Jupiter

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Posted by motoman 03/25/2009 @ 15:13

Tags : jupiter, solar system, astronomy and space, sciences

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BankAtlantic seeks foreclosure on Jupiter site - Bizjournals.com
BankAtlantic has filed a lawsuit targeting a site at the mouth of the Loxahatchee River in Jupiter. The Fort Lauderdale-based bank (NYSE: BBX) filed the lawsuit on May 8 in Palm Beach County Circuit Court against Severn Jupiter and managing members...
Jupiter man arrested in jewelry store robbery - TCPalm
Arrested were Anthony Barba, 23 of the 1100 block of Lakeshore Drive, Jupiter; Johnny James Gooden Jr, 23, of the 200 block of Thalia Circle, Palm Springs; Wilbert Grant, 21 of the 300 block of 22nd Street, Riviera Beach; and James Isaac Jones,...
STONE CRABS: Charlotte drops 7-4 game to Jupiter - Sun newspapers
Charlotte fell 7-4 to visiting Jupiter for the its third consecutive loss. Downs, a lefty, entered the game with not only the most impressive starting line on the team (5-0, 1.34 ERA), but with the second-lowest ERA in the Florida State League and was...
Jupiter Systems, World Leader in Display Wall Processors to ... - Business Wire (press release)
Jupiter Systems will exhibit in Hall 4, Booth #F47. “Jupiter Systems is a major provider of high-performance solutions used in security applications for command and control,” said Brady O. Bruce, VP of Marketing and Strategic Alliances....
The almanac - United Press International
The morning stars are Mars, Venus, Jupiter, Uranus and Neptune. The evening stars are Mercury and Saturn. Those born on this date are under the sign of Taurus. They include British statesman and scholar James Bryce in 1838; Swiss theologian Karl Barth...
Crabs fall behind early, lose to Jupiter - Sarasota Herald-Tribune
PORT CHARLOTTE – Another bad start doomed the Charlotte Stone Crabs in a 7-4 loss against the Jupiter Hammerheads on Monday night at Charlotte Sports Park. Charlotte starter Darin Downs (5-1) got roughed up early, giving up seven runs in the first two...
19 years of the Hubble telescope: First of a 2-part series - Newsday
Iconic images have included stars in the throes of birth and death, galaxies stalking galaxies and chunks of comet slamming into Jupiter. The spectacular scenes are merely grace notes to astronomers, who use the telescope to probe far-off specks of...
Cobras earn first tournament berth, Spanish River holds on to ... - Palm Beach Post
"This is my award," Hemings said after Park Vista defeated Jupiter 24-26, 25-19, 28-26, 26-24 in a boys volleyball state play-in match that qualified the Cobras for the state tournament for the first time. It's the second time this season that Park...
Telecommunications sales exec sells 3BD in Jupiter - Blockshopper
by Frank Lee, published May 11, 2009 · Stuart and Shawn Andrus sold a three-bedroom, two-bath home at 107 Faith Way in Jupiter to Timothy J. Bach for $480000 on March 3. The Andruses bought the property for $515000 in Oct. 2005....
Jupiter High School wins state title - Palm Beach Post
By JOSEPH KAIRALLA BOCA RATON — Quarterback Brittany Lear and a standout defense led Jupiter to a 16-0 win against Tallahassee-Leon and the Warriors' first flag football state championship Saturday. The victory over the two-time defending state...

Jupiter

This looping animation shows the movement of Jupiter's counter-rotating cloud bands. In this image, the planet's exterior is mapped onto a cylindrical projection.

Jupiter (pronounced /ˈdʒuːpɨtɚ/ (help·info)) is the fifth planet from the Sun and the largest planet within the Solar System. It is two and a half times as massive as all of the other planets in our Solar System combined. Jupiter is classified as a gas giant, along with Saturn, Uranus and Neptune. Together, these four planets are sometimes referred to as the Jovian planets.

The planet Jupiter is primarily composed of hydrogen with a small proportion of helium; it may also have a rocky core of heavier elements under high pressure. Because of its rapid rotation, Jupiter's shape is that of an oblate spheroid (it possesses a slight but noticeable bulge around the equator). The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century. Surrounding the planet is a faint planetary ring system and a powerful magnetosphere. There are also at least 63 moons, including the four large moons called the Galilean moons that were first discovered by Galileo Galilei in 1610. Ganymede, the largest of these moons, has a diameter greater than that of the planet Mercury.

Jupiter has been explored on several occasions by robotic spacecraft, most notably during the early Pioneer and Voyager flyby missions and later by the Galileo orbiter. The latest probe to visit Jupiter was the Pluto-bound New Horizons spacecraft in late February 2007. The probe used the gravity from Jupiter to increase its speed and adjust its trajectory toward Pluto, thereby saving years of travel. Future targets for exploration include the possible ice-covered liquid ocean on the Jovian moon Europa.

Jupiter is one of the four gas giants; that is, it is not primarily composed of solid matter. It is the largest planet in the Solar System, having a diameter of 142,984 km at its equator. Jupiter's density, 1.326 g/cm³, is the second highest of the gas giant planets, but lower than any of the four terrestrial planets.

Jupiter's upper atmosphere is composed of about 88-92% hydrogen and 8-12% helium by percent volume or fraction of gas molecules (see table to the right). Since a helium atom has about four times as much mass as a hydrogen atom, the composition changes when described in terms of the proportion of mass contributed by different atoms. Thus the atmosphere is approximately 75% hydrogen and 24% helium by mass, with the remaining one percent of the mass consisting of other elements. The interior contains denser materials such that the distribution is roughly 71% hydrogen, 24% helium and five percent other elements by mass. The atmosphere contains trace amounts of methane, water vapor, ammonia, and silicon-based compounds. There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, and sulfur. The outermost layer of the atmosphere contains crystals of frozen ammonia. Through infrared and ultraviolet measurements, trace amounts of benzene and other hydrocarbons have also been found.

The atmospheric proportions of hydrogen and helium are very close to the theoretical composition of the primordial solar nebula. However, neon in the upper atmosphere only consists of 20 parts per million by mass, which is about a tenth as abundant as in the Sun. Helium is also depleted, although to a lesser degree. This depletion may be a result of precipitation of these elements into the interior of the planet. Abundances of heavier inert gases in Jupiter's atmosphere are about two to three times that of the sun.

Based on spectroscopy, Saturn is thought to be similar in composition to Jupiter, but the other gas giants Uranus and Neptune have relatively much less hydrogen and helium. However, because of the lack of atmospheric entry probes, high quality abundance numbers of the heavier elements are lacking for the outer planets beyond Jupiter.

Jupiter is 2.5 times more massive than all the other planets in our Solar System combined — this is so massive that its barycenter with the Sun actually lies above the Sun's surface (1.068 solar radii from the Sun's center). Although this planet dwarfs the Earth (with a diameter 11 times as great) it is considerably less dense. Jupiter's volume is equal to 1,317 Earths, yet is only 318 times as massive. A Jupiter mass (MJ) is used to describe masses of other gas giant planets, particularly extrasolar planets.

Theoretical models indicate that if Jupiter had much more mass than it does at present, the planet would shrink. For small changes in mass, the radius would not change appreciably, and above about four Jupiter masses the interior would become so much more compressed under the increased gravitation force that the planet's volume would actually decrease despite the increasing amount of matter. As a result, Jupiter is thought to have about as large a diameter as a planet of its composition and evolutionary history can achieve. The process of further shrinkage with increasing mass would continue until appreciable stellar ignition is achieved as in high-mass brown dwarfs around 50 Jupiter masses. This has led some astronomers to term it a "failed star", although it is unclear whether or not the processes involved in the formation of planets like Jupiter are similar to the processes involved in the formation of multiple star systems.

Although Jupiter would need to be about 75 times as massive to fuse hydrogen and become a star, the smallest red dwarf is only about 30 percent larger in radius than Jupiter. In spite of this, Jupiter still radiates more heat than it receives from the Sun. The amount of heat produced inside the planet is nearly equal to the total solar radiation it receives. This additional heat radiation is generated by the Kelvin-Helmholtz mechanism through adiabatic contraction. This process results in the planet shrinking by about 2 cm each year. When it was first formed, Jupiter was much hotter and was about twice its current diameter.

Jupiter is thought to consist of a dense core with a mixture of elements, a surrounding layer of liquid metallic hydrogen with some helium, and an outer layer predominantly of molecular hydrogen. Beyond this basic outline, there is still considerable uncertainty. The core is often described as rocky, but its detailed composition is unknown, as are the properties of materials at the temperatures and pressures of those depths (see below). In 1997, the existence of the core was suggested by gravitational measurements. indicating a mass of from 12 to 45 times the Earth's mass or roughly 3%-15% of the total mass of Jupiter. The presence of a core during at least part of Jupiter's history is suggested by models of planetary formation involving initial formation of a rocky or icy core that is massive enough to collect its bulk of hydrogen and helium from the protosolar nebula. Assuming it did exist, it may have shrunk as convection currents of hot liquid metallic hydrogen mixed with the molten core and carried its contents to higher levels in the planetary interior. A core may now be entirely absent, as gravitational measurements aren't yet precise enough to rule that possibility out entirely.

The uncertainty of the models is tied to the error margin in hitherto measured parameters: one of the rotational coefficients (J6) used to describe the planet's gravitational moment, Jupiter's equatorial radius, and its temperature at 1 bar pressure. The JUNO mission, scheduled for launch in 2011, is expected to narrow down the value of these parameters, and thereby make progress on the problem of the core.

The core region is surrounded by dense metallic hydrogen, which extends outward to about 78 percent of the radius of the planet. Rain-like droplets of helium and neon precipitate downward through this layer, depleting the abundance of these elements in the upper atmosphere.

Above the layer of metallic hydrogen lies a transparent interior atmosphere of liquid hydrogen and gaseous hydrogen, with the gaseous portion extending downward from the cloud layer to a depth of about 1,000 km. Instead of a clear boundary or surface between these different phases of hydrogen, there is probably a smooth gradation from gas to liquid as one descends. This smooth transition happens whenever the temperature is above the critical temperature, which for hydrogen is only 33 K (see hydrogen).

The temperature and pressure inside Jupiter increase steadily toward the core. At the phase transition region where liquid hydrogen (heated beyond its critical point) becomes metallic, it is believed the temperature is 10,000 K and the pressure is 200 GPa. The temperature at the core boundary is estimated to be 36,000 K and the interior pressure is roughly 3,000–4,500 GPa.

Jupiter is perpetually covered with clouds composed of ammonia crystals and possibly ammonium hydrosulfide. The clouds are located in the tropopause and are arranged into bands of different latitudes, known as tropical regions. These are sub-divided into lighter-hued zones and darker belts. The interactions of these conflicting circulation patterns cause storms and turbulence. Wind speeds of 100 m/s (360 km/h) are common in zonal jets. The zones have been observed to vary in width, color and intensity from year to year, but they have remained sufficiently stable for astronomers to give them identifying designations.

The cloud layer is only about 50 km deep, and consists of at least two decks of clouds: a thick lower deck and a thin clearer region. There may also be a thin layer of water clouds underlying the ammonia layer, as evidenced by flashes of lightning detected in the atmosphere of Jupiter. (Water is a polar molecule that can carry a charge, so it is capable of creating the charge separation needed to produce lightning.) These electrical discharges can be up to a thousand times as powerful as lightning on the Earth. The water clouds can form thunderstorms driven by the heat rising from the interior.

The orange and brown coloration in the clouds of Jupiter are caused by upwelling compounds that change color when they are exposed to ultraviolet light from the Sun. The exact makeup remains uncertain, but the substances are believed to be phosphorus, sulfur or possibly hydrocarbons. These colorful compounds, known as chromophores, mix with the warmer, lower deck of clouds. The zones are formed when rising convection cells form crystallizing ammonia that masks out these lower clouds from view.

Jupiter's low axial tilt means that the poles constantly receive less solar radiation than at the planet's equatorial region. Convection within the interior of the planet transports more energy to the poles, however, balancing out the temperatures at the cloud layer.

The best known feature of Jupiter is the Great Red Spot, a persistent anticyclonic storm located 22° south of the equator that is larger than Earth. It is known to have been in existence since at least 1831, and possibly since 1665. Mathematical models suggest that the storm is stable and may be a permanent feature of the planet. The storm is large enough to be visible through Earth-based telescopes.

The oval object rotates counterclockwise, with a period of about six days. The Great Red Spot's dimensions are 24–40,000 km × 12–14,000 km. It is large enough to contain two or three planets of Earth's diameter. The maximum altitude of this storm is about 8 km above the surrounding cloudtops.

Storms such as this are common within the turbulent atmospheres of gas giants. Jupiter also has white ovals and brown ovals, which are lesser unnamed storms. White ovals tend to consist of relatively cool clouds within the upper atmosphere. Brown ovals are warmer and located within the "normal cloud layer". Such storms can last as little as a few hours or stretch on for centuries.

Even before Voyager proved that the feature was a storm, there was strong evidence that the spot could not be associated with any deeper feature on the planet's surface, as the Spot rotates differentially with respect to the rest of the atmosphere, sometimes faster and sometimes more slowly. During its recorded history it has traveled several times around the planet relative to any possible fixed rotational marker below it.

In 2000, an atmospheric feature formed in the southern hemisphere that is similar in appearance to the Great Red Spot, but smaller in size. This was created when several smaller, white oval-shaped storms merged to form a single feature—these three smaller white ovals were first observed in 1938. The merged feature was named Oval BA, and has been nicknamed Red Spot Junior. It has since increased in intensity and changed color from white to red.

Jupiter has a faint planetary ring system composed of three main segments: an inner torus of particles known as the halo, a relatively bright main ring, and an outer "gossamer" ring. These rings appear to be made of dust, rather than ice as is the case for Saturn's rings. The main ring is probably made of material ejected from the satellites Adrastea and Metis. Material that would normally fall back to the moon is pulled into Jupiter because of its strong gravitational pull. The orbit of the material veers towards Jupiter and new material is added by additional impacts. In a similar way, the moons Thebe and Amalthea probably produce the two distinct components of the gossamer ring.

Jupiter's broad magnetic field is 14 times as strong as the Earth's, ranging from 4.2 gauss (0.42 mT) at the equator to 10–14 gauss (1.0–1.4 mT) at the poles, making it the strongest in the Solar System (with the exception of sunspots). This field is believed to be generated by eddy currents — swirling movements of conducting materials—within the metallic hydrogen core. The field traps a sheet of ionized particles from the solar wind, generating a highly-energetic magnetic field outside the planet — the magnetosphere. Electrons from this plasma sheet ionize the torus-shaped cloud of sulfur dioxide generated by the tectonic activity on the moon Io. Hydrogen particles from Jupiter's atmosphere are also trapped in the magnetosphere. Electrons within the magnetosphere generate a strong radio signature that produces bursts in the range of 0.6–30 MHz.

At about 75 Jupiter radii from the planet, the interaction of the magnetosphere with the solar wind generates a bow shock. Surrounding Jupiter's magnetosphere is a magnetopause, located at the inner edge of a magnetosheath, where the planet's magnetic field becomes weak and disorganized. The solar wind interacts with these regions, elongating the magnetosphere on Jupiter's lee side and extending it outward until it nearly reaches the orbit of Saturn. The four largest moons of Jupiter all orbit within the magnetosphere, which protects them from the solar wind.

The magnetosphere of Jupiter is responsible for intense episodes of radio emission from the planet's polar regions. Volcanic activity on the Jovian moon Io (see below) injects gas into Jupiter's magnetosphere, producing a torus of particles about the planet. As Io moves through this torus, the interaction generates Alfven waves that carry ionized matter into the polar regions of Jupiter. As a result, radio waves are generated through a cyclotron maser mechanism, and the energy is transmitted out along a cone-shaped surface. When the Earth intersects this cone, the radio emissions from Jupiter can exceed the solar radio output.

The average distance between Jupiter and the Sun is 778 million km (about 5.2 times the average distance from the Earth to the Sun, or 5.2 AU) and it completes an orbit every 11.86 years. This is two-fifths the orbital period of Saturn, forming a 5:2 orbital resonance between the two largest planets in the Solar System. The elliptical orbit of Jupiter is inclined 1.31° compared to the Earth. Because of an eccentricity of 0.048, the distance from Jupiter and the Sun varies by 75 million km between perihelion and aphelion, or the nearest and most distant points of the planet along the orbital path respectively.

The axial tilt of Jupiter is relatively small: only 3.13°. As a result this planet does not experience significant seasonal changes, in contrast to Earth and Mars for example.

Jupiter's rotation is the fastest of all the Solar System's planets, completing a rotation on its axis in slightly less than ten hours; this creates an equatorial bulge easily seen through an Earth-based amateur telescope. This rotation requires a centripetal acceleration at the equator of about 1.67 m/s², compared to the equatorial surface gravity of 24.79 m/s²; thus the net acceleration felt at the equatorial surface is only about 23.12 m/s². The planet is shaped as an oblate spheroid, meaning that the diameter across its equator is longer than the diameter measured between its poles. On Jupiter, the equatorial diameter is 9275 km longer than the diameter measured through the poles.

Because Jupiter is not a solid body, its upper atmosphere undergoes differential rotation. The rotation of Jupiter's polar atmosphere is about 5 minutes longer than that of the equatorial atmosphere; three "systems" are used as frames of reference, particularly when graphing the motion of atmospheric features. System I applies from the latitudes 10° N to 10° S; its period is the planet's shortest, at 9h 50m 30.0s. System II applies at all latitudes north and south of these; its period is 9h 55m 40.6s. System III was first defined by radio astronomers, and corresponds to the rotation of the planet's magnetosphere; its period is Jupiter's "official" rotation.

Jupiter is usually the fourth brightest object in the sky (after the Sun, the Moon and Venus); however at times Mars appears brighter than Jupiter. Depending on Jupiter's position with respect to the Earth, it can vary in visual magnitude from as bright as −2.8 at opposition down to −1.6 during conjunction with the Sun. The angular diameter of Jupiter likewise varies from 50.1 to 29.8 arc seconds. Favorable oppositions occur when Jupiter is passing through perihelion, an event that occurs once per orbit. As Jupiter approaches perihelion in March 2011, there will be a favorable opposition in September 2010.

Earth overtakes Jupiter every 398.9 days as it orbits the Sun, a duration called the synodic period. As it does so, Jupiter appears to undergo retrograde motion with respect to the background stars. That is, for a period of time Jupiter seems to move backward in the night sky, performing a looping motion.

Jupiter's 12-year orbital period corresponds to the dozen astrological signs of the zodiac, and may have been the historical origin of the signs. That is, each time Jupiter reaches opposition it has advanced eastward by about 30°, the width of a zodiac sign.

Because the orbit of Jupiter is outside the Earth's, the phase angle of Jupiter as viewed from the Earth never exceeds 11.5°, and is almost always close to zero. That is, the planet always appears nearly fully illuminated when viewed through Earth-based telescopes. It was only during spacecraft missions to Jupiter that crescent views of the planet were obtained.

In 1610, Galileo Galilei discovered the four largest moons of Jupiter, Io, Europa, Ganymede and Callisto (now known as the Galilean moons) using a telescope; thought to be the first observation of moons other than Earth's. (It should be noted, however, that Chinese historian of astronomy, Xi Zezong, has claimed that Gan De, a Chinese astronomer, made the discovery of one of Jupiter's moons in 362 BC with the unaided eye. If accurate, this would predate Galileo's discovery by nearly two millennia.) Galileo's was also the first discovery of a celestial motion not apparently centered on the Earth. It was a major point in favor of Copernicus' heliocentric theory of the motions of the planets; Galileo's outspoken support of the Copernican theory placed him under the threat of the Inquisition.

During the 1660s, Cassini used a new telescope to discover spots and colorful bands on Jupiter and observed that the planet appeared oblate; that is, flattened at the poles. He was also able to estimate the rotation period of the planet. In 1690 Cassini noticed that the atmosphere undergoes differential rotation.

The Great Red Spot, a prominent oval-shaped feature in the southern hemisphere of Jupiter, may have been observed as early as 1664 by Robert Hooke and in 1665 by Giovanni Cassini, although this is disputed. The pharmacist Heinrich Schwabe produced the earliest known drawing to show details of the Great Red Spot in 1831.

The Red Spot was reportedly lost from sight on several occasions between 1665 and 1708 before becoming quite conspicuous in 1878. It was recorded as fading again in 1883 and at the start of the twentieth century.

Both Giovanni Borelli and Cassini made careful tables of the motions of the Jovian moons, allowing predictions of the times when the moons would pass before or behind the planet. By the 1670s, however, it was observed that when Jupiter was on the opposite side of the Sun from the Earth, these events would occur about 17 minutes later than expected. Ole Rømer deduced that sight is not instantaneous (a finding that Cassini had earlier rejected), and this timing discrepancy was used to estimate the speed of light.

In 1892, E. E. Barnard observed a fifth satellite of Jupiter with the 36-inch (910 mm) refractor at Lick Observatory in California. The discovery of this relatively small object, a testament to his keen eyesight, quickly made him famous. The moon was later named Amalthea. It was the last planetary moon to be discovered directly by visual observation. An additional eight satellites were subsequently discovered prior to the flyby of the Voyager 1 probe in 1979.

In 1932, Rupert Wildt identified absorption bands of ammonia and methane in the spectra of Jupiter.

Three long-lived anticyclonic features termed white ovals were observed in 1938. For several decades they remained as separate features in the atmosphere, sometimes approaching each other but never merging. Finally, two of the ovals merged in 1998, then absorbed the third in 2000, becoming Oval BA.

In 1955, Bernard Burke and Kenneth Franklin detected bursts of radio signals coming from Jupiter at 22.2 MHz. The period of these bursts matched the rotation of the planet, and they were also able to use this information to refine the rotation rate. Radio bursts from Jupiter were found to come in two forms: long bursts (or L-bursts) lasting up to several seconds, and short bursts (or S-bursts) that had a duration of less than a hundredth of a second.

Scientists discovered that there were three forms of radio signals being transmitted from Jupiter.

During the period July 16, 1994 to July 22, 1994, over 20 fragments from the comet Shoemaker-Levy 9 hit Jupiter's southern hemisphere, providing the first direct observation of a collision between two Solar System objects. This impact provided useful data on the composition of Jupiter's atmosphere.

Since 1973 a number of automated spacecraft have visited Jupiter. Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Reaching Jupiter from Earth requires a delta-v of 9.2 km/s, which is comparable to the 9.7 km/s delta-v needed to reach low Earth orbit. Fortunately, gravity assists through planetary flybys can be used to reduce the energy required to reach Jupiter, albeit at the cost of a significantly longer flight duration.

Beginning in 1973, several spacecraft have performed planetary flyby maneuvers that brought them within observation range of Jupiter. The Pioneer missions obtained the first close-up images of Jupiter's atmosphere and several of its moons. They discovered that the radiation fields in the vicinity of the planet were much stronger than expected, but both spacecraft managed to survive in that environment. The trajectories of these spacecraft were used to refine the mass estimates of the Jovian system. Occultations of the radio signals by the planet resulted in better measurements of Jupiter's diameter and the amount of polar flattening.

Six years later, the Voyager missions vastly improved the understanding of the Galilean moons and discovered Jupiter's rings. They also confirmed that the Great Red Spot was anticyclonic. Comparison of images showed that the Red Spot had changed hue since the Pioneer missions, turning from orange to dark brown. A torus of ionized atoms was discovered along Io's orbital path, and volcanoes were found on the moon's surface, some in the process of erupting. As the spacecraft passed behind the planet, it observed flashes of lightning in the night side atmosphere.

The next mission to encounter Jupiter, the Ulysses solar probe, performed a flyby maneuver in order to attain a polar orbit around the Sun. During this pass the spacecraft conducted studies on Jupiter's magnetosphere. However, since Ulysses has no cameras, no images were taken. A second flyby six years later was at a much greater distance.

In 2000, the Cassini probe, en route to Saturn, flew by Jupiter and provided some of the highest-resolution images ever made of the planet. On December 19, 2000, the spacecraft captured an image of the moon Himalia, but the resolution was too low to show surface details.

The New Horizons probe, en route to Pluto, flew by Jupiter for gravity assist. Closest approach was on February 28, 2007. The probe's cameras measured plasma output from volcanoes on Io and studied all four Galilean moons in detail, as well as making long-distance observations of the outer moons Himalia and Elara. Imaging of the Jovian system began September 4, 2006.

So far the only spacecraft to orbit Jupiter is the Galileo orbiter, which went into orbit around Jupiter on December 7, 1995. It orbited the planet for over seven years, conducting multiple flybys of all of the Galilean moons and Amalthea. The spacecraft also witnessed the impact of Comet Shoemaker-Levy 9 as it approached Jupiter in 1994, giving a unique vantage point for the event. However, while the information gained about the Jovian system from Galileo was extensive, its originally-designed capacity was limited by the failed deployment of its high-gain radio transmitting antenna.

An atmospheric probe was released from the spacecraft in July 1995, entering the planet's atmosphere on December 7. It parachuted through 150 km of the atmosphere, collecting data for 57.6 minutes, before being crushed by the pressure to which it was subjected by that time (about 22 times Earth normal, at a temperature of 153 °C). It would have melted thereafter, and possibly vaporized. The Galileo orbiter itself experienced a more rapid version of the same fate when it was deliberately steered into the planet on September 21, 2003 at a speed of over 50 km/s, in order to avoid any possibility of it crashing into and possibly contaminating Europa—a moon which has been hypothesized to have the possibility of harboring life.

NASA is planning a mission to study Jupiter in detail from a polar orbit. Named Juno, the spacecraft is planned to launch by 2011.

Because of the possibility of subsurface liquid oceans on Jupiter's moons Europa, Ganymede and Callisto, there has been great interest in studying the icy moons in detail. Funding difficulties have delayed progress. NASA's JIMO (Jupiter Icy Moons Orbiter) was cancelled in 2005. A European Jovian Europa Orbiter mission was also studied. Both of these missions were superseded by the Europa Jupiter System Mission (EJSM) which is a joint NASA/ESA proposal for exploration of Jupiter and its moons. In February 2009 it was announced that ESA/NASA had given this mission priority ahead of the Titan Saturn System Mission. ESA's contribution will still face funding competition from other ESA projects. Launch date will be around 2020. EJSM consists of the NASA-led Jupiter Europa Orbiter, and the ESA-led Jupiter Ganymede Orbiter.

Jupiter has 63 named natural satellites. Of these, 47 are less than 10 kilometres in diameter and have only been discovered since 1975. The four largest moons, known as the "Galilean moons", are Io, Europa, Ganymede and Callisto.

The orbits of Io, Europa, and Ganymede, some of the largest satellites in the Solar System, form a pattern known as a Laplace resonance; for every four orbits that Io makes around Jupiter, Europa makes exactly two orbits and Ganymede makes exactly one. This resonance causes the gravitational effects of the three large moons to distort their orbits into elliptical shapes, since each moon receives an extra tug from its neighbors at the same point in every orbit it makes. The tidal force from Jupiter, on the other hand, works to circularize their orbits.

The eccentricity of their orbits causes regular flexing of the three moons' shapes, with Jupiter's gravity stretching them out as they approach it and allowing them to spring back to more spherical shapes as they swing away. This tidal flexing heats the moons' interiors via friction. This is seen most dramatically in the extraordinary volcanic activity of innermost Io (which is subject to the strongest tidal forces), and to a lesser degree in the geological youth of Europa's surface (indicating recent resurfacing of the moon's exterior).

Before the discoveries of the Voyager missions, Jupiter's moons were arranged neatly into four groups of four, based on commonality of their orbital elements. Since then, the large number of new small outer moons has complicated this picture. There are now thought to be six main groups, although some are more distinct than others.

A basic sub-division is a grouping of the eight inner regular moons, which have nearly circular orbits near the plane of Jupiter's equator and are believed to have formed with Jupiter. The remainder of the moons consist of an unknown number of small irregular moons with elliptical and inclined orbits, which are believed to be captured asteroids or fragments of captured asteroids. Irregular moons that belong to a group share similar orbital elements and thus may have a common origin, perhaps as a larger moon or captured body that broke up.

Along with the Sun, the gravitational influence of Jupiter has helped shape the Solar System. The orbits of most of the system's planets lie closer to Jupiter's orbital plane than the Sun's equatorial plane (Mercury is the only planet that is closer to the Sun's equator in orbital tilt), the Kirkwood gaps in the asteroid belt are mostly due to Jupiter, and the planet may have been responsible for the Late Heavy Bombardment of the inner Solar System's history.

In addition to its moons, Jupiter's gravitational field controls numerous asteroids that have settled into the regions of the Lagrangian points preceding and following Jupiter in its orbit around the sun. These are known as the Trojan asteroids, and are divided into Greek and Trojan "camps" to commemorate the Iliad. The first of these, 588 Achilles, was discovered by Max Wolf in 1906; since then more than two thousand have been discovered. The largest is 624 Hektor.

Jupiter has been called the Solar System's vacuum cleaner, because of its immense gravity well and location near the inner Solar System. It receives the most frequent comet impacts of the Solar System's planets. In 1994 comet Shoemaker-Levy 9 (SL9, formally designated D/1993 F2) collided with Jupiter and gave information about the structure of the planet. It was thought that the planet served to partially shield the inner system from cometary bombardment. However, recent computer simulations suggest that Jupiter doesn't cause a net decrease in the number of comets that pass through the inner Solar System, as its gravity perturbs their orbits inward in roughly the same numbers that it accretes or ejects them.

The majority of short-period comets belong to the Jupiter family—defined as comets with semi-major axes smaller than Jupiter's. Jupiter family comets are believed to form in the Kuiper belt outside the orbit of Neptune. During close encounters with Jupiter their orbits are perturbed into a smaller period and then circularized by regular gravitational interaction with the Sun and Jupiter.

In 1953, the Miller-Urey experiment demonstrated that a combination of lightning and the chemical compounds that existed in the atmosphere of a primordial Earth could form organic compounds (including amino acids) that could serve as the building blocks of life. The simulated atmosphere included water, methane, ammonia and molecular hydrogen; all molecules still found in the atmosphere of Jupiter. However, the atmosphere of Jupiter has a strong vertical air circulation, which would carry these compounds down into the lower regions. The higher temperatures within the interior of the atmosphere breaks down these chemicals, which would hinder the formation of Earth-like life.

It is considered highly unlikely that there is any Earth-like life on Jupiter, as there is only a small amount of water in the atmosphere and any possible solid surface deep within Jupiter would be under extraordinary pressures. However, in 1976, before the Voyager missions, it was hypothesized that ammonia- or water-based life could evolve in Jupiter's upper atmosphere. This hypothesis is based on the ecology of terrestrial seas which have simple photosynthetic plankton at the top level, fish at lower levels feeding on these creatures, and marine predators which hunt the fish.

The planet Jupiter has been known since ancient times. It is visible to the naked eye in the night sky and can occasionally be seen in the daytime when the sun is low. To the Babylonians, this object represented their god Marduk. They used the roughly 12-year orbit of this planet along the ecliptic to define the constellations of their zodiac.

The Romans named it after Jupiter (Latin: Iuppiter, Iūpiter) (also called Jove), the principal god of Roman mythology, whose name comes from the Proto-Indo-European vocative form *dyeu ph2ter, meaning "god-father." The astronomical symbol for the planet, , is a stylized representation of the god's lightning bolt. The original Greek deity, Zeus, adopted by Romans, supplies the root zeno-, used to form some Jupiter-related words, such as zenographic.

Jovian is the adjectival form of Jupiter. The older adjectival form jovial, employed by astrologers in the Middle Ages, has come to mean "happy" or "merry," moods ascribed to Jupiter's astrological influence.

The Chinese, Korean, Japanese, and Vietnamese referred to the planet as the wood star, 木星, based on the Chinese Five Elements. The Greeks called it Φαέθων, Phaethon, "blazing". In Vedic Astrology, Hindu astrologers named the planet after Brihaspati, the religious teacher of the gods, and often called it "Guru," which literally means the "Heavy One". In the English language Thursday is rendered as Thor's day, with Thor being associated with the planet Jupiter in Germanic mythology.

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Moons of Jupiter

Jupiter and its four largest moons

Jupiter has 63 confirmed moons, giving it the largest retinue of moons with "reasonably secure" orbits of any planet in the Solar System. The most massive of them, the four Galilean moons, were discovered in 1610 by Galileo Galilei and were the first objects found to orbit a body that was neither Earth nor the Sun. From the end of the 19th century, dozens of much smaller Jovian moons have been discovered and have received the names of lovers, conquests, or daughters of the Roman god Jupiter, or his Greek equivalent, Zeus.

Eight of Jupiter's moons are regular satellites, with prograde and nearly circular orbits that are not greatly inclined with respect to Jupiter's equatorial plane. The Galilean satellites are spheroidal in shape, and so would be considered dwarf planets if they were in direct orbit about the Sun. The other four regular satellites are much smaller and closer to Jupiter; these serve as sources of the dust that makes up Jupiter's rings.

Jupiter's other 54 or 55 moons are tiny irregular satellites, whose prograde and retrograde orbits are much farther from Jupiter and have high inclinations and eccentricities. These moons were likely captured by Jupiter from solar orbits. There are 13 recently-discovered irregular satellites that have not yet been named, plus a 14th whose orbit has not yet been established.

The moons' physical and orbital characteristics vary widely. The four Galileans are all over 3000 km in diameter; the largest Galilean, Ganymede, is the largest object in the Solar System outside the Sun and the eight planets. All other Jovian moons are less than 250 km in diameter, with most barely exceeding five km. Even Europa, the smallest of the Galileans, is five thousand times more massive than all the non-Galilean moons combined. Orbital shapes range from nearly perfectly circular to highly eccentric and inclined, and many revolve in the direction opposite to Jupiter's spin (retrograde motion). Orbital periods range from seven hours (taking less time than Jupiter does to spin around its axis), to some 3000 times more (almost three Earth years).

Jupiter's regular satellites are believed to have formed from a circumplanetary disk, a ring of accreting gas and solid debris analogous to a protoplanetary disk. They may be the remnants of a score of Galilean-mass satellites that formed early in Jupiter's history.

Simulations suggest that, while the disk had a relatively low mass at any given moment, over time a substantial fraction (several tens of a percent) of the mass of Jupiter captured from the Solar nebula was processed through it. However, the disk mass of only 2% that of Jupiter is required to explain the existing satellites. Thus there may have been several generations of Galilean-mass satellites in Jupiter's early history. Each generation of moons would have spiraled into Jupiter, due to drag from the disk, with new moons then forming from the new debris captured from the Solar nebula. By the time the present (possibly fifth) generation formed, the disk had thinned out to the point that it no longer greatly interfered with the moons' orbits. The current Galilean moons were still affected, falling into and being partially protected by an orbital resonance which still exists for Io, Europa, and Ganymede. Ganymede's larger mass means that it would have migrated inward at a faster rate than Europa or Io.

The outer, irregular moons are thought to have originated from passing asteroids while the protolunar disk was still massive enough to absorb much of their momentum and thus capture them into orbit. Many broke up by the stresses of capture, or afterward by collisions with other small bodies, producing the families we see today.

The first claimed observation of one of Jupiter's moons is that of the Chinese astronomer Gan De around 364 BC. However, the first certain observations of Jupiter's satellites were those of Galileo Galilei in 1609. By March 1610, he had sighted the four massive Galilean moons with his 30x magnification telescope: Ganymede, Callisto, Io, and Europa. No additional satellites were discovered until E.E. Barnard observed Amalthea in 1892. With the aid of telescopic photography, further discoveries followed quickly over the course of the twentieth century. Himalia was discovered in 1904, Elara in 1905, Pasiphaë in 1908, Sinope in 1914, Lysithea and Carme in 1938, Ananke in 1951, and Leda in 1974. By the time Voyager space probes reached Jupiter around 1979, 13 moons had been discovered, while Themisto was observed in 1975, but due to insufficient initial observation data, it was lost until 2000. The Voyager missions discovered an additional three inner moons in 1979: Metis, Adrastea, and Thebe.

For two decades no additional moons were discovered; but between October 1999 and February 2003, researchers using sensitive ground-based detectors found another 32 moons, most of which were discovered by a team lead by Scott S. Sheppard and David C. Jewitt. These are tiny moons, in long, eccentric, generally retrograde orbits, and average of 3 km (1.9 mi) in diameter, with the largest being just 9 km (5.6 mi) across. All of these moons are thought to be captured asteroidal or perhaps cometary bodies, possibly fragmented into several pieces, but very little is actually known about them. A number of 14 additional moons were discovered since then, but not yet confirmed, bringing the total number of observed moons of Jupiter at 63. As of 2008, this is the most of any planet in the Solar System, but additional undiscovered, tiny moons may exist.

The Galilean moons of Jupiter (Io, Europa, Ganymede and Callisto) were named by Simon Marius soon after their discovery in 1610. However, until the 20th century these fell out of favor, and instead they were referred to in the astronomical literature simply as "Jupiter I", "Jupiter II", etc., or as "the first satellite of Jupiter", "Jupiter's second satellite", an so on. The names Io, Europa, Ganymede, and Callisto became popular in the 20th century, while the rest of the moons, usually numbered in Roman numerals V (5) through XII (12), remained unnamed. By a popular though unofficial convention, Jupiter V, discovered in 1892, was given the name Amalthea, first used by the French astronomer Camille Flammarion.

The other moons, in the majority of astronomical literature, were simply labeled by their Roman numeral (i.e. Jupiter IX) until the 1970s. In 1975, the International Astronomical Union's (IAU) "Task Group for Outer Solar System Nomenclature" granted names to satellites V–XIII, and provided for a formal naming process for future satellites to be discovered. The practice was to name that newly discovered moons of Jupiter after lovers and favorites of the god Jupiter (Zeus), and since 2004, after their descendants also. All of Jupiter's satellites from XXXIV (Euporie) are named after daughters of Jupiter or Zeus.

Some asteroids share the same names as moons of Jupiter: 9 Metis, 38 Leda, 52 Europa, 85 Io, 113 Amalthea, 239 Adrastea. Two more asteroids previously shared the names of Jovian moons until spelling differences were made permanent by the IAU: Ganymede and asteroid 1036 Ganymed; and Callisto and asteroid 204 Kallisto.

The moons of Jupiter are listed below by orbital period. Moons massive enough for their surfaces to have collapsed into a spheroid are highlighted in bold. These are the four Galilean moons, which are comparable in size to Earth's Moon. The four inner moons are much smaller. The irregular captured moons are shaded light gray when prograde and dark gray when retrograde.

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Rings of Jupiter

Formation of Jupiter's rings

The planet Jupiter has a system of rings, known as the rings of Jupiter or the Jovian ring system. It was the third ring system to be discovered in the Solar System, after those of Saturn and Uranus. It was first observed in 1979 by the Voyager 1 space probe and thoroughly investigated in the 1990s by the Galileo orbiter. It has also been observed by the Hubble Space Telescope and from Earth for the past 25 years. Ground-based observations of the rings require the largest available telescopes.

The Jovian ring system is faint and consists mainly of dust. It is comprised of four main components: a thick inner torus of particles known as the "halo ring"; a relatively bright, exceptionally thin "main ring"; and two wide, thick and faint outer "gossamer rings", named for the moons of whose material they are composed: Amalthea and Thebe.

The main and halo rings consist of dust ejected from the moons Metis, Adrastea and other unobserved parent bodies as the result of high-velocity impacts. High-resolution images obtained in February and March 2007 by the New Horizons spacecraft revealed a rich fine structure in the main ring.

In visible and near-infrared light, the rings have a reddish color, except the halo ring, which is neutral or blue in color. The size of the dust in the rings varies, but the cross-sectional area is greatest for nonspherical particles of radius about 15 μm in all rings except the halo. The halo ring is probably dominated by submicrometre dust. The total mass of the ring system (including unresolved parent bodies) is poorly known, but is probably in the range of 1011 to 1016 kg. The age of the ring system is not known, but it may have existed since the formation of Jupiter.

The rings of Jupiter was the third ring system to be discovered in the Solar System, after those of Saturn and Uranus. It was first observed in 1979 by the Voyager 1 space probe. It comprises four main components: a thick inner torus of particles known as the "halo ring"; a relatively bright, exceptionally thin "main ring"; and two wide, thick and faint outer "gossamer rings", named for the moons of whose material they are composed: Amalthea and Thebe. The principal attributes of the known Jovian Rings are listed in the table.

The narrow and relatively thin main ring is the brightest part of Jupiter's ring system. Its outer edge is located at a radius of about 129 000 km (1.806 RJ; RJ = equatorial radius of Jupiter or 71 398 km) and coincides with the orbit of Jupiter's smallest inner satellite, Adrastea. Its inner edge is not marked by any satellite and is located at about 122 500 km (1.72 RJ).

Thus the width of the main ring is around 6 500 km. The appearance of the main ring depends on the viewing geometry. In forward-scattered light the brightness of the main ring begins to decrease steeply at 128 600 km (just inward of Adrastea's orbit) and reaches the background level at 129 300 km—just outward of Adrastean orbit. Therefore Adrastea at 129 000 km clearly shepherds the ring. The brightness continues to increase in the direction of Jupiter and has a maximum near the ring’s center at 126 000 km, although there is a pronounced gap (notch) near the orbit of Metis at 128 000 km. The inner boundary of the main ring, in contrast, appears to fade off slowly from 124 000 to 120 000 km, merging into the halo ring. In forward-scattered light all Jovian rings are especially bright.

In back-scattered light the situation is different. The outer boundary of the main ring, located at 129 100 km, or slightly beyond the orbit of Adrastea, is actually very steep. The orbit of the moon is marked by a gap in the ring so there is a thin ringlet just outside its orbit. There is another ringlet just inside Adrastean orbit followed by a gap of unknown origin located at about 128 500 km. The third ringlet is found inward of the central gap outside the orbit of Metis. The ring’s brightness drops sharply just outward of the orbit of Metis thus forming the Metis notch. Inward of Metis's orbit the brightness of the ring rises much less than in forward-scattered light. So in the back-scattered geometry the main ring appears to consist of two different parts: a narrow outer part extending from 128 000 to 129 000 km, which itself includes three narrow ringlets separated by notches, and a fainter inner part from 122 500 to 128 000 km, which lacks any visible structure like in the forward-scattering geometry. The Metis notch serves as their boundary. The fine structure of the main ring was discovered in data from the Galileo orbiter and is clearly visible in back-scattered images obtained from New Horizons in February–March 2007. However observations by Hubble Space Telescope (HST), Keck and the Cassini spacecraft failed to detect it, probably due to insufficient spatial resolution.

Observed in back-scattered light the main ring appears to be razor thin, extending in the vertical direction no more than 30 km. In the side scatter geometry the ring thickness is 80–160 km, increasing somewhat in the direction of Jupiter. The ring appears to be much thicker in the forward-scattered light—about 300 km. One of the discoveries of the Galileo orbiter was the bloom of the main ring—a faint, relatively thick (about 600 km) cloud of material which surrounds its inner part. The bloom grows in thickness towards the inner boundary of the main ring, where it transitions into the halo.

Detailed analysis of the Galileo images revealed longitudinal variations of the main ring’s brightness unconnected with the viewing geometry. The Galileo images also showed some patchiness in the ring on the scales 500–1000 km.

In February–March 2007 New Horizons spacecraft conducted a deep search for new small moons inside the main ring. While no satellites larger than 0.5 km was found, the cameras of the spacecraft detected seven small clumps of ring particles. They orbit just inside the orbit of Adrastea inside a dense ringlet. The conclusion, that they are clumps and not small moons, is based on their azimuthally extended appearance. They subtend 0.1–0.3° along the ring, which correspond to 1000–3000 km. The clumps are divided into two groups of five and two members, respectively. The nature of the clumps is not clear, but their orbits are close to 115:116 and 114:115 resonances with Metis. So they can be wave like structures excited by this interaction.

Spectra of the main ring obtained by the HST, Keck, Galileo and Cassini have shown that particles forming it are red, i.e. their albedo is higher at longer wavelengths. The existing spectra span the range 0.5–2.5 μm. No spectral features have been found so far which can be attributed to particular chemical compounds, although the Cassini observations yielded evidence for absorption bands near 0.8 μm and 2.2 μm. The spectra of the main ring are actually very similar to Adrastea and Amalthea.

The properties of the main ring can be explained by the hypothesis that it contains significant amounts of dust with 0.1–10 μm particle sizes. This explains the stronger forward-scattering of light as compared to back-scattering. However, larger bodies are required to explain the strong back-scattering and fine structure in the bright outer part of the main ring.

The power law mentioned above allows estimation of the optical depth of the main ring: for the large bodies and for the dust. This optical depth means that the total cross section of all particles inside the ring is about 5000 km². The particles in the main ring are expected to have aspherical shapes. The total mass of the dust is estimated to be 107−109 kg. The mass of large bodies, excluding Metis and Adrastea, is 1011−1016 kg. It depends on their maximum size— the upper value corresponds to about 1 km maximum diameter. These masses can be compared with masses of Adrastea, which is about 2 × 1015 kg, Amalthea— about 2 × 1018 kg and Earth's Moon—7.4 × 1022 kg.

The presence of two populations of particles in the main ring explains why its appearance depends on the viewing geometry. The dust scatters light preferably in the forward direction and forms a relatively thick homogenous ring bounded by the orbit of Adrastea. In contrast, large particles, which scatter in the back direction, are confined inside the region between the orbits of Metis and Adrastea in a number of ringlets.

The dust is constantly being removed from the main ring by a combination of Poynting-Robertson drag and electromagnetic forces from the Jovian magnetosphere. Volatile materials, for example ices, evaporate quickly. The lifetime of dust particles in the ring is from 100 to 1000 years, so the dust must be continuously replenished in the collisions between large bodies with sizes from 1 cm to 0.5 km and between the same large bodies and high velocity particles coming from outside the Jovian system. This parent body population is confined to the narrow—about 1000 km—and bright outer part of the main ring, and includes Metis and Adrastea. The largest parent bodies must be less than 0.5 km in size. The upper limit on their size was obtained by New Horizons spacecraft. The previous upper limit, obtained from HST and Cassini observations, was near 4 km. The dust produced in collisions retains approximately the same orbital elements as the parent bodies and slowly spirals in the direction of Jupiter forming the faint (in back-scattered light) innermost part of the main ring and halo ring. The age of the main ring is currently unknown, but it may be the last remnant of a past population of small bodies near Jupiter.

The halo ring is the innermost and thickest Jovian ring. Its outer edge coincides with the inner boundary of the main ring approximately at the radius 122 500 km (1.72 RJ). From this radius the ring becomes rapidly thicker towards Jupiter. The true vertical extent of the halo is not known but the presence of its material was detected as high as 10 000 km over the ring plane. The inner boundary of the halo is relatively sharp and located at the radius 100 000 km (1.4 RJ), but some material is present further inward to approximately 92 000 km. Thus the width of the halo ring is about 30 000 km. Its shape resembles a thick torus without clear internal structure. In contrast to the main ring, the halo's appearance depends only slightly on the viewing geometry.

The halo ring appears brightest in forward-scattered light, in which it was extensively imaged by Galileo. While its surface brightness is much less than that of the main ring, its vertically (perpendicular to the ring plane) integrated photon flux is comparable due to its much larger thickness. Despite a claimed vertical extent of more than 20 000 km, the halo’s brightness is strongly concentrated towards the ring plane and follows a power law of the form z−0.6 to z−1.5, where z is altitude over the ring plane. The halo’s appearance in the back-scattered light, as observed by Keck and HST, is basically the same. However its total photon flux is several times lower than that of the main ring and is more strongly concentrated near the ring plane than in the forward-scattered light.

The spectral properties of the halo ring are different from the main ring. The flux distribution in the range 0.5–2.5 μm is flatter than in the main ring; the halo is not red and may even be blue.

The optical properties of the halo ring can be explained by the hypothesis that it comprises only dust with particle sizes less than 15 μm. Parts of the halo located far from the ring plane may consist of submicrometre dust. This dusty composition explains the much stronger forward-scattering, bluer colors and lack of visible structure in the halo. The dust probably originates in the main ring, a claim supported by the fact that the halo’s optical depth is comparable with that of the dust in the main ring. The large thickness of the halo can be attributed to the excitation of orbital inclinations and eccentricities of dust particles by the electromagnetic forces in the Jovian magnetosphere. The outer boundary of the halo ring coincides with location of a strong 3:2 Lorentz resonance. As Poynting-Robertson drag causes particles to slowly drift towards Jupiter, their orbital inclinations are excited while passing through it. The bloom of the main ring may be a beginning of the halo. The halo ring’s inner boundary is not far from the strongest 2:1 Lorentz resonance. In this resonance the excitation is probably very significant, forcing particles to plunge into the Jovian atmosphere thus defining a sharp inner boundary. Being derived from the main ring, the halo has the same age.

The Amalthea gossamer ring is a very faint structure with a rectangular cross section, stretching from the orbit of Amalthea at 182 000 km (2.54 RJ) to about 129 000 km (1.80 RJ). Its inner boundary is not clearly defined because of the presence of the much brighter main ring and halo. The thickness of the ring is approximately 2300 km near the orbit of Amalthea and slightly decreases in the direction of Jupiter. The Amalthea gossamer ring is actually the brightest near its top and bottom edges and becomes gradually brighter towards Jupiter; its top edge is brighter than the bottom edge. The outer boundary of the ring is relatively steep, especially at the top edge. There is a sharp drop in the brightness just inward of the orbit of Amalthea with an additional shelf-like structure. In forward-scattered light the ring appears to be about 30 times fainter than the main ring. In back-scattered light it has been detected only by the Keck telescope and the ACS (Advanced Camera for Surveys) on HST. Back-scattering images show additional structure in the ring: a peak in the brightness just inside the orbit of Amalthea. In 2002–2003 Galileo spacecraft had two passes through the gossamer rings. Its dust counter detected dust particles in the size range 0.2–5 μm and confirmed the results obtained form imaging.

The detection of the Amalthea gossamer ring from the ground, in Galileo images and the direct dust measurements have allowed the determination of the particle size distribution, which appears to follow the same power law as the dust in the main ring with q=2 ± 0.5. The optical depth of this ring is about 10−7, which is an order of magnitude lower than that of the main ring, but the total mass of the dust—107–109 kg—is comparable.

The Thebe gossamer ring is the faintest Jovian ring. It appears as a very faint structure with a rectangular cross section, stretching from the orbit of Thebe at 226 000 km (3.11 RJ) to about 129 000 km (1.80 RJ;). Its inner boundary is not clearly defined because of the presence of the much brighter main ring and halo. The thickness of the ring is approximately 8400 km near the orbit of Thebe and slightly decreases in the direction of the planet. The Thebe gossamer ring is brightest near its top and bottom edges and gradually becomes brighter towards Jupiter—much like the Amalthea ring. The outer boundary of the ring is not especially steep, stretching over 15 000 km. There is a barely visible continuation of the ring beyond the orbit of Thebe, extending up to 280 000 km (3.75 RJ) and called Thebe Extension. In forward-scattered light the ring appears to be about 3 times fainter than the Amalthea gossamer ring. In back-scattered light it has been detected only by the Keck telescope. Back-scattering images show a peak of brightness just inside the orbit of Thebe. In 2002–2003 the dust counter of the Galileo spacecraft detected dust particles in the size range 0.2–5 μm—similar to those in the Amalthea ring—and confirmed the results obtained form imaging.

The optical depth of the Thebe gossamer ring is about 3 × 10−8, which is three times lower than the Amalthea gossamer ring, but the total mass of the dust is the same—about 107–9 kg. However the particle size distribution of the dust is somewhat shallower than in the Amalthea ring. It follows a power law with q < 2. In the Thebe extension the parameter q may be even smaller.

The dust in the gossamer rings originates in essentially the same way as that in the main ring and halo. Its sources are the inner Jovian moons Amalthea and Thebe respectively. High velocity impacts by projectiles coming from outside the Jovian system eject dust particles from their surfaces. These particles initially retain the same orbits as their moons but then gradually spiral inward by Poynting-Robertson drag. The thickness of the gossamer rings is determined by vertical excursions of the moons due to their nonzero orbital inclinations. This hypothesis naturally explains almost all observable properties of the rings: rectangular cross-section, decrease of thickness in the direction of Jupiter and brightening of the top and bottom edges of the rings.

However some properties have so far gone unexplained, like the Thebe Extension, which may be due to unseen bodies outside Thebe's orbit, and structures visible in the back-scattered light. One possible explanation of the Thebe extension is influence of the electromagnetic forces from the Jovian magnetosphere. When the dust enters the shadow behind Jupiter, it loses its electrical charge fairly quickly. Since the small dust particles partially corotate with the planet, they will move outward during the shadow pass creating an outward extension of the Thebe gossamer ring. The same forces can explain a dip in the particle distribution and ring's brightness, which occurs between the orbits of Amalthea and Thebe.

The analysis of gossamer ring's images revealed that a peak in the brightness just inside the Amalthea's orbit may be due to the dust particles trapped at the leading (L4) and trailing (L5) Lagrange points of Amalthea. The higher brightness of the observed top edge of the Amalthea gossamer ring may also be caused by the this trapped dust. The particles may be present at the leading and trailing Lagrange points of Thebe as well. This discovery implies that there are two particle populations in the gossamer rings: one slowly drifts in the direction of Jupiter as described above, while another remains near a source moon trapped in 1:1 resonance with it.

The existence of the Jovian rings was inferred from observations of the planetary radiation belts by Pioneer 11 spacecraft in 1975. In 1979 the Voyager 1 spacecraft obtained a single overexposed image of the ring system. More extensive imaging was conducted by Voyager 2 in the same year, which allowed rough determination of the ring’s structure. The superior quality of the images obtained by the Galileo orbiter between 1995 and 2003 greatly extended the existing knowledge about the Jovian rings. Ground-based observation of the rings by the Keck telescope in 1997 and 2002 and the HST in 1999 revealed the rich structure visible in back-scattered light. Images transmitted by the New Horizons spacecraft in February–March 2007 allowed observation of the fine structure in the main ring for the first time. In 2000, the Cassini spacecraft en route to Saturn conducted extensive observations of the Jovian ring system. Future missions to the Jovian system will provide additional information about the rings.

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Sailor Jupiter

In her first Senshi form, Sailor Jupiter demonstrates her power over lightning with "Sparkling Wide Pressure"

Sailor Jupiter (セーラージュピター ,Sērā Jupitā?) is one of the central characters in the Sailor Moon metaseries. Her real name is Makoto Kino (木野 まこと ,Kino Makoto?, or Lita Kino in the English versions), a strong schoolgirl who can transform into one of the series' specialized heroines, the Sailor Senshi.

Sailor Jupiter is the third member of the Sailor Team to be discovered by Sailor Moon, and serves as the "muscles" of the group. In addition to being physically tough, she is able to manipulate electricity and uses some plant-based powers. Her friends rarely use her full given name, normally shortening it to Mako-chan.

Aside from the main body of the Sailor Moon series, Makoto features in her own manga short story, Mako's Depression. A number of image songs featuring her character have been released as well, including the contents of three different CD singles.

Makoto's strong, independent personality is hinted at in her most striking physical feature—her unusual height. She is stated at her first appearance in the series to be very tall, and considerable notice is taken in the Japanese versions, although this trait is downplayed in English translations (as her relative height is not all that uncommon in the West). She is also physically very strong, and in fact was rumored to have been kicked out of her previous school for fighting. She is introduced to the series after transferring to Azabu Jūban Junior High, where Usagi and Ami are students, and where she stands out all the more because her school uniform is different from everyone else's; unable to find anything in her size, the school's administration tells her to wear her old one. It has a long skirt, which when coupled with her curly hair, was a common visual cue for a tough or delinquent girl at the time the series was created. However, unlike these delinquent girls, her curly hair is natural. Despite her tough appearance, she is very gentle. She always wears pink rose earrings and a sea-green hair tie, even when transformed.

One of the most consistent characters across the many versions of the series, Makoto is always depicted as simultaneously the most masculine and most feminine of the younger Senshi. She is tall, strong, physical, and practices martial arts and other sports, but at the same time is rather busty and an excellent cook and house-cleaner. Her most closely-held dream is to marry young and own a cake and flower shop, and she loves romance novels. Her favorite class is home economics and her least favorite is physics. After entering high school, she also joins the cooking and gardening clubs. She likes all foods, but especially cherry pie, and meatloaf, and her favorite colors are green and pink. She loves horses and hates cheaters.

Her domestic talents are explained as a deliberate effort to overcome her tomboyishness. In the anime, she is given the additional character trait of being highly prone to random crushes. In the live-action series she enjoys shopping, but eschews "girly" things; she cooks, but also physically overpowers bullies; she reorganizes her home, but does so with a sledgehammer. She insists that she is not the least bit feminine, and seems surprised and touched when someone tells her she is.

This dual nature comes from a need to be self-sufficient: in the manga continuity her parents died in a plane crash when she was very young and she has since then looked after herself. She is self-sufficient almost to a fault, and becomes extremely nervous anytime an airplane passes overhead. In the anime, Makoto lives alone, but it is never explicitly stated that her parents are dead — in the English adaptation, she says she cannot take care of a cat because her mother is allergic — and later in the series she is shown boarding an airplane without any mention of fear. In Pretty Guardian Sailor Moon, Makoto's parents' death is told in a flashback in Act 6, but how they died is not mentioned.

Makoto has at least one former boyfriend; the importance of this subplot, as well as her level of obsession with cute men, varies wildly between adaptations. Fans of the anime typically have a perception of Makoto as extremely boy-crazy; a recurring gag is her obsession with people who look like the older classmate (sempai) who once broke her heart (unnamed except in the English dub, where he is called Freddy). In the manga, her "sempai" is mentioned only once or twice, and in the live-action drama is an integral part of why Makoto feels she needs to be alone. In each version, there are mentions of other men who were very briefly a part of her life. Makoto is generally attracted to Motoki Furuhata, especially in the anime, but only in the live-action show do they become close. By the end of the direct-to-DVD Special Act, they are engaged to be married.

One quirk of Makoto's was made famous among English-speaking fans due to the translation of a particular anime scene. The girls are arguing over which of them should play the part of Snow White in a play. In Japanese, Makoto insists that she would be best for the role because she has the largest breasts. In the English adaptation, she still points at her chest, but states instead that she has the most "talent." As a reference to this, anime fans occasionally use the term "talented" as a euphemism for "busty.

As a character with different incarnations, special powers, transformations and a long lifetime virtually spanned between the Silver Millennium era and the 30th century, Makoto gains multiple aspects and aliases as the series progresses.

Makoto's Senshi identity is Sailor Jupiter. She wears a uniform colored in green and pink, with rose-shaped earrings and green, laced-up boots. In the manga and live-action series she has a belt carrying a small ball of potpourri. She is given specific titles throughout the various series, including Soldier of Protection, Herculean Jupiter, Soldier of Thunder and Courage,, and Soldier of Caring. Her personality is no different from when she is a civilian, although certain powers are unavailable to her in that form.

In Japanese, the name for the planet Jupiter is Mokusei (木星 ?), the first kanji meaning 'tree' and the second indicating a celestial object. Although the Roman planet-name is used, Sailor Jupiter's dominant element is wood due to this aspect of Japanese mythology. Unusually, most of her attacks are based in her secondary power, which is lightning in reference to the Roman god Jupiter. She is by far the physically-strongest of the Guardian Senshi, able to lift a full-grown man above her head or to stop a stone pillar from falling. In the early manga, she always has a short antenna coming from her tiara, which serves as a lightning rod; eventually this takes on the same role as in the anime, and extends upward only when she summons lightning. It does not appear in the live-action series.

As she grows stronger, Sailor Jupiter gains additional powers, and at key points her uniform changes to reflect this. The first change takes place in Act 37 of the manga, when she obtains the Jupiter Crystal and her outfit becomes similar to that of Super Sailor Moon. She is not given a new title. A similar event is divided between Episodes 143 and 154 of the anime, and she is given the name Super Sailor Jupiter. A third, manga-only form appears in Act 42, unnamed but analogous to Eternal Sailor Moon (sans wings).

In the Silver Millennium, Sailor Jupiter was also the Princess of her home planet. She was among those given the duty of protecting Princess Serenity of the Moon Kingdom. As Princess Jupiter, she dwelt in Io Castle and wore a green gown — she appears in this form in the original manga, as well as in supplementary art. Naoko Takeuchi once drew her in the arms of Nephrite, but no further romantic link between them was established in the manga or anime, In the stage musicals, it is stated that the two of them were in love at the time of the Moon Kingdom, and this is also implied in the Another Story video game.

Makoto is not shown using any special powers in her civilian form, although she is unusually strong for a teenage girl. She must first transform into a Sailor Senshi by raising a special device (pen, bracelet, wand, or crystal) into the air and shouting a special phrase, originally "Jupiter Power, Make-up!" As she becomes more powerful and obtains new transformation devices, this phrase changes to evoke Jupiter Star, Planet, or Crystal Power. In the anime, Sailor Jupiter's transformation sequence evolves slightly over time, whether to update the background images or to accommodate changes to her uniform or a new transformation device, but the animation remains essentially the same. They all involve electric charges forming an atom path which encircles her body.

In the manga, Sailor Jupiter's first named attack is Flower Hurricane, which is immediately followed by calling down lightning. Emphasis is quickly placed upon her electric-based powers, and these are the norm in all versions of the series. Her primary attack for the first story arc and most of the second is Supreme Thunder, for which she calls down lightning from the sky with a tiny lightning rod that extends from the stone on her tiara (or, in the live-action series, with her leg). Although she channels this power, she is not immune to its effects, and can use her body to focus the electricity in a suicide move. It is upgraded twice for one-off attacks in the anime series: once to Supreme Thunder Dragon, and much later to Super Supreme Thunder.

In the second story arc Sailor Jupiter gains Sparkling Wide Pressure, which, aside from a manga-only power called Coconut Cyclone, remains her primary attack for the rest of the second story arc, all of the third, and much of the fourth. When she takes on her second Senshi form (Super Sailor Jupiter in the anime), she acquires a special item, a wreath of oak leaves, which is described in the manga as "the emblem of thunder and lightning." It appears in her hair and enables her to use Jupiter Oak Evolution.

Sailor Jupiter's earrings, large pink roses, are occasionally significant. She wears them in both her Senshi and civilian forms, and can use them as a projectile weapon if she needs to. When they first meet in the manga, Usagi thinks the roses have a nice fragrance, and late in the anime the sight of them brings her back from temporary memory loss because it reminds her of Tuxedo Mask. Much more important, in the manga, are the Jupiter Crystal and Leaves of Oak. The former is Makoto's Sailor Crystal and the source of all of her power, which becomes especially important in the fifth story arc. In the live-action series, she frequently uses unnamed electric attacks, and is given a tambourine-like weapon (the Sailor Star Tambo) by Artemis. In the final episode, the Tambo transforms into a lance.

Makoto is present in the original proposal for a hypothetical Codename: Sailor V anime, but her name is given as Mamoru Chino. Creator Naoko Takeuchi confirms that this character eventually became Makoto, and writes that the original concept was quite different—Makoto was not only tough, but in fact was meant to be the leader of a female gang as well as a smoker. A very similar name was later given to the series' male protagonist, Mamoru Chiba.

Certain background details of Makoto's character were chosen symbolically—for instance, her Western astrological sign is given as Sagittarius, which in astrology corresponds to the planet Jupiter. In reference to a popular Japanese belief, her blood type is given as O, supposedly indicating friendliness and vanity.

In an early DiC promotional tape that advertised Sailor Moon to television stations, Makoto was called Sara. Another preliminary name, appearing on Kodansha's English website in an advertisement for the series, was Maggie.

The official Sailor Moon character popularity polls listed Makoto Kino and Sailor Jupiter as separate entities. In 1992, readers ranked them at eleventh and fifth respectively, out of thirty eight choices. One year later, now with fifty choices, Jupiter dropped to the eleventh most popular while Makoto was twelfth most popular. In 1994, with fifty one choices, Sailor Jupiter was the seventeenth most popular character and Makoto was eighteenth. In early 1996, with fifty one choices, Makoto was the twenty third most popular character and Jupiter was the twenty seventh.

A five-book series was published, one book on each of the Guardian Senshi and Sailor Moon. Makoto's was released in 1996. This book was later translated into English by Mixx.

In the original anime production of Sailor Moon, Makoto is voiced by Emi Shinohara. For the English-language dub, the voice of "Lita" is provided by Susan Roman. She is the only significant human character in the English-language dub to be played by the same voice actor through the entire series run. Patricia Tollett provides English vocals for songs sung by Lita in the English dub.

In the musical version, Makoto has been portrayed by 12 actresses: Noriko Kamiyama, Marie Sada, Takako Inayoshi, Emika Satoh, Akari Tonegawa, Chiho Oyama, Emi Kuriyama, Yuriko Hayashi, Ayano Sugimoto, Kaori Sakata, Karina Okada and Mai Watanabe.

In Pretty Guardian Sailor Moon, Makoto is played by Myū Azama. Also, child actress Misho Narumi portrays Makoto in flashbacks, dream sequences, and childhood photos.

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Source : Wikipedia