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Jupiter (planet): characteristics, composition, orbit, movement, structure

Jupiter is the largest planet in the solar system and one of the brightest in the night sky throughout the year, which is why it was named after the king of the Roman gods. In Roman mythology, the god Jupiter is the greatest of gods, equivalent to the god Zeus in Greek mythology. 

Observing its orbit relative to the Sun, Jupiter is the fifth planet in the solar system and has at least 79 natural satellites. Its diameter is 11 times the diameter of the Earth and, after the Sun, it is the largest and heaviest object in the solar system.

Humanity has contemplated Jupiter since ancient times, but Galileo Galilei was the first to observe the planet with a telescope and discover four of its main satellites in 1610.

Galileo observed the characteristic bands of Jupiter and the four Galilean satellites, whose names are Io, Europa, Ganymede and Callisto. Galileo’s discoveries completely changed the conceptions of the Earth and humanity’s place in the Universe, as it was the first time that celestial bodies were observed revolving around a star other than our planet.

His observations supported several revolutionary ideas for his time: the first was that the Earth was not the center of the universe and the second, not least, that there were “other worlds” outside of it, as Galileo called Jupiter’s satellites.

Jupiter General Resources

Size and mass

Jupiter is the fifth planet, taking into account the orbital radius in relation to the Sun. The fourth planet is Mars, but between them there is a boundary: the asteroid belt.

Planets with an orbit smaller than the asteroid belt are rocky, while those with a larger orbit are gas or icy giants. Jupiter is the first of them and also the one with the greatest volume and mass.

Jupiter’s mass, equivalent to 300 Earth masses, is so large that it doubles in value the sum of the mass of the remaining planets in the solar system. As for its volume, it is the equivalent of 1,300 Earths.


Jupiter turns so fast around its own axis that it makes a complete turn in 9 hours and 50 minutes. This is 2.4 times faster than the Earth’s rotation speed and no planet in the solar system exceeds it. 

Its orbital period, that is, the time needed to make a complete revolution around the Sun, is 12 years.


Despite being five times farther from the Sun than our planet, its large size and characteristic clouds make sunlight reflect perfectly on its surface, which is why it is one of the brightest stars in the night sky.

When viewed with a telescope, only its tallest clouds are visible, which have some stationary and some moving areas, forming a pattern of bands along their equator.

The darker bands are called the belts and the lighter areas . They are relatively stable, although they gradually change shape and color, circling the planet in opposite directions.

White clouds are the result of updrafts that cool, forming ammonia crystals. These currents then curve laterally to descend again, in the darker bands.

Reddish, yellow and brown color

The reddish, yellowish and brown color diversity seen on Jupiter is the result of the different molecules present in the Jovian clouds. And Mong bands and belts form giant storms and vortices, which can be seen as dots or spots.

These storms are practically permanent and, among them, the Great Red Spot, first observed in the 17th century by Robert Hooke, a distinguished contemporary physicist and Isaac Newton’s rival, stands out.

The Great Red Spot is at least 300 years old, however, observations indicate that its colossal size, larger than Earth, has been shrinking in recent decades.

As for the Jovian atmosphere, it is quite thick. Its depth is not known exactly, but it is estimated to be hundreds of kilometers.


The chemical composition of its atmosphere is very similar to that of a star: 80% hydrogen, 17% helium and small proportions of water vapor, methane and ammonia. 

Atmospheric pressure increases with depth, to the point that the hydrogen gas liquefies, forming an ocean of liquid hydrogen, at a pressure so high that it behaves like a metal. That would be the lower edge of the Jovian atmosphere.

Jupiter’s ocean of metallic liquid hydrogen is hotter than the solar surface, on the order of 10,000°C, and quite bright.

Jupiter likely has a very dense core composed of heavy metal elements, but more data is needed to support this claim.

Summary of Jupiter’s Physical Characteristics

-Mass: 1.9 × 10 27 kg

Equatorial radius : 71,492 km, equivalent to 11 times the Earth’s radius.

– Polar radius : 66854 km.

-Shape: flattened at the poles by a factor of 0.065.

-Average radius of the orbit: 7.78 x 10 8 km, equivalent to 5.2 AU

– Inclination of the rotation axis : 3º12 in relation to the orbital plane.

Related:   Dwarf galaxy: formation, evolution, characteristics, examples

-Temperature : -130ºC (clouds)

-Gravity: 24.8 m / s 2

-Next magnetic field:  Yes, 428 μT at the equator.

-Atmosphere: dense atmosphere of hydrogen and helium.

-Density: 1336 kg / m 3

– Satellites: 79 known.

-Rings: Yes, weak and dusty.

Jupiter Structure

Jupiter’s outermost layer is composed of clouds and is 50 km thick. Underneath this cloud layer is another layer, mainly hydrogen and helium, 20,000 km thick.

The transition between the gas phase and the liquid phase is gradual as pressure increases with depth.

Under this liquid layer and as a result of extreme pressures, the electrons in the hydrogen and helium atoms separate from their nuclei and become free electrons that move in a sea of ​​liquid metallic hydrogen.

Deeper down, there may be a solid core 1.5 times the diameter of Earth, but 30 times heavier than our planet. And, as it is a planet composed of gas and liquid, due to its tremendous speed of rotation, the planet adopts a flat shape at its poles.

When and how to observe Jupiter

Jupiter looks bright white and is easily observable at twilight. Not to be confused with Venus, which is also very bright.

At first glance, Jupiter shines brighter in the night sky than Sirius, the brightest star, and is always close to some zodiacal constellation, which can vary depending on the year, in an environment of 30 degrees.

With good fixed-mount binoculars or a small telescope, Jupiter appears as a white disk with smooth bands.

The four Galilee satellites are easily visible with a small telescope: Ganymede, Io, Europa and Callisto. Satellite positions vary from day to day, and sometimes only three can be seen, as some are behind or in front of the planet.

There are several mobile apps that allow you to identify and search for planets and stars in the sky. Among them, Sky Maps stands out for being one of the first. In this way, Jupiter’s position is located at any time.

translation movement

Jupiter’s orbit is elliptical and focuses off the Sun’s center due to its enormous mass. It takes 11.86 years to cover it with a speed of 13.07 km / s.

Now, it is always claimed that the planets revolve around the center of the Sun, which is pretty accurate for almost everyone except Jupiter.

It is because Jupiter is so massive that the center of rotation, barycenter or center of mass of the Sun-Jupiter system moves towards Jupiter, leaving it outside the solar body.

According to calculations, the barycenter of the Sun-Jupiter system is 1.07 times the solar radius, ie outside the Sun.

The perihelion is the shortest distance between the orbit of Jupiter and the focus of the ellipse, located in the centroid of the Sun-Jupiter system. Its value is 816.62 million kilometers.

On the contrary, aphelion is the longest distance between focus and orbit, which in the case of Jupiter is 740.52 million kilometers.

The eccentricity of the orbit indicates how far it is from the circular shape. Jupiter’s orbit has an eccentricity of 0.048775 and is calculated by dividing the distance from the center of the ellipse to the focus by the length of the semi-major axis of the ellipse. 

rotary movement

The sidereal period of rotation of Jupiter around its own axis is 9 hours 55 minutes and 27.3 seconds. The axis of rotation has an inclination of 3.13° with respect to the axis of orbital rotation.

To be so bulky, Jupiter has the shortest rotation period of any planet in the solar system.

Jupiter Satellites

Giant planets are characterized by having a large number of satellites or moons. So far, 79 Jupiter satellites have been counted, but the largest and best known are the four satellites discovered by Galileo Galilei in 1610, which in order of proximity are:

-Io, it’s ⅓ the diameter of the Earth

-Europe, ¼ the diameter of the earth

Ganymede, from parts of the Earth’s diameter

-Calisto, just below ⅖ parts of the Earth’s diameter

These four satellites together have 99.99% of the mass of all Jovian satellites and rings.

Between Jupiter and the Galilean satellites, there are four small interior satellites discovered relatively recently (1979).

Outside the Galilee satellites is the regular satellite group  10 in total, plus the retrograde satellite group , of which sixty-one are known to date (61).

In order of the orbital radio, four groups of satellites are defined:

  1. Interior satellites (4) with orbits between 128,000 and 222,000 km.
  2. The Galilean satellites (4) have orbits between 422,000 km for Io and 1,883,000 km for Callisto. Together they have 99.99% of the mass of all Jovian satellites.
  3. Regular satellites (10) between 7,284,000 km and 18,928,000 km.
  4. Retrograde satellites (61) from 17,582,000 km to 28,575,000 km.

Jupiter also has rings. They are in lower orbit than the Galilee satellites and between the orbits of the inner satellites. These rings are thought to have arisen as a result of an interior satellite impacting a meteoroid.

Galilean Satellites

The four Galilee satellites form a very interesting group, as experts believe they meet the conditions for eventual colonization in the future.


It has intense volcanic activity, the surface is permanently renewed with molten lava from its interior.

Io’s heating energy mainly comes from the intense tidal force produced by Jupiter’s enormous gravity.


It is the second of Galilee’s satellites in order of distance, but the sixth of Jupiter’s satellites. Its name comes from Greek mythology, in which Europe is the lover of Zeus (Jupiter in Roman mythology).

It is only slightly smaller than the Moon and has a solid crust of frozen water. It has a sparse atmosphere of oxygen and other gases. Its softly fluted surface is the smoothest star in the solar system, with only a few craters.

Beneath Europa’s ice crust, an ocean is believed to exist whose motion, driven by the tidal forces of the giant Jupiter, causes tectonic activity on the satellite’s icy surface. In this way, cracks and grooves appear on its smooth surface.

Many experts believe that Europe is capable of receiving some kind of life.


It is the largest satellite in the solar system, has a rocky and ice mantle with an iron core. Its size is slightly larger than the planet Mercury, at almost half its mass.

There is evidence that an ocean of salt water may exist below its surface. ESA (European Space Agency) considered visiting it until 2030.

As is common in the solar system, Ganymede’s orbit is in resonance with the orbits of Europa and Io: when Ganymede completes one turn, Europa completes two, while Io makes four complete turns.


It is the fourth Galilean satellite with a size practically equal to Mercury’s, but with a third of its weight. It has no orbital resonance with the other satellites, but it is rotating synchronously with Jupiter, always showing the same face of the planet.

The surface has abundant ancient craters and is mostly rock and ice. It probably has an inland ocean, at least 100 kilometers thick.

There is no evidence of tectonic activity, so its craters were certainly caused by meteorite impacts. Its atmosphere is thin, composed of molecular oxygen and carbon dioxide, with a very intense ionosphere. 


Jupiter has a thick atmosphere composed mainly of 87% hydrogen, followed by 13% helium. Other gases present in proportions below 0.1% are hydrogen sulfide, water vapor and ammonia.

The planet’s clouds contain ammonia crystals, and their reddish color likely comes from molecules that contain sulfur or phosphorus. The lower, invisible clouds contain ammonium hydrosulfide.

Due to the presence of storms in the deeper layers, it is very likely that these layers contain clouds composed of water vapor.

Internal structure

Inside Jupiter, hydrogen and helium are in liquid form, due to the high pressures caused by their immense gravity force and thick atmosphere.

At depths greater than 15,000 kilometers below the liquid’s surface, hydrogen atoms are so compressed and their nuclei so close together that electrons separate from the atoms and enter the conduction band, forming liquid metallic hydrogen .

Physical models suggest that deeper there is a rocky core composed of heavy atoms. Initially, they estimated a core of 7 Earth masses, but more recent models envisage a core with a mass between 14 and 18 Earth masses.

It is important to be sure that this nucleus exists, because the answer depends on whether the theory of planetesimal formation of planets is true.

In this theory, planets are formed from solid particle nuclei, giving rise to larger heavy solid objects, which would act as gravitational condensation nuclei, which over millions of years would form planets.

Jupiter’s Magnetosphere

Due to Jupiter’s intense magnetic field, the planet has an extensive magnetosphere, to the point that, if it were not invisible, it would be seen in Earth’s sky with a size similar to that of the Moon. 

No planet in the solar system surpasses Jupiter in terms of the strength and extent of the magnetic field.

Charged particles from the solar wind get trapped and rotate around the magnetic field lines, but float or move along the field lines.

As the magnetic lines emerge from one pole and join the other, the charged particles gain kinetic energy and concentrate at the poles, ionizing and stimulating the gases in Jupiter’s polar atmosphere, with the consequent emission of light radiation.

Missions to Jupiter

Since 1973, Jupiter has been visited by several missions from NASA, the American space agency responsible for space exploration programs.

Missions like Pioneer 10 and 11, Galileo and Cassini studied Jupiter’s satellites. Preliminary data indicate that some of them have conditions favorable to life and also to establish bases with human beings.

The American space agency NASA and the European space agency ESA have new missions to Jupiter among their plans, mainly to study the satellite Europa in more detail.


Pioneer 10 was the first space probe to fly over Jupiter in December 1973. That same year, in April, the Pioneer 11 probe was dispatched, reaching Jovian orbit in December 1974.

In these missions, the first close-up photos of Jupiter and the Galilee satellites were taken. The planet’s magnetic field and radiation belts were also measured.


Also launched in 1973, the Voyager 1 and Voyager 2 missions once again visited the king of planets in the solar system.

The data collected by these missions provided extraordinary and hitherto unknown information about the planet and its satellites. For example, Jupiter’s ring system was first detected and the satellite Io was also found to have intense volcanic activity.


It was launched in 1995 for a seven-year sweep, but the probe had serious problems with the main antenna. Despite this, he managed to send valuable information about Jupiter’s satellites.

The mission discovered underground oceans in Europe and provided more information about Io’s active volcanoes.

Galileo ended when the exploration probe crashed into Jupiter to avoid the collision and subsequent contamination of the frozen surface of Europe.


In December 2000, the Cassini / Huygens mission on Saturn obtained data comparable to the Voyager missions, but due to technological improvements, they were of much better quality.

New Horizons

En route to Pluto, the New Horizons space probe visited the planet Jupiter in 2007.


The most recent of the Jupiter missions is the Juno space probe, which entered orbit with the planet on July 5, 2016. Juno’s mission is the study of the Jovian atmosphere as well as its magnetosphere and auroras.

This mission is expected to provide the data needed to determine which main models are compatible with existing data from Jupiter and thus compare them with models that claim that such a core does not exist.

Trivia about Jupiter

-It is the largest in diameter of the four giant planets: Jupiter, Saturn, Uranus and Neptune.

-In the volume occupied by Jupiter, there are 1,300 Earth-sized planets.

– Jupiter has a massive mass, it is two and a half times the sum of the masses of the seven remaining planets in the solar system.

– Its solid core is believed to have formed just a million years after the formation of the primordial gas and dust disk that gave rise to the solar system, 4.5 billion years ago.  

-Jupiter is the planet in the solar system that has the shortest day: its rotation period is only 9 hours and 55 minutes.

-It is the most radioactive planet in the solar system, in addition to the sunlight reflected by its atmosphere, it also provides its own radiation, mainly in the infrared range.

-Jupiter has the largest satellite in the solar system: Ganymede, with a radius 1.5 times that of the Moon and 0.4 times the radius of Earth.

-80% of its atmosphere is made up of hydrogen, followed by helium, which contributes 17%. The rest are other gases such as water vapor, methane, ammonia and ethane.

Jupiter’s clouds are made of ammonium crystals that form a thin layer about 50 km thick. But its entire atmosphere is on the order of 20,000 km, making it the thickest of all the planets in the solar system.

-It is the planet that has the largest and most durable anticyclonic vortex known in the solar system: the Great Red Spot. With over 300 years of existence, its size is greater than two diameters of the Earth.

-It has an extremely dense core of iron, nickel and liquid metallic hydrogen.

-It has an intense magnetic field capable of producing permanent auroras.

-It is the solar planet with the greatest acceleration due to gravity, which is estimated to be 2.5 times the Earth’s gravity at the edge of its atmosphere.

– Very recent surveys indicate an abundance of water in the equatorial zone, based on data analysis from the Juno space mission. A February 10, 2020 NASA report in the journal Nature Astronomy indicates that 0.25% of the planet’s equatorial atmosphere is made up of water molecules.

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