Jupiter (planet)

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Jupiter  Astronomical symbol of Jupiter
Jupiter in natural colors with the shadow of the moon Europa, photographed by the Cassini spacecraft
Jupiter in natural colors with the shadow of the moon Europa , from photos of the telescopic camera of the Cassini space probe on December 7, 2000
Properties of the orbit
Major semi-axis 5.204  AU
(778.51 million km)
Perihelion - aphelion 4,950-5,459 AU
eccentricity 0.0489
Inclination of the plane of the orbit 1.304 °
Sidereal orbital period 11  a  315  d
Synodic period 398.88 days
Mean orbital velocity 13.06 km / s
Smallest - largest distance to earth 3.934-6.471 AU
Physical Properties
Equatorial diameter * ≈11 earth diameter
142,984 km
Pole diameter * 133,708 km
Dimensions ≈318 earth masses
2.47 times the mass of all other planets
1.899 · 10 27  kg
Medium density 1.326 g / cm 3
Main components
(proportion of fabric in the upper layers)
Gravitational acceleration * 24.79 m / s 2
Escape speed 59.5 km / s
Rotation period 9 h 55 min 30 s
Inclination of the axis of rotation 3.13 °
Geometric albedo 0.538 (geometric) 0.503 ± 0.012 (Bondsche or bolometric)
Max. Apparent brightness −2.94 m
Temperature *
min. - average - max.
165 K  (−108  ° C )
* based on the zero level of the planet
Moons 79 + ring system
Size comparison between Earth (left) and Jupiter
Size comparison between Earth (left) and Jupiter

With an equatorial diameter of around 143,000 kilometers, Jupiter is the largest planet in the solar system . At an average distance of 778 million kilometers, it is the fifth planet from the sun . It is named after the main Roman god Jupiter .

Like Saturn, Uranus and Neptune, the planet has no solid surface. The almost parallel stripes already visible in the small telescope are colored bands of cloud. Due to its chemical composition, Jupiter is one of the gas planets . These "gas giants" form the group of outer planets in the solar system ; they are also known as Jupiter-like (Jovian) planets. In this group, Jupiter is the innermost planet; it runs around the sun on the other side of the asteroid belt .

Up to 1980, 16 moons were known , including 6 with a diameter of only about 20 km. The Voyager spacecraft of the 1980s discovered over 40 other satellites; 79 moons are known since 2019. The four largest so-called Galilean moons Ganymed, Callisto, Io and Europa have diameters between 5262 and 3122 km and were discovered as early as 1610.

Jupiter is the third brightest object in the night sky after the moon and Venus ; Mars can only rarely be slightly brighter. In Babylonia it was considered a royal star because of its golden yellow light (see also Star of Bethlehem ). Its astronomical symbol is ♃.

Orbit and rotation


Jupiter goes in an approximately circular orbit with an eccentricity of 0.0489 around the sun. Its point closest to the Sun, the perihelion , is 4.95  AU and its point furthest from the Sun , the aphelion , is 5.46 AU. Its orbit is slightly inclined towards the ecliptic at 1.305 ° . It takes Jupiter 11 years, 315 days and 3 hours to orbit the sun.

Because of its slight inclination (1.3 °), Jupiter always moves close to the ecliptic . The almost exactly 12-year orbital period means that every year it moves in the zodiac around one constellation and its best visibility ( opposition ) occurs annually one month later.

Jupiter has an important function in the solar system. Since it is 2.47 times as heavy as all other planets put together, it forms an essential component of the mass equilibrium in the solar system. Jupiter and Saturn combine over 90 percent of the mass of all planets. The dominant gas giant stabilizes the asteroid belt through its mass . Without Jupiter, statistically speaking, an asteroid from the asteroid belt would hit the earth every 100,000 years, presumably making life impossible. The existence of a Jupiter-like planet in a solar system could therefore be a prerequisite for life on a planet closer to the star; however, not all astronomers share this view.

Furthermore, there are Trojans on Jupiter's orbit that accompany the planet on Lagrange points L 4 and L 5 .

The flattening of Jupiter can be seen in comparison to the outline (red line) of a sphere. False color image from the Hubble Space Telescope .


Jupiter is the planet in the solar system that rotates fastest on its axis. Its rotation period is almost ten hours, which, due to the centrifugal forces, leads to a flattening of Jupiter at the poles . In addition, Jupiter as a gas planet does not rotate like a rigid body, but its (visually observable) surface is in differential rotation . The equatorial regions take 9 hours 50 minutes 30 seconds and the polar regions take 9 hours 55 minutes 41 seconds.The equatorial regions are referred to as system I and the polar regions as system II . Its axis of rotation is only slightly inclined by 3.13 ° to the normal of its orbit around the sun. In contrast to other planets, Jupiter has no distinct seasons . The precession of the rotation axis is model calculations in the order of 500,000 years.

Physical Properties

Size and temperature comparison between the sun , Gliese 229 A + B , Teide 1 and Jupiter
Jupiter in size comparison to other celestial bodies (picture 2, far right, and picture 3, far left, next to Wolf 359 )

Jupiter is the most massive planet in the solar system. It is about 2.5 times as massive as all the other seven planets combined. It is the only planet in the solar system whose common center of gravity with the sun lies slightly outside the sun with about 1.068 solar radii. Jupiter's mass corresponds to 318  earth masses or the 1048th part of the solar mass .

Jupiter is not only the heaviest, but also the largest planet in the solar system with a diameter of around 143,000 kilometers. Its diameter is around eleven times that of the earth or a tenth of the diameter of the sun. Like all gas giants, it has a lower mean density of 1.326 g / cm³ than earth-like planets.

It shows a relatively strong flattening . The apparent angular diameter is 32 to 48 , depending on the distance to the earth . In a cloud layer south of the equator is the largest cyclone in the solar system, the Great Red Spot (GRF), which was observed 300 years ago. In addition, Jupiter has a small ring system and 79 known moons , of which the four largest, the Galilean moons Ganymede , Callisto , Europa and Io , can also be seen with small telescopes. The up to five equatorial stripes can also be observed with simple telescopes.

Jupiter has almost the maximum size of a "cold" body made of hydrogen. Even if it had ten times its mass, its volume would not be significantly larger, but the gas would compress more. In this context, “cold” means that no hydrogen fuses into helium in the celestial body and heats it up to form a star. The class of brown dwarfs begins at about 13 times the mass of Jupiter . In brown dwarfs, which occupy a special position between planets and stars, the first nuclear fusion processes are already taking place, but not yet hydrogen burning . From about 70 Jupiter masses hydrogen begins to burn and with it the class of the smallest stars, the red dwarfs . The transitions between stars, brown dwarfs and planets are fluid.

Overall, Jupiter's composition is similar to the gas disk from which the sun evolved around 4.5 billion years ago. There are similarities in structure to Saturn , whereby Saturn has a lower proportion of helium.

The temperature is 165 K (−108  ° C ) at a pressure of the gas layer of 100  kPa (1  bar , this is generally defined as zero level , i.e. “surface”  for gas planets ) and 112 at a pressure of 10 kPa (0.1 bar) K (−161 ° C). The zero level averages 71,492 km at the Jupiter equator.


Jupiter has no solid surface and no clearly delimited atmosphere. Almost the entire planet consists of gases, and the gas envelope changes into a supercritical state without phase transition with increasing depth . It could have a solid core.

the atmosphere

Zones, belts and cyclones in Jupiter's atmosphere (cylinder projection)

From the outside, Jupiter shows itself in differently colored bands and swirls of clouds, in white, red, orange, brown, yellow and sometimes also blue tones. The clouds ( aerosols ) contain crystals of frozen ammonia and possibly ammonium hydrogen sulfide and are in the tropopause of the gas giant.

The bands run around the planet at different latitudes in an east-west direction. The lighter bands are areas called the darker belts . The zones are cooler than the belts, denser, and contain ascending gases. Its light color is believed to come from ammonia ice. The cause of the dark color of the belts is still uncertain, but it is believed that they contain phosphorus , sulfur and possibly hydrocarbons .

The zones and belts move in relation to the interior of Jupiter, the rotation of which is known from its magnetic field, with different relative flow velocities (“zonal flow”) in east and west directions. They are bounded by strips of high wind speed called jets . Jets heading east are found at the transition from zones to belts (viewed from the equator), while jets heading west are found at the transition from belts to zones. Turbulence and hurricanes develop on the jets . The “zonal flow” disappears near the poles of Jupiter and there are no pronounced band structures here either.

The cloud cover of Jupiter is about 50 km thick and consists of at least two layers: a dense lower layer and a thinner upper layer. There might also be a thin layer of water clouds under the ammonia cloud layer as lightning is observed in the atmosphere. The lightning is caused by the polarity of the water, which allows electrical charges to separate. These electrical discharges on Jupiter can be a thousand times stronger than lightning bolts on Earth.

Jupiter's outside area also contains hydrogen sulfide and other oxides and sulfides . The ammonia can also react with hydrogen sulphide in deeper layers to form clouds of ammonium sulphide smoke .

Upper layers

The main components (in amount of substance or number of atoms) of the outdoor area are hydrogen (89.8 ± 2% by volume) and helium ( 10.2 ± 2% by volume ) and, to a lesser extent, methane ( 0.3 ± 0, 2% by volume ) and ammonia ( 260 ± 40 ppm by volume ). Since a helium atom has about four times the mass of a hydrogen atom, the mass fraction of helium is correspondingly higher: The mass distribution therefore corresponds to about 75% hydrogen, 24% helium and 1% other elements. Furthermore, traces of chemical compounds of the elements oxygen , carbon , sulfur and many other elements were found, including noble gases such as e.g. B. Neon were found.

internal structure

Schematic section to show the internal structure

Since the temperature of the planet's hydrogen is above the critical temperature , it is in the supercritical state, so that the pressure increases with increasing depth, but the physical state does not change. Therefore, no surface can be defined as an interface .

At a greater depth, at a pressure of more than a few hundred gigapascals, the hydrogen changes into an electrically conductive phase, which is called metallic because of its conductivity . It is assumed that Jupiter has a rock- ice core below about a quarter of its radius with up to about 20 times the mass of the earth, which consists of heavy elements . The interior of the planet consists of over 87% hydrogen and helium, as well as between 3 and 13% other elements.


Big red spot

The Great Red Spot in Jupiter's atmosphere, here an image taken by the Juno spacecraft on July 11, 2017, is the largest cyclone in the solar system. It has been around for at least 200 years, possibly much longer.

Apart from the light and dark equatorial cloud bands parallel falls of Jupiter, especially the Great Red Spot on (GRF, or English GRS for Great Red Spot) . The Great Red Spot is a huge oval anticyclone that is currently about one and a half earth's diameter in length in the direction of rotation. It is not connected to any solid surface, but is very stable between two bands of cloud at about 22 ° south latitude . It is enclosed on its north side by a westward jet stream and on its south side by an eastward blowing wind stream. Photos from the Voyager 2 spacecraft also showed that the Great Red Spot is drifting westward at a speed of around half a degree per day.

It is possible that the Great Red Spot was described by the English naturalist Robert Hooke as early as 1664 and then followed for a longer period from 1665 by Giovanni Domenico Cassini . But since there are no reports at all for the next 120 years, these early observations may have referred to a different phenomenon. It is certain that the stain was first registered in 1830; Since then, it has been continuously observed and researched - but only from 1878 onwards. Samuel Heinrich Schwabe recorded it on a representation made in 1831, as did William Rutter Dawes in 1851 and A. Mayer and Lawrence Parsons, 4th Earl of Rosse in the 1870s, on their drawings of the giant planet.

In the 1880s, the Great Red Spot became particularly well visible, at 40,000 km in length and 14,000 km in width, it had its largest ever observed extent and was accordingly studied in detail. The pronounced, huge cloudscape is therefore extremely durable. For comparison: on earth, wind eddies in the atmosphere usually dissolve again within a few weeks.

Due to its size, the Great Red Spot is already visible in amateur telescopes. Its distinctive color is clearly redder than the surrounding area, but it is not a deep, bright red, but fluctuates around a rather light orange over the years. For a successful finding, observers can orientate themselves on the indentation caused by it on the southern edge of the dark southern equatorial belt ; this is known as the Bay of the Great Red Spot (Red Spot Hollow) .

It is not known which chemical elements are responsible for the red color. However, at the end of 2009 the “southern equatorial belt” disappeared, so that the Great Red Spot is now even more visible on a very wide, white band.

Since 1930, and especially between 2012 and 2014, the storm has become smaller and more circular. Observations with the Hubble Space Telescope in May 2014 showed the smallest extent ever measured at around 16,500 kilometers in the direction of the longer axis. The cause is suspected by NASA interactions with other smaller storms.

The shape and color of the Great Red Spot can change significantly within a few years. It protrudes up to 8 km above the surrounding cloud systems and is also significantly cooler than them. The period of rotation of the spot is about 6 earth days. However, it has been decreasing lately, perhaps due to the shrinkage of the stain.

On July 11, 2017, the US research probe Juno flew over the red spot at an altitude of around 9,000 km.

Other cyclones

The Great Red Spot, "red spot junior" and the third red spot that appeared in May 2008, recorded by the Hubble telescope.

According to new research, Jupiter is subject to a 70-year climate cycle . During this period, a number of hurricanes form - cyclones and anticyclones, which disintegrate again after a certain time. In addition, the subsiding of the major storms causes temperature differences between the poles and the equator of up to ten  Kelvin , which are otherwise prevented due to the constant gas mixing caused by the storms.

In addition to the conspicuous red spot, a structure called the white oval (English oval BA) has been known for a long time , the extent of which, at about the diameter of the earth, is less than that of the red spot. The white oval had developed from 1998 onwards from three storms known since the 1930s. In 2006 a color change to red was observed through recordings of the Hubble space telescope , so that in the future this structure may be given the name Second Red Spot or Little Red Spot , in English red spot junior . More recent measurements determined wind speeds of up to 600 km / h inside.

A third red spot was discovered in May 2008, which was first believed to coincide with the Great Red Spot around August. The new red spot emerged from a previously whitish, oval storm area. The change in color indicates that the clouds are rising to greater heights. The upper cloud limit of the Great Red Spot is also at this altitude. In mid-July 2008, Jupiter's largest cyclone, the Great Red Spot, devoured the third red spot, as observations with the Hubble Space Telescope show.

Southern tropical disorder

In 1901 the "veil" was sighted, a sometimes 72,000 km long haze cloud that was at the latitude of the Great Red Spot, but rotated slightly (around 25 km / h) faster than it around the planet and therefore rotated it about every two years passed, interacting with him. This “veil” is now called the Southern Tropical Disturbance. As she approached the Great Red Spot from the west, she was drawn to it, and it tore matter from the veil into its vortex. After the encounter, the Southern Tropical Disturbance dragged the Great Red Spot from its surroundings a few thousand kilometers behind it, until it finally swung back to its original position.

As a result of the interaction, the rotation times of the disturbance and the spot became equal to one another. Southern Tropical Fault has not been observed since 1940 and appears to have disappeared.

Energy balance

Jupiter radiates 335 (± 26) petawatts (i.e. 5.444 ± 0.425 W / m 2 ) more heat than the 501 (± 25) petawatts (i.e. 8.157 ± 0.407 W / m 2 ) it absorbs from the Sun (Jupiter receives 12.564 W / m 2 from the sun, that's about a quarter of its mean solar constant, 50.50 W / m 2 ). Contributions to the energy balance are a slow cooling of the solid core by 1 K per million years and gravitational binding energy through contraction of the shell by about 3 cm per year. The latter is the so-called Kelvin-Helmholtz mechanism . In the 2nd edition of his book (2009), Patrick Irwin gave a value of only 1 mm per year, which corresponds to a specific strength of this internal heat of 7.5 W / m 2 (instead of 5.444 ± 0.425 W / m 2 ). Measurements of the Cassini probe (during the flyby of Jupiter on December 30, 2000) confirmed this value of the internal heat (7.485 ± 0.163 W / m 2 ). The separation of hydrogen and helium may also contribute.

Above the Great Red Spot , the atmosphere is a few hundred degrees warmer than elsewhere. It is believed that the storm gives off energy in the form of acoustic radiation or gravity waves , which are converted into thermal energy in the atmosphere.

Magnetic field

Magnetosphere of Jupiter. There is a torus of plasma around the orbits of Io (green) and Europa (blue). ENA indicates the emission of high-energy neutral atoms ( English energetic neutral atoms ).

Jupiter has the largest magnetic field of all planets in the solar system. On the surface, the equatorial strength of the field is around 400 microtesla and at the poles between 1040 and 1400 microtesla. It is 10 to 20 times as strong as the earth's magnetic field (approx. 30 µT at the equator and approx. 60 µT at the poles) and much larger. Jupiter's magnetic north pole is close to its geographic south pole. The axis of the magnetic north pole is inclined by about 10 ° to the axis of rotation. The fictitious axis between the magnetic north pole and the magnetic south pole does not go directly through the center of the planet, but slightly past it, similar to what is the case with the earth.

The exact origin of the magnetic field in Jupiter is still unclear, but it is certain that the metallic hydrogen and the rapid rotation period of Jupiter play a decisive role.

On the side facing the sun, the magnetic field extends about 5 to 7 million kilometers into space . On the side facing away from the sun, it protrudes a good 700 million kilometers into space and thus almost extends into Saturn's orbit. The reason for this asymmetry is the solar wind , which forms a shock front . As a result, seen from the sun, the magnetic field in front of the planet is compressed and stretched behind it. The constant interaction with the solar wind means that the exact dimensions of the magnetic field can fluctuate greatly. Any fluctuations on the side facing the sun can be particularly strong . When the solar wind is weak, the magnetic field can reach up to 16 million kilometers into space. The fluctuations in the magnetic field were investigated by the two Voyager 1 and 2 probes, among others .

The space occupied by the magnetic field is called the magnetosphere . The magnetosphere of Jupiter is so large that it (if you could see it from Earth) would occupy five times the area of ​​the full moon. Apart from the sun's magnetosphere, it is by far the largest object in the solar system.

The strong magnetic field constantly traps charged particles, so that rings and disks of charged particles form around Jupiter. These charged particles originate on the one hand from the solar wind - a comparable effect can be found on Earth in the form of the Van Allen Belt - and on the other hand - in larger quantities - from the moons of Jupiter, especially Io. For example, a torus of charged sulfur and oxygen atoms can be found around the orbit of Io and around the orbit of Europe, although the origin of the charged particles of the plasma of this torus has not yet been clarified.

Fluctuations in the magnetic field constantly create radiation that emanates from Jupiter. This so-called synchrotron radiation can be measured as Jupiter bursts on shortwave (for example as part of the Radio JOVE project ) or in the decimeter wave range and also leads to water evaporation on Europe's surface.

The magnetic field can be roughly divided into three parts: The inner area is ring-shaped and extends about 10 Jupiter radii. Within this part, different regions can be distinguished, which are defined by different electron and proton concentrations . The middle part of the magnetic field extends from 10 to about 40 Jupiter radii. This part is flattened in the shape of a disk. The outer region of the magnetic field is mainly characterized by the interaction of the magnetic field with the solar wind, and its shape therefore depends on its strength.

Ring system

Rings of Jupiter

Jupiter has a very weak ring system , which has been suspected since the Pioneer 11 mission in 1974 and which Voyager 1 was able to photograph for the first time in 1979. When the probe entered the shadow of Jupiter on March 5, 1979, the rings could be seen in the backlight.

The origin of the rings remained unknown for a long time, and terrestrial observation proved extremely difficult, since the rings consist of dust grains, most of which are no larger than the particles of the smoke of a cigarette. In addition, the dust particles are almost black and therefore hardly visible: They have an albedo of only 5%, i.e. they swallow 95% of the sunlight that hits it, which is already weak there.

Another reason the rings are so small is that they slowly spiral towards Jupiter and eventually be sucked up by it in the distant future. The spiral rotation has different causes. On the one hand, Jupiter's strong magnetic field causes the dust particles to be electrically charged. These collide with other charged particles that Jupiter catches from the solar wind , for example , which ultimately slows the particles down. A second effect, which also slows down the dust particles, is the absorption and subsequent remission of light. The dust particles lose orbital angular momentum . This effect is called the Poynting-Robertson effect . Both effects together cause the dust to disappear from the rings within a period of about 100,000 years.

Main ring photographed by
Galileo on November 9, 1996

The origin of the rings could only be clarified through the Galileo mission. The fine dust probably came from the small rocky moons of Jupiter. The moons are constantly bombarded by small meteorites . Due to the low gravity of the moons, a large part of the ejection is thrown into the orbit of Jupiter and thus constantly refills the rings.

The Main Ring, for example, consists of the dust from the moons Adrastea and Metis . Two other weaker rings (Gossamer rings) are connected to the outside. The material for these rings comes mainly from Thebe and Amalthea . In addition, an extremely thin ring was discovered in an outer orbit, which has a diameter of over 640,000 km and whose particles move up to 20 ° outside the equatorial plane of Jupiter. This ring orbits Jupiter in the opposite direction. The origin of this ring has not yet been clarified. However, it is believed to be composed of interplanetary dust .

Inside the main ring is a halo of dust grains that extends over an area of ​​92,000 to 122,500 km, measured from the center of Jupiter. The main ring extends from above the halo line from 130,000 km to about the orbit of Adrastea. Above the orbit of Metis, the strength of the main ring decreases noticeably. The thickness of the main ring is less than 30 km.

The inner Gossamer Ring, fed by Amalthea, extends from the outer boundary of the main ring to Amalthea's orbit at about 181,000 km from the center of Jupiter. The outer Gossamer ring extends from 181,000 km to about 221,000 km and is thus between the orbits of Amalthea and Thebe.


The four Galilean moons true to scale in photomontage in front of the Great Red Spot (from above: Io , Europa , Ganymed and Callisto ) .

Jupiter has 79 known moons (as of July 13, 2018). They can be divided into several groups:

The Galilean moons Io, Europa, Ganymede and Callisto with diameters between 3122 and 5262 km (earth diameter 12,740 km) were discovered independently by Galileo Galilei and Simon Marius in 1610 . All other moons, with the exception of Amalthea, discovered in 1892, were not found until the 20th or 21st century. The Galilean moons are the largest moons of Jupiter and have only slightly inclined orbits close to the planets. The first mathematical calculation of the orbits of Jupiter's moons was carried out in 1945 by Pedro Elias Zadunaisky in his dissertation with Beppo Levi .

  • Io has a diameter of 3,643 km and orbits Jupiter at a distance of 421,600 km. It consists of an iron core and a jacket. Io has a very thin atmosphere, consisting mainly of sulfur dioxide . Since geological processes take place in its interior, there are numerous volcanoes on its surface.
  • Europe has an iron core and a stone mantle, over which lies a possibly 100 km deep ocean of water, the surface of which is frozen to an ice crust for 10 to 20 km. Its diameter is 3,122 km, its distance to Jupiter 670,900 km.
  • Ganymede is at a distance of 1,070,000 km. Its diameter is 5262 km. This makes it the largest moon in the solar system. It consists of an iron core, a rock jacket and an ice jacket. It also has its own magnetic field.
  • Callisto is 4,821 km in diameter and 1,883,000 km away from Jupiter. It consists of a mixture of iron and stone and an ice crust. Researchers found on it signs of carbon and nitrogen compounds , which are essential for life. There are also likely layers of liquid water inside Callisto.

In addition to the Galilean moons, there are four other moons on orbits close to the planets and only slightly inclined: Metis , Adrastea , Amalthea and Thebe . With diameters of 20 to 131 km, these are much smaller than the Galilean moons. Their orbits are all within that of Io. It is believed that these eight inner moons formed simultaneously with Jupiter.

The remaining moons are small to very small objects with radii between 1 and 85 km and were probably captured by Jupiter. Some of them still have numerical codes as temporary names until they are finally named by the International Astronomical Union (IAU).

Presumably during the 1960s, Comet Shoemaker-Levy 9 came under the planet's gravitational forces and was forced into a strongly elliptical orbit (eccentricity> 0.99, apojovium up to 0.33 AU). In July 1992, the quasi-satellite Jupiter passed within the Roche boundary and broke into 21 fragments, which crashed two years later on the planet.


Conjunction of full moon and Jupiter on April 10, 2017. Next to Jupiter (bottom right) the four Galilean moons (from left): Io, Ganymede, Europa and Callisto.
Jupiter with two moons and their shadows on an astronomical drawing from the 19th century ( Trouvelot , 1881)
Jupiter with bands of clouds and moons III and IV; right now II appears behind the planet. Drawing Geof July 13, 2021, 30 cm reflecting telescope, 165x, south above

Jupiter is clearly visible to the naked eye at night about 3/4 of the year . With its bright yellow sheen, it is the third brightest object in the night sky after the moon and Venus . Its 12-year orbit was calculated exactly in ancient times, as was that of the 4 other clear-sighted planets.

In 1610 Galileo Galilei first observed Jupiter with a telescope and discovered its four largest moons Ganymede, Callisto, Io and Europa. These four are therefore referred to as the Galilean moons . In the telescope, from about 50 times magnification, Jupiter's equatorial cloud bands and sometimes the shadows of its moons can be observed.

About every 20 years, seen from Earth, there is a major conjunction between the planets Jupiter and Saturn .

Exploration with space probes

Jupiter has already been visited by several space probes , with some missions using the planet as a kind of springboard to get to their actual goals with the help of a swing-by maneuver on Jupiter.

Previous missions

Pioneer 10 and 11

Pioneer 10 was the first spacecraft to pass Jupiter on December 3, 1973 at a distance of approximately 130,000 km. Exactly one year later, on December 3, 1974, Pioneer 11 followed , which came within 43,000 km of the planet's cloud ceiling. The two Pioneer space probes provided important data about the magnetosphere of Jupiter and took the first, still relatively low-resolution, close-ups of the planet.

Voyager 1 and 2

Voyager 1 flew through the Jupiter system in March 1979, followed by Voyager 2 in July 1979. The Voyager space probes provided new information about the Galilean moons, were able to detect volcanic activity on Io for the first time and discovered the rings of Jupiter. They also took the first close-ups of the planet's atmosphere.


In February 1992 the solar probe Ulysses passed Jupiter at a distance of about 450,000 km (6.3 Jupiter radii). The probe was thrown out of the ecliptic plane and entered a polar solar orbit. Ulysses examined the magnetosphere of Jupiter, but could not provide any images of the planet because there was no camera on board.


Galileo is being prepared for launch

The first orbiter around Jupiter was NASA 's Galileo probe , which entered orbit around the planet on December 7, 1995 after a little more than six years in flight. Already on the way to Jupiter in 1994 Galileo was able to observe how the comet Shoemaker-Levy 9 struck Jupiter, which is still 238 million kilometers away from the probe, and triggered explosions the size of the earth in the planet's atmosphere. Despite the distance, Galileo was able to capture images of the direct impacts that took place on the far side.

Galileo orbited Jupiter for over seven years and made multiple fly-bys of the Galilean moons. Among other things, Galileo observed volcanic eruptions on Io, provided evidence of a hidden ocean on Europe and examined the movement of clouds in Jupiter's atmosphere. However, due to the failure of the space probe's primary antenna, only a fraction of the originally planned amount of scientific data could be transmitted to Earth.

Artist's impression of the entry of
Galileo's atmospheric capsule

In addition to the orbiter, Galileo's mission also included an entry capsule that entered Jupiter's atmosphere and provided various data on temperature, pressure, wind speed and chemical composition. In July 1995, the capsule separated from the mother probe at a distance of 82 million kilometers from Jupiter. On December 7, 1995, the capsule plunged into Jupiter's atmosphere at a speed of 170,000 km / h at an angle of about 9 °, was slowed down with the help of a heat shield and a few minutes later a parachute unfolded. The capsule then provided data for 57.6 minutes while hanging on the parachute, moving about 160 km into the atmosphere before it was destroyed by external pressure. In the last few seconds the probe registered a pressure of 22 bar and a temperature of +152 ° C.

The primary mission at Jupiter was originally only planned for 23 months until December 1997, but was then extended three times because the equipment and drive were still functional and good results could be expected. On September 21, 2003, Galileo was finally directed into Jupiter's atmosphere, as the probe would later not have been steerable due to lack of fuel and failure of the electronics due to the high radiation dose received from the probe over the past few years. There was a risk that Galileo could fall on Jupiter's moon Europa and contaminate it with terrestrial bacteria . This would have made future missions to investigate traces of life on Jupiter's moons more difficult.

Projection of the southern hemisphere of Jupiter with the help of Cassini


The Cassini-Huygens space probe passed the Jupiter system on its way to Saturn at the end of 2000 / beginning of 2001 and made numerous measurements and recordings in the process. At the same time, Galileo was also operating in the Jupiter system, making it possible for the first time to study the planet and its magnetosphere with two space probes at the same time. Cassini flew past Jupiter on December 30, 2000 at a distance of about 10 million kilometers and provided, among other things, some of the highest-resolution global images of the planet.

New Horizons

The New Horizons space probe , which was launched on January 19, 2006 and subsequently examined Pluto , collected data on the giant planet during its flyby of Jupiter in February and March 2007. The spacecraft was supposed to observe cloud movements on Jupiter, examine the planet's magnetosphere, and look for auroras and lightning bolts in Jupiter's atmosphere. However, only little scientific data could be obtained about the four large Galilean moons, as the probe passed them at a great distance. New Horizons made its closest approach to Jupiter on February 28, 2007 at about 32 Jupiter radii. This is about a third of the distance Cassini-Huygens passed Jupiter.

Current missions


Computer simulation of the Juno spacecraft in front of Jupiter

On August 5, 2011, NASA 's Juno probe took off for Jupiter. On July 4, 2016, it swung into an elliptical polar orbit around Jupiter, which brought it up to 4,100 kilometers from the cloud ceiling. Originally, the probe was then supposed to swing into a shorter orbit with an orbital period of eleven days. The original planned primary mission of the probe should last about a year and include 33 such orbits. After problems with the engines, the initial orbit with an orbit of 53.4 days was retained as a precaution; the mission duration of the primary mission and the mission objectives have been changed accordingly.

Juno is now not only exploring - as originally planned - the magnetic field and the atmosphere of Jupiter, but can now also explore the Jupiter magnetosphere and its outer boundary, the magnetopause, as well as its interaction with the solar wind . High-resolution recordings have been made since 2016. From images published in 2021 from just 50,000 km away, NASA concludes that the jet streams extend 3,000 km into the gas planet.

A special feature of the probe is its energy supply: for the first time on a mission to one of the outer planets, its systems are operated entirely with solar energy.

Canceled and planned missions

After the discovery of a water ocean on the moon Europa, the interest of planetary researchers in the detailed study of the icy moons of Jupiter increased. For this purpose, the Jupiter Icy Moons Orbiter (JIMO) mission was designed at NASA . The plan was to launch a large space probe in 2017 that would use a nuclear reactor as an energy source for its ion thrusters and instruments. JIMO was supposed to orbit the three great ice moons of Jupiter - Callisto, Ganymede and Europa - one after the other and examine them with the help of a powerful radar and many other instruments. In 2005, JIMO's funding was stopped due to its complexity and many technical difficulties.

For 2020 NASA and ESA proposed the joint Europa Jupiter System Mission / Laplace, which envisaged at least two orbiters, each of which should enter an orbit around Europe and Ganymede and should explore the entire Jupiter system with a revolutionary depth. After the realization of the project was called into question by budget cuts at NASA, ESA decided to carry out the independent JUICE mission . This will in June 2022 with an Ariane 5 ECA launch rocket, to reach Jupiter in January 2030 in a Jupiter orbit and after two years and more flybys of Europa and Callisto in orbit around 2,032 Ganymede occur. NASA is also planning the Europa Clipper, a space probe to investigate Europe; it is scheduled to start in the mid-2020s.

Cultural history

Allegorical representation of Jupiter as ruler of the zodiac signs Pisces and Sagittarius, Sebald Beham , 16th century

Due to its great brightness, the planet Jupiter was already in ancient times in the first half of the third millennium BC. In ancient Egypt known as Hor-wepesch-taui ("who illuminates the heavenly realms"). In Mesopotamia it was called Sag-me-gar . The Babylonians later identified him as mul bab-bar ("white star") with the god Marduk .

Aristotle mentions the planet in his work "Meteorologica" in 350 BC. At an apparent merging with a fixed star in the constellation Gemini .

The name of Jupiter, Latin Iū (p) piter , comes from the Urindo-European call form (vocative) * d (i) i̯éu̯ ph₂tér (pronounced: 'djé-u-pechtér') "Heaven, father!" Which is the actual Latin Basic form (nominative) Diēspiter (from * d (i) i̯ḗu̯s ph₂tḗr ) has displaced. The translation "God the Father" would be anachronistic.

The term joviality is not of ancient origin, but rather arises from the Italian gioviale, first attested in Dante's Paradiso , "under the influence of Jupiter" (in the astrological sense, that means "happy, cheerful"), perhaps with the help of gioia "joy, pleasure" , and probably got into German via the synonymous French ( jovial ). In German, the adjective has taken on the meaning of "affable, emphasized benevolent when dealing with lower-ranking people".

In astrology , Jupiter stands for expansion , happiness , religion and philosophy, among other things . It is assigned to the element fire , the zodiac sign Sagittarius (before the discovery of Neptune also that of Pisces ) and the ninth house .

See also


  • Fran Bagenal , T. Dowling, W. McKinnon (Eds.): Jupiter: The Planet, Satellites and Magnetosphere. Cambridge University Press, 2004, ISBN 0-521-81808-7 .
  • Guillaume Cannat, Didier Jamet: Jupiter and Saturn - the most beautiful images of the space probes Galileo and Cassini. From the Franz. By Gottfried Riekert. Delius Klasing, Bielefeld 2007, ISBN 978-3-7688-1877-3 .
  • Alexander J. Dessler: Physics of the Jovian magnetosphere. Cambridge University Press, 1983, ISBN 0-521-24558-3 .
  • John W. McAnally: Jupiter and how to observe it. Springer, London 2008, ISBN 978-1-85233-750-6 .

Web links

Commons : Jupiter  - album with pictures, videos and audio files
Wikibooks: Jupiter  - learning and teaching materials

Individual evidence

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