Jupiter can rightfully be called the most "weighty" planet in the solar system, because if you add together all the other planets, including our Earth, then their total mass will be 2.5 times less than that of this giant. Jupiter possesses very powerful radiation, the level of which in the solar system is exceeded only by the sun.
Everyone knows the rings of Saturn, but Jupiter also has a lot of satellites. To date, scientists know exactly 67 such satellites, of which 63 are well studied, but it is assumed that Jupiter has at least a hundred satellites, and most of them were discovered in recent decades. Judge for yourself: at the end of the 70s of the 20th century, only 13 satellites were registered, and later on, ground-based telescopes of the new generation made it possible to detect more than 50 more.
Most of Jupiter's moons have a small diameter - from 2 to 4 km. Astronomers classify them as Galilean, internal and external.
Galilean satellites
The largest moons of Jupiter: Io, Europa, Ganymede and Callisto were discovered by Galileo Galilei in 1610, and they got their name after him. Their formation took place after the formation of the planet, from the gas and dust that surrounded it.
And about
Io got its name in honor of the beloved Zeus, so it would be more correct to speak of her in the feminine gender. It is the fifth moon of Jupiter and is the most volcanically active body in the solar system. Io is about the same age as Jupiter itself - 4.5 billion years. Like our Moon, Io is always turned to Jupiter with only one side, and its diameter is not much larger than the lunar one (3642 km versus 3474 km for the Moon). The distance from Jupiter to Io is 350 thousand km. It ranks fourth in size among the satellites in the solar system.
On the satellites of the planets, and on the planets of the solar system themselves, volcanic activity is extremely rare. Currently, only four cosmic bodies are known in the solar system, where it manifests itself. This is Earth, Neptune's moon Triton, Saturn's moon Enceladus and Io, which is the undisputed leader in this four in terms of volcanic activity.
The scale of the eruptions on Io is such that it can be clearly seen from space. Suffice it to say that sulfuric magma from volcanoes erupts up to 300 km (12 such volcanoes have already been discovered), and giant lava flows have covered the entire surface of the satellite, with a wide variety of colors. And in the atmosphere of Io, sulfur dioxide predominates, which is due to high volcanic activity.
Real picture!
Animation of the eruption in Pater Tvashtar, composed of five images taken by the New Horizons spacecraft in 2007.
Io is quite close to Jupiter (by cosmic standards, of course) and constantly experiences the massive effect of its gravity. It is gravity that explains the tremendous friction inside Io caused by tidal forces, as well as the constant deformation of the satellite, heating its interior and surface. In some parts of the satellite, the temperature reaches 300 ° C. Along with Jupiter, Io is influenced by the forces of gravity from two other satellites - Ganymede and Europa, which mainly causes additional heating of Io.
The eruption of the Pele volcano on Io, captured by the Voyager 2 spacecraft.
Unlike volcanoes on Earth, which most of the time "sleep" and erupt only for a fairly short period of time, on the incandescent Io volcanic activity is not interrupted, and peculiar rivers and lakes are formed from the flowing molten magma. The largest molten lake known to date has a diameter of 20 km and contains an island of solidified sulfur.
However, the interaction of the planet and its satellite is not one-sided. Although Jupiter, thanks to its powerful magnetic belts, takes up to 1000 kg of matter from Io every second, which practically doubles its magnetosphere. The movement of Io through its magnetosphere generates such powerful electricity that violent thunderstorms rage in the planet's upper atmosphere.
Europe
Europe got its name in honor of another beloved of Zeus - the daughter of the Phoenician king, whom he abducted in the form of a bull. This moon is the sixth farthest from Jupiter, and is about the same age as it, that is, 4.5 billion years. However, Europa's surface is much younger (about 100 million years), so there are practically no meteorite craters on it, which appeared during the formation of Jupiter and its satellites. Only five such craters with a diameter of 10 to 30 km were found.
The orbital distance of Europa from Jupiter is 670,900 km. The diameter of Europa is smaller than that of Io and the Moon - only 3100 km, and it is also always turned to its planet with one side.
The maximum surface temperature at the equator of Europe is minus 160 ° C, and at the poles - minus 220 ° C. Although the entire surface of the satellite is covered with a layer of ice, scientists believe that it is hiding a liquid ocean. Moreover, the researchers believe that some forms of life exist in this ocean thanks to thermal springs located next to underground volcanoes, that is, the same as on Earth. In terms of the amount of water, Europe is twice as fast as the Earth.
Two models of the structure of Europe
The surface of Europa is riddled with cracks. The most common hypothesis explains this by the influence of tidal forces on the ocean coast below the surface. It is likely that the rise of water under the ice higher than usual occurs when the satellite approaches Jupiter. If this is true, then the appearance of cracks on the surface is precisely caused by the constant rises and falls of the water level.
According to a number of scientists, sometimes water masses break through the surface, like lava during a volcanic eruption, and then these masses freeze. This hypothesis is supported by icebergs that can be seen on the surface of the satellite.
In general, the surface of Europa does not have elevations higher than 100 m, therefore it is considered one of the smoothest bodies in the solar system. Europe's thin atmosphere contains mainly molecular oxygen. Apparently, this is due to the decomposition of ice into hydrogen and oxygen under the influence of solar radiation, as well as other hard radiation. As a result, molecular hydrogen quickly evaporates from Europa's surface due to its lightness and weak gravity on Europa.
Ganymede
The satellite got its name in honor of the handsome youth whom Zeus brought to Olympus and made the cupbearer at the feasts of the gods. Ganymede is the largest satellite in the solar system. Its diameter is 5268 km. If its orbit was not around Jupiter, but around the Sun, it would be considered a planet. The distance between Ganymede and Jupiter is about 1070 million km. It is the only satellite in the solar system that has its own magnetosphere.
About 60% of the satellite is occupied by strange bands of ice, which were the result of active geological processes that took place 3.5 billion years ago, and 40% is an ancient powerful ice crust covered with many craters.
Possible internal structure of Ganymede
Ganymede's core and silicate mantle generate heat that makes the underground ocean possible. According to scientists, it is located 200 km below the surface, while in Europa, a large ocean is located closer to the surface.
But the thin layer of the atmosphere of Ganymede, consisting of oxygen, is similar to the atmosphere found in Europa. Compared to other moons of Jupiter, flat craters on Ganymede practically do not form a hill and do not have a depression in the center, as do craters on the Moon. This appears to be due to the slow, gradual movement of the soft ice surface.
Callisto
The satellite Callisto got its name in honor of another lover of Zeus. With a diameter of 4820 km, it is the third largest satellite in the solar system, and it is about 99% of the diameter of Mercury, while the mass of the satellite is three times less than that of this planet.
The age of Callisto, like that of Jupiter and other Galilean satellites, is also about 4.5 billion years old, but its distance to Jupiter is much larger than other satellites, almost 1.9 million kilometers. Due to this, the rigid radiation field of the gas giant does not affect it.
Callisto's surface is one of the oldest surfaces in the solar system - about 4 billion years old. All of it is covered with craters, so that over time, each meteorite necessarily fell into an existing crater. Callisto lacks violent tectonic activity, its surface does not warm up after formation, so it has retained its ancient appearance.
According to many scientists, Callisto is covered by a thick layer of ice, under which is the ocean, and in the center of the satellite contains rocks and iron. Its thin atmosphere is made up of carbon dioxide.
The Valhalla crater with a total diameter of about 3800 km deserves special attention on Callisto. It is made up of a bright central region with a diameter of 360 km, surrounded by ridge concentric rings with a radius of up to 1900 kilometers. This whole picture resembles circles on the water from a stone thrown into it, only in this case the role of the "stone" was played by a large asteroid 10-20 km in size. Valhalla is considered the largest formation around an impact crater in the solar system, although the crater itself is only 13th in size.
Valhalla - the impact pool on the Callisto satellite
As already mentioned, Callisto is outside the rigid radiation field of Jupiter, therefore it is considered as the most suitable object (after the Moon and Mars) for the construction of a space base. Ice can serve as a source of water, and from Callisto itself it will be convenient to explore another moon of Jupiter - Europa.
It will take 2 to 5 years to fly to Callisto. The first manned mission is planned to be sent no earlier than 2040, although the flight may begin later.
Model of the internal structure of Callisto
Shown: ice crust, a possible water ocean, and a core of rocks and ice.
Jupiter's inner moons
The inner moons of Jupiter are so named because of their orbits, which are very close to the planet and are located within the orbit of Io, which is the closest Galilean satellite to Jupiter. There are four inner satellites: Metis, Amalthea, Adrastea and Thebes.
Amalthea, 3D model
Jupiter's faint ring system is replenished and supported not only by inner moons, but also by small inner moons, which are still invisible. Jupiter's main ring is supported by Metis and Adrastea, while Amalthea and Thebes have to maintain their own weak outer rings.
Of all the inner satellites, Amalthea is the most interesting with its deep red surface. The fact is that this has no analogues in the solar system. There is a hypothesis that this color of the surface is explained by the inclusions of minerals and sulfur-containing substances into the ice, but this does not clarify the reason for this color. It is more likely that the capture of this moon by Jupiter occurred from the outside, as is regularly the case with comets.
Jupiter's outer moons
The outer group consists of small satellites with a diameter of 1 to 170 km, which move in elongated orbits with a strong inclination to the equator of Jupiter. To date, 59 such external satellites are known. Unlike the inner satellites, which move in their own orbits in the direction of Jupiter's rotation, most of the outer satellites move in their orbits in the opposite direction.
Orbits of Jupiter's moons
Since some small satellites have nearly identical orbits, it is assumed that they are remnants of larger satellites destroyed by Jupiter's gravity. In pictures taken from spacecraft flying by, they look like shapeless boulders. Obviously, Jupiter's gravitational field captured some of them during their free flight in space.
Jupiter's rings
Along with satellites, Jupiter also has its own system, like other gas giants in the solar system: Saturn, Uranus and Neptune. The rings of Saturn, discovered by Galileo in 1610, look much more spectacular and more noticeable, since they consist of shiny ice, while in Jupiter it is just an insignificant dusty structure. This explains their late discovery, when a spacecraft first reached the Jupiter system in the 1970s.
Galileo's image of the main ring in forward-scattered light
Jupiter's ring system is formed by four main components:
Halo - a thick torus of particles, resembling in appearance a donut or a disc with a hole;
The main ring is very thin and quite bright;
Two outer rings, wide but weak, called "spider rings".
The Halo and the Main Ring are composed mainly of dust from Metis, Adrastea, and probably several other smaller satellites. The halo is approximately 20 to 40 thousand km wide, although its main mass is located no further than several hundred kilometers from the plane of the ring. The halo shape, according to a popular hypothesis, is due to the effect of electromagnetic forces inside the Jupiter magnetosphere on dust particles in the ring.
Spiderweb rings are very thin and transparent, like a spider's web, they were named after the material of the satellites of Jupiter, Amalthea and Thebes that form them. The outer edges of the Main Ring are outlined by the satellites Adrastea and Metis.
Jupiter's rings and inner moons
"Missing star" - this is how many astronomers call Jupiter. Undoubtedly, Jupiter occupies a special place in the solar system, if only because it is almost 2.5 times larger than all the planets combined. It also has very powerful radiation, the level of which is only lower than that of the Sun.
Although the stars did not come out of Jupiter, it has its own "system in the system". A huge number of satellites revolve around it, compared to other planets. It is impossible to say exactly how many satellites Jupiter has, since scientists assume that there are at least 100 of them, but to date 79 have been registered.
Volcanic eruption on Io
They are usually divided into 3 groups: Galilean, internal and external. The largest and first ones were discovered by Galileo in 1610 - these are Io, Callisto and Ganymede, named after ancient heroes.
And about
The closest gallium satellite to Jupiter. It is famous for its volcanoes - Io has the most active volcanic activity of all space objects in the solar system. Volcanic craters are located on its entire surface. The lava emitted by them has a fairly diverse spectrum of colors - from yellow to brown and even black. It is the products of volcanic eruptions that form the surface of Io, which is predominantly orange in color.
Europe
It has a very interesting surface relief, over the origin of which scientists have been puzzling over for several decades. It is a kind of network of cracks and breaks of a block of ice that makes up the "outer shell" of Europe. It is assumed that the presence of the ocean under the ice causes the appearance of warm water that rises from the depths and, freezing, tears apart the ice surface.
Ganymede
It is distinguished by its majesty in relation to other satellites and not only Jupiter. It is covered with a thick layer of ice and has a strong magnetic field comparable to that of some planets. Scientists assume in the bowels of Ganymede the presence of an ocean similar to the Earth, which determines such electrical conductivity of waters. If Ganymede was not a satellite, he could become another planet.
Callisto
Covered with a huge number of craters, which are not observed in any cosmic body. This fact testifies to the very ancient origin of Callisto and his lack of geological activity.
Reverse satellites
Such satellites move towards all other satellites of Jupiter, and the position of the orbit is slightly tilted in relation to their planet. Such features and a significant distance from Jupiter suggest that in the past these are ordinary asteroids caught in the gravitational pull of Jupiter. They are “marked” with the letter e at the end of their names - Sinope, Karma, Ananke and Pasiphae.
A short popular science film about Jupiter
Rise of Europa captured by the Cassini spacecraft.
To date, about 180 planetary satellites have been discovered in the solar system. The development of astronomy, as well as the use of interplanetary flying vehicles for the study of outer space, makes it possible to fix celestial bodies of an ever-smaller size in it, therefore this figure is constantly increasing. More than half of the discovered satellites are located on the moons of Jupiter, the largest planet orbiting the Sun.
Today their number is estimated at 79, but it is rather arbitrary and scientists say that in fact there are at least a hundred of them. 50 satellites already have their own names - traditionally they are called female names in honor of the beloved and numerous daughters of Jupiter (Zeus). In ancient times, the deities did not differ in special morality and legibility, therefore, among the satellites of Jupiter, Ganymede was also a beautiful young man who liked the almighty thunderer and therefore was kidnapped by him. The remaining 29 celestial bodies, discovered relatively recently, do not yet have their own names.
The role of Jupiter's moons in the development of astronomy
Pictured from left to right is Ganymede, Callisto, Io and Europa. These satellites are among the largest in the solar system and can be observed with a small telescope.
Jupiter became the first planet in the solar system to have satellites, apart from the moon, a satellite of the Earth. This was done by Galileo Galilei, who in 1610 with the help of a telescope discovered small stars next to the giant, which behaved unusual compared to other celestial objects. After observing their movements for several days, he realized that they revolve around Jupiter, which means that they are not independent planets, but its satellites. This is how Ganymede, Europa, Io and Callisto were discovered.
Measuring the speed of light
In the 17th century, scientists did not have an exact idea of the finiteness of the speed of light, so it was important to experimentally find out how it spreads - instantly or not. Jupiter's moons were able to help solve this problem. If light waves from any sources propagated instantly, then the position of celestial bodies in the sky, recorded by the observer, would fully correspond to the actual one. If this radiation has a finite velocity, then the real picture will be distorted due to the different distances of the objects under consideration.
In 1675, the Dane Ole Roemer, carried out calculations of the location of Jupiter's satellites for two cases: the first - the Earth and the gas giant are on one side of the Sun, the second - on different sides. Having identified the discrepancies between calculations and observations, he came to the correct conclusion that the speed of light has a finite value, but could not accurately calculate it due to the lack of accurate data at that time on the remoteness of the orbits of the Earth and Jupiter from the Sun.
Failed star
Jupiter, processed image of the Voyager 1 probe
The gas giant has formed its own mini-structure within the solar system with numerous satellites of various sizes orbiting around it. This fact, the chemical composition of its atmosphere (hydrogen and helium), as well as its truly impressive dimensions make it possible to call Jupiter a failed star. However, its mass is not enough for the occurrence of a thermonuclear reaction, which means that it will never be able to become it. But if Jupiter was an order of magnitude heavier, then in the solar system there would be not one luminary, but as many as two - the researchers of the Universe know brown dwarfs that have a mass about 12-80 times greater than that of the largest planet in the solar system, which are among the lightest "Weight category" stars.
Energy of Jupiter
The study of the largest planet in the solar system showed that it emits about 2.5 times more energy than it receives from the outside, which indicates the presence of some internal sources of this phenomenon. Moreover, the radiation of Jupiter is in a very wide range of waves, including the visible spectrum.
A generally accepted explanation for this fact has not yet been found. It is assumed that the processes of phase transition of metallic hydrogen into the molecular phase can serve as energy sources. Also, most researchers agree that the core of the planet is heated due to internal compression and has a temperature, according to various sources, from 20,000 ° C to 30,000 ° C.
Jupiter's moons classification
If the planet has many satellites, then for the sake of convenience, it is customary to divide them into three main groups: main, internal and external. The main satellites are the largest satellites, of which Jupiter has four: Ganymede, Europa, Io and Callisto. They are also often called "Galilean", after the Italian astronomer who discovered them. Regions of space around the central planet are subdivided in relation to the orbits of the main satellites into inner and outer regions. Depending on which of these parts of the space is any other satellite, it has a name: "internal" or "external".
The inner satellites are much smaller than the Galilean ones and rotate in orbits 1.8-3.1 times the radius of Jupiter, that is, very close to its conditional surface.
The main satellites are located somewhat further, occupying a ring 20 times the planet's radius, with the closest of them - Io - located six radii from the center of rotation. The inner and main celestial bodies that make up Jupiter's suite rotate in the equatorial plane.
The outer satellites are located at a distance of 2-50 million km from the center of the planet. Their dimensions in the bulk are estimated at several kilometers, but there are several relatively large (the largest is 170 km). These celestial bodies usually have irregular shapes, elliptical orbits, and different inclinations to the equatorial plane.
Some of them rotate in the direction opposite to the rotation of the planet and the rest of the satellites. By calculation, it is possible to determine the area of gravitational attraction of any body (the so-called Hill sphere), which for Jupiter is about 50 million km. This is a possible frontier for searching for satellites.
Jupiter has four internal satellites, and they are all located inside the orbit of Io, the Galilean satellite closest to the planet.
They are called Adrastea, Amalthea, Metis and Thebes. The largest of them - Amalthea - has an irregular shape, is heavily pitted with craters and in terms of its size (270x165x150 km) occupies the fifth place in the Jupiter system. Thebes is about half the size (116x98x84 km) and resembles an ellipsoid in shape. The other two satellites - Adrastea and Metis - have dimensions of 25x20x15 km and 60x40x34 km, respectively.
All four minor planets are classified as regular, that is, they rotate in the same direction as the main satellites, and their orbits are located in the equatorial plane and are close to circular.
Moving almost at the same distance from Jupiter, Metis and Adrastea outstrip its rotation around its own axis, which leads to the emergence of tidal forces, inexorably bringing them closer to the planet's surface. Therefore, it is very likely that they will eventually fall on her.
Amalthea
Amalthea
The most interesting of these satellites is Amalthea, discovered in 1892 by Edward Barnard. The dark red color of its surface is unparalleled in the solar system. Recent studies have suggested that it consists mainly of ice with inclusions of minerals and sulfur-containing substances.
Such conclusions can be made by the low density of the celestial body (900 kg / m3;) and the data of the analysis of its radiation. But this hypothesis does not explain the color of the satellite. If we take it as a basis, then we can talk about the extra-Jupiterian origin of this body, since an ice satellite could not have formed near the surface of Jupiter.
External satellites
The external satellites, and currently there are 59 of them, differ in a significantly larger scatter of parameters and characteristics than those of the main and internal ones. All of them revolve in elliptical orbits with a large angle of inclination to the equatorial plane. All external satellites, which were able to observe the spacecraft passing by, visually resemble shapeless boulders with a surface eaten away by wanderings.
They can be classified by the values of the semi-major axis and the angle of inclination of rotation to the plane of Jupiter's equator, as well as its direction. Some of the satellites move in very close orbits and, apparently, are pieces of a larger celestial body that collapsed as a result of a collision with another cosmic object. Closer to the planet are satellites rotating in the same direction as the main ones.
Irregular satellites
Further satellites with reverse motion are located. They are divided into groups: Ananke, Karme, Himalia and Pasiphae. In each of these families, one large (more than 14 km in size) and a number of small (less than 4 km) bodies are distinguished.
The similarity of the trajectories of motion, most likely, indicates the common origin of satellites of the same group, which is additionally confirmed by the analysis of their velocities, which differ insignificantly from each other. A number of satellites have not yet been classified and are waiting for their researchers.
The study of celestial bodies revolving in the distant outer orbits of Jupiter is interesting because they have undergone little change since their formation and therefore carry information about the nature of the solar system.
Most likely, some of them flew freely in outer space from other regions of the galaxy and were captured by the gravitational field of the giant planet. Therefore, the analysis of their chemical composition will allow you to learn more not only about Jupiter and its satellites, but also about the structure of the Universe as a whole.
The main (Galilean) satellites
Crescent moons of planets and largest moons of the solar system
The main satellites of Jupiter were formed simultaneously with it and have orbits close to circular. They rotate in the equatorial plane at a distance from 420 thousand km to almost 2 million km from the center of the planet's core. There are four such satellites in the gas giant's system. Their names, in order of distance from the planet, are Io, Europa, Ganymede, and Callisto. The structure density of these satellites depends on the distance from the planet. The closer the satellite is to Jupiter, the greater the specific gravity of the material of which it is composed. So for Io, the density is 3530 kg / m3, and for Callisto - 1830 kg / m3. All these celestial bodies, like the Moon in relation to the Earth, always face their planet with one side.
All satellites of Jupiter are at least one and a half larger than the Moon, and Ganymede, the largest satellite of the solar system, exceeds the size of its smallest planet, Mercury, by 8% (in diameter). True, due to its low density (1936 kg / m3;), it is less than twice as large as this planet. Scientists believe that before the main satellites were more, and they all formed from one cloud of gas and dust. Subsequently, some of them, under the influence of gravitational forces, fell to the surface of Jupiter, and only four remained, observed today.
Some features of the Galilean satellites
Close and long-term study by astronomers of many countries, as well as several interplanetary space missions that transmitted their observations to Earth, made it possible to obtain a lot of interesting data on the main satellites of Jupiter.
And about
Io is the most volcanically active celestial body in the solar system. The proximity of massive Jupiter leads to a fracture of the satellite surface and activation of sulfur emissions, giving it an orange-yellow color. Most likely, its surface is composed of a mixture of ice and rocks.
Europe
Europe is completely covered with a crust of water ice, under which a liquid ocean can be hidden, the volume of which is more than twice the volume of water on Earth. Moreover, in photographic images, the satellite surface has a mesh structure, which suggests the presence of faults, cracks and thawed patches. It is assumed that there is also water on Ganymede and Callisto. Europe can have twice as much water as Earth. Again, the planet's gravity is believed to heat the interior and keep it warm.
Ganymede is the largest moon, larger than the planet Mercury. It is the only one in the solar system that has its own magnetic field.
Callisto, the fourth moon, has one of the most densely cratered surfaces. Unlike others, the surface of Callisto is very ancient, with impact craters, its age is billions of years.
If you look at the northwest part of the sky after sunset (southwest in the northern hemisphere), you will find one bright point of light that stands out easily in relation to everything around it. This is a planet that shines with an intense and even light.
Today, people can explore this gas giant like never before. After a five-year journey and decades of planning, NASA's Juno spacecraft has finally reached Jupiter's orbit.
Thus, humanity is witnessing the entry into a new stage of exploration of the largest of the gas giants in our solar system. But what do we know about Jupiter and from what base should we enter this new scientific milestone?
Size matters
Jupiter is not only one of the brightest objects in the night sky, but also the largest planet in the solar system. It is precisely because of its size that Jupiter is so bright. Moreover, the mass of the gas giant is more than twice the mass of all other planets, moons, comets and asteroids in our system combined.
The sheer size of Jupiter suggests that it may have been the very first planet to form in the orbit of the Sun. It is believed that the planets arose from debris left after an interstellar cloud of gas and dust combined during the formation of the Sun. At the beginning of its life, our then young star generated a wind that blew away most of the remaining interstellar cloud, but Jupiter was able to partially hold it back.
Moreover, Jupiter contains a recipe for what the solar system itself is made of - its components correspond to the content of other planets and small bodies, and the processes that occur on the planet are fundamental examples of the synthesis of materials for the formation of such amazing and diverse worlds as the planets of the solar system ...
King of the planets
Given the excellent visibility, Jupiter, along with, and, people have observed in the night sky since ancient times. Regardless of culture and religion, humanity considered these objects to be unique. Even then, observers noted that they do not remain motionless within the constellation patterns, like stars, but move according to certain laws and rules. Therefore, the ancient Greek astronomers ranked these planets as the so-called "wandering stars", and later from this name the very term "planet" appeared.
It is remarkable how accurately ancient civilizations designated Jupiter. Not knowing then that he was the largest and most massive of the planets, they named this planet in honor of the Roman king of the gods, who was also the god of the sky. In ancient Greek mythology, the analogue of Jupiter is Zeus, the supreme deity of Ancient Greece.
However, Jupiter is not the brightest of the planets, this record belongs to Venus. There are strong differences in the trajectories of Jupiter and Venus across the sky, and scientists have already explained why this is due. It turns out that Venus, being an inner planet, is located close to the Sun and appears as an evening star after sunset or a morning star before sunrise, while Jupiter, being an outer planet, is able to wander throughout the sky. It was this movement, along with the planet's high brightness, that helped the ancient astronomers mark Jupiter as the King of the planets.
In 1610, from late January to early March, astronomer Galileo Galilei observed Jupiter with his new telescope. He easily identified and tracked the first three and then four bright points of light in its orbit. They formed a straight line on either side of Jupiter, but their positions were constantly and steadily changing in relation to the planet.
In his work, which is called Sidereus Nuncius ("Interpretation of the Stars", lat. 1610), Galileo confidently and completely correctly explained the movement of objects in orbit around Jupiter. Later, it was his conclusions that became proof that all objects in the sky did not rotate in orbit, which led to a conflict between the astronomer and the Catholic Church.
So, Galileo was able to find four main moons of Jupiter: Io, Europa, Ganymede and Callisto - satellites that scientists today call the Galilean moons of Jupiter. Decades later, astronomers were able to identify other satellites, the total number of which is currently 67, which is the largest number of satellites orbiting the planet of the solar system.
Great red spot
Saturn has rings, Earth has blue oceans, and Jupiter has striking, bright and swirling clouds formed by the very rapid rotation of the gas giant on its axis (every 10 hours). The formations observed on its surface in the form of spots represent the formations of dynamic weather conditions in Jupiter's clouds.
For scientists, the question remains how deep to the surface of the planet these clouds pass. It is believed that the so-called Great Red Spot - a huge storm on Jupiter, discovered on its surface back in 1664, is constantly shrinking and decreasing in size. But even now, this massive storm system is roughly twice the size of Earth.
Recent observations by the Hubble Space Telescope indicate that, beginning in the 1930s, when consistent observation of the object began, its size could have been reduced by half. Currently, many researchers say that the decrease in the size of the Great Red Spot is happening at an ever faster pace.
Radiation hazard
Jupiter has the strongest magnetic field of all planets. At the poles of Jupiter, the magnetic field is 20 thousand times stronger than on Earth, it extends millions of kilometers into space, while reaching the orbit of Saturn.
The heart of Jupiter's magnetic field is believed to be a layer of liquid hydrogen hidden deep within the planet. The hydrogen is under such high pressure that it becomes liquid. Thus, given that electrons inside hydrogen atoms are capable of moving, it takes on the characteristics of a metal and is capable of conducting electricity. Given Jupiter's fast rotation, such processes create an ideal environment for creating a powerful magnetic field.
Jupiter's magnetic field is a real trap for charged particles (electrons, protons and ions), some of which fall into it from solar winds, and others from Jupiter's Galilean moons, in particular, from volcanic Io. Some of these particles move towards the poles of Jupiter, creating spectacular auroras around them that are 100 times brighter than those on Earth. Another part of the particles, which are captured by the magnetic field of Jupiter, forms its radiation belts, which are many times larger than any version of the Van Allen belts on Earth. Jupiter's magnetic field accelerates these particles to such an extent that they move in belts at almost the speed of light, creating the most dangerous radiation zones in the solar system.
Weather on Jupiter
The weather on Jupiter, like everything else about the planet, is very majestic. Above the surface, storms are constantly raging, which constantly change their shape, grow thousands of kilometers in literally a few hours, and their winds swirl the clouds at a speed of 360 kilometers per hour. It is here that the so-called Great Red Spot is present, it is a storm that has been going on for several hundred Earth years.
Jupiter is wrapped in clouds of ammonia crystals that can be seen as stripes of yellow, brown and white. Clouds are usually located at specific latitudes, also known as tropical regions. These stripes are formed by blowing air in different directions at different latitudes. Lighter shades of areas where the atmosphere rises are called zones. The dark regions where the air currents descend are called belts.
GIF 
When these opposing streams interact with each other, storms and turbulence appear. The depth of the cloud layer is only 50 kilometers. It consists of at least two levels of clouds: lower, denser and upper, thinner. Some scientists believe there is still a thin layer of water clouds underneath the ammonia layer. Lightning on Jupiter can be a thousand times more powerful than lightning on Earth, and there is practically no good weather on the planet.
Despite the fact that most of us, when we mention rings around the planet, Saturn comes to mind with its pronounced rings, Jupiter also has them. Jupiter's rings are mostly composed of dust, making them difficult to distinguish. The formation of these rings is believed to have been due to Jupiter's gravity, which captured material ejected from its moons as a result of their collisions with asteroids and comets.
The planet is a record holder
In summary, it is safe to say that Jupiter is the largest, most massive, fastest rotating, and most dangerous planet in the solar system. It has the strongest magnetic field and the largest number of known satellites. In addition, it is believed that it was he who captured the pristine gas from the interstellar cloud that gave birth to our sun.
The gas giant's strong gravitational influence helped move material in our solar system, pulling ice, water and organic molecules from the outer, cold regions of the solar system to the interior, where these valuable materials could be captured by the earth's gravitational field. This is also indicated by the fact that n The first planets that astronomers discovered in the orbits of other stars almost always belonged to the class of so-called hot Jupiters - exoplanets whose masses are similar to the mass of Jupiter, and the location of their stars in orbit is close enough to cause a high surface temperature.
And now that the Juno spacecraft already in orbit of this majestic gas giant, the scientific world has the opportunity to find out some of the secrets of the formation of Jupiter. Will the theory be confirmed that did it all start with a rocky core, which then attracted a huge atmosphere, or is the origin of Jupiter more like the formation of a star formed from a solar nebula? For these other questions, scientists plan to find answers during Juno's next 18-month mission. dedicated to a detailed study of the King of the Planets.
The first recorded mention of Jupiter was recorded by the ancient Babylonians in the 7th or 8th century BC. Jupiter is named after the king of the Roman gods and the god of the sky. The Greek equivalent is Zeus, the lord of lightning and thunder. Among the inhabitants of Mesopotamia, this deity was known as Marduk, the patron saint of the city of Babylon. The Germanic tribes referred to the planet as Donar, which was also known as Thor.
Galileo's discovery of four moons of Jupiter in 1610 was the first evidence of the rotation of celestial bodies not only in the orbit of the Earth. This discovery also became additional evidence of Copernicus' heliocentric model of the solar system.
Of the eight planets in the solar system, Jupiter has the shortest day. The planet rotates at a very high speed and makes a revolution on its axis every 9 hours and 55 minutes. This rapid rotation causes a flattening effect on the planet, which is why it sometimes looks flattened.
One revolution in orbit around the Sun for Jupiter takes 11.86 Earth years. This means that when viewed from Earth, the planet appears to be moving very slowly in the sky. Jupiter needs months to move from one constellation to another.
Parts of the material about satellites, there were only three of them - the Moon near the Earth and two satellites of Mars. Today we are talking about satellites of just one planet, but the number of satellites on a planet is simply incredible.
Jupiter occupies a special place in the solar system, because it is almost two and a half times larger than all the planets combined. Jupiter is so massive that their common center of mass with the Sun lies above the surface of the Sun.
The common center of mass of Jupiter with the Sun is indicated by a point
Jupiter has very powerful radiation, in the solar system the level is higher only in the sun. In comparison with other planets, a huge number of satellites revolve around it.
Thanks to ground-based observations of the Jupiter system, thirteen satellites were known by the end of the 70s. In 1979, while flying past Jupiter, the Voyager 1 spacecraft discovered three more satellites. Later, with the help of new-generation ground-based telescopes, 51 more satellites of Jupiter were discovered.
The vast majority of satellites are 2-4 kilometers in diameter. Scientists assume that Jupiter has at least a hundred satellites, but, as already mentioned, 67 have been registered to date, and 63 have been well studied.
The moons of Jupiter are divided into three groups: Galilean, internal and external. Let's start with the Galileans.
Galilean satellites
The four largest moons - Io, Europa, Ganymede and Callisto were discovered by Galileo Galilei in 1610, and therefore they are now called "Galilean". These moons were formed from the gas and dust that surrounded Jupiter after its formation.
Galilean moons of Jupiter. From left to right, in order of distance from Jupiter: Io, Europa, Ganymede, Callisto
Size comparison. In the top row, from left to right, in order of distance from Jupiter: Io, Europa, Ganymede, Callisto. Below the Earth and the Moon
And about
Io, the fifth moon of Jupiter, is the most volcanic active body in the solar system. Its age is four and a half billion years; Jupiter is about the same age. The satellite is always turned to its planet with one side. The distance from the surface of Jupiter to Io is 350 thousand kilometers. Its diameter is 3642 kilometers - slightly more than that of the Moon (3474 kilometers). It is the fourth largest satellite in the solar system.
Volcanic activity on satellites is an extremely rare phenomenon in the solar system and Io in our system is the undoubted favorite for this indicator. It is one of the four currently known cosmic bodies in the solar system, which are undergoing volcanic activity. Besides him: Earth, Triton (satellite of Neptune) and Enceladus (satellite of Saturn). Venus (Beta region) is also "suspected" of volcanism, but no active volcanoes have yet been observed on it.
The eruptions on Io are gigantic and can be clearly seen from space. Volcanoes spew sulfur to a height of three hundred kilometers. On the surface of the satellite, many lava flows and over a hundred calderas are clearly visible, but there are no impact craters; the entire surface is covered with gray in various colorful forms. Io's atmosphere contains mainly sulfur dioxide due to its high volcanic activity.
Animation of the eruption in Pater Tvashtar, composed of five images taken by the New Horizons spacecraft in 2007
Due to its proximity to Jupiter, the planet's enormous gravitational forces act on the satellite, which causes tidal forces that create tremendous friction inside the satellite, so both the interior of Io and its surface are warming up. The planet's gravitational forces are constantly pulling and deforming the satellite. Some parts of the satellite are heated to three hundred degrees Celsius; also on Io, twelve volcanoes have been discovered, spewing magma to a height of three hundred kilometers.
Pele eruption on Io, captured by Voyager 2
In addition to Jupiter, Io is affected by the gravitational forces of other satellites - Ganymede and Europa. The main influence is exerted by the Europa satellite, providing its additional heating. Unlike terrestrial volcanoes, which have a long "sleep" time and a relatively short period of eruptions, the volcanoes of a hot satellite are always active. The constantly flowing molten magma forms rivers and lakes. The largest molten lake is twenty kilometers in diameter and contains an island of frozen sulfur.
Io's movement through Jupiter's magnetosphere generates powerful electricity, causing severe thunderstorms in the upper atmosphere of Jupiter. But not only Jupiter is bad from their interaction - its powerful magnetic belts take 1000 kilograms of substances from Io every second. This further enhances Jupiter's magnetosphere, effectively doubling its size.
Europe
Europa is the sixth satellite in terms of distance from Jupiter. Its surface is covered with a layer of ice, scientists believe that there is a liquid ocean under it. Europa is about four and a half billion years old - about the same age as Jupiter.
Since the satellite's surface is young (about one hundred million years old), there are almost no meteorite craters on it, which appeared in large numbers 4.5 billion years ago. Scientists have found only five craters on the surface of Europa, their diameter is 10-30 kilometers.
The orbital distance of Europa from Jupiter is 670,900 kilometers. The satellite is turned to the planet all the time with one side, its diameter is 3100 kilometers, therefore, Europa is smaller than the Moon, but larger than Pluto. The surface temperature of Europe at the equator never rises above minus 160 degrees Celsius, and at the poles above minus 220 degrees Celsius.
Two models of the structure of Europe
Scientists speculate that there is an ocean deep beneath the moon's surface, and that life forms may be found in that ocean. They can exist thanks to thermal springs near underground volcanoes, just like on Earth. The amount of water in Europe is twice as much as on our planet.
Fluctuations in the shape of Europa, associated with tides, causing it to stretch, then round again
The surface of the satellite is covered with cracks. Many believe it is caused by tidal forces on the ocean below the surface. It is possible that the water under the ice rises higher than usual when the moon comes close to Jupiter. And if so, the constant rise and fall of the water level has caused many cracks observed on the surface. Many scientists believe that the ocean below the surface sometimes breaks through cracks (like lava from a volcano) and then freezes. Icebergs observed on the surface of Europa's satellite may be proof of this theory.
Europa is one of the smoothest bodies in the solar system - there are no heights of more than a hundred meters on it. The atmosphere on the satellite is rarefied, and consists mainly of molecular oxygen. This is likely the result of the decomposition of ice into hydrogen and oxygen under the influence of solar radiation and other hard radiation. Molecular hydrogen quickly evaporates from the satellite's surface, since it is light enough, and Europa's gravitational force is weak.
Ganymede
Ganymede is the largest satellite in the solar system. Its diameter is 5268 kilometers, which is 2% more than that of Titan (the second largest satellite in the solar system) and 8% more than that of Mercury. If it orbit around the sun rather than around Jupiter, it would be classified as a planet. The distance from Ganymede to the surface of Jupiter is approximately 1,070,000 kilometers. It is the only satellite in the solar system with its own magnetosphere.
The surface of Ganymede is divided into two groups. The first is a strange strip of ice generated by active geological processes three and a half billion years ago, which occupies 60% of the surface. The second group (the remaining 40% of the surface, respectively) is an ancient thick ice crust covered with numerous craters.
Possible internal structure of Ganymede
The heat that comes from the core and silicate mantle allows the underground ocean to exist. It is believed to be located two hundred kilometers below the surface, unlike Europa, which has a large ocean closer to the surface.
The satellite's atmosphere is thin and composed of oxygen, similar to that found in Europa. The craters on Ganymede are almost flat and very flat compared to craters on other moons. They do not have a central depression characteristic of craters on the Moon. This is likely due to the slow and gradual movement of the soft ice surface.
Callisto
Callisto is the third largest satellite in the solar system. Its diameter is 4820 km, which is about 99% of the diameter of Mercury, and its mass is only a third of the mass of this planet. Callisto is about 4.5 billion years old, roughly the same age as Ganymede, Europa, Io, and Jupiter itself. The satellite is located at a distance of almost 1.9 million kilometers (1,882,700 km) from the planet. Due to its great distance from the planet, it is outside the rigid radiation field of the gas giant.
Callisto
Callisto has one of the oldest surfaces in the solar system - approximately four billion years old. It is all covered with craters, and each new impact of the meteorite will certainly fall into the already formed crater. The ancient surface has survived to this day due to the absence of violent tectonic activity and heating of the satellite's surface since its formation.
Many scientists believe that Callisto is covered with a huge layer of ice, under which the ocean is located, and the center of Callisto contains rocks and iron. Callisto's atmosphere is thin and consists of carbon dioxide.
One of the most notable places on Callisto is the Valhalla crater. The crater consists of a bright central region with a diameter of 360 km, around it there are ridges in the form of concentric rings with a radius of up to 1900 kilometers: they diverge from it like rings from a stone thrown into the water. In general, the diameter of Valhalla is about 3800 kilometers. It is the largest area formed around an impact crater in the entire solar system. The crater itself is only in thirteenth place in the solar system in size. Such a structure arose due to a collision of a satellite with a relatively large asteroid 10–20 kilometers in size.
Valhalla - the impact pool on the Callisto satellite
Since Callisto is outside the hard radiation field of Jupiter, it is considered as a priority object (after the Moon and Mars) for the construction of a space base. Water can be extracted from the ice of the satellite, and from its surface to conduct research on another satellite of Jupiter - Europa. The flight to Callisto can take anywhere from two to five years. It is assumed that the first manned mission to this satellite will go no earlier than 2040, and possibly even later.
Model of the internal structure of Callisto. Shown: ice crust, a possible water ocean and a core of rocks and ice
Jupiter's inner moons
Why are they internal? The fact is that the orbits of these satellites are located very close to Jupiter and they are all inside the orbit of Io, the closest Galilean satellite to the planet. There are only four of them: Metis, Amalthea, Adrastea and Thebes.
The leading side of Amalthea (Jupiter on the right, north from above). Pan crater is visible on the upper right edge, Gaia (with bright slopes) on the lower. Color photo of Voyager 1 (1979)
Amalthea, 3D model
These moons, as well as a series of as yet invisible inner small moons, supplement and support Jupiter's faint ring system. Metis and Adrastea help support Jupiter's main ring, while Amalthea and Thebes support their own weak outer rings.
Of the satellites of the inner group, Amalthea is of the greatest interest. The surface of this satellite has a dark red color, which has no analogues in the solar system. Scientists assume that it consists mainly of ice with inclusions of minerals and sulfur-containing substances, but this hypothesis does not explain the color of the satellite. Most likely, Jupiter captured the satellite from the outside, as it does regularly with comets.
Jupiter's outer moons
The outer group consists of small satellites, ranging in diameter from one to one hundred and seventy kilometers. They move along elongated and strongly inclined orbits to the equator of Jupiter. There are currently 59 satellites in the outer constellation. Satellites that are located close to the planet move in their orbits in the direction of Jupiter's rotation, and most of the distant satellites move in the opposite direction.
Orbits of Jupiter's moons
Some small satellites move in almost the same orbits, it is believed that all these are the remnants of larger satellites, which were destroyed by the force of gravity of Jupiter. All external satellites, which were observed by spacecraft flying by, outwardly resemble shapeless boulders. Most likely, some of them flew freely in space until they were captured by Jupiter's gravitational field.
Jupiter's rings
In addition to satellites, Jupiter has a ring system. Yes, Jupiter also has rings. In addition, all four gas giants in our solar system have them. But unlike Saturn, which has shiny ice rings, Jupiter's rings have a slight dusty structure. That is why the rings of Saturn were discovered back in 1610 by Galileo, and the faint rings of Jupiter only in the 1970s, when the spacecraft first visited the Jupiter system.
Galileo's image of the main ring in forward-scattered light
Jupiter's ring system has four main components: a "halo" - a thick torus of particles, a relatively bright and very thin "Main Ring", and two wide and faint outer rings known as "spider rings".
The “main ring” and halo consist mainly of dust from Metis, Adrastea, and possibly several other satellites. The halo has the shape of a donut, its width is about twenty to forty thousand kilometers, although most of its material lies within a few hundred kilometers from the plane of the ring. Its shape is believed to be related to the electromagnetic forces within Jupiter's magnetosphere acting on the dust particles in the ring.
"Spiderweb rings" - rings thin and transparent like a spider web, named after the material of the satellites that form them: Amalthea and Thebes. The outer edges of the Main Ring outline the satellites Adrastea and Metis.
Jupiter's rings and inner moons
We say goodbye to Jupiter and its satellites and continue our journey further. In the next article, we will disassemble the moons and rings of Saturn.
