, if Jupiter had more mass, it would ignite hydrogen into helium and be a star. The most distinctive feature of this planet, other than its large size, are the distinct color bands and Great Red Spot. While the other gas giants have banded weather, none is quite as distinct or as colorful as Jupiter. The colors are due to trace chemicals at different cloud depths. The Red Spot is an enormous hurricane-like storm that has run unabated for over 400 years, ever since it was first noticed. Second, Jupiter is the first of four giant planets composed primarily of gas. If you watched the Star Wars movie, "Empire Strikes Back," you will recall the scene on the gas planet where Lando was mining. This memorable scene is not feasible on Jupiter, but serves to make a connection for you. The reason such a manned station is not presently possible is that we do not have the technology to deal with the lethal radiation trapped within the magnetic field of Jupiter. This feature makes Jupiter impossible for humans to get within a 3 million km distance of the planet without suffering immediately lethal radiation poisoning. Jupiter has a ring system, similar to Saturn, but far less grand and invisible from Earth's telescopic view. Perhaps the most exciting aspect of Jupiter may be its Galilean moons, Io, Europa, Ganymede, and Callisto. Each of these 4 large moons has a fascinating geology, with Io being the most volcanic body in the Solar System, and Europa having a liquid ocean beneath its crust of ice. With so many moons, such large size, and complicated weather, Jupiter requires the most time for study, with the possible exception of Mars. We have learned much about this mini-solar system from Pioneer 10 and 11, Voyager 1 and 2, Ulysses, Galileo, and Cassini spacecraft.

Planetary data

Mass (kg), and mass relative to Earth

1.900 x 1027kg = 317.833 earths

Equatorial diameter (km)

142,984

Mean density (gm/cm3)

1.314

Acceleration of gravity (m/s2)

22.88

Velocity of escape (km/s)

59.5

Period of rotation

9.841 hours

Period of revolution

11.86222 years

Aphelion (AU)

5.4541

Aphelion (km)

815,920,000

Perihelion (AU)

4.9525

Perihelion (km)

740,880,000

Mean orbital distance from the sun (AU)

5.2033

Mean orbital distance from the sun (km)

778,400,000

Orbital velocity (km/s)

13.06

Eccentricity

.0482

Oblateness

0.0648

Inclination to the ecliptic

1.308 degrees

Inclination of the equator to the orbit

3.08 degrees

Number of natural satellites

63 as of January, 2009

Names of natural satellites

Metis, Adrastea, Amalthea, Thebe, Io, Europa, Ganymede, Callisto, Themisto, Leda, Himalia, Lysithea, Elara, Carpa, Euporie, Orthosie, Euanthe, Thyome, Mneme, Harpalyke, Hermipae, Praxidike, Thelxinae, Iocaste, Ananke, Arche, Pasithae, Chaldene, Kale, Isonoe, Aitne, Erinome, Taygete, Carme, Kaylke, Eukelade, Kallichore, Helike, Eurydome, Autonoe, Sponde, Pasiphea, Megaclite, Sinope, Hegemone, Aoede, Callirrhoe, Cyllene, plus 14 more new moons without names.

More Information on the Planet Jupiter from the Nine Planets Website

Much of the information below is direct from the Nine Planets Website. Some material has been altered by me for this course, while other items and comments are directly copied. I hope to maintain a continuous update of this material to keep up with the findings from space satellites and telescopes.

Jupiter is the fifth planet from the Sun and by far the largest. Jupiter is more than twice as massive as all the other planets combined (318 times Earth).
orbit: 778,330,000 km (5.20 AU) from Sun
diameter: 142,984 km (equatorial)
mass: 1.900x1027kg
Jupiter (a.k.a. Jove; Greek Zeus) was the King of the Gods, the ruler of Olympus and the patron of the Roman state. Zeus was the son of Cronus (Saturn).


Jupiter is the fourth brightest object in the sky (after the Sun, the Moon and Venus; at some times Mars is also brighter), and therefore it has been known since prehistoric times. Galileo's discovery, in 1610, of Jupiter's four large moons Io, Europa, Ganymede and Callisto (now known as the Galilean moons) was the first discovery of a center of motion not apparently centered on the Earth. It was a major point in favor of Copernicus's heliocentric theory of the motions of the planets. Galileo's outspoken support of the Copernican theory got him in trouble with the Inquisition, but it was his observational evidence that really put an end to geocentrism.

 

 

 

 

Jupiter was first visited by Pioneer 10 in 1973 and later by Pioneer 11, Voyager 1, Voyager 2 and Ulysses. The spacecraft Galileo orbited around Jupiter and its large moons for 8 years before JPL engineers sent it plunging into the atmosphere of Jupiter. During the summer of 2002 Cassini flew by Jupiter en route to Saturn and returned some very nice images.

 

The gas planets do not have solid surfaces, their gaseous material simply gets denser with depth (the radii and diameters quoted for the planets are for levels corresponding to a pressure of 1 atmosphere). What we see when looking at these planets is the tops of clouds high in their atmospheres (slightly above the 1 atmosphere level). Of interest here is that you would not find sudden transitions from a solid core to a liquid mantle to a gaseous atmosphere. The phase changes between layers is very subtle and spread over great depths such that if it were possible to probe deep into the interior of Jupiter, you would not notice when you changed layers.

COMPOSITION OF JUPITER

Jupiter is about 90% hydrogen and 10% helium (by numbers of atoms, 75/25% by mass) with traces of methane, water, ammonia and "rock". This is very close to the composition of the primordial Solar Nebula from which the entire solar system was formed, and close to the levels of gas content in our Sun. Saturn has a similar composition, but Uranus and Neptune have much less hydrogen and helium.

Our knowledge of the interior of Jupiter (and the other gas planets) is highly indirect and likely to remain so for some time. (The data from Galileo's atmospheric probe goes down only about 150 km below the cloud tops.) If you have forgotten by now, on December 7, 1995, the Galileo spacecraft dropped a probe into the Jovian atmosphere to try to learn what was under the visible uppermost cloud layers. The probe lived for less than opne hour, plummeting to a depth of roughly 150 miles before we lost its transmission. Shortly thereafter, the spaceprobe encountered increasing atmospheric pressures and heat such that the probe itself was atomized. While it penetrated only a short distance, we did learn a few things from this mission. Detailed probe data is available within this course.

 

 

 

STRUCTURE OF JUPITER

Jupiter probably has a core of rocky material amounting to something like 10 to 15 Earth-masses.

Above the core lies the main bulk of the planet in the form of liquid metallic hydrogen. This exotic form of the most common of elements is possible only at pressures exceeding 4 million bars, as is the case in the interior of Jupiter (and Saturn). Liquid metallic hydrogen consists of ionized protons and electrons (like the interior of the Sun but at a far lower temperature). At the temperature and pressure of Jupiter's interior hydrogen is a liquid, not a gas. It is an electrical conductor and the source of Jupiter's magnetic field. This layer probably also contains some helium and traces of various "ices".

 

 

The outermost layer is composed primarily of ordinary molecular hydrogen and helium which is liquid in the interior and gaseous further out. The atmosphere we see is just the very top of this deep layer. Water, carbon dioxide, methane and other simple molecules are also present in tiny amounts.

CLOUDS OF JUPITER

Three distinct layers of clouds are believed to exist consisting of ammonia ice, ammonium hydrosulfide and a mixture of ice and water. However, the preliminary results from the Galileo probe show only faint indications of clouds (one instrument seems to have detected the topmost layer while another may have seen the second). But the probe's entry point was unusual -- Earth-based telescopic observations and more recent observations by the Galileo orbiter suggest that the probe entry site may well have been one of the warmest and least cloudy areas on Jupiter at that time.

 

 

 

One thing we do know ... Jupiter's outer atmosphere is cold, at 165K, and dominated by Hydrogen and Helium gases. The farther one descends into those clouds, the hotter one would become and the more intense the pressure one would feel.

Data from the Galileo atmospheric probe also indicate that there is much less water than expected. The expectation was that Jupiter's atmosphere would contain about twice the amount of oxygen (combined with the abundant hydrogen to make water) as the Sun. But it now appears that the actual concentration much less than the Sun's. Also surprising was the high temperature and density of the uppermost parts of the atmosphere.

Jupiter and the other gas planets have high velocity winds which are confined in wide bands of latitude. The winds blow in opposite directions in adjacent bands. Slight chemical and temperature differences between these bands are responsible for the colored bands that dominate the planet's appearance. The light colored bands are called zones; the dark ones belts. The bands have been known for some time on Jupiter, but the complex vortices in the boundary regions between the bands were first seen by Voyager. The data from the Galileo probe indicate that the winds are even faster than expected (more than 400 mph) and extend down into the atmosphere at least as far as the probe was able to observe; they may extend down thousands of kilometers into the interior. Jupiter's atmosphere was also found to be quite turbulent. This indicates that Jupiter's winds are driven in large part by its internal heat rather than from solar input as on Earth.

The vivid colors seen in Jupiter's clouds are probably the result of subtle chemical reactions of the trace elements in Jupiter's atmosphere, perhaps involving sulfur whose compounds take on a wide variety of colors, but the details are unknown. The colors correlate with the cloud's altitude: blue lowest, followed by browns and whites, with reds highest. Sometimes we see the lower layers through holes in the upper ones. The cloud is not as famous as Jupiter's Great Red Spot, known here instead as Jupiter's Brown Spot (oh how creative the science team is in generating appropriate names for objects they find). I am here reminded of a quaint little question, "What's brown and sits on the piano bench? Why Beethoven's Last Movement." Ha ha ha!

 

 

 

THE GREAT RED SPOT

The Great Red Spot (GRS) has been seen by Earthly observers for more than 300 years (its discovery is usually attributed to Cassini, or Robert Hooke in the 17th century). The GRS is an oval about 12,000 by 25,000 km, big enough to hold two Earths. Other smaller but similar spots have been known for decades. Infrared observations and the direction of its rotation indicate that the GRS is a high-pressure region whose cloud tops are significantly higher and colder than the surrounding regions. Similar structures have been seen on Saturn and Neptune. It is not known how such structures can persist for so long. I recall a "NOVA" special a while back that mentioned some relationship between the actions of the GRS and a "standing wave," but the physics behind this theory are beyond the scope of this course, to mention nothing about my own uncertainty about standing waves:)

 

Jupiter radiates more energy into space than it receives from the Sun. The interior of Jupiter is hot: the core is probably about 20,000 K. The heat is generated by the Kelvin-Helmholtz mechanism, the slow gravitational compression of the planet. (Jupiter does NOT produce energy by nuclear fusion as in the Sun; it is much too small and hence its interior is too cool to ignite nuclear reactions.) This interior heat probably causes convection deep within Jupiter's liquid layers and is probably responsible for the complex motions we see in the cloud tops. Saturn and Neptune are similar to Jupiter in this respect, but oddly, the planet Uranus is not. As I mentioned at the top of the page, Jupiter is similar to the Sun in almost every aspect except in mass. The theoretical lower limit if mass required to ignite thermonuclear fusion is .08 Suns. Jupiter is not at this level, but if Jupiter had 80 times more material, its core pressures would be sufficient to generate the requisite heat for fusion ignition and then Jupiter would be a star. Indeed, in the movie, "2010, a Space Odessy" Jupiter ignites into a star. But this scenario, although based on some fact, is not possible due to the lack of mass ... a lot of mass in fact.

Jupiter is just about as large in diameter as a gas planet can be. If more material were to be added, it would be compressed by gravity such that the overall radius would increase only slightly. A star can be larger only because of its internal (nuclear) heat source. The process of thermonuclear fusion exerts tremendous outward pressure that counteracts gravity's inward pressure. This is why stars are so large.

JUPITER'S LETHAL MAGNETIC FIELD

Jupiter has a huge magnetic field, much stronger than Earth's. Its magnetosphere extends more than 650 million km (past the orbit of Saturn!). (Note that Jupiter's magnetosphere is far from spherical -- it extends "only" a few million kilometers in the direction toward the Sun.) Jupiter's moons therefore lie within its magnetosphere, a fact which may partially explain some of the activity on Io. Unfortunately for future space travelers and of real concern to the designers of the Voyager and Galileo spacecraft, the environment near Jupiter contains high levels of energetic particles trapped by Jupiter's magnetic field. This "radiation" is similar to, but much more intense than, that found within Earth's Van Allen belts. It would be immediately fatal to an unprotected human being. The Galileo atmospheric probe discovered a new intense radiation belt between Jupiter's ring and the uppermost atmospheric layers. This new belt is approximately 10 times as strong as Earth's Van Allen radiation belts. Surprisingly, this new belt was also found to contain high energy helium ions of unknown origin. In the "Voyager" video we show at school, Ed Stone discusses how Jupiter's magnetic field can be so immense. Io is erupting 2 tons of material per second into space, and this material is trapped within Jupiter's magnetic field and Io's orbit, forming a donut-shaped torus. This torus is thought to be responsible for inflating the magnetic field of Jupiter some three times what it might otherwise be.

RINGS OF JUPITER

Jupiter has rings like Saturn's, but much fainter and smaller (right). They were totally unexpected and were only discovered when two of the Voyager 1 scientists insisted that after traveling 1 billion km it was at least worth a quick look to see if any rings might be present. Everyone else thought that the chance of finding anything was nil, but there they were. It was a major coup. They have since been imaged in the infra-red from ground-based telescopes and by Galileo.

Unlike Saturn's, Jupiter's rings are dark (albedo about .05). They're probably composed of very small grains of rocky material, and unlike Saturn's rings, they seem to contain no ice.

Particles in Jupiter's rings probably don't stay there for long (due to atmospheric and magnetic drag). The Galileo spacecraft found clear evidence that the rings are continuously resupplied by dust formed by micrometeor impacts on the four inner moons, which are very energetic because of Jupiter's large gravitational field. The inner halo ring is broadened by interactions with Jupiter's magnetic field.

In July 1994, Comet Shoemaker-Levy 9 collided with Jupiter with spectacular results (left). The effects were clearly visible even with amateur telescopes. The debris from the collision was visible for nearly a year afterward with Hubble Space Telescope.

 

When it is in the nighttime sky, Jupiter is often the brightest "star" in the sky (it is second only to Venus, which is seldom visible in a dark sky). The four Galilean moons are easily visible with binoculars; a few bands and the Great Red Spot can be seen with a small astronomical telescope. There are several Web sites that show the current position of Jupiter (and the other planets) in the sky. More detailed and customized charts can be created with a planetarium program such as Starry Night.


Jupiter's Satellites/Moons

Jupiter has 63 known satellites: the four large Galilean moons, 12 smaller named ones that have been known since at least 1980, plus 47more small ones that have recently been discovered since the Voyager flybys. To learn more about these new moons, go to Scott Sheppard's web site, or the University of Hawaii's Irregular Satellite page.


Jupiter is very gradually slowing down due to the tidal drag produced by the Galilean satellites. Also, the same tidal forces are changing the orbits of the moons, very slowly forcing them farther from Jupiter.

Io, Europa and Ganymede are locked together in a 1:2:4 orbital resonance and their orbits evolve together. Callisto is almost part of this rotation/revolution relationship as well. In a few hundred million years, Callisto will be locked in too, orbiting at exactly twice the period of Ganymede (eight times the period of Io).

Jupiter's satellites are named for other figures in the life of Zeus (mostly his lovers).
Many more small moons have been discovered recently but have not as yet been officially named.

Jupiter's Moons of Earliest Discovery

Satellite Name

Distance

Radius

Mass

Discoverer

Year

Metis

128,000 km

20 km

9.56e16 kg

Synnott

1979

Adrastea

129,000 km

10 km

1.91e16 kg

Jewitt

1979

Amalthea

181,000 km

98 km

7.17e18 kg

Barnard

1892

Thebe

222,000 km

50

7.77e17 kg

Synnott

1979

Io

422,000 km

1815 km

8.94e22 kg

Galileo

1610

Europa

671,000 km

1569 km

4.80e22 kg

Galileo

1610

Ganymede

1,070,000 km

2631 km

1.48e23 kg

Galileo

1610

Callisto

1,883,000 km

2400 km

1.08e23 kg

Galileo

1610

Leda

11,094,000 km

8 km

5.68e15 kg

Kowal

1974

Himalia

11,480,000 km

93 km

9.56e18 kg

Perrine

1904

Lysithea

11,720,000 km

18 km

7.77e16 kg

Nicholson

1938

Elara

11,737,000 km

38 km

7.77e17 kg

Perrine

1905

Ananke

21,200,000 km

15 km

3.82e16 kg

Nicholson

1951

Carme

22,600,000 km

20 km

9.56e16 kg

Nicholson

1938

Pasiphae

23,500,000 km

25 km

1.91e17 kg

Melotte

1908

Sinope

23,700,000 km

18 km

7.77e16 kg

Nicholson

1914

Moons of Jupiter discovered since Voyager 1 and 2 and recently named by the IAU.

Satellite Name

Distance

Radius

Mass

Discoverer

Year

Themisto

7,507,000 km

9 km

 

 

2000

Euporie

19,302,000 km

2 km

 

 

2001

Orthosie

20,721,000 km

2 km

 

 

2001

Enanthe

20,799,000 km

3 km

 

 

2001

Thyone

20,940,000 km

4 km

 

 

2001

Harpalyke

21,105,000 km

4 km

 

 

2000

Hermippe

21,131,000 km

4 km

 

 

2001

Praxidike

21,147,000 km

7 km

 

 

2000

Iocaste

21,269,000 km

5 km

 

 

2000

Pasithee

23,096,000 km

2 km

 

 

2001

Chaldene

23,179,000 km

4 km

 

 

2000

Kale

23,217,000 km

2 km

 

 

2001

Isonoe

23,217,000 km

4 km

 

 

2000

Aitne

23,231,000 km

3 km

 

 

2001

Erinome

23,279,000 km

3 km

 

 

2000

Taygete

23,360,000 km

5 km

 

 

2000

Kalyke

23,583,000 km

5 km

 

 

2000

Eurydome

22,865,000 km

3 km

 

 

2001

Autonoe

23,039,000 km

4 km

 

 

2001

Sponde

23,487,000 km

2 km

 

 

2001

Megaclite

23,806,000 km

6 km

 

 

2000

Callirrhoe

24,102,000 km

7 km

 

 

1999

S/2000 J11

12,555,000 km

4 km

 

 

2000

S/2002/ J1

22,931,000 km

3 km

 

 

2002

 

*Values for the smaller moons are approximate* (distance is from Jupiter's center to the mean orbital distance). There are 2 as yet unnamed moons discovered in 2000 and 2002, along with a new listing of 21 more moons discovered in 2003 ... and it seems that the list will continue to grow!

Since the Voyager mission in 1979, 45 more moons of Jupiter have been discovered through various means. To learn more about these discoveries, check out the websites below. Some of them are receiving their new names.

11 new moons discovered = 28 moons

11 more new moons discovered = 39 moons

Now the count is at 63 moons

Mildly interesting from this chart is that Nicholson discovered 4 moons, but over a 37 year period. This man must have enjoyed looking through his telescope and making detailed drawings of star positions to notice something so small and insignificant as the smaller moons of Jupiter are.

THE BEGINNING OF A STUDY OF THE 4 GALILEAN MOONS OF JUPITER

Io is the innermost of the Galilean moons and the moon that altered the expectations of the Voyager ground team. The Voyager science members expected the moons of the solar system to be quite bland and geologically lifeless. The discovery of active volcanism on Io was totally unexpected. As Larry Soderblom explains in the "Voyager" video, "the closer and closer we got to Io, the more the surface showed nothing at all like craters." In fact, Io is such an active volcanic object, its entire surface gets a new coat of material every 100,000 years. To learn more about this fascinating moon, click on the image of Io to your left.

 

 

 

 

 

 

Europa is the second Galilean moon out from Jupiter, and this object is almost as smooth as a cue ball, or perhaps even my own head! Scientists have found the surface to be covered with a 100 km thick layer of water ice. The gargantuan faults are areas where the surface ice has cracked and liquid from the interior has welled up and flooded out. Indeed, a close look at the surface is very much like looking at polar ice on the Earth. To learn more about Europa, click on the image to your left.

 

 

 

Ganymede is the third Galilean moon away from Jupiter's clouds, and is the largest moon in the solar system. Its geology is more complicated than Io or Europa, but far less active, if at all anymore. Scientists were stunned to find that Ganymede has a magnetic field, so its interior must still be molten. It seems to be covered by ices and dirt. To learn more abouy Ganymede, click on the image to your left.

 

 

 

 

 

Callisto is the outermost of the Galilean moons, and perhaps owns the title of "oldest surface" in the solar system. This moon is literally saturated with craters. It is just a little smaller than Ganymede, and also boasts a magnetic field. To learn more about Callisto, click on the image to your left.

 

 

 

 

Below is a comparison of the four Galilean moons, looking at the full global image, major geologic features, and a close-up of each moon's terrain.

This image below is a comparison of the interiors of the four Galilean moons as believed to be on the basis of data collected by the Galileo spacecraft.

As mentioned above, Jupiter has faint rings composed of rocky material probably ejected from the meteoric impacts on the inner moons of the planet. To learn more about these rings, click on the image to your left.

 

 

 


Jupiter's Rings

Name of Ring

Distance

Width

Halo

100,000 km

22,800 km

Main

122,800 km

6,400 km

Gossamer

129,200 km

214,200 km

Distance is from the center of Jupiter to the inner edge of the ring.

Jupiter is the JPL website that can offer more information to you, as well as some interesting connecting links.

JUPITER IS STRUCK BY A COMET

Whoa! What's this? I put this here in case you did not notice it earlier. In the summer of 1994, Jupiter was hit by a series of comet fragments in spectular fashion. The comet named Shoemaker-Levy 9 after the codiscoverers, put on a display that even I was able to see from my backyard in Minneapolis. Check out the SL9 web site to learn more about this event, and then start thinking ,"What if the Earth were hit by a comet?"

 

 

Galileo Space Mission

So much of what we have learned about Jupiter comes from the highly successful satellite, Galileo. On September 17, 2003, the satellite was turned off after completing the objectives of its mission. Overall, the satellite served the NASA and JPL engineers for 14 years. To read a press release of the final days of the satellite, connect to the press release. To see the full set of images taken by the Galileo spacecraft, go to mission images.

The Latest Image of Jupiter ... "best ever photograph of the planet from an Earth-based telescope"

Amazing image of Jupiter taken in infrared light on the night of 17 August 2008 with the Multi-Conjugate Adaptive Optics Demonstrator (MAD) prototype instrument mounted on ESO's Very Large Telescope. This false colour photo is the combination of a series of images taken over a time span of about 20 minutes, through three different filters (2, 2.14, and 2.16 microns). The image sharpening obtained is about 90 milli-arcseconds across the whole planetary disc, a real record on similar images taken from the ground. This corresponds to seeing details about 300 km wide on the surface of the giant planet. The great red spot is not visible in this image as it was on the other side of the planet during the observations. The observations were done at infrared wavelengths where absorption due to hydrogen and methane is strong. This explains why the colours are different from how we usually see Jupiter in visible-light. This absorption means that light can be reflected back only from high-altitude hazes, and not from deeper clouds. These hazes lie in the very stable upper part of Jupiter's troposphere, where pressures are between 0.15 and 0.3 bar. Mixing is weak within this stable region, so tiny haze particles can survive for days to years, depending on their size and fall speed. Additionally, near the planet's poles, a higher stratospheric haze (light blue regions) is generated by interactions with particles trapped in Jupiter's intense magnetic field.
Credit: ESO/F. Marchis, M. Wong, E. Marchetti, P. Amico, S. Tordo

 

Here are some questions that I would like you to answer regarding Jupiter and its moons.

1) Briefly give a physical description of the planet Jupiter.

2) What is the most distinctive feature on Jupiter?

3) If Jupiter was more massive (say 80 times more) what would Jupiter become?

4) What causes the different colors in Jupiter's bands of clouds?

5) What was the spectacular discovery when Voyager 1 went past Io?

6) Why is there so much interest in the moon Europa?

7) In what way is Jupiter similar to Saturn?

8) What crashed into Jupiter in the summer of 1994?

9) What satellite missions have visited Jupiter?

10) What makes a manned mission to Jupiter almost impossible?

Once you believe that you know the answers to these questions, please go to the Jupiter Quiz page and submit your responses to me.

There is so much to Juipiter, in fact more than an entire high school course could possibly hold, and as time goes by, perhaps more of the interesting Jupiter information from Galileo, can be included in this course. For now though, it is time to move on. Please go to the Saturn page, back to one of the Inner Planets (Mercury, Venus, Earth, or Mars), or return to Introduction to the Gas Giants, or the Planet Introduction, or the Syllabus.


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