Jupiter (planet)
Jupiter is the largest planet in the solar system and the fifth in order of distance from the Sun. It is a gas giant that is part of the so-called outer planets. It gets its name from the Roman god Jupiter (Zeus in Greek mythology). It is one of the brightest natural objects in a clear night sky, surpassed only by the Moon, Venus, and sometimes Mars.
This is the planet that shines brightest throughout the year depending on its phase. It is also, after the Sun, the largest celestial body in the solar system, with a mass almost two and a half times that of the other planets together (with a mass 318 times greater than that of Earth and three times greater than that of Earth). Saturn, in addition to being, in terms of volume, 1321 times larger than Earth). It is also the oldest planet in the solar system, being even older than the Sun; this discovery was made by researchers at the University of Münster in Germany.
Jupiter is a massive gaseous body, formed mainly by hydrogen and helium, lacking a defined interior surface. Among the atmospheric details, the Great Red Spot (a huge anticyclone located in the tropical latitudes of the southern hemisphere), the structure of clouds in dark bands and bright areas, and the global atmospheric dynamics determined by intense zonal winds alternating in latitude and with speeds up to 140 m/s (504 km/h).
Main features
Jupiter is the most massive planet in the solar system: it is about 2.48 times the sum of the masses of all the other planets combined. Despite this, it is not the most massive planet known: more than a hundred extrasolar planets that have been discovered have masses similar to or greater than that of Jupiter. Jupiter also has the fastest rotation rate of the planets. of the solar system: it rotates on its axis in a little less than ten hours. This rotation rate is deduced from measurements of the planet's magnetic field. The atmosphere is divided into regions with strong zonal winds with rotation periods ranging from 9:50:30 a.m. in the equatorial zone to 9:55:40 a.m. in the rest of the planet.
The planet is known for a huge weather formation, the Great Red Spot, easily visible to amateur astronomers given its vast size, larger than Earth's. Its atmosphere is permanently covered in clouds that allow to trace the atmospheric dynamics and show a high degree of turbulence.
Taking the distance from the Sun as a reference, Jupiter is the fifth planet in the solar system. Its orbit is approximately 5 AU, about 750,000,000 (seven hundred fifty million) kilometers from the Sun.
Mass
Jupiter's mass is such that its barycenter with the Sun is actually above its surface (1.068 solar radius, from the center of the Sun). Despite being much larger than Earth (with eleven times as large in diameter), is considerably less dense. Jupiter's volume is equivalent to that of 1,321 Earths, but its mass is only 318 times greater. The Jupiter mass unit (Mj) is used to measure masses of other gas planets, especially extrasolar planets and brown dwarfs.
The smallest known red dwarf has only 30% more radius than Jupiter, yet it is hundreds of times its mass. Although the planet would need to be about 15 times its mass to trigger the ²H (deuterium) fusion reactions to become a brown dwarf, Jupiter radiates more heat than it receives from the scant sunlight that reaches it. The difference in heat released is generated by Kelvin-Helmholtz instability through adiabatic contraction (shrinkage). The consequence of this process is a gradual and slow reduction in its diameter by about two centimeters each year. According to this theory, after its formation, Jupiter was much hotter and had almost twice its current diameter.
If it were only four times as massive, the interior could become much more compressed by the increase in gravitational force, which would in the appropriate proportion decrease in volume despite the increase in mass. As a result, it is speculated that Jupiter has reached one of the largest diameters that a planet with these characteristics and evolution can achieve. The reduction in volume by an increase in mass during planetary formation could continue until sufficient pressure was reached to initiate nuclear fusion processes, such as in brown dwarfs, with a few tens of times the Jovian mass. This has led some astronomers to call it a "failed star", although it is not clear whether the processes involved in the formation of planets like Jupiter resemble the processes of creating multiple star systems.
Atmosphere
Jupiter's atmosphere does not present a clear border with the planet's liquid interior; the transition occurs gradually. It is composed mostly of hydrogen (87%) and helium (13%), as well as containing methane, water vapor, ammonia and hydrogen sulfide, all of which are < 0.1% of the composition of the total atmosphere.
Gangs and Zones
The English amateur astronomer A.S. Williams made the first systematic study of Jupiter's atmosphere in 1896. Jupiter's atmosphere is divided into dark belts called bands and light regions called zones, all aligned in the direction of parallels. The bands and zones delimit a system of alternating wind currents in the direction of latitude and generally of great intensity; for example, winds at the equator blow at speeds of around 100 m/s (360 km/h). In the North Equatorial Band, the winds can reach 140 m/s (500 km/h). The rapid rotation of the planet (9 h 55 min 30 s) makes the Coriolis forces very intense, being decisive in the atmospheric dynamics of the planet.
The Great Red Spot
The English scientist Robert Hooke observed a large meteorological formation in 1664 that could be the Great Red Spot (GRS, Great Red Stain). However, there do not appear to be any subsequent reports of the observation of such a phenomenon until the 20th century. In any case, it varies a lot both in color and intensity. Images obtained by the Yerkes Observatory at the end of the 19th century show an elongated red spot, occupying the same range of latitudes but with twice the longitudinal extent. Sometimes it is a deep red, and very noticeable indeed, and at other times it pales to insignificance. Historically, the Great Red Spot was originally thought to be a gigantic mountain top or plateau jutting out above the clouds. This idea was, however, discarded in the 19th century when the composition of hydrogen and helium in the atmosphere was verified spectroscopically and it was determined that it was a fluid planet. The current size of the Great Red Spot is about two and a half times that of Earth. Meteorologically, the Great Red Spot is a huge anticyclone that is very stable over time. The winds on the periphery of the vortex have a speed close to 400 km/h.
The Little Red Spot
In March 2006, it was announced that a second red spot about half the size of the Great Red Spot had formed. This second red spot was formed from the merger of three large white ovals present on Jupiter since the 1940s, called BC, DE and FA, and merged into one between 1998 and 2000, giving rise to a single white oval. named White Oval BA, whose color evolved into the same shades as the Great Red Spot in early 2006.
The reddish coloration of both spots can be produced when gases from the inner atmosphere of the planet rise in the atmosphere and undergo the interaction of solar radiation. Infrared measurements suggest that both spots rise above the main clouds. The change, therefore, from a white oval to a red spot could be a sign that the storm is gaining strength. On April 8, 2006, Hubble's Advanced Tracking Camera took new images of the young storm.
Cloud Structure
Jupiter's upper clouds are probably made of frozen crystals of ammonia. The reddish color is given by some type of unknown coloring agent although compounds of sulfur or phosphorus are suggested. Below the visible clouds, Jupiter quite possibly possesses denser clouds of a chemical compound called ammonium hydrosulfide, NH4HS. At a pressure around 5-6 Pa there is possibly an even denser layer of water clouds. One of the proofs of the existence of such clouds is the observation of electrical discharges compatible with deep storms at these pressure levels. Such convective storms can sometimes extend from 5 Pa to 300-500 hPa, about 150 km in vertical.
Disappearance of the subequatorial belt
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At the end of April 2010, different amateur astronomers[who?] noticed that Jupiter had altered the color of the traditionally dark subequatorial belt, making the southern part appear completely white and very homogeneous. The phenomenon took place when Jupiter was in opposition to the Sun, thus being observable from Earth. Several hypotheses are considered to explain this change, the most probable is a change in the color of the clouds without substantial changes in the height or quantity of particles that form them. This phenomenon of apparent disappearance of a band occurs semi-cyclically on Jupiter, having been observed on several occasions before, particularly in 1993 when it was studied in detail.
Image gallery of the clouds of Jupiter
Image of Hubble Space Telescope showing the two red spots of Jupiter
High resolution image of the Great Jupiter Red Blade taken by Voyager 1 probe in 1979
Photograph by Jupiter obtained by the Cassini mission in December 2000
Southern Hemisphere of Jupiter captured on 17 February 2020, during an approach to the Juno space probe.
Projection of the planet from the south pole made by the Cassini probe.
Internal structure
In the interior of the planet, hydrogen, helium and argon (noble gas that accumulates on the surface of Jupiter) are progressively compressed. Molecular hydrogen is compressed in such a way that it becomes a metallic liquid at depths of about 15,000 km below the surface. Lower down it is assumed that there is a rocky core made up mainly of icy and denser materials, about 7 Earth masses (although a recent model increases the mass of the central core of this planet between 14 and 18 Earth masses, and other authors think that there may be no such nucleus, as well as the possibility that the nucleus was originally larger, but that convective currents of hot metallic hydrogen would have caused it to lose mass). The existence of the different layers is determined by the study of the gravitational potential of the planet, measured by the different space probes. If the inner core exists, it would prove the theory of planetary formation from a disk of planetesimals. Jupiter is so massive that it has not yet released the heat accumulated in its formation, and therefore has a significant internal source of heat energy that has been precisely measured to be 5.4 W/m². This means that the interior of the planet is effectively mixed at least to levels close to water clouds at 5 bar.
The same model mentioned before, which gives a greater mass to the core of the planet, considers that it has an internal structure formed by concentric cylinders that rotate at different speeds —the equatorial ones (which are the external ones) faster than the internal ones—, in a similar way to the Sun; The Juno mission, which was launched on August 5, 2011 and entered orbit around the planet on July 4, 2016, is expected to be able to determine with its measurements of Jovian gravity the internal structure of the planet.
Magnetosphere
Jupiter has a large magnetosphere formed by a strong magnetic field. Jupiter's magnetic field could be seen from Earth occupying an area equivalent to that of the full Moon despite being much farther away. Jupiter's magnetic field is in fact the largest structure in the solar system after the Sun's magnetic field. Charged particles are picked up by the Jovian magnetic field and driven towards the polar regions where they produce impressive auroras. On the other hand, the particles ejected by the volcanoes of the satellite Io form a rotating toroid in which the magnetic field traps additional material that is conducted through the field lines over the upper atmosphere of the planet.
It is thought that the origin of the magnetosphere is due to the fact that in the deep interior of Jupiter, hydrogen behaves like a metal due to the very high pressure. Metals are, of course, excellent conductors of electrons, and the rotation of the planet produces currents, which in turn produce a large magnetic field.
The Pioneer probes confirmed the existence of the Jovian magnetic field and its intensity, being more than 10 times stronger than the Earth's containing more than 20,000 times the energy associated with the Earth's field. The Pioneers discovered that the shock wave from the Jovian magnetosphere extends 26 million kilometers from the planet, with the magnetic tail extending beyond the orbit of Saturn.
Variations in the solar wind cause rapid variations in the size of the magnetosphere. This aspect was studied by the Voyager probes. It was also discovered that charged atoms were ejected from the Jovian magnetosphere with great intensity and were capable of reaching Earth's orbit. Electric currents were also found flowing from Jupiter to some of its satellites, particularly Io and also to a lesser extent Europa.
Satellites
Galilean satellites
The main satellites of Jupiter were discovered by Galileo Galilei on January 7, 1610, which is why they are called Galilean satellites. They receive their names from Greek mythology, although in Galileo's time they were called by Roman numerals depending on their order of proximity to the planet. Galileo originally named the satellites "Mediceans" in honor of Cosimo de' Medici, Duke of Florence. The discovery of these satellites constituted a turning point in the already long dispute between those who supported the idea of a geocentric system, that is, with the Earth at the center of the universe, and the Copernican (or heliocentric system, that is, with the Sun in the center of the solar system), in which it was much easier to explain the movement and the very existence of Jupiter's natural satellites.
The four main satellites are very different from each other. Io, the innermost, is a volcanic world with a constantly renewing surface and heated by tidal effects caused by Jupiter and Europa. Europa, the next satellite, is an icy world under which the presence of liquid oceans of water and even the presence of life. Ganymede, with a diameter of 5,268 km, is the largest satellite in the entire solar system. It is composed of an iron core covered by a layer of rock and ice. Callisto is characterized by being the body with the largest number of craters produced by impacts in the entire solar system.
| Name | Diameter (km) | Mass (kg) | Middle orbital radio radio (km) | Orbital period |
|---|---|---|---|---|
| Io | 3.643,2 | 8,94×1022 | 421,600 | 1,769138 days |
| Europe | 3.122 | 4,8×1022 | 671.100 | 3,551181 days |
| Ganymede | 5.262 | 1,48×1023 | 1,070,400 | 7,154553 days |
| Calisto | 4.821 | 1,08×1023 | 1,882,700 | 16,68902 days |
Minor satellites
In addition to the aforementioned Galilean satellites, various space probes sent to Jupiter and observations from Earth have increased the total number of Jupiter's satellites to 79. These smaller satellites can be divided into two groups:
- Amaltea Group: four small satellites revolve around Jupiter in internal orbits to those of the Galilean satellites. This group is composed (in order of distance) by Metis, Adrastea, Amaltea and Tebe.
- Irregular satellites: it is a large group of satellites in very distant orbits of Jupiter; in fact, they are so far from this that the gravity of the Sun perceptibly distorts their orbits. With the exception of Himalia, they are generally small satellites. In turn, this group can be divided into two, graduates and retrogrades. Most of these objects have a very different origin from that of larger satellites, possibly captured bodies and not formed in their current orbits. Others may be the remnants of impacts and fragmentations of previous larger bodies. Members of this group include Aedea, Aitné, Ananké, Arce, Autónoe, Caldona, Cale, Cálice, Calírroe, Carmé, Carpo, Cilene, Elara, Erínome, Euante, Eukélade, Euporia, Eurídome, Harpálice, Hegémone, Heliké, Hermipée, Hexte
Trojan Asteroids
In addition to its satellites, Jupiter's gravitational field controls the orbits of numerous asteroids that lie at the Lagrange points preceding and following Jupiter in its orbit around the Sun. These asteroids are called Trojan asteroids and are divided on Greek and Trojan bodies to commemorate the Iliad. The first of these asteroids to be discovered was 588 Achilles, by Max Wolf in 1906. Hundreds of Trojan asteroids are known today. The largest of them all is the asteroid 624 Hector.
Ring system
Jupiter has a faint ring system that was discovered by the Voyager 1 probe in March 1979. The main ring is about 6,400 km wide, orbits the planet 122,800 km from its center, and has a thickness vertical less than ten kilometers. Its optical thickness is so reduced that it has only been observed by the Voyager 1 and 2 and Galileo space probes.
The rings have three segments: the innermost called halo (shaped like a torus instead of a ring), the intermediate one, which is considered the main one because it is the brightest, and the outer one, dimmer but larger. The rings are made of dust instead of ice like Saturn's rings. The main ring is probably composed of material from the Adrastea and Metis satellites; this material is gradually pulled towards Jupiter thanks to its strong gravity. In turn, it is replaced by the impacts on these satellites that are in the same orbit as the main ring. The Amalthea and Thebes satellites perform a similar task, supplying material to the outer ring.
Formation of Jupiter
Theories of planet formation are of two types:
- formation from an ice core of a mass around 10 times the Earth mass capable of attracting and accumulating the gas of the nebula protosolar,
- early formation for direct gravitational collapse as would occur in the case of a star.
Both models have very different implications for the general models of formation of the solar system and of extrasolar planet systems. In both cases the models have difficulties in explaining the overall size and mass of the planet, its orbital distance of 5 au, which seems to indicate that Jupiter did not move substantially from the region of formation, and the chemical composition of its atmosphere, particularly its atmosphere. noble gases, enriched with respect to the Sun. The study of the internal structure of Jupiter, and in particular, the presence or absence of an inner core would allow us to distinguish both possibilities.
The properties of the planet's interior can be explored remotely from gravitational disturbances detected by a nearby space probe.
There are currently proposals for space missions for the next decade that could answer these questions.
Impact of comet SL9
In July 1994, Comet Shoemaker-Levy 9 slammed into Jupiter's atmosphere. The comet had been broken up by the action of Jupiter's gravity into 20/22 fragments in a previous and close pass through the planet.
Numerous observatories carried out intensive campaigns to observe the planet on the occasion of this unique event, including the Hubble Space Telescope and the Galileo probe, which was still approaching the planet at that time. The impacts showed the formation of impressive fireballs in the minutes after each impact, from which analysis the mass of each of the comet fragments could be deduced. Debris left in the atmosphere was observed as expanding black clouds for weeks propagating like shock waves. Its properties made it possible to analyze both properties of the comet and of the Jovian atmosphere and its deep interior by methods analogous to those of terrestrial seismology. The remains of the comet could be detected for several years in the upper atmosphere of Jupiter's southern hemisphere, present as fine dark particles and through a higher atmospheric concentration of certain chemical compounds contributed by the comet.
It has been estimated that Jupiter, due to its great mass, perturbs cometary regions such as the Oort cloud, attracting most of the comets that fall on the inner solar system. However, it also brings them closer to itself, so it is difficult to estimate the importance of Jupiter in the arrival of comets on Earth.
Recent Impacts
On July 19, 2009 Anthony Wesley, an Australian amateur astronomer announced the discovery of a black spot about the same size as the diameter of the Moon that had appeared in Jupiter's atmosphere in the southern subpolar region. This spot was possibly caused by an asteroidal or cometary impact with the planet. Scientists at the Propulsion Laboratory (JPL) in Pasadena confirmed the impact using the NASA Infrared Telescope Facility (IRTF) located on the Hawaiian island of Mauna Kea.
The impacting object, with an estimated diameter of about 500 meters, caused an increase in temperature in the upper layers of the Jovian atmosphere at the impact site and a large cloud of dark dust particles that formed the smudge of great extension and that continued to be observable for several months in a progressively fainter form as the impact debris was dispersed by the winds of Jupiter's atmosphere. At the moment it is unknown if the object that hit Jupiter was an asteroid or a comet. The impact, discovered by chance, occurred 15 years after the impact of Comet Shoemaker-Levy 9.
On June 3, 2010, almost a year later, Anthony Wesley and Christopher Go (amateur astronomer from the Philippines) simultaneously observed the appearance of an intense flash of light on Jupiter in a very localized region that corresponds to the impact of an asteroidal or cometary body smaller than in 2009. The flash, which lasted a few seconds, occurred in equatorial latitudes and at the moment does not appear to have left any observable material remnants in the Jovian atmosphere.
Jupiter Space Exploration
Jupiter has been visited by several NASA space missions since 1973.
The Pioneer 10 and Pioneer 11 missions conducted preliminary flyby exploration of the planet. The Pioneer 10 probe flew by Jupiter for the first time in history in December 1973. The Pioneer 11 probe followed just a year later. The first close-up photos of Jupiter and the Galilean satellites were taken, its atmosphere was studied, its magnetic field was detected, and its radiation belts were studied.
The Voyager 1 and Voyager 2 missions visited Jupiter in 1979, revolutionizing the knowledge of the planet and its satellites and also discovering its ring system. It was discovered that Io had extraordinary volcanic activity and that Jupiter also had rings.
In 1995, the Galileo mission, consisting of a probe and an orbiter, began a seven-year mission to explore the planet. Although the mission had significant problems with the main antenna that relayed the data back to Earth, it managed to send information of unprecedented quality over Jupiter's satellites, discovering the subsurface oceans of Europa and several examples of active volcanism on Io. The mission concluded by launching the orbiter against the planet itself to avoid a future collision with Europa that could contaminate its ice.
In December 2000, the Cassini/Huygens space mission performed a far flyby on its journey to Saturn, yielding a data set comparable in quantity to the flybys made by Voyager but with better quality of observations.
In late February 2007, the planet Jupiter was visited by the New Horizons probe on its journey to Pluto.
On July 5, 2016, the space probe Juno entered orbit to study the atmosphere, magnetosphere, and aurorae of this planet.
Missions dedicated to the observation of Jupiter and its satellite Europa are being studied by the space agencies NASA and ESA.
How to locate it
Just like the rest of the planets more external than the Earth in its orbit with respect to the Sun, Jupiter can occupy any part of the ecliptic or be hidden behind the Sun. It does not happen like Venus and Mercury, that because they have their orbits closer to the Sun than that of the Earth, we can only locate them in the direction of the Sun and in its vicinity. Since Jupiter's brightness is always greater than magnitude -2, (its brightest at best opposition reaches magnitude -2.9) Jupiter is visible to the naked eye, and appears in the sky as a rounded stellar-like object. and pale in color, usually being the second most luminous planet with the naked eye, after Venus. In exceptional circumstances, when the opposition of Mars coincides near the perihelion of its elliptical orbit, the brightness of Mars can reach magnitude -2.97, exceeding the brightness of Jupiter, but only for a few days. With even an amateur telescope, it is possible to see the cloud bands of the Jovian atmosphere and its largest satellites.
Jupiter's apparent motion relative to the star background is direct except near opposition. Jupiter will appear to go retrograde about 60 days before opposition and will remain so for a period of approximately 121 days, apparently moving “backward” through an angle of 9.9° before returning to motion. straight.