Giant planets. What are the inner planets? How many planets are inner?

Space has long attracted people's attention. Astronomers began studying the planets of the Solar System back in the Middle Ages, examining them through primitive telescopes. But a thorough classification and description of the structural features and movements of celestial bodies became possible only in the 20th century. With the advent of powerful equipment, state-of-the-art observatories and spacecraft, several previously unknown objects were discovered. Now every schoolchild can list all the planets of the solar system in order. A space probe has landed on almost all of them, and so far man has only visited the Moon.

What is the Solar System

The Universe is huge and includes many galaxies. Our Solar System is part of a galaxy containing more than 100 billion stars. But there are very few that are like the Sun. Basically, they are all red dwarfs, which are smaller in size and do not shine as brightly. Scientists have suggested that the solar system was formed after the emergence of the Sun. Its huge field of attraction captured a gas-dust cloud, from which, as a result of gradual cooling, particles of solid matter formed. Over time, celestial bodies were formed from them. It is believed that the Sun is now in the middle of its life path, so it, as well as all the celestial bodies dependent on it, will exist for several more billions of years. Near space has been studied by astronomers for a long time, and any person knows what planets of the solar system exist. Photos of them taken from space satellites can be found on the pages of various information resources devoted to this topic. All celestial bodies are held by the strong gravitational field of the Sun, which makes up more than 99% of the volume of the Solar System. Large celestial bodies rotate around the star and around its axis in one direction and in one plane, which is called the ecliptic plane.

Planets of the Solar System in order

In modern astronomy, it is customary to consider celestial bodies starting from the Sun. In the 20th century, a classification was created that includes 9 planets of the solar system. But recent space exploration and new discoveries have pushed scientists to revise many provisions in astronomy. And in 2006, at an international congress, due to its small size (a dwarf with a diameter not exceeding three thousand km), Pluto was excluded from the number of classical planets, and there were eight of them left. Now the structure of our solar system has taken on a symmetrical, slender appearance. It includes the four terrestrial planets: Mercury, Venus, Earth and Mars, then comes the asteroid belt, followed by the four giant planets: Jupiter, Saturn, Uranus and Neptune. On the outskirts of the solar system there is also a space that scientists call the Kuiper Belt. This is where Pluto is located. These places are still little studied due to their remoteness from the Sun.

Features of the terrestrial planets

What allows us to classify these celestial bodies as one group? Let us list the main characteristics of the inner planets:

• relatively small size;
• hard surface, high density and similar composition (oxygen, silicon, aluminum, iron, magnesium and other heavy elements);
• presence of atmosphere;
• identical structure: a core of iron with nickel impurities, a mantle consisting of silicates, and a crust of silicate rocks (except for Mercury - it has no crust);
• a small number of satellites - only 3 for four planets;
• rather weak magnetic field.

Features of the giant planets

As for the outer planets, or gas giants, they have the following similar characteristics:

• large sizes and weights;
• they do not have a solid surface and consist of gases, mainly helium and hydrogen (therefore they are also called gas giants);
• liquid core consisting of metallic hydrogen;
• high rotation speed;
• a strong magnetic field, which explains the unusual nature of many processes occurring on them;
• there are 98 satellites in this group, most of which belong to Jupiter;
• The most characteristic feature of gas giants is the presence of rings. All four planets have them, although they are not always noticeable.

The first planet is Mercury

It is located closest to the Sun. Therefore, from its surface the star appears three times larger than from the Earth. This also explains the strong temperature changes: from -180 to +430 degrees. Mercury moves very quickly in its orbit. Maybe that’s why it got such a name, because in Greek mythology Mercury is the messenger of the gods. There is practically no atmosphere here and the sky is always black, but the Sun shines very brightly. However, there are places at the poles where its rays never hit. This phenomenon can be explained by the tilt of the rotation axis. No water was found on the surface. This circumstance, as well as the abnormally high daytime temperature (as well as the low nighttime temperature) fully explain the fact of the absence of life on the planet.

Venus

If you study the planets of the solar system in order, then Venus comes second. People could observe it in the sky back in ancient times, but since it was shown only in the morning and evening, it was believed that these were 2 different objects. By the way, our Slavic ancestors called it Mertsana. It is the third brightest object in our solar system. People used to call it the morning and evening star, because it is best visible before sunrise and sunset. Venus and Earth are very similar in structure, composition, size and gravity. This planet moves very slowly around its axis, making a full revolution in 243.02 Earth days. Of course, conditions on Venus are very different from those on Earth. It is twice as close to the Sun, so it is very hot there. The high temperature is also explained by the fact that thick clouds of sulfuric acid and an atmosphere of carbon dioxide create a greenhouse effect on the planet. In addition, the pressure at the surface is 95 times greater than on Earth. Therefore, the first ship that visited Venus in the 70s of the 20th century stayed there for no more than an hour. Another peculiarity of the planet is that it rotates in the opposite direction compared to most planets. Astronomers still know nothing more about this celestial object.

Third planet from the Sun

The only place in the Solar System, and indeed in the entire Universe known to astronomers, where life exists is Earth. In the terrestrial group it has the largest size. What else are her

1. The highest gravity among the terrestrial planets.
2. Very strong magnetic field.
3. High density.
4. It is the only one among all the planets that has a hydrosphere, which contributed to the formation of life.
5. It has the largest satellite compared to its size, which stabilizes its tilt relative to the Sun and influences natural processes.

The planet Mars

This is one of the smallest planets in our Galaxy. If we consider the planets of the solar system in order, then Mars is the fourth from the Sun. Its atmosphere is very rarefied, and the pressure on the surface is almost 200 times less than on Earth. For the same reason, very strong temperature changes are observed. The planet Mars has been little studied, although it has long attracted the attention of people. According to scientists, this is the only celestial body on which life could exist. After all, in the past there was water on the surface of the planet. This conclusion can be drawn from the fact that there are large ice caps at the poles, and the surface is covered with many grooves, which could be dried up river beds. In addition, there are some minerals on Mars that can only be formed in the presence of water. Another feature of the fourth planet is the presence of two satellites. What makes them unusual is that Phobos gradually slows down its rotation and approaches the planet, while Deimos, on the contrary, moves away.

What is Jupiter famous for?

The fifth planet is the largest. The volume of Jupiter would fit 1300 Earths, and its mass is 317 times that of Earth. Like all gas giants, its structure is hydrogen-helium, reminiscent of the composition of stars. Jupiter is the most interesting planet, which has many characteristic features:

• it is the third brightest celestial body after the Moon and Venus;
• Jupiter has the strongest magnetic field of any planet;
• it completes a full revolution around its axis in just 10 Earth hours - faster than other planets;
• An interesting feature of Jupiter is the large red spot - this is how an atmospheric vortex rotating counterclockwise is visible from Earth;
• like all giant planets, it has rings, although not as bright as Saturn’s;
• this planet has the largest number of satellites. He has 63 of them. The most famous are Europa, where water was found, Ganymede - the largest satellite of the planet Jupiter, as well as Io and Calisto;
• Another feature of the planet is that in the shadow the surface temperature is higher than in places illuminated by the Sun.

Planet Saturn

It is the second largest gas giant, also named after the ancient god. It is composed of hydrogen and helium, but traces of methane, ammonia and water have been found on its surface. Scientists have found that Saturn is the rarest planet. Its density is less than that of water. This gas giant rotates very quickly - it makes one revolution in 10 Earth hours, as a result of which the planet is flattened from the sides. Huge speeds on Saturn and the wind - up to 2000 kilometers per hour. This is faster than the speed of sound. Saturn has another distinctive feature - it holds 60 satellites in its field of gravity. The largest of them, Titan, is the second largest in the entire solar system. The uniqueness of this object lies in the fact that by examining its surface, scientists for the first time discovered a celestial body with conditions similar to those that existed on Earth about 4 billion years ago. But the most important feature of Saturn is the presence of bright rings. They circle the planet around the equator and reflect more light than the planet itself. Four is the most amazing phenomenon in the solar system. What's unusual is that the inner rings move faster than the outer rings.

- Uranus

So, we continue to consider the planets of the solar system in order. The seventh planet from the Sun is Uranus. It is the coldest of all - the temperature drops to -224 °C. In addition, scientists did not find metallic hydrogen in its composition, but found modified ice. Therefore, Uranus is classified as a separate category of ice giants. An amazing feature of this celestial body is that it rotates while lying on its side. The change of seasons on the planet is also unusual: for as many as 42 Earth years, winter reigns there, and the Sun does not appear at all; summer also lasts 42 years, and the Sun does not set during this time. In spring and autumn, the star appears every 9 hours. Like all giant planets, Uranus has rings and many satellites. As many as 13 rings revolve around it, but they are not as bright as those of Saturn, and the planet contains only 27 satellites. If we compare Uranus with the Earth, then it is 4 times larger than it, 14 times heavier and is located at a distance from the Sun of 19 times the path to the star from our planet.

Neptune: the invisible planet

After Pluto was excluded from the number of planets, Neptune became the last from the Sun in the system. It is located 30 times further from the star than the Earth, and is not visible from our planet even with a telescope. Scientists discovered it, so to speak, by accident: observing the peculiarities of the movement of the planets closest to it and their satellites, they concluded that there must be another large celestial body beyond the orbit of Uranus. After discovery and research, interesting features of this planet were revealed:

• due to the presence of a large amount of methane in the atmosphere, the color of the planet from space appears blue-green;
• Neptune's orbit is almost perfectly circular;
• the planet rotates very slowly - it makes one circle every 165 years;
• Neptune is 4 times larger than Earth and 17 times heavier, but the force of gravity is almost the same as on our planet;
• the largest of the 13 satellites of this giant is Triton. It is always turned to the planet with one side and slowly approaches it. Based on these signs, scientists suggested that it was captured by the gravity of Neptune.

There are about one hundred billion planets in the entire Milky Way galaxy. So far, scientists cannot study even some of them. But the number of planets in the solar system is known to almost all people on Earth. True, in the 21st century, interest in astronomy has faded a little, but even children know the names of the planets of the solar system.

The planets of the Solar System are divided into internal (in which the orbits are located inside the Earth's orbit) and external (orbits larger than the Earth's orbit). Both (inner planets) and , (outer planets) are easily accessible for various studies.

Keeping an eye on the inner planet from Earth, you will notice the following points: a conjunction where the planet is located behind the Sun and is not visible. After a certain time, the planet on the left emerges from behind the Sun and becomes available for contemplation in the rays of the evening dawn in the west.

Little by little, the planet is able to reach the greatest distance from the Sun, at which the conditions of evening visibility are most favorable, and then begins to approach the Sun and again connects with the Sun, appearing before it. If the plane of its orbit coincided with the flat orbit of the Earth, then at the moment the planet would be projected on the disk of the Sun and could become visible as a black spot. Usually the planet is located below or above the Sun and does not enter into conjunction.

After conjunctions, the planet comes to the right side of the Sun, reaches western elongation, goes through the close crescent to disk phase, and is visible in the east in the morning. Then the movement changes in the opposite direction, from right to left, when the planet moves towards the Sun, decreasing in the size of the angle, and approaches the full phase.

Following its exit from behind the Sun, the planet is visible in perfect phase, and in eastern elongation only half of the entire illuminated disk is visible, then the phase decreases, but the angular size of the crescent increases as the planet approaches the Earth.

The inner planet does not move far from the Sun and is always observed in the rays of the evening or morning dawn. The magnitude of Mercury's elongation is not very large - no more than twenty-eight degrees Celsius; the rest of the time Mercury always hides near the Sun, and is visible only next to elongation.

Venus is capable of moving away from the Sun by forty-five to forty-eight degrees and is easily noted as an evening or morning star as the brightest object in the sky. In approximately 1.5 years, the position of Venus will repeat.

The outer planets are capable of moving away from the Sun at any distance, and are always visible in perfect phase. While the outer planet is visible in the west after sunset, it is able to move among the stars in a straight motion like the Sun.

solar system

According to a scientific hypothesis, our system formed from a dark gas and dust cloud 4.6 billion years ago. As a result of powerful transformations, the cloud turned into a young system with a central yellow star, planets, asteroids and various cosmic bodies.

Structure of the Solar System

Our system includes a star of medium brightness - the Sun, and 8 classical planets that revolve around it in elliptical orbits at various distances. It is noteworthy that until 2006 there were 9 planets in the system, the last one being Pluto. However, as a result of new discoveries, Pluto was reclassified, and as a result it acquired the status of a dwarf planet along with Ceres, Eris and other similar objects.

K, Pluto has a moon Charon, which is half the size of the dwarf planet. Further reclassification of Pluto into a double planet is being considered, but today there is not enough information about the structure of the cosmos for such a classification.

The inner and outer planets are separated by an asteroid belt.

What are the inner planets

The planets of the system are divided into small warm (inner) and cold gas supergiants (outer). The first type includes Mercury, Venus, Mars and Earth. To the outer ones - Juriter, Saturn, Uranus, Neptune. The inner planets have a solid core and consist of metals, gases (oxygen, hydrogen and others), and other heavy elements. The largest are Earth and Venus with sizes of 1 and 0.81, respectively. Earth and Mars have satellites. In particular, the “blue” planet has the Moon, the “red” planet has Phobos and Deimos, which translates as “fear” and “horror”. This name for the moons of Mars is due to the fact that the object was named after the god of war Mars (aka Ares).

The inner planets are significantly smaller in size than the gas giants.

The inner and outer planets are separated by a wide asteroid belt that extends between Mars and Jupiter. Unlike gas giants, rocky planets do not have rings made of asteroid debris, gas and dust. The smallest Uranus is 14 times larger than the largest “warm” planet - Earth.

In the scientific world, it is believed that on Earth-like planets the possibility of the emergence or presence of life is higher than on gas giants. Largely due to the favorable climate and internal structure of such planets. In this regard, the search for such space objects is receiving increased attention from astronomers and scientists.

Giant planets- the largest bodies in the solar system after the Sun: Jupiter, Saturn, Uranus and Neptune. They are located beyond the Main Asteroid Belt and are therefore also called the “outer” planets.
Jupiter and Saturn are gas giants, meaning they consist mainly of gases that are in a solid state: hydrogen and helium.
But Uranus and Neptune were identified as ice giants, since in the thickness of the planets themselves, instead of metallic hydrogen, there is high-temperature ice.
Giant planets many times larger than the Earth, but compared to the Sun, they are not large at all:

Computer calculations have shown that giant planets play an important role in protecting the inner terrestrial planets from asteroids and comets.
Without these bodies in the solar system, our Earth would be hit by asteroids and comets hundreds of times more often!
How do giant planets protect us from the falls of uninvited guests?

You've probably heard about "space slalom", when automatic stations sent to distant objects in the solar system perform "gravitational maneuvers" near some planets. They approach them along a pre-calculated trajectory and, using the force of their gravity, accelerate even more, but do not fall onto the planet, but “shoot” the word from a sling at an even greater speed than at the entrance and continue their movement. This saves fuel, which would be needed for acceleration with engines alone.
In the same way, giant planets throw asteroids and comets outside the solar system, which fly past them, trying to break through to the inner planets, including the Earth. Jupiter, with its brothers, increases the speed of such an asteroid, pushes it out of its old orbit, it is forced to change its trajectory and flies into the cosmic abyss.
So, without giant planets, life on Earth would probably be impossible due to constant meteorite bombardment.

Well, now let’s briefly get acquainted with each of the giant planets.

Jupiter is the largest giant planet.

First in order from the Sun, among the giant planets, is Jupiter. It is also the largest planet in the solar system.
Sometimes they say that Jupiter is a failed star. But to start its own process of nuclear reactions, Jupiter does not have enough mass, and quite a lot. Although, the mass is slowly growing due to the absorption of interplanetary matter - comets, meteorites, dust and solar wind. One of the options for the development of the Solar system shows that if this continues, then Jupiter may well become a star or a brown dwarf. And then our Solar system will become a double star system. By the way, double star systems are a common occurrence in the Cosmos around us. There are much fewer single stars, like our Sun.

There are calculations showing that Jupiter is already emitting more energy than it absorbs from the Sun. And if this is really the case, then nuclear reactions must already be taking place, otherwise there is simply nowhere for the energy to come from. And this is a sign of a star, not a planet...


This image also shows the famous Great Red Spot, also called the “eye of Jupiter.” This is a giant vortex that has apparently existed for hundreds of years.

In 1989, the Galileo spacecraft was launched towards Jupiter. Over 8 years of work, he took unique photographs of the giant planet itself, the satellites of Jupiter, and also carried out many measurements.
One can only guess what is going on in the atmosphere of Jupiter and in its depths. The Galileo probe, having descended 157 km into its atmosphere, survived for only 57 minutes, after which it was crushed by a pressure of 23 atmospheres. But he managed to report powerful thunderstorms and hurricane winds, and also transmitted data on composition and temperature.
Ganymede, the largest of the moons of Jupiter, is also the largest of the moons of the planets in the Solar System.
At the very beginning of the research, in 1994, Galileo observed the fall of Comet Shoemaker-Levy onto the surface of Jupiter and sent back images of this disaster. This event could not be observed from Earth - only residual phenomena that became visible as Jupiter rotated.

Next comes an equally famous body of the solar system - the giant planet Saturn, which is known primarily for its rings. Saturn's rings are made up of ice particles ranging in size from dust grains to fairly large chunks of ice. With an outer diameter of 282,000 kilometers, Saturn's rings are only about ONE kilometer thick. Therefore, when viewed from the side, Saturn's rings are not visible.
But, Saturn also has satellites. About 62 satellites of Saturn have now been discovered.
Saturn's largest moon is Titan, which is larger than the planet Mercury! But, it consists largely of frozen gas, that is, it is lighter than Mercury. If Titan is moved into Mercury's orbit, the icy gas will evaporate and Titan's size will greatly decrease.
Another interesting satellite of Saturn, Enceladus, attracts scientists because there is an ocean of liquid water under its icy surface. And if so, then life is possible in it, because the temperatures there are positive. Powerful water geysers have been discovered on Enceladus, shooting hundreds of kilometers high!

The Cassini research station has been orbiting Saturn since 2004. During this time, a lot of data was collected about Saturn itself, its moons and rings.
The automatic station "Huygens" was also landed on the surface of Titan, one of Saturn's moons. This was the first ever landing of a probe on the surface of a celestial body in the Outer Solar System.
Despite its considerable size and mass, the density of Saturn is approximately 9.1 times less than the density of the Earth. Therefore, the acceleration of gravity at the equator is only 10.44 m/s². That is, having landed there, we would not have felt the increased gravity.

Uranus is an ice giant.

The atmosphere of Uranus consists of hydrogen and helium, and the interior is made of ice and solid rocks. Uranus appears to be a fairly calm planet, unlike the violent Jupiter, but vortices have still been noticed in its atmosphere. If Jupiter and Saturn are called gas giants, then Uranus and Neptune are ice giants, since in their depths there is no metallic hydrogen, but instead there is a lot of ice in various high-temperature states.
Uranus emits very little internal heat and is therefore the coldest of the planets in the solar system - a temperature of -224°C is recorded on it. Even on Neptune, which is further from the Sun, it is warmer.
Uranus has satellites, but they are not very large. The largest of them, Titania, is more than half the diameter of our Moon.

No, I didn't forget to rotate the photo :)

Unlike other planets in the solar system, Uranus seems to lie on its side - its own axis of rotation lies almost in the plane of rotation of Uranus around the Sun. Therefore, it turns to the Sun either with the South or North poles. That is, a sunny day at the pole lasts 42 years, and then gives way to 42 years of “polar night”, during which the opposite pole is illuminated.

This image was taken by the Hubble telescope in 2005. The rings of Uranus, the lightly colored south pole, and a bright cloud in the northern latitudes are visible.

It turns out that not only Saturn decorated himself with rings!

It is curious that all the planets bear the names of Roman gods. And only Uranus is named after a god from ancient Greek mythology.
The acceleration of gravity at the equator of Uranus is 0.886 g. That is, the gravity on this giant planet is even less than on Earth! And this despite its enormous mass... This is again due to the low density of the ice giant Uranus.

Spacecraft have flown past Uranus, taking pictures along the way, but detailed studies have not yet been carried out. True, NASA plans to send a research station to Uranus in the 2020s. The European Space Agency also has plans.

Neptune is the farthest planet in the solar system, after Pluto was "demoted" to the "dwarf planets". Like the other giant planets, Neptune is much larger and heavier than Earth.
Neptune, like Saturn, is an icy giant planet.

Neptune is quite far from the Sun and therefore became the first planet discovered through mathematical calculations, rather than through direct observations. The planet was visually discovered through a telescope on September 23, 1846 by astronomers at the Berlin Observatory, based on preliminary calculations by the French astronomer Le Verrier.
It is curious that, judging by the drawings, Galileo Galii observed Neptune long before this, back in 1612, with his first telescope! But... he did not recognize the planet in it, mistaking it for a fixed star. Therefore, Galileo is not considered the discoverer of the planet Neptune.

Despite its significant size and mass, Neptune's density is approximately 3.5 times less than the density of Earth. Therefore, at the equator the gravity is only 1.14 g, that is, almost the same as on Earth, like the two previous giant planets.

1. How is the name “wandering stars” translated from Greek?

2. Name the inner planets.

3. Which planets are outer?

Even ancient people noticed constantly moving stars in the sky, and the Greeks called them that "wandering stars" that is, in Greek "planets".
There are nine planets in the solar system: Mercury, Mars, Venus, Earth, Neptune, Uranus, Saturn, Jupiter, Pluto.

Inner planets- Mercury, Mars, Venus, Earth.

Planets belonging to this group are small in size and mass; the average density of these planets is several times higher than the density of water; they rotate slowly around their axes; they have few companions (they have Mercury and Venus they don't exist at all Mars- two, y Earth- one).

The similarity of the terrestrial planets does not exclude some differences. For example, Venus, unlike other planets, rotates in the direction opposite to its movement around the Sun, and is 243 times slower than the Earth.
Circulation period Mercury(i.e., the year of this planet) is only 1/3 greater than the period of its rotation around its axis.
The angles of inclination of the axes to the planes of their orbits are Earth and at Mars approximately the same, but completely different Mercury and Venus. Same as Earth, there are seasons Mars, although almost twice as long as on Earth.

Similarities and differences are also found in the atmospheres of the terrestrial planets. Unlike Mercury, which, like Moon, practically devoid of atmosphere, Venus and Mars possess it.
Venus has a very dense atmosphere, mainly consisting of carbon dioxide and sulfur compounds. Atmosphere Mars on the contrary, it is extremely rarefied and also poor in oxygen and nitrogen. Surface pressure Venus almost 100 times more, and Mars almost 150 times less than at the surface Earth.

Outer planets include Neptune, Uranus, Saturn, Jupiter, Pluto.

GIANT PLANETS Jupiter, Saturn, Uranus and Neptune does not at all correspond to our ideas of comfort: very cold, terrible gas composition (methane, ammonia, hydrogen, etc.), practically no solid surface - only a dense atmosphere and an ocean of liquid gases. All this is very unlike Earth. However, in the era of the origin of life, the Earth was completely different from what it is now. Its atmosphere was more reminiscent of Venusian and Jupiterian, except that it was warmer. Therefore, in the near future, a search for organic compounds in the atmosphere of the giant planets will certainly be carried out.

The giant planets are far from the Sun, and regardless of the nature of the seasons, low temperatures always prevail on them. On Jupiter there is no change of seasons at all, since the axis of this planet is almost perpendicular to the plane of its orbit. There is a peculiar change of seasons on the planet Uranus, since the axis of this planet is inclined to the orbital plane at an angle of 8¦.

Giant planets are distinguished by a large number of satellites; 16 of them have been discovered so far on Jupiter, Saturn - 17, Uranus- 16 and y Neptune- 8. Giant planets have an interesting feature - they are rings, which were found not only in Saturn, but also Jupiter, Uranus and Neptune.

The most important feature of the structure of giant planets is that these planets have a solid surface. They consist mainly of light elements - hydrogen and helium.