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Jupiter is the fifth planet from the Sun and by far the largest and most massive. Jupiter is a gas giant and has no physical surface. It is one of the outer planets and is described as the 'lead' of the giants. Jupiter is home to its windy and marbled surface, with storms, like the Great Red Spot, apparent on the surface.

Its marbled appearance is caused by a projection-like effect under the surface where ionization happens. This effects happens to the other Jovian planets, but they are less intense.[1]

Jupiter is also commonly referred to as a failed star, due to it having the components of a star, but not enough mass. It would take around 12J to start deuterium fusion and become a brown dwarf (Y type)[2] and a further 80-100J for its core to sustain thermonuclear fusion.[3]

Jupiter has a total of 97 moons, the second most amount in the solar system behind Saturn, most of them being retrograde irregulars. Aside from the insignificant ones, there are 4 major moons, or so called 'Galilean Moons:' Io, Europa, Ganymede and Callisto. These moons are all larger then Pluto with Ganymede being larger then the planet Mercury. These moons have their own interesting features on them, and also have to do with atmospheric tides on Jupiter as well.

Jupiter and Saturn are commonly referred to as Jovian Giants, joined with the Ice Giants to form the outer planets. Jupiter, like other outer planets, has rings, however they are very tenuous and hard to spot with an average telescope.[1]

Physical Characteristics

Being by far the largest out of the planets, Jupiter has a lot of interesting features and physical characteristics both above and below the surface. It's mass nearly triples that of Saturn's and it has the fastest rotational speed out of any of the planets, causing its oblateness.

Atmosphere

Main page: Atmosphere of Jupiter

Atmospheric-composition-of-Jupiter

A diagram of the lower section of Jupiter's atmosphere.

The atmosphere of Jupiter is adorned with a variety of vibrant stripes and spots. It is believed that the gas planet has three distinct cloud layers in its "skies," which together span 70 kilometers. The first two of these layers are composed of ammonia structures, whether that is solo-stalactite formations or general vapour. The last of these layers is composed of water vapour.[1]

The planet's atmosphere is primarily composed of molecular hydrogen (H2) and helium (He). These elements and structures can be ionized and set into multiple different bands apparent on its surface. The layers of the atmosphere can be distinguished by temperature changes of these molecules and compounds.[4]

The highest of these layers is the exosphere or the 'gateway to outer space.' The exosphere is where these molecules can escape, as there is no longer any boundaries keeping it in. The thermosphere is the thermatic part of the atmosphere, heated by the magnetosphere, driving heat and what not and causing this ionization effect. This heat also causes light and its own glow, heating its internals and breathing life into polar aurorae. The stratosphere is where its convection is, and also where compounds clump due to the rise of heat from the troposphere. These compounds can range from ammonia, water ice and ammonia ice, as foretold by the paragraph above. The troposphere is the lowest of these layers, and not much is known about it, however it may have a larger density than the other atmospheric layers, similar to Earth's troposphere, with the only difference being the abundance of gaseous hydrogen and helium.[5]

Jupiter also has bands on the surface, such as temperate, tropical or polar bands. These bands are mainly stable due to gravity from the thermosphere and heat from the ionization of molecular structures, forming molecular coded bands. Io, the innermost of the major moons, also affects Jupiter's magnetosphere due to its radiation.[6]

Vortices and Cyclones

The Great Red Spot as seen by Juno

The Great Red Spot as captured by Juno.

There are many cyclonic systems on Jupiter, but only 3 of them have got official names. Depending on their atmospheric pressure and using the Coriolis effect, we can determine what type of cyclone they are. Most Jovian cyclones are white and generally have no features. They are also typically round.

The Great Red Spot is the largest cyclone on Jupiter. It is an anticyclone roughly 2 times the diameter of Earth and is primarily red, consisting of hydrogen, helium and ammonia hydrosulfide ice. This cyclone has been lasting for well over 200 years. Although it is not the largest cyclone by technicality by cyclone classifications,[7] it is the largest known anti-cyclone, nearly doubling second place, Neptune's Great Dark Spot.[8]

Interior

Jupiter Diagram

A diagram of Jupiter's interiors.

The internals of Jupiter are vastly unknown, however we have been getting some data on what could possibly reside in its core. The mantle is heavily debated and whether it is ~70% of the layer ratio is unknown. The mantle contains liquid molecular hydrogen and helium with the lower layers starting to form liquid metallic hydrogen. The core is ultimately dense, full to the brim with liquid metallic hydrogen and several transition metals and metalloids as well as several compounds.

The composition of the inner layers is still heavily debated due to the complexity of data available. These claims are likely, however there is a chance that the interior could be much different.[9]

Rings

Giove - Gli anelli nell'infrarosso

A set of infrared images showing the Main and Gossamer rings.

The rings of Jupiter are by far the thinnest planetary rings in the solar system with 3 main rings and 2 subdivisions. The structure of the rings are messy and appear to be distorted by that of the inner moons, mainly Amalthea and Thebe.[10]

The largest of these rings is the Main ring, which spans around 10 thousand kilometers. Further in, a very thick and sparse ring known as the Halo, which has a thickness of a tenfold compared to Main. The Halo ring is very faint, but using reflectivity, it is extremely bright, leaving scientists to believe the Halo ring is heavily packed. Adrastea and Metis both shepherd these rings respectively.

The outer ring, also known as the Gossamer ring, is a faint set of two subdivisions, one being manned by Amalthea, and the other by Thebe. The names of the rings are named respectively by their shepherd moons. Further out, there is a sparse ring reaching as far out as Io, known as the Thebe Extension.

Rings of Jupiter
Gossamer Rings AmaltheaThebe • Thebe Extension
"Classical" Rings Halo • Main

Formation

HL Tau protoplanetary disk

The protoplanetary disk of the star HL Tauri, showing us a peek of how planets, like Jupiter, formed.

The formation of Jupiter has many different theories on how Jupiter formed and how it preformed in its early life. All theories agree that Jupiter formed from a protoplanetary disk, and along with Saturn, were one of the first planets to form. The abundance of gas in the area allowed both of these planets to exponentially grow until their regions were cleared out, dominating the middle section of the solar system.[11]

Core accretion, although helpful for digressing how to terrestrials formed, overestimates the formations of the gas giants. Two ways of solving this is adding in a Fifth Giant, which is considered more due to its role later, or assuming that the densities and Hills sphere of the gas giants were significantly weaker back then due to competing planetesimals.

Due to the fast formations of the gas giants, they dominated the solar system heavily, especially with the formations of the rocky planets. The Jumping-Jupiter scenario explains why the rocky planets are how they are, with the scenario explaining how Jupiter and Saturn migrating into the inner solar system, before Jupiter was pulled out by Saturn back into an orbit further where they originally were. This may also describe why there are an abundance of Greek and Trojan asteroids as well as how Mars may have formed.[12]

Nice Model

The hypotheses of a fifth additional giant also helps to describe the Nice model and how it affected Jupiter. The resonances between all of the gas giants (3J:2S, 3S:2F, 2F:1N, 3N:2U) were all synchronized. Following the break of the resonance of Jupiter and Saturn, gravity permutations began pushing Neptune outwards, breaking Neptune's resonance with other gaseous planets. The eventful gravity pulls and tugs on this additional giant would lead to the migration of most outer planets and the imminent ejection of the fifth giant.[13]

Moons

Main page: Moons of Jupiter

Jupiter has a total of 97 moons[14], having the second most amount, but three times as less as Saturn. These moons are usually larger in comparison of other moons, especially the further inner moons, Galilean and some irregular outers. Like other lunar groups, they are distributed via their orbital inclines, distances and orbital motions. The largest groups are the Carme and Ananke groups, both retrograde respectively, both amassing roughly 20+ moons in the groups. The other groups, excluding Pasiphae, are comprised of a small amount of moons.

Amalthea PIA02532

Amalthea, the largest out of the inner moons.

Inner

The inner moons of Jupiter are 4 small and irregularly shaped moons, however, their orbits are regular and are very tidy compared to other groups. The innermost is Metis, however it is closely followed by Adrastea. It is possible that the two of them, both being the smaller out of the four, formed by the Halo ring, however, with their heavily damaged bodies with tons of craters, it is likely that they formed much earlier than the Halo's formation. The other two are Amalthea and Thebe, both being significantly larger than the other two. These two moons are much more elongated compared to the inner two.

Galilean

Io from Juno New

Io, the innermost of the Galilean moons.

The Galilean moons, or sometimes nicknamed Jupiter's Major Moons, are the four largest moons of Jupiter, each with their own unique characteristics. They range in size from just smaller than the Moon to the size of Mercury. These moons may have formed around the same time as when the Nice model occurred due to an influx of debris and materials.

The innermost is Io, considered to be the most volcanically active object in the solar system. Its surface is forever changing due to major plumes, and its colour is likely due to the amount of molten igneous on the surface. Io is the third largest out of the group, however, it is the most oblate out of the group due to pulls from Jupiter and polyrhythmic timed pulls by two other moons — Europa and Ganymede (2:1 E, 4:1 G), which in turn causes tidal heating.[15]

Europa is the smallest out of the group and is considered to be the polar opposite of Io, a cold, ice like world. Scarps and ice ridges cover the surface of the moon, with their being a subsurface ocean likely underneath the surface. Life could potentially live in this subsurface ocean, however there is major debates, especially with the interior of the moon.[16]

GanymedeTrueColour

Ganymede, the largest of the Galilean moons.

Ganymede is the largest out of the group, known for being larger than the planet of Mercury. The surface is young, however there is signs of ancient regions on the surface. Ganymede has the largest known magnetosphere out of any moon with it being the only one. Despite being so large in diameter, Ganymede has no atmosphere known. It's likely that the reason for this is due to Jupiter and its proximity to Jupiter, on the contrary to Titan, who is quite far away from Saturn.[17]

The last is Callisto, whom is the furthest out of the group, being the most cratered and the second largest, barely being smaller than Mercury. Although looking dead and dreary, it is possible that, like Europa, there is a subsurface ocean. There is not much interesting about Callisto, other than its major abundance of craters on the surface.[18]

Outer

Pasithee-discovery-CFHT-annotated

Pasiphae's discovery images.

The outer moons of Jupiter are an abundant amount of small, rocky and irregular moons. These moons orbit much further away than the major moons, with the closest, Themisto, being nearly a triple further than Callisto. After Themisto, Leda is nearly double that distance from Themisto. There are many groups, usually separated by their orbital motions and inclinations. The innermost of the groups, besides singular Themisto, is the Himalia group, a set of inner prograde moons. After that, the Carpo group, a set of two moons, slightly different from the Himalia group. After Himalia and its group, there is another singular moon, Valetudo.

Ananke is the next group in line and the first set of retrograde moons. It is by far the most diverse, as their orbital distances are heavily split apart. Although their distances, the group mainly does not mix with other groups in their orbital distances, however this isn't the case for the final two groups, Carme and Pasiphae, each with a large number of moons. The furthest moon from Jupiter currently known is Kore who belongs to the Pasiphae group.

Moons of Jupiter
Regular Inner Moons MetisAdrasteaAmaltheaThebe
Galilean (Major) Moons IoEuropaGanymedeCallisto
Irregular Prograde Themisto Themisto
Valetudo Valetudo
Himalia Group LedaErsaS/2018 J 2HimaliaPandiaLysitheaElaraS/2011 J 3Dia
Carpo Group S/2018 J 4Carpo
Irregular Retrograde Carme Group CarmeS/2022 J 1S/2022 J 2S/2016 J 3PasitheeS/2017 J 8S/2021 J 6S/2003 J 24ChaldeneS/2017 J 2IsonoeS/2021 J 4KallichoreErinomeKaleEireneAitneEukeladeArcheTaygeteS/2011 J 1HerseS/2003 J 19S/2010 J 1S/2003 J 9S/2017 J 5KalykeS/2018 J 3S/2021 J 5S/2003 J 10S/2017 J 11
Ananke Group EuporieS/2003 J 18EuphemeS/2021 J 3S/2016 J 1MnemeEuantheS/2003 J 16HarpalykeOrthosieS/2022 J 3HelikeS/2021 J 2PraxidikeS/2017 J 3S/2021 J 1S/2003 J 12S/2017 J 7ThelxinoeThyoneS/2003 J 2AnankeIocasteHermippeS/2017 J 9S/2017 J 10
Pasiphae Group PhilophrosyneEurydomeS/2011 J 2S/2003 J 4S/2016 J 4S/2017 J 6HegemonePasiphaeSpondeMegacliteCylleneSinopeS/2017 J 1AoedeAutonoeCallirrhoeS/2003 J 23Kore


Orbital Characteristics

Jupiter Orbit

A video of Jupiter's orbit. HTO's are marked in pink whilst Greek and Trojan camp asteroids are marked in green.

Orbit

The orbit of Jupiter is much less uncertain and non-regular compared to other planets. Orbiting at 4.9 to 5.5 AU, the planet also has an inclination of 1.305° with respect to Earth's equator, which is quite high compared to other planetary bodies (the only two planets with an inclination greater are Saturn and Mercury). The orbit of Jupiter, however, is stable compared to other planetary bodies, likely because of its mass.[19]

Jupiter has an orbital period of 11.8 years and an eccentricity of roughly 0.04.

Jupiter-saturn web-1

A comparison of Jupiter and Saturn, showing their many similarities.

Relations

Jupiter has many relations with other planetary regions and bodies in a physical matter, such as gravitational pull or similarities. Jupiter is the most massive planet in the solar system, which equals down to massive gravitational pulls.

Jupiter has a pull effect on the Sun. Due to its mass and gravity exertion, it pulls the Sun off of its barycenter, and the pair orbit on their paths in a Pluto-Charon like fashion.[20] Jupiter also has a major effect on the asteroid belt, tugging and pulling on it. This effect causes asteroids to stay in the belt mainly due to the immense gravity of Jupiter, but also pulls some asteroids out of it. This has likely caused the formation of the Hilda's Triangle and the leading group and following group of the Trojans.

The planets relations with Saturn follow through with multiple similarities and comparisons to one and another. They are both the only planets to have a diameter above 100K km, they both have seperate temperate, tropical and polar bands, they have a similar atmosphere to one and another, they both have moons which are larger than Mercury, and on the topic of moons, they also have a huge amount of moons creating a sort of mini-solar system. Physically, they do pull on one and another, tempering with each others orbit ever so slightly. Their fast rotations on their axis, both being under 13 hours respectively, cause their shapes to slightly bulge out at the equator, making them ellipsoids. Jupiter has relations with the other gas giants, however they aren't as impactful.[21]

Observation

Jupiter is usually the fourth brightest object in the sky, behind Venus, the Moon and the Sun. As such, it has been known since ancient times due to it's brightness. The angular diameter is known to vary, from 50.1 to 30.5 arcseconds, due to it's varied proximity. Jupiter experiences optical retrograde motion.[22]

Pre-Telescopic

The first recorded observations of Jupiter are heavily contested, however the furthest back claim was by the Babylonians around 800 B.C. The Chinese used Jupiter as their time for their 12 earthly branches. Eventually, this relation with Jupiter would cooperatively lead to the Chinese zodiac, which would be used all around Asia. They represented Jupiter as a mythological god, controlling the heavens above and opposite of where Jupiter is in the sky.[23] A Chinese astronomer claimed he saw something in alignment with Jupiter, as Jupiter moved, so did it. If this had been confirmed, this would have been the first known observation of a Jovian moon, and the first observation of a moon other then our own.[24] Astronomers who observed Jupiter with the naked eye, could tell that Jupiter would take around 11.8 years to orbit around the sky once.

Jupiter as viewed by an amateur telescope

Jupiter as viewed by an amateur telescope.

Post-Telescopic

The Italian polymath, Galileo Galilei, used his own telescope in 1610 to try and observe Jupiter, and with it, came the first observations and the discoveries of the Galilean moons, promptly named after him. Just one day later, Simon Marius independently discovered the Galilean moons, but did not publish his findings until 1614. In retrospect of their discoveries, Marius was allowed to name the four moons, which he named Io, Europa, Ganymede and Callisto.[25] These findings heavily supported the heliocentric models, which Galileo loudly supported. Cassini later began to observe Jupiter in the 1960's, and found that Jupiter's atmospheric conditions rotated in opposite directions from other bands.[26]

In 1664, the first claimed observations of the Great Red Spot, were observed by Robert Hooke, however Cassini claimed to have observed it first in 1965. The spot was reported to have faded many times, however, it's likely that they did not observe the side where the spot was on. Ole Rømer used the intersections of eclipses of that of the Galilean moons to deduct that light was not instantaneous, and measured how fast it really was. 2 centuries later, a 'gifted astronomer,' Edward Barnard, observed a fifth satellite, which was later confirmed, and named Amalthea. It was the last planetary moon to be discovered directly by a visual observer through a telescope, however, Thebe may have been observed as well by many astronomers, however these are all subjective claims.

Jupiter and Io (2007)

Jupiter and Io as captured by New Horizons.

Exploration

In 1973 and 1974, both the Pioneer 10 and 11 probes flew past Jupiter, capturing the first close up images of the first three of the Galilean moons and Jupiter itself. These observations made by the probes allowed new data on how the moons of Jupiter orbit. The Great Red Spot was also imaged heavily by Pioneer 11, detailing the first known images of the storm. The Ulysses probe made two known flybys around Jupiter, however, it did not capture any images, as its main focus was to observe the Sun. Cassini, in 2001, although its primary focus was to visit Saturn, made a flyby of Jupiter and brought back the most detailed image of Jupiter at that time.[27]

New Horizons flew by Jupiter in 2007 and captured major photos of the planet and some of its moons during a flyby to Pluto, gaining speed and encountering a new window for its Kuiper belt exploration. Many moons have been discovered primarily throughout these missions.[28]

Voyager 1 Approaching Jupiter

A bunch of images compiled together showing the approach of Voyager 1 and the rotation of its bands.

The Voyager Missions

The Voyager 1 and 2 space probes both explored Jupiter and its moons in depth during 1979-1985. The two expeditionary probes sent back new data about the planet, and captured some of the first large pictures for its timespan.[29]

The first of the Voyager missions reached Jupiter in 1979, detailing the first major data of Jupiter and later taking some photos of the planetary body. Around this time, Jupiter's rings were observed and later discovered, as well as two new moons, Thebe and Metis. The revelation of active volcanic activity on Io, one of Jupiter's moons, was arguably one of the most astonishing findings. It marked the first observation active volcanoes on another celestial body within the Solar System. Eventually, Voyager 1 left the Jovian system, but recorded some important data and found new discoveries.[6]

Later in the same year, Voyager 2 made its approach of the Jovian system. It recorded more important data and brought more new information. It imaged some of Jupiter's most important moons, mainly Io and Europa, and also recorded more volcanic eruptions on Io. Europa displayed a large number of intersecting linear features, however, with the help of Voyager 2, it was deducted that they were scarps. The probe left Jupiter 2 days later.

Jupiter's Southern Hemisphere - Juno

The first ever detailed image of Jupiter's south pole, and one of the most detailed images of Jupiter.

Juno, Europa Clipper and JUICE

Juno, the first ever probe designated to orbit Jupiter, launched in 2011 and reached Jupiter in 2016. The missions primary target was to observe the Jovian system and discover new data.[30]

As it reached Jupiter in 2016, it intersected into a polar-orbit using orbital processing methods to slowly lower it away from the solar plane. It began to take extremely detailed images of Jupiter and its innermost major moon Io and then later took some images of Europa and Ganymede. It later found that Jupiter isn't all that organized, finding out that Jupiter's magnetosphere is chaotic, and that its bands sometimes merge and split.[30]

The Europa Clipper was launched in 2024 and is on its way to Europa[31], whilst JUICE is also on its way to the Jovian system. Both probes are intended to orbit the planet.[32]

Gallery

See Also

References and Footnotes

  1. 1.0 1.1 1.2 NASA | Jupiter Overview
  2. IOP Science | THE DEUTERIUM-BURNING MASS LIMIT FOR BROWN DWARFS AND GIANT PLANETS
  3. Astronomy.com | Why is Jupiter not a star or a brown dwarf?
  4. Bibliography: Universe: The Definitive Visual Guide, by DK and Martin Rees (2015)
  5. Space | Jupiter's Atmosphere: Composition & the Great Red Spot
  6. 6.0 6.1 WebArchive (Apr 2016) | NASA | Voyager - Jupiter
  7. Saturn's White Spot would be the largest known cyclonic type storm in the solar system by technicality.
  8. Britannica | Great Red Spot | Facts, Size, & Definition
  9. ScienceAlert | Jupiter Has No Surface. Here's How That's Actually Possible.
  10. Astrophysics Data System | Jupiter's ring system: New results on structure and particle properties
  11. Space | How Was Jupiter Formed?
  12. Reasons to Believe | Jumping Jupiter Scenario Reveals More Evidence for Design
  13. Astrophysics Data System | Young Solar System's Fifth Giant Planet?
  14. S/2017 J 10 and S/2017 J 11 were confirmed on April 30, 2025.
  15. NASA | Io
  16. NASA | Europa
  17. NASA | Ganymede
  18. NASA | Callisto
  19. Planet Facts | Orbit & Rotation of Jupiter: Planet Jupiter’s Year, Day & Revolution
  20. HowStuffWorks | If You Think Jupiter Orbits the Sun, You're Mistaken
  21. Scope the Galaxy | Jupiter vs Saturn (The Similarities And Differences)
  22. WebArchive (Jan 2005) | NASA | Jupiter
  23. JSTOR | The Beginnings of Chinese Astronomy
  24. Astrophysics Data System | The Discovery of Jupiter's Satellite Made by Gan-De 2000 Years Before Galileo
  25. Astrophysics Data System | 400th Anniversary of Marius's Book with the First Image of an Astronomical Telescope and of Orbits of Jovian Moons
  26. WebArchive (Jan 2022) | The Galileo Project
  27. Bibliography: By Jupiter: Odysseys to a Giant by Burgess, Eric (1982)
  28. NASA | Pluto-Bound New Horizons Provides New Look at Jupiter System
  29. NASA Science | Mission Overview
  30. 30.0 30.1 NASA Jet Propulsion Laboratory | Juno - Jupiter Missions
  31. NASA Science | Europa Clipper
  32. ESA | JUICE
The Planets and Dwarf Planets
Planets
Inner: (MercuryVenusEarthMars) Outer: (JupiterSaturnUranusNeptune)
Dwarf Planets (and candidates)
CeresPlutoHaumeaMakemakeQuaoarOrcusErisGonggongSedna