12 julio, 2024

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

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

Observing its orbit with respect 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 Earth’s diameter 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 findings completely changed the conceptions about the place of the Earth and humanity in the Universe, since it was the first time that celestial bodies revolving around another body other than our planet were observed.

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, and no less important, that outside it there were «other worlds», as Galileo called Jupiter’s satellites.

General characteristics of Jupiter

size and mass

Jupiter is the fifth planet taking into account the orbital radius with respect to the Sun. The fourth planet is Mars, but between the two there is a border: the asteroid belt.

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

The mass of Jupiter, equivalent to 300 terrestrial masses, is so great that it doubles in value to the sum of the mass of the rest of the planets of the solar system. As for its volume, it is the equivalent of 1300 Earths.


Jupiter spins so fast around its own axis that it completes one revolution 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 it takes to go around the Sun completely, is 12 years.


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

When observed with a telescope, only its highest clouds are visible, which have some stationary zones and others in movement, forming a pattern of bands along its equatorial line.

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

White clouds are the result of cooling updrafts, forming ammonium crystals. These currents then curve to the sides to descend again, in the darker belts.

Reddish, yellow and brown color

The diversity of reddish, yellowish, and brown colors seen on Jupiter are the result of the different molecules present in the Jovian clouds. ANDGigantic storms and vortices form between the bands and belts, which can be seen as dots or spots.

These storms are practically permanent and among all of them the Great Red Spot stands out, observed for the first time in the 17th century by Robert Hooke, a notable contemporary physicist and rival of Isaac Newton.

The Great Red Spot is at least 300 years old, yet 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 at 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 such an extent that hydrogen gas liquefies, forming an ocean of liquid hydrogen, at a pressure so high that it behaves like metal. This would be the lower border 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 most likely has a very dense core composed of heavy metallic elements, but more data is needed to substantiate this claim.

Summary of the physical characteristics of Jupiter

-Mass: 1.9×1027 kg

-Equatorial radius: 71492 km, equivalent to 11 times the radius of the Earth.

polar radius: 66854 km.

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

-Mean radius of the orbit: 7.78 x 108 km, equivalent to 5.2 AU

Tilt of the axis of rotation: 3º12 with respect to the orbital plane.

-Temperature: -130ºC (clouds)

-Gravity: 24.8 m/s2

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

-Atmosphere: Dense atmosphere of hydrogen and helium.

-Density: 1336kg/m3

-Satellites: 79 known.

-Rings: Yes, wispy and composed of dust.

Jupiter structure

Jupiter’s outermost layer is made up of clouds and is 50 km thick. Under this layer of clouds there is another layer, mainly of hydrogen and helium, with a thickness of 20,000 km.

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

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

At greater depths, there could be a solid core 1.5 times the Earth’s diameter, but 30 times heavier than our planet. And since it is a planet made up of gas and liquid, due to its tremendous speed of rotation, the planet takes on a flattened shape at its poles.

When and how to observe Jupiter

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

To the naked eye Jupiter shines brighter in the night sky than Sirius, the most luminous star and it is always close to some zodiacal constellation, which can vary according to the year, in an environment of 30 degrees.

With good steady-state binoculars or a small telescope, Jupiter appears as a smoothly banded white disk.

The four Galilean satellites are easily visible with a small telescope: Ganymede, Io, Europa, and Callisto. The positions of the satellites vary from one day to the next, and sometimes only three are visible, since some of them are behind or in front of the planet.

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

Translation movement

Jupiter’s orbit is elliptical and has its focus off the center of the Sun 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 said that the planets revolve around the center of the Sun, which is pretty accurate for almost all except Jupiter.

This is because Jupiter is so massive that the center of spin, barycenter, or center of mass of the Sun-Jupiter system moves toward Jupiter, outside the solar body.

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

He perihelion is the smallest distance between the orbit of Jupiter and the focus of the ellipse, located at the barycenter of the Sun-Jupiter system. Its value is 816.62 million kilometers.

On the contrary, the aphelion is the greatest distance between the focus and the 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 semimajor axis of the ellipse.

Rotatory motion

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

For being so bulky, Jupiter has the shortest rotation period of all the planets in the solar system.

Jupiter satellites

Giant planets are characterized by having a large number of satellites or moons. To date, 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, has ⅓ the diameter of the Earth

-Europe, with ¼ of the earth’s diameter

-Ganymede, ⅖ parts of the diameter of the Earth

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

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

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

To the outside of the Galilean satellites is the group of regular Satellites, 10 in total, plus the group of retrograde satellites, of which sixty-one (61) are known to date.

By order of orbital radius, four groups of satellites are defined:

interior satellites (4) with orbits between 128,000 to 222,000 km.
Galilean satellites (4) Their orbits range from 422,000 km for Io to 1,883,000 km for Callisto. Together they have 99.99% of the mass of all Jovian satellites.
regular satellites (10) Between 7,284,000 km to 18,928,000 km.
retrograde satellites (61) from 17,582,000 km to 28,575,000 km.

Jupiter also has rings. They are in lower orbit than the Galilean satellites and between the orbits of the inner satellites. It is thought that these rings arose as a result of the impact of some inner satellite with a meteoroid.

Galilean satellites

The four Galilean satellites make up a very interesting group, since experts believe that they meet the conditions for eventual colonization in the future.


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

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


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

It is only slightly smaller than the Moon and has a solid crust…

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