Information about the scientific studies of the planets of the solar system. How many of them

After the successful experience of sending Soviet automatic interplanetary stations to the Moon in 1959, in the early 60s. In our country, the first launches of spacecraft to the planets of the solar system were undertaken: in 1961 to Venus and in 1962 to Mars. AMS "Venera-1" covered the distance to Venus in 97 days, AMS "Mars-1" spent more than 230 days on the flight Earth - Mars. Subsequently, the flight time to Venus was increased to 117-120 days, since the rate of approach to the planet was lower, which facilitated the descent in the atmosphere and soft landing on the planet.

Flights to Mars, depending on its position in orbit, take from 6 to 10 months.

The first hard landing on Venus was carried out by the Soviet Venera-3 station on March 1, 1966; manufactured AMS Venera-7 on December 15, 1970. In October 1975, the first artificial satellite of Venus, Venera-9, went into orbit.

The first transmission of images of the surface of another planet (Mars) was carried out by the American spacecraft Mariner-4 in July 1965, the first artificial satellite of Mars was Mariner-9 (USA) on November 14, 1971, and two weeks later The Soviet AMS "Mars-2" and "Mars-3" became artificial satellites of the planet. The first soft landing on the surface of Mars was made by the Mars-3 descent vehicle in early December 1971.

An approach to Mercury with the transmission of images of its surface at close range was carried out by the American spacecraft Mariner-10 in March 1974, an approach to Jupiter was carried out by Pioneer-10 (USA) in December 1974. the same "Mariner-10" in February 1974, the first panoramic images of the surface of Venus from it were transmitted by the Soviet AMS "Venera-9" and "Venera-10" in October 1975, and panoramic images of the surface of Mars - American descent vehicles "Viking-1" and "Viking-2", starting from July 20, 1976

The use of spacecraft has greatly expanded the possibility of exploring the planets. The main methods of scientific research in this case are the following:

1. Direct photography of the planet from a more or less close distance or small areas of its surface, both from the orbit or flyby trajectory, and from the planet's surface itself. Examples of the application of this method have already been given above. Sometimes shooting was carried out using light filters (Mars-3, Mariner-10).

The resulting images are transmitted to Earth by a method that has long been used in "terrestrial" television: the image is expanded line by line into a chain of signals that are transmitted by an antenna station to Earth, and then a beam in the cathode ray tube of the TV turns the received signal back into an image. This image, photographed from the TV screen, then undergoes lengthy processing aimed at eliminating interference, distortions and defects, as well as special marks from the TV screen, which serve to orient the image, but are unnecessary when considering the view of the planet's surface.

2. Measurement of the pressure and temperature of the planet's atmosphere during descent is carried out using pressure gauges (operating on the principle of an aneroid barometer) and resistance thermometers, density is measured by density meters of various types (ionization, tuning fork, etc.). A detailed description of the design of these devices is available in the book by A. D. Kuzmin and M. Ya. Marov "Physics of the planet Venus" (M .: "Nauka", 4974) and in other books and articles listed in the bibliography at the end of the book.

In addition to direct measurements, the parameters of the planet's atmosphere and their change in altitude can be calculated from the rate of descent of the apparatus, since its aerodynamic characteristics are known. Experience has shown that this method gives good agreement with the previous one.

3. Measurement of the chemical composition of the atmosphere. Produced using gas analyzers of various types. Typically, each gas analyzer is designed to determine the content of a particular gas.

4. The study of the upper layers of the atmosphere by the method of radio transmission. This method consists in the fact that the spacecraft, entering (for an earthly observer) behind the disk of the planet or leaving it, sends a radio wave of a certain length (waves from 8 cm to 6 m are used). Passing through the atmosphere of the planet, the radio wave experiences refraction (refraction) and defocusing due to the fact that the refractive index of the atmosphere decreases with height. Therefore, a wave that has passed through higher layers of the atmosphere is refracted less than one passing through lower layers (Fig. 18).

As a result, the entire beam of radio waves expands and the signal intensity weakens. Depending on the refractive index, the frequency of the signal also changes.

If the planet has an ionosphere, then in the ionospheric layers, on the contrary, the radio beam is focused and the signal is amplified.

Rice. 18. Method of radio translucence (scheme).

Since the spacecraft is moving, the radio beam sent by it, crossing successively the upper and lower layers of the planet's atmosphere (or in reverse order - when leaving behind the planet), experiences either amplification or attenuation, which makes it possible to build a model of the upper layers of the atmosphere, including the ionosphere (in lower layers, the beam weakens so much that it is no longer possible to receive a signal).

5. Spectral observations of the glow of atmospheric gases in ultraviolet rays make it possible to register the most intense, the so-called resonant spectral lines. These include the famous hydrogen line (Lyman-alpha) at a wavelength of 1216 A, an oxygen triplet with a wavelength of 1302-1305 A, and a number of others. Investigation of the glow of these lines Provides information about the composition and density of the atmosphere up to the highest altitudes. Recall that the ultraviolet region of the spectrum is completely inaccessible to observations from the Earth.

6. Measurements of the content of charged particles in the atmosphere and near planetary space using ion traps; measurements of the velocity and flux of charged particles in the planet's magnetosphere.

7. Measurements of the planet's magnetic field strength and study of the structure of its magnetosphere using sensitive magnetometers.

8. Various methods for studying the physical properties and composition of the planet's soil; determination of the content of radioactive elements using gamma spectrometers, determination of the dielectric constant of soil using an onboard radar, chemical analysis of soil samples taken by descent vehicles, measurement of soil density with a density meter, etc.

9. Study of the relief of Mars by the intensity of the absorption bands of the main component of its atmosphere - carbon dioxide.

10. The study of the gravitational field of the planet by the movement of its artificial satellites or spacecraft flying past it.

11. Study of the planet's own thermal and radio emission from close distances in a wide range of wavelengths - from microns to decimeters.

This list is far from complete. Some methods will be described or mentioned below when presenting the results of planetary studies. However, already from this list one can see how diverse the methods of space exploration of planets are, what rich opportunities they present to scientists. It is not surprising that in just 15 years these studies have given us an enormous amount of information about the nature of the planets.

This is a system of planets, in the center of which is a bright star, the source of energy, heat and light - the Sun.
According to one theory, the Sun was formed along with the solar system about 4.5 billion years ago as a result of the explosion of one or more supernovae. Initially, the solar system was a cloud of gas and dust particles, which, in motion and under the influence of their mass, formed a disk in which a new star, the Sun, and our entire solar system arose.

At the center of the solar system is the Sun, around which nine large planets revolve in orbits. Since the Sun is displaced from the center of the planetary orbits, then during the cycle of revolution around the Sun, the planets either approach or move away in their orbits.

There are two groups of planets:

Terrestrial planets: and . These planets are small in size with a rocky surface, they are closer than others to the Sun.

Giant planets: and . These are large planets, consisting mainly of gas, and they are characterized by the presence of rings consisting of ice dust and many rocky pieces.

But does not fall into any group, because, despite its location in the solar system, it is located too far from the Sun and has a very small diameter, only 2320 km, which is half the diameter of Mercury.

Planets of the solar system

Let's start a fascinating acquaintance with the planets of the solar system in order of their location from the Sun, and also consider their main satellites and some other space objects (comets, asteroids, meteorites) in the gigantic expanses of our planetary system.

Rings and moons of Jupiter: Europa, Io, Ganymede, Callisto and others...
The planet Jupiter is surrounded by a whole family of 16 satellites, and each of them has its own, unlike other features ...

Rings and moons of Saturn: Titan, Enceladus and more...
Not only the planet Saturn has characteristic rings, but also on other giant planets. Around Saturn, the rings are especially clearly visible, because they consist of billions of small particles that revolve around the planet, in addition to several rings, Saturn has 18 satellites, one of which is Titan, its diameter is 5000 km, which makes it the largest satellite in the solar system ...

Rings and moons of Uranus: Titania, Oberon and others...
The planet Uranus has 17 satellites and, like other giant planets, thin rings encircling the planet, which practically do not have the ability to reflect light, therefore they were discovered not so long ago in 1977 quite by accident ...

Rings and moons of Neptune: Triton, Nereid and others...
Initially, before the exploration of Neptune by the Voyager 2 spacecraft, it was known about two satellites of the planet - Triton and Nerida. An interesting fact is that the Triton satellite has a reverse direction of orbital motion, and strange volcanoes were also discovered on the satellite that spewed nitrogen gas like geysers, spreading a dark mass (from liquid to vapor) for many kilometers into the atmosphere. During its mission, Voyager 2 discovered six more satellites of the planet Neptune...

Exploring the Planets of the Solar System

Until the end of the 20th century, it was generally accepted that there were nine planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto. But recently, a lot of objects have been discovered beyond the orbit of Neptune, some of them similar to Pluto, and others even larger than it. Therefore, in 2006, astronomers refined the classification: 8 largest bodies - from Mercury to Neptune - are considered classical planets, and Pluto became the prototype of a new class of objects - dwarf planets. The 4 planets closest to the Sun are called terrestrial planets, and the next 4 massive gas bodies are called giant planets. Dwarf planets mainly inhabit the area beyond the orbit of Neptune - the Kuiper belt.

moon

The Moon is a natural satellite of the Earth and the brightest object in the night sky. Formally, the Moon is not a planet, but it is significantly larger than all the dwarf planets, most satellites of the planets, and is not much inferior in size to Mercury. There is no atmosphere familiar to us on the Moon, there are no rivers and lakes, vegetation and living organisms. The force of gravity on the Moon is six times less than on Earth. Day and night with temperature drops up to 300 degrees last for two weeks. Nevertheless, the Moon is increasingly attracting earthlings with the opportunity to use its unique conditions and resources. Therefore, the Moon is our first step in getting to know the objects of the solar system.

The moon has been well studied both with the help of ground-based telescopes and thanks to the flights of more than 50 spacecraft and ships with astronauts. The Soviet automatic stations "Luna-3" (1959) and "Zond-3" (1965) photographed for the first time the eastern and western parts of the hemisphere of the Moon, invisible from Earth. Artificial satellites of the Moon explored its gravitational field and relief. Self-propelled vehicles "Lunokhod-1 and -2" transmitted to Earth a lot of pictures and information about the physical and mechanical properties of the soil. Twelve American astronauts with the help of the Apollo spacecraft in 1969-1972. visited the Moon, where they conducted surface studies at six different landing sites on the visible side, installed scientific equipment there and brought back to Earth about 400 kg of lunar rocks. The probes "Luna-16, -20 and -24" performed drilling in automatic mode and delivered lunar soil to Earth. The new generation spacecraft Clementine (1994), Lunar Prospector (1998-99) and Smart-1 (2003-06) received more accurate information about the relief and gravitational field of the Moon, as well as found on the surface deposits of hydrogen-bearing materials, possibly water ice. In particular, an increased concentration of these materials is found in permanently shaded depressions near the poles.

The Chinese apparatus "Change-1", launched on October 24, 2007, photographed the lunar surface and collected data to compile a digital model of its relief. March 1, 2009 the device was dropped on the surface of the moon. On November 8, 2008, the Indian spacecraft Chandrayan 1 was launched into a selenocentric orbit. On November 14, the probe separated from it, making a hard landing near the south pole of the moon. The apparatus worked for 312 days and transmitted data on the distribution of chemical elements over the surface and on the heights of the relief. The Japanese AMS "Kaguya" and two additional microsatellites "Okina" and "Oyuna", operating in 2007-2009, completed the scientific program of lunar exploration and transmitted data on the heights of the relief and the distribution of gravity on its surface with high accuracy.

A new important stage in the study of the Moon was the launch on June 18, 2009 of two American AMS "Lunar Reconnaissance Orbiter" (Lunar Orbital Reconnaissance) and "LCROSS" (satellite for observation and detection of lunar craters). October 9, 2009 AMS "LCROSS" was sent to the crater Cabeo. The spent stage of the Atlas-V rocket weighing 2.2 tons first fell to the bottom of the crater. Approximately four minutes later, the LCROSS AMS (weight 891 kg) fell there, which before falling rushed through the dust cloud raised by the stage, having managed to do the necessary research until the death of the device. American researchers believe that they still managed to find some water in a cloud of lunar dust. Lunar Reconnaissance Orbiter continues to explore the Moon from a polar lunar orbit. On board the spacecraft is the Russian LEND instrument (lunar research neutron detector) designed to search for frozen water. In the region of the South Pole, he discovered a large amount of hydrogen, which may be a sign of the presence of water there in a bound state.

In the near future, the exploration of the moon will begin. Already today, projects are being developed in detail to create a permanent habitable base on its surface. Long-term or permanent presence on the Moon of replacement crews of such a base will make it possible to solve more complex scientific and applied problems.

The Moon moves under the influence of gravity, mainly two celestial bodies - the Earth and the Sun at an average distance of 384,400 km from the Earth. At apogee, this distance increases to 405,500 km, and at perigee it decreases to 363,300 km. The period of revolution of the Moon around the Earth with respect to distant stars is about 27.3 days (sidereal month), but since the Moon revolves around the Sun together with the Earth, its position relative to the Sun-Earth line repeats after a slightly longer period of time - about 29.5 days (synodic month). During this period, a complete change of lunar phases takes place: from the new moon to the first quarter, then to the full moon, to the last quarter and again to the new moon. The rotation of the Moon around its axis occurs at a constant angular velocity in the same direction in which it revolves around the Earth, and with the same period of 27.3 days. That is why from the Earth we see only one hemisphere of the Moon, which we call so - visible; and the other hemisphere is always hidden from our eyes. This hemisphere, which is not visible from the Earth, is called the far side of the Moon. The figure formed by the physical surface of the Moon is very close to a regular sphere with an average radius of 1737.5 km. The surface area of ​​the lunar globe is about 38 million km 2, which is only 7.4% of the earth's surface area, or about a quarter of the area of ​​the earth's continents. The ratio of the masses of the Moon and the Earth is 1:81.3. The average density of the Moon (3.34 g / cm 3) is much less than the average density of the Earth (5.52 g / cm 3). The force of gravity on the Moon is six times less than on Earth. On a summer afternoon, near the equator, the surface warms up to +130°C, in some places even higher; and at night the temperature drops to -170 °C. Rapid cooling of the surface is also observed during lunar eclipses. Two types of regions are distinguished on the Moon: light - continental, occupying 83% of the entire surface (including the reverse side), and dark regions, called seas. Such a division arose as early as the middle of the 17th century, when it was assumed that there really was water on the Moon. In terms of mineralogical composition and content of individual chemical elements, lunar rocks in dark areas of the surface (seas) are very close to terrestrial rocks such as basalts, and in light areas (continents) - to anorthosites.

The question of the origin of the Moon is still not completely clear. Features of the chemical composition of lunar rocks suggest that the Moon and the Earth were formed in the same region of the solar system. But the difference in their composition and internal structure makes us think that both of these bodies were not a single whole in the past. Most of the large craters and huge depressions (multi-ring basins) appeared on the surface of the lunar ball during the period of heavy bombardment of the surface. About 3.5 billion years ago, as a result of internal heating, basalt lavas poured onto the surface from the bowels of the Moon, filling lowlands and round depressions. Thus the lunar seas were formed. On the reverse side, due to the thicker crust, there were significantly fewer effusions. On the visible hemisphere, the seas occupy 30% of the surface, and on the reverse - only 3%. Thus, the evolution of the lunar surface was basically completed about 3 billion years ago. Meteor bombardment continued, but with less intensity. As a result of long-term processing of the surface, the upper loose layer of the rocks of the Moon was formed - regolith, several meters thick.

Mercury

The planet closest to the Sun is named after the ancient god Hermes (among the Romans Mercury) - the messenger of the gods and the god of dawn. Mercury is at an average distance of 58 million km or 0.39 AU. from the sun. Moving along a highly elongated orbit, it approaches the Sun at a distance of 0.31 AU at perihelion, and at a distance of 0.47 AU at its maximum distance, making a complete revolution in 88 Earth days. In 1965, it was established by radar methods from the Earth that the period of rotation of this planet is 58.6 days, that is, in 2/3 of its year it completes a complete revolution around its axis. The addition of axial and orbital motions leads to the fact that, being on the Sun-Earth line, Mercury always turns the same side towards us. A solar day (the time interval between the upper or lower culminations of the Sun) continues on the planet for 176 Earth days.

At the end of the 19th century, astronomers tried to draw the dark and light details observed on the surface of Mercury. The most famous are the works of Schiaparelli (1881-1889) and the American astronomer Percival Lovell (1896-1897). Interestingly, the astronomer T. J. C. even announced in 1901 that he had seen craters on Mercury. Few people believed in this, but subsequently the 625-kilometer crater (Beethoven) turned out to be in the place marked by Xi. In 1934, the French astronomer Eugène Antoniadi mapped the "visible hemisphere" of Mercury, since it was then believed that only one of its hemispheres was always illuminated. Individual details on this map Antoniadi gave names that are partially used on modern maps.

It was possible for the first time to make truly reliable maps of the planet and see the fine details of the surface topography thanks to the American space probe Mariner-10, launched in 1973. It approached Mercury three times and transmitted television images of various parts of its surface to Earth. In total, 45% of the planet's surface was filmed, mainly the western hemisphere. As it turned out, its entire surface is covered with many craters of different sizes. It was possible to clarify the value of the radius of the planet (2439 km) and its mass. Temperature sensors made it possible to establish that during the day the surface temperature of the planet rises to 510 ° C, and at night it drops to -210 ° C. The strength of its magnetic field is about 1% of the strength of the earth's magnetic field. More than 3 thousand photographs taken during the third approach had a resolution of up to 50 m.

The free fall acceleration on Mercury is 3.68 m/s 2 . An astronaut on this planet will weigh almost three times less than on Earth. Since it turned out that the average density of Mercury is almost the same as that of the Earth, it is assumed that Mercury has an iron core, which occupies about half the volume of the planet, over which the mantle and silicate shell are located. Mercury receives 6 times more sunlight per unit area than Earth. Moreover, most of the solar energy is absorbed, since the surface of the planet is dark, reflecting only 12-18 percent of the incident light. The surface layer of the planet (regolith) is highly crushed and serves as excellent thermal insulation, so that at a depth of several tens of centimeters from the surface the temperature is constant - about 350 degrees K. Mercury has an extremely rarefied helium atmosphere created by the "solar wind" that blows the planet. The pressure of such an atmosphere at the surface is 500 billion times less than at the Earth's surface. In addition to helium, an insignificant amount of hydrogen, traces of argon and neon were detected.

The American AMS "Messenger" (Messenger - from the English Courier), launched on August 3, 2004, made its first flight around Mercury on January 14, 2008 at a distance of 200 km from the surface of the planet. She photographed the eastern half of the previously unphotographed hemisphere of the planet. The studies of Mercury were carried out in two stages: first survey from the flyby flight trajectory during two encounters with the planet (2008), and then (September 30, 2009) - detailed. The entire surface of the planet was surveyed in various ranges of the spectrum and color images of the terrain were obtained, the chemical and mineralogical composition of rocks was determined, and the content of volatile elements in the near-surface soil layer was measured. The laser altimeter measured the heights of the surface relief of Mercury. It turned out that the height difference of the relief on this planet is less than 7 km. During the fourth rendezvous, on March 18, 2011, AMS "Messenger" should enter the orbit of the artificial satellite of Mercury.

According to the decision of the International Astronomical Union, craters on Mercury are named after figures: writers, poets, artists, sculptors, composers. For example, the largest craters with a diameter of 300 to 600 km were named Beethoven, Tolstoy, Dostoevsky, Shakespeare and others. There are exceptions to this rule - one crater with a diameter of 60 km with a ray system is named after the famous astronomer Kuiper, and another crater with a diameter of 1.5 km near the equator, taken as the origin of longitudes on Mercury, is named Hun Kal, which is in the language of the ancient Maya means twenty. It was agreed to draw a meridian through this crater, with a longitude of 20°.

The plains are given the names of the planet Mercury in various languages, such as Sobkow Plain or Odin Plain. There are two plains named for their location: the Northern Plain and the Zhara Plain, located in the region of maximum temperatures at 180° longitude. The mountains bordering this plain were called the mountains of Heat. A distinctive feature of the relief of Mercury is the extended ledges, which received the names of marine research vessels. The valleys are named after radio astronomy observatories. Two ridges are named Antoniadi and Schiaparelli, in honor of the astronomers who made the first maps of this planet.

Venus

Venus is the planet closest to the Earth, it is closer to the Sun than us and therefore it is illuminated by it brighter; finally, it reflects sunlight very well. The fact is that the surface of Venus is covered under a powerful cover of the atmosphere, which completely hides the surface of the planet from our view. In the visible range, it cannot be seen even from the orbit of the artificial satellite of Venus, and, nevertheless, we have "images" of the surface, which were obtained by radar.

The second planet from the Sun is named after the ancient goddess of love and beauty Aphrodite (among the Romans - Venus). The average radius of Venus is 6051.8 km, and the mass is 81% of the mass of the Earth. Venus revolves around the Sun in the same direction as the other planets, making a complete revolution in 225 days. The period of its rotation around its axis (243 days) was determined only in the early 1960s, when radar methods began to be used to measure the speeds of planetary rotation. Thus, the daily rotation of Venus is the slowest among all the planets. In addition, it occurs in the opposite direction: unlike most planets, in which the directions of orbiting and rotation around the axis coincide, Venus rotates around the axis in the direction opposite to the orbital movement. If you look formally, then this is not a unique property of Venus. For example, Uranus and Pluto also rotate in the opposite direction. But they rotate almost "lying on their side", and the axis of Venus is almost perpendicular to the orbital plane, so it is the only one that "really" rotates in the opposite direction. That is why the solar day on Venus is shorter than the time of its rotation around the axis and is 117 Earth days (for other planets, the solar day is longer than the rotation period). A year on Venus is only twice as long as a solar day.

The atmosphere of Venus is 96.5% carbon dioxide and almost 3.5% nitrogen. Other gases - water vapor, oxygen, sulfur oxide and dioxide, argon, neon, helium and krypton - add up to less than 0.1%. But it should be borne in mind that the Venusian atmosphere is about 100 times more massive than ours, so there is, for example, five times more nitrogen in mass than in the Earth's atmosphere.

The foggy haze in the atmosphere of Venus extends upwards to a height of 48-49 km. Further up to a height of 70 km there is a cloud layer containing droplets of concentrated sulfuric acid, and hydrochloric and hydrofluoric acids are also present in the uppermost layers. The clouds of Venus reflect 77% of the sunlight falling on them. At the top of the highest mountains of Venus - the Maxwell Mountains (about 11 km high) - the atmospheric pressure is 45 bar, and at the bottom of the Diana Canyon - 119 bar. As you know, the pressure of the earth's atmosphere at the surface of the planet is only 1 bar. The powerful atmosphere of Venus, consisting of carbon dioxide, absorbs and partially transmits about 23% of solar radiation to the surface. This radiation heats the surface of the planet, but thermal infrared radiation from the surface passes through the atmosphere back into space with great difficulty. And only when the surface is heated to about 460-470 ° C, the outgoing energy flux is equal to the incoming to the surface. It is because of this greenhouse effect that the surface of Venus maintains a high temperature regardless of the latitude of the area. But in the mountains, over which the thickness of the atmosphere is less, the temperature is several tens of degrees lower. Venus was explored by more than 20 spacecraft: Venus, Mariners, Pioneer Venus, Vega and Magellan. In 2006, the Venera Express probe worked in orbit around it. Scientists were able to see the global features of the surface relief of Venus thanks to radar sounding from the Pioneer-Venus (1978), Venera-15 and -16 (1983-84) and Magellan (1990-94) orbiters .). Ground-based radar allows you to "see" only 25% of the surface, and with much lower detail resolution than spacecraft are capable of. For example, Magellan obtained images of the entire surface with a resolution of 300 m. It turned out that most of the surface of Venus is occupied by hilly plains.

Elevations account for only 8% of the surface. All noticeable details of the relief got their names. On the first ground-based radar images of individual parts of the surface of Venus, the researchers used various names, of which now remain on the maps - the Maxwell mountains (the name reflects the role of radiophysics in Venus research), the Alpha and Beta regions (the two brightest details of the relief of Venus in the radar images are named after the first letters of the Greek alphabet). But these names are exceptions to the rules of naming adopted by the International Astronomical Union: astronomers have decided to call the details of the relief of the surface of Venus by female names. Large elevated areas were named: Land of Aphrodite, Land of Ishtar (in honor of the Assyrian goddess of love and beauty) and Land of Lada (Slavic goddess of love and beauty). Large craters are named after outstanding women of all times and peoples, and small craters bear personal female names. On the maps of Venus, you can find such names as Cleopatra (the last queen of Egypt), Dashkova (director of the St. Petersburg Academy of Sciences), Akhmatova (Russian poetess) and other famous names. Of the Russian names, there are Antonina, Galina, Zina, Zoya, Lena, Masha, Tatyana and others.

Mars

The fourth planet from the Sun, named after the god of war Mars, is 1.5 times farther from the sun than the Earth. One orbit around Mars takes 687 Earth days. The orbit of Mars has a noticeable eccentricity (0.09), so its distance from the Sun varies from 207 million km at perihelion to 250 million km at aphelion. The orbits of Mars and Earth lie almost in the same plane: the angle between them is only 2°. Every 780 days, Earth and Mars are at a minimum distance from each other, which can range from 56 to 101 million km. These planetary encounters are called oppositions. If at this moment the distance between the planets is less than 60 million km, then the opposition is called great. Great confrontations occur every 15-17 years.

The equatorial radius of Mars is 3394 km, 20 km more than the polar one. In terms of mass, Mars is ten times smaller than the Earth, and in terms of surface area it is 3.5 times smaller. The period of the axial rotation of Mars was determined by ground-based telescopic observations of the contrasting details of the surface: it is 24 hours 39 minutes and 36 seconds. The axis of rotation of Mars is deflected by an angle of 25.2° from the perpendicular to the plane of the orbit. Therefore, Mars also experiences a change of seasons, but the seasons are almost twice as long as on Earth. Due to the elongation of the orbit, the seasons in the northern and southern hemispheres have different durations: summer in the northern hemisphere lasts 177 Martian days, and in the southern hemisphere it is 21 days shorter, but at the same time warmer than summer in the northern hemisphere.

Due to its greater distance from the Sun, Mars receives only 43% of the energy that falls on the same area of ​​​​the earth's surface. The average annual temperature on the surface of Mars is about -60 °C. The maximum temperature there does not exceed a few degrees above zero, and the minimum was recorded at the northern polar cap and is -138 °C. During the day, the surface temperature changes significantly. For example, in the southern hemisphere at a latitude of 50°, the typical temperature in mid-autumn varies from -18°C at noon to -63°C at night. However, already at a depth of 25 cm below the surface, the temperature is almost constant (about -60 ° C), regardless of the time of day and season. Large changes in temperature on the surface are explained by the fact that the atmosphere of Mars is very rarefied, and at night the surface cools quickly, and during the day it is quickly heated by the Sun. The atmosphere of Mars is 95% carbon dioxide. Other constituents: 2.5% nitrogen, 1.6% argon, less than 0.4% oxygen. The average pressure of the atmosphere at the surface is 6.1 mbar, i.e., 160 times less than the pressure of the earth's air at sea level (1 bar). In the deepest depressions on Mars, it can reach 12 mbar. The atmosphere of the planet is dry, there is practically no water vapor in it.

The polar caps of Mars are multi-layered. The lower, main layer, several kilometers thick, is formed by ordinary water ice mixed with dust; this layer is preserved in the summer, forming permanent caps. And the observed seasonal changes in the polar caps occur due to the upper layer less than 1 meter thick, consisting of solid carbon dioxide, the so-called "dry ice". The area covered by this layer grows rapidly in winter, reaching the 50° parallel, and sometimes even crossing this line. In spring, as the temperature rises, the upper layer evaporates, and only a permanent cap remains. The “darkening wave” of surface areas observed with the change of seasons is explained by the change in the direction of the winds, constantly blowing in the direction from one pole to another. The wind carries away the top layer of loose material - light dust, exposing areas of darker rocks. During periods when Mars passes perihelion, the heating of the surface and atmosphere increases, and the balance of the Martian environment is disturbed. The wind speed increases to 70 km/h, whirlwinds and storms begin. Sometimes more than a billion tons of dust rises and is held in suspension, while the climatic situation on the entire Martian globe changes dramatically. Duration of dust storms can reach 50 - 100 days. The exploration of Mars by spacecraft began in 1962 with the launch of the Mars-1 probe. The first images of areas of the surface of Mars were transmitted by Mariner-4 in 1965, and then by Mariner-6 and -7 in 1969. The Mars-3 descent vehicle managed to make a soft landing. Based on the images of Mariner 9 (1971), detailed maps of the planet were compiled. He transmitted to Earth 7329 images of Mars with a resolution of up to 100 m, as well as photographs of his satellites - Phobos and Deimos. A whole flotilla of four Mars-4, -5, -6, -7 spacecraft, launched in 1973, reached the vicinity of Mars in early 1974. Due to a malfunction of the onboard braking system, Mars-4 passed at a distance about 2200 km from the surface of the planet, having performed only its photography. "Mars-5" carried out remote studies of the surface and atmosphere from the orbit of an artificial satellite. The Mars 6 lander made a soft landing in the southern hemisphere. Data on the chemical composition, pressure and temperature of the atmosphere were transmitted to Earth. "Mars-7" passed at a distance of 1300 km from the surface without fulfilling its program.

The flights of two American Vikings launched in 1975 were the most productive. On board the vehicles were television cameras, infrared spectrometers for recording water vapor in the atmosphere, and radiometers for obtaining temperature data. The Viking 1 lander made a soft landing on Chris Plain on July 20, 1976, and Viking 2 on Utopia Plain on September 3, 1976. Unique experiments were carried out at the landing sites in order to detect signs of life in the Martian soil. A special device captured a soil sample and placed it in one of the containers containing a supply of water or nutrients. Since any living organisms change their habitat, the instruments had to record this. Although some changes in the environment in a tightly closed container were observed, the presence of a strong oxidizing agent in the soil could lead to the same results. This is why scientists have not been able to confidently attribute these changes to bacteria. The orbital stations took detailed photographs of the surface of Mars and its satellites. Based on the data obtained, detailed maps of the planet's surface, geological, thermal and other special maps were compiled.

The task of the Soviet stations "Phobos-1, -2", launched after a 13-year break, included the study of Mars and its satellite Phobos. As a result of an incorrect command from the Earth, Phobos-1 lost its orientation, and communication with it could not be restored. "Phobos-2" entered the orbit of the artificial satellite of Mars in January 1989. Data on temperature changes on the surface of Mars and new information about the properties of the rocks that make up Phobos were obtained by remote methods. 38 images were obtained with a resolution of up to 40 m, the temperature of its surface was measured, which is 30 °C at the hottest points. Unfortunately, it was not possible to carry out the main program for the study of Phobos. Communication with the device was lost on March 27, 1989. The series of failures did not end there. The American spacecraft "Mars-Observer", launched in 1992, also did not fulfill its task. Communication with it was lost on August 21, 1993. It was not possible to put the Russian Mars-96 station on the flight path to Mars.

One of NASA's most successful projects is the Mars Global Surveyor, launched on November 7, 1996 to map the surface of Mars in detail. The device also serves as a telecommunications satellite for the Spirit and Opportunity rovers, delivered in 2003 and still operating today. In July 1997, the Mars Pathfinder delivered to the planet the first robotic rover, the Sojerner, weighing less than 11 kg, which successfully investigated the chemical composition of the surface and meteorological conditions. The rover maintained contact with the Earth through the lander. NASA's automatic interplanetary station "Mars Reconnaissance Satellite" began its work in orbit in March 2006. Using a high-resolution camera on the surface of Mars, it was possible to distinguish details of 30 cm in size. "Mars Odyssey", "Mars - Express" and "Mars reconnaissance satellite continue research from orbit. The device "Phoenix" worked in the polar region from May 25 to November 2, 2008. He was the first to drill the surface and discover ice. The Phoenix delivered a digital library of science fiction to the planet. Programs for the flight of astronauts to Mars are being developed. Such an expedition will take more than two years, because in order to return, they will have to wait for a convenient relative position of Earth and Mars.

On modern maps of Mars, along with the names assigned to landforms that are identified from satellite images, the old geographical and mythological names proposed by Schiaparelli are also used. The largest elevated area, with a diameter of about 6000 km and a height of up to 9 km, was named Tharsis (as Iran was called on ancient maps), and a huge ring depression in the south with a diameter of more than 2000 km was named Hellas (Greece). Densely cratered areas of the surface were called lands: the Land of Prometheus, the Land of Noah, and others. The valleys are given the names of the planet Mars from the languages ​​of different peoples. Large craters are named after scientists, and small craters are named after settlements on Earth. Four giant extinct volcanoes rise above the surrounding area to a height of up to 26 m. The largest of them, Mount Olympus, located on the western outskirts of the Arsida mountains, has a base with a diameter of 600 km and a caldera (crater) at the top with a diameter of 60 km. Three volcanoes - Mount Askriyskaya, Mount Pavlina and Mount Arsia - are located on the same straight line at the top of the Tharsis Mountains. The volcanoes themselves tower over Tharsis for another 17 km. In addition to these four, more than 70 extinct volcanoes have been found on Mars, but they are much smaller in area and in height.

To the south of the equator is a giant valley up to 6 km deep and over 4,000 km long. It was called the Valley of the Mariner. Many smaller valleys have also been identified, as well as furrows and cracks, indicating that in ancient times there was water on Mars and, therefore, the atmosphere was denser. Under the surface of Mars in some areas there should be a layer of permafrost, several kilometers thick. In such regions, on the surface near the craters, frozen flows unusual for terrestrial planets are visible, which can be used to judge the presence of subsurface ice.

With the exception of the plains, the surface of Mars is heavily cratered. Craters tend to look more eroded than those on Mercury and the Moon. Traces of wind erosion can be seen everywhere.

Phobos and Deimos are natural satellites of Mars

The satellites of Mars were discovered during the great opposition of 1877 by the American astronomer A. Hall. They were named Phobos (translated from Greek Fear) and Deimos (Horror), since in ancient myths the god of war was always accompanied by his children - Fear and Horror. Satellites are very small in size and have an irregular shape. The semi-major axis of Phobos is 13.5 km, and the minor one is 9.4 km; at Deimos, respectively, 7.5 and 5.5 km. The Mariner 7 probe photographed Phobos against the background of Mars in 1969, and Mariner 9 transmitted many images of both satellites, which show that their surfaces are uneven, abundantly covered with craters. Several close approaches to the satellites were made by the Viking and Phobos-2 probes. The best photographs of Phobos show relief details up to 5 meters in size.

The orbits of the satellites are circular. Phobos revolves around Mars at a distance of 6000 km from the surface with a period of 7 hours 39 minutes. Deimos is 20,000 km away from the planet's surface, and its orbital period is 30 hours and 18 minutes. The periods of rotation of satellites around the axis coincide with the periods of their revolution around Mars. The major axes of the figures of the satellites are always directed towards the center of the planet. Phobos rises in the west and sets in the east 3 times per Martian day. The average density of Phobos is less than 2 g/cm 3 , and the free fall acceleration on its surface is 0.5 cm/s 2 . A person would weigh only a few tens of grams on Phobos and could, by throwing a stone with his hand, make it forever fly into space (the separation velocity on the surface of Phobos is about 13 m/s). The largest crater on Phobos has a diameter of 8 km, comparable to the smallest diameter of the satellite itself. On Deimos, the largest depression has a diameter of 2 km. Small craters on the surfaces of the satellites are dotted in much the same way as the Moon. With a general similarity, an abundance of finely fragmented material covering the surfaces of the satellites, Phobos looks more “ragged”, and Deimos has a smoother surface covered with dust. On Phobos, mysterious furrows have been discovered that cross almost the entire satellite. Furrows are 100-200 m wide and stretch for tens of kilometers. Their depth is from 20 to 90 meters. There are several about the origin of these furrows, but so far there is no convincing enough explanation, as well as an explanation for the origin of the satellites themselves. Most likely, these are asteroids captured by Mars.

Jupiter

Jupiter is called the "king of the planets" for a reason. It is the largest planet in the solar system, exceeding the Earth by 11.2 times in diameter and 318 times in mass. Jupiter has a low average density (1.33 g / cm 3), since it is almost entirely composed of hydrogen and helium. It is located at an average distance of 779 million km from the Sun and spends about 12 years per orbit. Despite its gigantic size, this planet rotates very quickly - faster than the Earth or Mars. The most surprising thing is that Jupiter does not have a solid surface in the generally accepted sense - it is a gas giant. Jupiter leads the group of giant planets. Named after the supreme god of ancient mythology (the ancient Greeks - Zeus, the Romans - Jupiter), it is five times further from the Sun than the Earth. Due to the rapid rotation, Jupiter is strongly oblate: its equatorial radius (71,492 km) is 7% larger than the polar one, which is easy to see when viewed through a telescope. The force of gravity at the planet's equator is 2.6 times greater than on Earth. Jupiter's equator is tilted only 3° to its orbit, so there are no seasons on the planet. The inclination of the orbit to the plane of the ecliptic is even less - only 1 °. Every 399 days, the opposition of the Earth and Jupiter is repeated.

Hydrogen and helium are the main components of this planet: by volume, the ratio of these gases is 89% hydrogen and 11% helium, and by mass 80% and 20%, respectively. The entire visible surface of Jupiter is dense clouds, forming a system of dark belts and bright zones north and south of the equator to the parallels of 40 ° north and south latitude. Clouds form layers of brownish, red and bluish hues. The periods of rotation of these cloud layers turned out to be not the same: the closer they are to the equator, the shorter period they rotate. So, near the equator, they complete a revolution around the planet's axis in 9 hours and 50 minutes, and at middle latitudes - in 9 hours and 55 minutes. Belts and zones are areas of downdrafts and updrafts in the atmosphere. Atmospheric currents parallel to the equator are supported by heat flows from the depths of the planet, as well as the rapid rotation of Jupiter and the energy of the Sun. The visible surface of the zones is located approximately 20 km above the belts. At the boundaries of belts and zones, strong turbulent motions of gases are observed. The hydrogen-helium atmosphere of Jupiter has a huge extent. The cloud cover is located at an altitude of about 1000 km above the "surface", where the gaseous state changes to liquid due to high pressure.

Even before the flights of spacecraft to Jupiter, it was established that the heat flux from the bowels of Jupiter is twice the influx of solar heat received by the planet. This may be due to the slow sinking towards the center of the planet of heavier substances and the ascent of lighter ones. The fall of meteorites on the planet can also be a source of energy. The color of the belts is explained by the presence of various chemical compounds. Closer to the poles of the planet, at high latitudes, clouds form a continuous field with brown and bluish spots up to 1000 km across. Jupiter's most famous feature is the Great Red Spot, an oval formation of varying size located in the southern tropical zone. At present, it has dimensions of 15,000 × 30,000 km (i.e., two globes will be freely located in it), and a hundred years ago, observers noted that the size of the Spot was twice as large. Sometimes it is not visible very clearly. The Great Red Spot is a long-lived vortex in the atmosphere of Jupiter, making a complete revolution around its center in 6 Earth days. The first study of Jupiter at close range (130,000 km) took place in December 1973 using the Pioneer-10 probe. Observations made by this apparatus in ultraviolet rays showed that the planet has an extended hydrogen and helium corona. The upper cloud layer appears to be cirrus ammonia, while below is a mixture of hydrogen, methane, and frozen ammonia crystals. An infrared radiometer showed that the temperature of the outer cloud cover is about -133 °C. A powerful magnetic field was discovered and a zone of the most intense radiation was registered at a distance of 177 thousand km from the planet. The plume of Jupiter's magnetosphere is noticeable even beyond the orbit of Saturn.

The path of Pioneer 11, which flew at a distance of 43,000 km from Jupiter in December 1974, was calculated differently. He passed between the radiation belts and the planet itself, avoiding a dose of radiation dangerous for electronic equipment. An analysis of color images of the cloud layer obtained by a photopolarimeter made it possible to reveal the features and structure of the clouds. The height of the clouds turned out to be different in belts and zones. Even before the Pioneer-10 and -11 flights from Earth, with the help of an astronomical observatory flying on an airplane, it was possible to determine the content of other gases in Jupiter's atmosphere. As expected, the presence of phosphine, a gaseous compound of phosphorus with hydrogen (PH 3), was detected, which gives color to the cloud cover. When heated, it decomposes with the release of red phosphorus. The unique mutual arrangement in the orbits of the Earth and the giant planets, which took place from 1976 to 1978, was used to sequentially study Jupiter, Saturn, Uranus and Neptune using the Voyager 1 and 2 probes. Their routes were calculated in such a way that it was possible to use the gravity of the planets themselves to accelerate and turn the flight path from one planet to another. As a result, the flight to Uranus took 9 years, not 16, as it would have been according to the traditional scheme, and the flight to Neptune - 12 years instead of 20. Such a mutual arrangement of the planets will be repeated only after 179 years.

On the basis of data obtained by space probes and theoretical calculations, mathematical models of Jupiter's cloud cover are constructed and ideas about its internal structure are refined. In a somewhat simplified form, Jupiter can be represented as shells with a density that increases towards the center of the planet. At the bottom of the atmosphere with a thickness of 1500 km, the density of which increases rapidly with depth, there is a layer of gas-liquid hydrogen with a thickness of about 7000 km. At the level of 0.9 of the planet's radius, where the pressure is 0.7 Mbar and the temperature is about 6500 K, hydrogen passes into a liquid-molecular state, and after another 8000 km - into a liquid metallic state. Along with hydrogen and helium, the composition of the layers includes a small amount of heavy elements. The inner core, 25,000 km in diameter, is metallosilicate, including water, ammonia, and methane. The temperature in the center is 23,000 K and the pressure is 50 Mbar. Saturn has a similar structure.

63 known satellites revolve around Jupiter, which can be divided into two groups - internal and external, or regular and irregular; the first group includes 8 satellites, the second - 55. The satellites of the inner group circulate in almost circular orbits, practically lying in the plane of the planet's equator. The four satellites closest to the planet - Adrastea, Metis, Amalthea and Theba have diameters from 40 to 270 km and are within 2-3 radii of Jupiter from the center of the planet. They differ sharply from the four satellites following them, located at a distance of 6 to 26 radii of Jupiter and having much larger dimensions, close to the size of the Moon. These large satellites - Io, Europa, Ganymede and Callisto were discovered at the beginning of the 17th century. almost simultaneously Galileo Galilei and Simon Marius. They are usually called the Galilean satellites of Jupiter, although the first tables of the motion of these satellites were compiled by Marius.

The outer group consists of small - with a diameter of 1 to 170 km - satellites moving in elongated and strongly inclined orbits to Jupiter's equator. At the same time, five satellites closer to Jupiter move along their orbits in the direction of rotation of Jupiter, and almost all more distant satellites move in the opposite direction. Detailed information about the nature of the surfaces of the satellites was obtained by spacecraft. Let us dwell in more detail on the Galilean satellites. The diameter of the closest satellite to Jupiter, Io, is 3640 km, and its average density is 3.55 g/cm 3 . The bowels of Io are heated due to the tidal influence of Jupiter and the perturbations introduced into the motion of Io by its neighbors - Europa and Ganymede. Tidal forces deform Io's outer layers and heat them up. In this case, the accumulated energy breaks out to the surface in the form of volcanic eruptions. From the mouths of volcanoes, sulfur dioxide and sulfur vapor are ejected at a speed of about 1 km / s to a height of hundreds of kilometers above the surface of the satellite. Although Io's equatorial region averages about -140°C, there are hot spots ranging in size from 75 to 250 km, where temperatures reach 100-300°C. The surface of Io is covered with eruptions and has an orange color. The average age of details on it is small - about 1 million years. The relief of Io is mostly flat, but there are several mountains from 1 to 10 km high. The atmosphere of Io is very rarefied (practically it is a vacuum), but a gas tail stretches behind the satellite: radiation of oxygen, sodium and sulfur vapors, products of volcanic eruption, was detected along Io's orbit.

The second of the Galilean satellites, Europa, is somewhat smaller in size than the Moon, its diameter is 3130 km, and the average density of matter is about 3 g/cm3. The surface of the satellite is dotted with a network of light and dark lines: apparently, these are cracks in the ice crust resulting from tectonic processes. The width of these faults varies from a few kilometers to hundreds of kilometers, and the length reaches thousands of kilometers. Estimates of crustal thickness range from a few kilometers to tens of kilometers. In the bowels of Europe, the energy of tidal interaction is also released, which maintains the mantle in liquid form - the subglacial ocean, possibly even warm. It is not surprising, therefore, that there is an assumption about the possibility of the existence of the simplest forms of life in this ocean. Based on the average density of the satellite, there should be silicate rocks under the ocean. Since there are very few craters on Europa, which has a fairly smooth surface, the age of the details of this orange-brown surface is estimated at hundreds of thousands and millions of years. The high-resolution images taken by Galileo show individual irregularly shaped fields with elongated parallel ridges and valleys, reminiscent of highways. In a number of places, dark spots stand out, most likely these are deposits of matter taken out from under the ice layer.

According to the American scientist Richard Greenberg, the conditions for life on Europa should be sought not in the deep subglacial ocean, but in numerous cracks. Due to the tidal effect, the cracks periodically narrow and expand to a width of 1 m. When the crack narrows, the ocean water goes down, and when it starts to expand, the water rises along it almost to the very surface. Through the ice plug, which prevents water from reaching the surface, the sun's rays penetrate, carrying the energy necessary for living organisms.

The largest satellite in the Jupiter system - Ganymede has a diameter of 5268 km, but its average density is only twice that of water; this suggests that about 50% of the satellite's mass is ice. Numerous craters covering areas of dark brown color testify to the ancient age of this surface, about 3-4 billion years. The younger areas are covered with systems of parallel grooves formed by lighter material during the stretching of the ice crust. The depth of these furrows is several hundred meters, the width is tens of kilometers, and the length can reach up to several thousand kilometers. Some Ganymede craters have not only light ray systems (similar to the moon), but sometimes dark ones.

The diameter of Callisto is 4800 km. Based on the average density of the satellite (1.83 g / cm 3), it is assumed that water ice makes up about 60% of its mass. The thickness of the ice crust, like that of Ganymede, is estimated at tens of kilometers. The entire surface of this satellite is completely dotted with craters of various sizes. It does not have extended plains or systems of furrows. Craters on Callisto have a weakly expressed shaft and shallow depth. A unique detail of the relief is a multi-ring structure with a diameter of 2600 km, consisting of ten concentric rings. The surface temperature at the equator of Callisto reaches -120 °C at noon. The satellite has its own magnetic field.

On December 30, 2000, the Cassini probe passed near Jupiter, heading towards Saturn. At the same time, a number of experiments were carried out in the vicinity of the “king of the planets”. One of them was aimed at detecting the very rarefied atmospheres of the Galilean satellites during their eclipse by Jupiter. Another experiment consisted in recording radiation from Jupiter's radiation belts. Interestingly, in parallel with the work of Cassini, the same radiation was recorded using ground-based telescopes by schoolchildren and students in the United States. The results of their research were used along with the Cassini data.

As a result of the study of the Galilean satellites, an interesting hypothesis was put forward that in the early stages of their evolution, the giant planets radiated huge heat fluxes into space. Jupiter's radiation could melt the ice on the surface of three Galilean moons. On the fourth - Callisto - this should not have happened, since it is 2 million km away from Jupiter. Therefore, its surface is so different from the surfaces of satellites closer to the planet.

Saturn

Among the giant planets, Saturn stands out for its remarkable ring system. Like Jupiter, it is a huge, rapidly spinning ball composed primarily of liquid hydrogen and helium. Orbiting around the Sun at a distance 10 times farther than the Earth, Saturn completes a complete revolution in a nearly circular orbit in 29.5 years. The angle of inclination of the orbit to the plane of the ecliptic is only 2 °, while the equatorial plane of Saturn is tilted 27 ° to the plane of its orbit, so the change of seasons is inherent in this planet.

The name of Saturn goes back to the Roman counterpart of the ancient titan Kronos, the son of Uranus and Gaia. This second largest planet exceeds the Earth in volume by 800 times, and in mass by 95 times. It is easy to calculate that its average density (0.7 g/cm 3 ) is less than the density of water - uniquely low for the planets of the solar system. The equatorial radius of Saturn along the upper boundary of the cloud layer is 60,270 km, and the polar radius is several thousand kilometers less. Saturn's rotation period is 10 hours 40 minutes. Saturn's atmosphere contains 94% hydrogen and 6% helium (by volume).

Neptune

Neptune was discovered in 1846 as a result of an accurate theoretical prediction. After studying the movement of Uranus, the French astronomer Le Verrier determined that the seventh planet is affected by the attraction of an equally massive unknown body, and calculated its position. Guided by this forecast, the German astronomers Halle and D'Arrest discovered Neptune. Later it turned out that, starting from Galileo, astronomers marked the position of Neptune on maps, but mistook it for a star.

Neptune is the fourth of the giant planets, named after the god of the seas in ancient mythology. The equatorial radius of Neptune (24,764 km) is almost 4 times the radius of the Earth, and in terms of mass, Neptune is 17 times larger than our planet. The average density of Neptune is 1.64 g/cm3. It revolves around the Sun at a distance of 4.5 billion km (30 AU), making a complete cycle in almost 165 Earth years. The plane of the planet's orbit is inclined by 1.8° to the plane of the ecliptic. The inclination of the equator to the plane of the orbit is 29.6°. Due to the great distance from the Sun, the illumination on Neptune is 900 times less than on Earth.

Data transmitted by Voyager 2, which passed within 5,000 km of the surface of Neptune's cloud layer in 1989, revealed details of the planet's cloud cover. The stripes on Neptune are weakly expressed. A large dark spot the size of our planet, discovered in the southern hemisphere of Neptune, is a giant anticyclone that completes a revolution in 16 Earth days. This is an area of ​​high pressure and temperature. Unlike the Great Red Spot on Jupiter, which drifts at 3 m/s, the Great Dark Spot on Neptune moves westward at 325 m/s. A smaller dark spot located at 74° S. sh., has shifted 2000 km to the north in a week. A light formation in the atmosphere, the so-called "scooter", was also distinguished by a fairly fast movement. In some places, the wind speed in the atmosphere of Neptune reaches 400-700 m/s.

Like other giant planets, Neptune's atmosphere is mostly hydrogen. Helium accounts for about 15%, and 1% for methane. The visible cloud layer corresponds to a pressure of 1.2 bar. It is assumed that at the bottom of the Neptunian atmosphere there is an ocean of water saturated with various ions. A significant amount of methane appears to be stored deeper in the planet's icy mantle. Even at a temperature of thousands of degrees, at a pressure of 1 Mbar, a mixture of water, methane and ammonia can form solid ice. The hot icy mantle probably accounts for 70% of the mass of the entire planet. About 25% of the mass of Neptune should, according to calculations, belong to the core of the planet, consisting of oxides of silicon, magnesium, iron and its compounds, as well as rocks. A model of the internal structure of the planet shows that the pressure in its center is about 7 Mbar, and the temperature is about 7000 K. Unlike Uranus, the heat flux from the interior of Neptune is almost three times the heat received from the Sun. This phenomenon is associated with the release of heat during the radioactive decay of substances with a large atomic weight.

Neptune's magnetic field is twice as weak as that of Uranus. The angle between the axis of the magnetic dipole and the axis of rotation of Neptune is 47°. The center of the dipole is shifted by 6000 km to the southern hemisphere, so the magnetic induction at the south magnetic pole is 10 times higher than at the north.

The rings of Neptune are generally similar to the rings of Uranus, with the only difference being that the total area of ​​matter in the rings of Neptune is 100 times smaller than in the rings of Uranus. Separate arcs of the rings surrounding Neptune were discovered during the occultations of the stars by the planet. The images of Voyager 2 show open formations around Neptune, which are called arches. They are located on a solid outermost ring of low density. The diameter of the outer ring is 69.2 thousand km, and the width of the arches is about 50 km. Other rings located at distances from 61.9 thousand km to 62.9 thousand km are closed. During observations from the Earth, by the middle of the twentieth century, 2 satellites of Neptune were found - Triton and Nereid. Voyager 2 discovered 6 more satellites ranging in size from 50 to 400 km and specified the diameters of Triton (2705 km) and Nereid (340 km). In 2002-03 during observations from the Earth, 5 more distant satellites of Neptune were discovered.

The largest satellite of Neptune - Triton revolves around the planet at a distance of 355 thousand km with a period of about 6 days in a circular orbit inclined by 23 ° to the planet's equator. At the same time, it is the only one of the inner satellites of Neptune moving in orbit in the opposite direction. Triton's axial rotation period coincides with its orbital period. The average density of Triton is 2.1 g/cm3. The surface temperature is very low (38 K). In satellite images, most of Triton's surface is a plain with many cracks, which is why it resembles a melon crust. The South Pole is surrounded by a bright polar cap. Several depressions with a diameter of 150 - 250 km were found on the plain. Probably, the ice crust of the satellite was repeatedly processed as a result of tectonic activity and the fall of meteorites. Triton, apparently, has a stone core with a radius of about 1000 km. It is assumed that an ice crust about 180 km thick covers a water ocean about 150 km deep, saturated with ammonia, methane, salts and ions. Triton's rarefied atmosphere is mostly nitrogen, with small amounts of methane and hydrogen. Snow on Triton's surface is nitrogen frost. The polar cap is also formed by nitrogen frost. Amazing formations found on the polar cap - dark spots, elongated to the northeast (about fifty of them were found). They turned out to be gas geysers, rising to a height of up to 8 km, and then turning into plumes stretching for about 150 km.

Unlike the rest of the inner satellites, Nereid moves in a very elongated orbit, with its eccentricity (0.75) more like the orbit of comets.

Pluto

Pluto, after its discovery in 1930, was considered the smallest planet in the solar system. In 2006, by decision of the International Astronomical Union, it was deprived of the status of a classical planet and became the prototype of a new class of objects - dwarf planets. So far, the group of dwarf planets, in addition to it, includes the asteroid Ceres and several recently discovered objects in the Kuiper belt, beyond the orbit of Neptune; one of them even exceeds the size of Pluto. There is no doubt that other similar objects will be found in the Kuiper belt; so there may be quite a lot of dwarf planets in the solar system.

Pluto revolves around the sun in 245.7 years. At the time of its discovery, it was quite far from the Sun, taking the place of the ninth planet in the solar system. But Pluto's orbit, as it turns out, has a significant eccentricity, so in each orbital cycle it is closer to the Sun than Neptune for 20 years. At the end of the 20th century, there was just such a period: on January 23, 1979, Pluto crossed the orbit of Neptune, so that it turned out to be closer to the Sun and formally became the eighth planet. It remained in this status until March 15, 1999. Having passed through the perihelion of its orbit (29.6 AU) in September 1989, Pluto is now moving towards aphelion (48.8 AU), which it will reach in 2112, and the first complete revolution around the Sun after its discovery will complete only in 2176.

To understand the interest of astronomers in Pluto, you need to remember the history of its discovery. At the beginning of the 20th century, observing the movement of Uranus and Neptune, astronomers noticed some strangeness in their behavior and suggested that beyond the orbits of these planets there is another, undiscovered, gravitational influence of which affects the movement of known giant planets. Astronomers have even calculated the supposed location of this planet - "Planet X" - although not very confidently. After a long search, in 1930 the American astronomer Clyde Tombaugh discovered the ninth planet, named after the god of the underworld - Pluto. However, the discovery, apparently, was accidental: subsequent measurements showed that the mass of Pluto is too small for its gravity to noticeably affect the movement of Neptune and, especially, Uranus. The orbit of Pluto turned out to be much more elongated than that of other planets, and noticeably inclined (17 °) to the ecliptic, which is also not typical for planets. Some astronomers tend to think of Pluto as a "wrong" planet, more like a steroid or a lost moon of Neptune. However, Pluto has its own satellites, and at times there is also an atmosphere, when the ice covering its surface evaporates in the region of the perihelion of the orbit. In general, Pluto has been studied very poorly, since not a single probe has yet flown to it; Until recently, even such attempts have not been made. But in January 2006, the New Horizons (NASA) spacecraft launched to Pluto, which should fly past the planet in July 2015.

By measuring the intensity of sunlight reflected by Pluto, astronomers have found that the apparent brightness of the planet changes periodically. This period (6.4 days) was taken as the period of Pluto's axial rotation. In 1978, the American astronomer J. Christie drew attention to the irregular shape of the image of Pluto in photographs taken with the best angular resolution: a blurry spot in the image often covered a protrusion on one side; its position also changed with a period of 6.4 days. Christie concluded that Pluto has a rather large satellite, which was named Charon after the mythical boatman who transported the souls of the dead along the rivers in the underground kingdom of the dead (the ruler of this kingdom, as you know, was Pluto). Charon appears either from the north or from the south of Pluto, so it became clear that the satellite's orbit, like the axis of rotation of the planet itself, is strongly inclined to the plane of its orbit. Measurements have shown that the angle between Pluto's axis of rotation and the plane of its orbit is about 32°, and the rotation is reversed. Charon's orbit lies in the equatorial plane of Pluto. In 2005, two more small satellites were discovered - Hydra and Nix, orbiting further than Charon, but in the same plane. Thus, Pluto with its satellites resembles Uranus, which rotates, "lying on its side."

Charon's rotation period, which is 6.4 days, coincides with the period of its movement around Pluto. Like the Moon, Charon always faces the planet on one side. This is characteristic of all satellites moving close to the planet. Surprisingly, Pluto is also facing Charon always with the same side; in this sense they are equal. Pluto and Charon are a unique binary system, very compact and having an unprecedentedly high ratio of the masses of the satellite and the planet (1:8). The ratio of the masses of the Moon and the Earth, for example, is 1:81, while other planets have similar ratios much less. Essentially, Pluto and Charon are a double dwarf planet.

The best images of the Pluto-Charon system were taken by the Hubble Space Telescope. They were able to determine the distance between the satellite and the planet, which turned out to be only about 19,400 km. Using the eclipses of stars by Pluto, as well as the mutual eclipses of the planet by its satellite, it was possible to refine their sizes: the diameter of Pluto, according to recent estimates, is 2300 km, and the diameter of Charon is 1200 km. The average density of Pluto is in the range from 1.8 to 2.1 g / cm 3, and Charon - from 1.2 to 1.3 g / cm 3. Apparently, the internal structure of Pluto, consisting of rocks and water ice, differs from the structure of Charon, which is more like the ice satellites of the giant planets. Charon's surface is 30% darker than Pluto's. The color of the planet and satellite is also different. Apparently, they formed independently of each other. Observations have shown that in the perihelion of the orbit, the brightness of Pluto increases markedly. This gave grounds to assume the appearance of a temporary atmosphere near Pluto. During the occultation of the star by Pluto in 1988, the brightness of this star decreased gradually over several seconds, from which it was finally established that Pluto had an atmosphere. Its main component, most likely, is nitrogen, and other components may contain methane, argon, and neon. The thickness of the haze layer is estimated at 45 km, and the atmosphere itself - at 270 km. The methane content should change depending on the position of Pluto in its orbit. Pluto passed perihelion in 1989. Calculations show that some of the deposits of frozen methane, nitrogen and carbon dioxide present on its surface in the form of ice and hoarfrost pass into the atmosphere as the planet approaches the Sun. Pluto's maximum surface temperature is 62 K. Charon's surface appears to be formed by water ice.

So, Pluto is the only planet (albeit a dwarf one) whose atmosphere either appears or disappears, like a comet during its movement around the Sun. Using the Hubble Space Telescope in May 2005, two new satellites of the dwarf planet Pluto were discovered, called Nix and Hydra. The orbits of these satellites are located beyond the orbit of Charon. Nyx is about 50,000 km from Pluto, and Hydra is about 65,000 km. The New Horizons mission, launched in January 2006, is designed to explore the vicinity of Pluto and the Kuiper Belt.

Most of the planets in the solar system were discovered in ancient times. Since then, they have been observed regularly. Mercury, Venus, Mars, Jupiter and Saturn are visible to the naked eye, so it is impossible to say exactly who and when first discovered them.

You can read more about the planets of the solar system on our website: http://website/index.php/3-planeti-solnechnoy-sistemi.
The closest planet to the Sun is little Mercury. Its orbit is close to the Sun (on an astronomical scale) - the average distance between Mercury and the Sun is "only" 57,900,000 km.

It is difficult to establish a date for the discovery of this planet, but the earliest known observation of Mercury was recorded in the collection Babylonian astronomical tables by Assyrian astronomers around the 14th century BC. uh. The Sumerian name can be read as "jumping planet". Initially, the planet was associated with the god Ninurta (the god of a happy war), and in later records it is called "Naboo" in honor of the god of wisdom and scribal art.
In ancient Greece during Hesiod the planet was known under the names Στίλβων ("Stilbon") and Ἑρμάων ("Hermaon") - a form of the name of the god Hermes. Later, the Greeks began to call the planet "Apollo".
There is an assumption that the name "Apollo" corresponded to visibility in the morning sky, and "Hermes" ("Hermaon") in the evening. The Romans named the planet after the god of commerce Mercury, who is equivalent to the Greek god Hermes, because he moves through the sky faster than the other planets. Claudius Ptolemy in his work "Hypotheses about the planets" wrote about the possibility of moving the planet through the disk of the Sun. But such a transit has never been observed because a planet like Mercury is too small to observe, or because the moment of transit occurs infrequently.
Observed Mercury and in ancient China, there he was called Chen-xing (辰星), "Morning Star". The synodic period of Mercury was recognized by Chinese scientists as 115.91 days. In modern Chinese, Korean, Japanese and Vietnamese cultures, the planet began to be called "Water Star" (水星).
In Indian mythology Mercury was called Budha. This god, the son of Soma, was presiding on Wednesdays. In Germanic paganism the god Odin was also associated with the planet Mercury and with the environment. Mayan Indians they represented Mercury as an owl (or, perhaps, as four owls: two corresponded to the morning appearance of Mercury, and two to the evening), which was the messenger of the afterlife. In Hebrew, Mercury was called "Kochav Hama" ("solar planet").
Medieval observations of Mercury in the northern parts of Europe were hampered by the fact that the planet is always observed at dawn - morning or evening - against the background of the twilight sky and rather low above the horizon (especially in northern latitudes). The period of its best visibility occurs several times a year (lasting about 10 days). Even during these periods, it is not easy to see Mercury with the naked eye (a relatively dim star against a fairly light sky background).
There is a legend that Nicolaus Copernicus regretted that he never saw Mercury in his entire life. Indeed, in the work of Copernicus "On the rotations of the celestial spheres" not a single example of observations of Mercury is given. But he described the planet using the observations of other astronomers. As he himself said, Mercury can still be "caught" from the northern latitudes, showing patience and cunning.
Mercury was first seen through a telescope Galileo Galilei at the beginning of the 17th century, but his telescope was not powerful enough to observe the phases of Mercury. In 1631 Pierre Gassendi made the first telescopic observation of the passage of a planet across the disk of the Sun, but the moment of passage was calculated before that Johannes Kepler. In 1639 Giovanni Zupi using a telescope, he discovered that the orbital phases of Mercury are similar to the phases of the Moon and Venus - this finally confirmed that Mercury revolves around the Sun.
A very rare astronomical event is the overlapping of one planet's disk by another, observed from Earth. Venus overlaps Mercury every few centuries, and this event was observed only once in history - May 28, 1737 John Bevis at the Royal Greenwich Observatory. The next Venus occultation of Mercury will be December 3, 2133.
The difficulties accompanying the observation of Mercury led to the fact that for a long time it was studied less than the other planets.
The proximity of the Sun creates some problems for the telescopic study of Mercury. So, for example, the Hubble telescope has never been used and will not be used to observe this planet. Its device does not allow observations of objects close to the Sun - if you try to do this, the equipment will receive irreversible damage.
Mercury is the least explored terrestrial planet. Telescopic methods of its study in the 20th century were supplemented by radio astronomy, radar and research using spacecraft.
The latest research data on Mercury:
Mercury's surface temperature: 600 K at the subsolar point and 150 K on the unlit side.
The reflective properties of Mercury and the Moon are similar.
Mercury rotation period: 59 days.
In the picture you see Mariner 10, the first spacecraft to reach Mercury.
Two spacecraft were sent to study Mercury: Mariner 10 flew past Mercury three times in 1974-1975; the maximum approach was 320 km. Several thousand pictures were taken. Further studies from Earth showed the possibility of the existence of water ice in polar craters.
Of all the planets visible to the naked eye, only Mercury has never had its own artificial satellite. NASA is currently on a second mission to Mercury called Messenger. The device was launched on August 3, 2004, and in January 2008 it flew around Mercury for the first time. To enter orbit around the planet in 2011, the device made two more gravitational maneuvers near Mercury.
The European Space Agency (ESA), together with the Japanese Aerospace Exploration Agency (JAXA), is developing the Bepi Colombo mission to explore the surface of Mercury and its depth, as well as to observe the planet's magnetic field and magnetosphere. The launch of the device is planned for 2013.
More opportunities have appeared for ground-based observations of Mercury using CCD radiation receivers and subsequent computer processing of images. On March 17, 2011, the Messenger interplanetary probe entered the orbit of Mercury. According to the first studies, the planet's magnetic field is not symmetrical about the poles; thus, different numbers of solar wind particles reach the north and south poles of Mercury. An analysis was also made of the prevalence of chemical elements on the planet. Research is ongoing.
Russia plans to send the first landing station "Mercury-P" to the planet. The project was planned for 2019, but was significantly pushed back.

Venus was also observed already in ancient times - it is easy to see it in the sky, because. in brilliance, it far exceeds the brightest stars. For millennia, it has been capturing the eyes of a person to itself. The planet is named after the goddess of love. She has a solid white color. Like Mercury, Venus has periods of morning and evening visibility, so in ancient times it was believed that morning and evening Venus were different stars. Through a telescope, one can easily observe the change in the apparent phase of the planet's disk. He was first observed in 1610 Galileo.
On Earth, one can observe the passage of Venus across the disk of the Sun, when this planet is visible from the Earth through a telescope in the form of a small black disk against the background of the huge Sun. For the first time, the passage of Venus across the disk of the Sun was observed on December 4, 1639 by an English astronomer. Jeremiah Horrocks, but first he calculated this phenomenon.
"The phenomenon of Venus on the Sun" observed and M. V. Lomonosov June 6, 1761. This phenomenon was observed all over the world, but only M.V. Lomonosov drew attention to the fact that when Venus came into contact with the disk of the Sun, a “shine as thin as hair” appeared around the planet. The same bright halo was observed during the descent of Venus from the solar disk. Thus, the presence of an atmosphere on Venus was discovered, and this was a hundred years before the discovery of spectral analysis!
Venus has been intensively studied with the help of spacecraft. The first spacecraft intended for the study of Venus was the Soviet Venera-1 (February 12, 1961), Soviet apparatuses of the Venera and Vega series, American Mariner, Pioneer-Venera-1, Pioneer Venus 2, Magellan, European Venus Express, Japanese Akatsuki. In 1975, the spacecraft Venera-9 and Venera-10 transmitted the first photographs of the surface of Venus to Earth. But the conditions on the surface of Venus are such that none of the spacecraft has worked on the planet for more than two hours. Roskosmos plans to send the Venera-D station with a satellite of the planet and a more tenacious probe, which should work on the surface of the planet for at least a month.

The exploration of Mars also began a very long time ago - more than 3.5 thousand years ago in ancient Egypt. The planet was named after Mars, the ancient Roman god of war (corresponding to the ancient Greek Ares). Mars is sometimes referred to as the "red planet" because of the reddish hue of the surface given to it by iron oxide. Mars has moons Phobos and Deimos.
Descriptions of the position of Mars have been preserved, compiled Babylonian astronomers who developed a number of mathematical methods for predicting the position of the planet. Using the data of the Egyptians and Babylonians, ancient Greek philosophers and astronomers developed a detailed geocentric model to explain the motion of the planets. Several centuries later Indian and Islamic astronomers calculated the size of Mars and its distance from Earth. Johannes Kepler introduced a more accurate elliptical orbit of Mars, coinciding with the observed one.
In 1659 Francesco Fontana, considering Mars through a telescope, made the first drawing of the planet - in the form of a black spot.
In 1660, two polar caps were added to the black spot, added Jean Dominique Cassini.
In 1888 Giovanni Schiaparelli gave the first names to individual details of the surface: the seas of Aphrodite, Eritrean, Adriatic, Cimmerian; lakes of the Sun, Lunar and Phoenix.
The heyday of telescopic observations of Mars came at the end of the 19th - the middle of the 20th century.
Since the 1960s, the AMS of the USSR (programs "Mars" and "Phobos"), ESA and the USA (programs "Mariner", "Viking", "Mars Global Surveyor" and others) have been engaged in the study of Mars.
Mars is currently being actively explored. There are three active AMSs in Mars orbit:
"Martian reconnaissance satellite"
Mars Express with Marsis radar
"Mars Odysseus"
Mars rovers operate on the surface of the planet:
Opportunity (since January 25, 2004) as part of the Mars Exploration Rover program
Curiosity (since August 6, 2012) as part of the Mars Science Laboratory program.
Although Mars has been studied much better than other planets, it is still a mystery to us.

Jupiter

Along with Saturn, Uranus and Neptune, Jupiter is a gas giant. This planet has been known to people since ancient times, which is reflected in the mythology and religious beliefs of various cultures: Mesopotamian, Babylonian, Greek and others. The modern name of Jupiter comes from the name of the ancient Roman supreme god of thunder. Jupiter has natural satellites. To date, scientists know 67 moons of Jupiter.
At the beginning of the 17th century Galileo Galilei studied Jupiter with the help of the telescope he invented and discovered the four largest satellites of the planet. In the 1660s Giovanni Cassini observed spots and stripes on the "surface" of the giant. In 1671, observing the eclipses of the moons of Jupiter, Danish astronomer Ole Römer found that the true position of the satellites did not match the calculated parameters, and the magnitude of the deviation depended on the distance to the Earth. Based on these observations, Römer concluded that the speed of light was finite and set its value at 215,000 km/s (the current value is 299,792.458 km/s).
Since the second half of the 20th century, Jupiter has been actively studied both with the help of ground-based telescopes (including radio telescopes) and with the help of spacecraft - the Hubble telescope and a number of probes. Since the 1970s, 8 NASA interplanetary vehicles have been sent to the planet: Pioneers, Voyagers, Galileo and others.
Jupiter has been studied exclusively by US NASA spacecraft.
Jupiter appears to the naked eye as a bright star. Due to its huge size, even small telescopes can see lightly colored cloud bands and a large red spot on its disk.

Gas giant. Named after the Roman god of agriculture. Saturn has a prominent ring system, consisting mainly of ice particles, a smaller amount of heavy elements and dust. Seeing Saturn for the first time through a telescope in 1609-1610, Galileo Galilei noticed that Saturn does not look like a single celestial body, but like three bodies almost touching each other, and suggested that these are two large "companions" (satellites) of Saturn. In 1633 Gassendi drew a bright ring around Saturn. In 1656 Huygens confirms that there is a thin flat ring around Saturn that does not touch the planet. In 1675 Cassini discovers a gap in the rings, which is later called the Cassini gap, and Encke in 1837 d. finds a second gap. V 1852 Lassell establishes that the ring of Saturn is almost transparent, which means that it cannot be solid. In addition, he suggested that this ring consists of individual particles located very close to each other, so they seem to be a continuous ribbon. In 1895 Keeler finds that separate parts of the rings rotate at different speeds, and this also confirms Lassell's assumption that the rings cannot be solid.
Saturn has 62 known natural satellites with a confirmed orbit, 53 of which have their own names. Most of the satellites are small and consist of rocks and ice.
Huygens also discovered the largest satellite of Saturn - Titan. There were no further significant discoveries until 1789, when W. Herschel discovered two more satellites - Mimas and Enceladus. Then a group of British astronomers discovered the Hyperion satellite, with a shape very different from spherical. In 1899, William Pickering discovered Phoebe, which belongs to the class of irregular satellites and does not rotate synchronously with Saturn like most satellites. The period of its revolution around the planet is more than 500 days, while the circulation goes in the opposite direction. In 1944 by Gerard Kuiper It was discovered the presence of a powerful atmosphere on another satellite - Titan. This phenomenon is unique for a satellite in the solar system. In the 1990s, Saturn, its moons and rings were repeatedly studied by the Hubble Space Telescope.
Saturn is being explored by automatic interplanetary stations (AMS) "Cassini-Huygens", "Voyager" (program), "Pioneer-11". In 2009, a joint American-European project between NASA and ESA appeared to launch the AMS Titan Saturn System Mission to study Saturn and its moons Titan and Enceladus. During it, the station will fly to the Saturn system for 7-8 years, and then become a satellite of Titan for two years. It will also launch a probe balloon into the atmosphere of Titan and a lander (possibly floating).
The planet is visible from Earth to the naked eye.

uranium was discovered March 13, 1781 by English astronomer William Herschel. While studying the starry sky with his telescope, he noticed that Uranus was moving relative to the stars. Other people have seen Uranus before, even marked it on star charts, but they didn't realize it wasn't a star.
Outside the orbit of Saturn are two planets that have much in common with each other - Uranus and Neptune. Uranus has 27 known natural satellites.
The planet is named after the Greek god of the sky. Uranus is 19 times farther from the Sun than Earth. The journey of Uranus in orbit lasts more than 84 years. When the brilliance of Uranus reaches its maximum, it can be seen with the naked eye, like a star. Uranus is distinguished from other planets by the fact that it makes its way in orbit around the Sun on its side. Maybe he collided with some celestial body and overturned? Uranus also has rings they were discovered in 1977. However, they are barely visible.
NASA's Voyager 2 spacecraft and the Hubble space telescope are exploring Uranus.

Neptune is the eighth and most distant planet in the solar system. The planet was named after the Roman god of the seas.
Based on small deviations in the orbit of Uranus, John Adams and Urbain Le Verrier predicted the existence of another, more distant planet. September 23, 1846 at the request of Le Verrier Johann Galle found a new planet - Neptune.
Many people have seen Neptune before, including Galileo Galilei, who, while observing Jupiter, spotted a "star" now believed to be Neptune. Neptune became the first planet discovered through mathematical calculations, and not through regular observations.
Neptune has natural satellites, as well as a fragmented ring system, discovered back in the 1960s, but not reliably confirmed by Voyager 2 until 1989. Triton is an amazing satellite of Neptune, it orbits in the opposite direction to Neptune.
Voyager 2 explores Neptune. Voyager 2 made its closest approach to Neptune on August 25, 1989. It turned out that Neptune is one of the most beautiful planets in the solar system.

The most distant planet in our solar system is Pluto. She was discovered February 18, 1930 by American astronomer Clyde Tombaugh. He photographed the same part of the night sky on different days, as a result of which he discovered an object moving relative to the stars. Further observations showed that this object is a planet.
However, there are serious disagreements about this. Pluto doesn't behave like a planet. Pluto's elongated orbit is more like a comet. Due to the fact that Pluto is very far away, it is difficult to see it. Even in the most powerful telescopes, it is visible as a tiny circle. But observations made with advanced technology suggest that Pluto is similar to Neptune's moon, Triton. At first Pluto was classified as a planet, but now it is considered one of the largest objects (perhaps the largest) in the Kuiper belt.

The solar system in which we live is gradually being studied more and more by earthly researchers.

We will consider the stages and results of the research:

• Mercury
• Venus,
• moon,
• Mars
• Jupiter
• Saturn
• uranium,
• Neptune.

Terrestrial planets and satellite of the Earth

Mercury.

Mercury is the closest planet to the Sun.

In 1973, the American probe Mariner 10 was launched, with the help of which for the first time it was possible to draw sufficiently reliable maps of the surface of Mercury. In 2008, the eastern hemisphere of the planet was photographed for the first time.

However, Mercury remains at the time of 2018 the least studied planet of the terrestrial group - Venus, Earth and Mars. Mercury is small, has a disproportionately large molten core, and has less oxidized material than its neighbors.

In October 2018, the launch of the Bepi Colombo mission to Mercury, a joint project of the European and Japanese Space Agency, is expected. The result of the seven-year journey should be the study of all the features of Mercury and an analysis of the reasons for the appearance of such features.

Venus.

Venus has been explored by more than 20 spacecraft, mostly Soviet and American. The relief of the planet could be seen with the help of radar sounding of the planet's surface by spacecraft "Pioneer-Venus" (USA, 1978), "Venus-15 and -16" (USSR, 1983-84) and "Magellan" (USA, 1990). -94 years).

Ground-based radar allows you to "see" only 25% of the surface, and with much lower detail resolution than spacecraft are capable of. For example, Magellan obtained images of the entire surface with a resolution of 300 m. It turned out that most of the surface of Venus is occupied by hilly plains.

From the latest studies of Venus, we note the mission of the European Space Agency Venus Express to study the planet and the features of its atmosphere. Observation of Venus took place from 2006 to 2015, in 2015 the device burned up in the atmosphere. Thanks to these studies, a picture of the southern hemisphere of Venus was obtained, as well as information was obtained on the recent volcanic activity of the giant volcano Idunn, which has a diameter of 200 kilometers.

Moon.

The first object of close attention from earthlings was the Moon.

Back in 1959 and 1965, the Soviet Luna-3 and Zond-3 spacecraft first photographed the "dark" hemisphere of the satellite, invisible from Earth.

In 1969, humans landed on the moon for the first time. The most famous American astronaut to walk on the moon is Neil Armstrong. In total, 12 American expeditions visited the Moon with the help of the Apollo spacecraft. As a result of research, about 400 kilograms of lunar rock were brought to Earth.

Subsequently, due to the gigantic costs of the lunar program, manned flights to the moon ceased. Lunar exploration began to be carried out with the help of automatic and Earth-controlled spacecraft.

In the last quarter of a century, a new stage in the study of the Moon is taking place. As a result of studies of the spacecraft "Clementine" in 1994, "Lunar Prospector" in 1998-1999, and "Smart-1" in 2003-2006, terrestrial researchers were able to obtain newer and more accurate data. In particular, deposits of presumably water ice were discovered. A large number of these deposits have been discovered near the lunar poles.

And in 2007, it was the turn of Chinese spacecraft. Chanye-1, which was launched on October 24, became such a device. On November 8, 2008, the Indian spacecraft Chandrayan 1 was launched into lunar orbit. The moon is one of the main goals in the development of near space by mankind.

Mars.

The next target for earthly explorers is the planet Mars. The first research vehicle that laid the foundation for the study of the Red Planet was the Soviet Mars-1 probe. According to the data of the American apparatus "Mariner - 9" received in 1971, it was possible to compile detailed maps of the surface of Mars.

With regard to modern research, we note the following research. So, in 2008, the Phoenix spacecraft managed to drill the surface for the first time and detect ice.

And in 2018, the MARSIS radar, which is installed aboard the European Space Agency's Mars Express orbiter, was able to provide the first evidence that there is liquid water on Mars. This conclusion follows from the lake of considerable size discovered at the south pole, hidden under the ice.

giant planets

Jupiter.

Jupiter was first explored at close range in 1973 using the Soviet Pioneer 10 probe. The flights of the American Voyager spacecraft carried out in the 1970s were also important for the study of Jupiter.

From modern research, we note this fact. In 2017, a team of American astronomers led by Scott S. Sheppard, searching for a potential ninth planet outside Pluto's orbit, accidentally discovered new moons around Jupiter. There were 12 such moons. As a result, the number of Jupiter's satellites increased to 79.

Saturn.

In 1979, the Pioneer 11 spacecraft, exploring the vicinity of Saturn, was able to detect a new ring around the planet, measure the temperature of the atmosphere and reveal the boundaries of the planet's magnetosphere.

In 1980, Voyager 1 transmitted clear images of Saturn's rings for the first time. From these images, it became clear that the rings of Saturn are composed of thousands of individual narrow rings. Also, 6 new satellites of Saturn were found.

The greatest contribution to the study of the giant planet was made by the Cassini spacecraft, which worked in the orbit of Saturn from 2004 to 2017. With the help of it, it was possible to establish, in particular, what the upper atmosphere of Saturn consists of and the features of its chemical interaction with materials that come from the rings.

Uranus.

The planet Uranus was discovered in 1781 by astronomer W. Herschel. Uranus is an ice giant.

In 1977, it was discovered that Uranus also has its own rings.

Remark 1

Voyager 2 was the only spacecraft to visit Uranus in 1986. He photographed the planet, found 2 new rings and 10 new moons of Uranus.

Neptune.

Neptune is a giant planet and the first planet discovered through mathematical calculations.

Voyager 2 is the only spacecraft to have been there so far. It passed near Neptune in 1989, revealing some details of the planet's atmosphere, as well as a giant Earth-sized anticyclone in the southern hemisphere.

Dwarf planets

Dwarf planets are those celestial bodies that revolve around the Sun and have enough mass to maintain their own spherical shape. Such planets are not satellites of other planets, but, unlike planets, they cannot clear their orbit from other space objects.

Dwarf planets include de-listed Pluto, Makemake, Ceres, Haumea, and Eris.

Remark 2

Note that there is still debate about Pluto whether to consider it a planet or a dwarf planet.

Planet Nine

On January 20, 2016, Caltech astronomers Konstantin Batygin and Michael Brown hypothesized the existence of a massive trans-Neptunian planet beyond Pluto's orbit. However, to date, Planet Nine has not been discovered.