Essay

Solar system and its origin

Introduction

solar planet terrestrial

The solar system consists of a central celestial body - the star of the Sun, 9 large planets orbiting around it, their satellites, many small planets - asteroids, numerous comets and the interplanetary medium. The major planets are arranged in order of distance from the Sun as follows: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto. One of important issues related to the study of our planetary system - the problem of its origin. The solution to this problem has natural scientific, ideological and philosophical significance. For centuries and even millennia, scientists have tried to figure out the past, present and future of the Universe, including solar system.

Itemstudying this work: The solar system, its origin.

Goal of the work:study of the structure and features of the Solar system, characterization of its origin.

Job objectives:consider possible hypotheses for the origin of the Solar System, characterize the objects of the Solar System, consider the structure of the Solar System.

Relevance of the work:it is currently believed that the solar system is quite well studied and devoid of any serious secrets. However, branches of physics have not yet been created that make it possible to describe the processes occurring immediately after the Big Bang; nothing can be said about the causes that gave rise to it; complete uncertainty remains regarding physical nature dark matter. The solar system is our home, so it is necessary to be interested in its structure, its history and prospects.

1. Origin of the Solar System

.1 Hypotheses about the origin of the solar system

The history of science knows many hypotheses about the origin of the solar system. These hypotheses appeared before many became known. important patterns Solar system. The significance of the first hypotheses is that they tried to explain the origin celestial bodies as the result of a natural process rather than an act of divine creation. In addition, some early hypotheses contained correct ideas about the origin of celestial bodies.

In our time, there are two main scientific theories of the origin of the Universe. According to the steady state theory, matter, energy, space and time have always existed. But the question immediately arises: why is no one now able to create matter and energy?

The most popular theory of the origin of the Universe, supported by most theorists, is the big bang theory.

The Big Bang theory was proposed in the 20s of the 20th century by scientists Friedman and Lemaitre. According to this theory, our Universe was once an infinitesimal clump, super-dense and heated to very high temperatures. This unstable formation suddenly exploded, space rapidly expanded, and the temperature of the flying high-energy particles began to decrease. After about the first million years, the hydrogen and helium atoms became stable. Under the influence of gravity, clouds of matter began to concentrate. As a result, galaxies, stars, and other celestial bodies were formed. The stars aged, supernovas exploded, after which heavier elements appeared. They formed stars of a later generation, such as our Sun. As evidence that a big explosion occurred at one time, they talk about the red shift of light from objects located on long distances and microwave background radiation.

In fact, the explanation of how and where it all started is still serious problem. Or there was nothing from which everything could begin - no vacuum, no dust, no time. Or something existed, in which case it requires an explanation.

A huge problem with the big bang theory is how the supposed primordial high-energy radiation scattered into different sides, could combine into structures such as stars, galaxies and galaxy clusters. This theory assumes the presence additional sources masses that provide the corresponding values ​​of the force of attraction. The matter, which was never discovered, was called Cold dark matter. For galaxies to form, such matter must make up 95-99% of the Universe.

Kant developed a hypothesis according to which, at first, cosmic space was filled with matter in a state of chaos. Under the influence of attraction and repulsion, matter changed over time into more diverse forms. Elements with greater density, according to the law of universal gravitation, attracted less dense ones, as a result of which separate clumps of matter were formed. Under the influence of repulsive forces rectilinear movement particles to the center of gravity was replaced by a circular one. As a result of the collision of particles around individual clumps, planetary systems were formed.

A completely different hypothesis about the origin of the planets was presented by Laplace. At an early stage of its development, the Sun was a huge, slowly rotating nebula. Under the influence of gravity, the proto-sun contracted and took on an oblate shape. As soon as the force of gravity at the equator was balanced by the centrifugal force of inertia, a giant ring was separated from the proto-sun, which cooled and broke into separate clumps. From them the planets were formed. This ring separation occurred several times. The satellites of the planets were formed in a similar way. Laplace's hypothesis was unable to explain the redistribution of momentum between the Sun and the planets. For this and other hypotheses according to which planets are formed from hot gas, the stumbling block is the following: a planet cannot form from hot gas, since this gas expands very quickly and dissipates in space.

Big role The works of our compatriot Schmidt played a role in developing views on the origin of the planetary system. His theory is based on two assumptions: the planets formed from a cold cloud of gas and dust; this cloud was captured by the Sun as it orbited the center of the Galaxy. Based on these assumptions, it was possible to explain some patterns in the structure of the Solar system - the distribution of planets by distance from the Sun, rotation, etc.

There were many hypotheses, but while each of them explained part of the research well, it did not explain the other part. When developing a cosmogonic hypothesis, it is first necessary to resolve the question: where did the matter from which the planets eventually formed come from? There are three possible options here:

1.Planets are formed from the same gas and dust cloud as the Sun (I. Kant).

2.The cloud from which the planets were formed is captured by the Sun during its revolution around the center of the Galaxy (O.Yu. Schmidt).

3.This cloud separated from the Sun during its evolution (P. Laplace, D. Jeans, etc.)

1.2 Theory of the origin of the Earth

The process of formation of planet Earth, like any of the planets, had its own characteristics. The earth was born around 5 109years ago at a distance of 1 a. e. from the Sun. Approximately 4.6-3.9 billion years ago, it was intensively bombarded with interplanetary debris and meteorites; as they fell to Earth, their substance was heated and crushed. The primary substance was compressed under the influence of gravity and took the shape of a ball, the depths of which heated up. Mixing processes took place, chemical reactions, lighter silicate rocks were squeezed out from the depths to the surface and formed the earth’s crust, while heavier ones remained inside. The heating was accompanied by violent volcanic activity, vapors and gases burst out. At first, the terrestrial planets did not have atmospheres, like Mercury and the Moon. The activation of processes on the Sun caused an increase in volcanic activity, the hydrosphere and atmosphere were born from magma, clouds appeared, and water vapor condensed in the oceans.

The formation of oceans has not stopped on Earth to this day, although it is no longer an intensive process. The earth's crust is renewed, volcanoes emit huge amounts of carbon dioxide and water vapor into the atmosphere. The Earth's primary atmosphere consisted mainly of CO 2. A sharp change in the composition of the atmosphere occurred approximately 2 billion years ago; it is associated with the creation of the hydrosphere and the origin of life. Carboniferous plants absorbed most of the CO 2and saturated the atmosphere with O 2. Over the past 200 million years, the composition of the earth's atmosphere has remained virtually unchanged. Deposits prove this coal and thick layers of carbonate deposits in sedimentary rocks. They contain large amounts of carbon, which was previously part of the atmosphere in the form of CO2 and CO.

The existence of the Earth is divided into 2 periods: early history and geological history.

I. Early Earth History is divided into three phases: the birth phase, the melting phase of the outer sphere and the primary crust phase (lunar phase).

Birth phase lasted 100 million years. During the birth phase, the Earth acquired approximately 95% of its present mass.

The melting phase dates back to 4.6-4.2 billion years ago. The Earth remained a cold cosmic body for a long time, only at the end of this phase, when intensive bombardment of large objects began, strong heating and then complete melting of the substance occurred outer zone and the inner zone of the planet. The phase of gravitational differentiation of matter began: heavy chemical elements went down, light ones went up. Therefore, in the process of differentiation of matter, heavy chemical elements (iron, nickel, etc.) were concentrated in the center of the Earth, from which the core was formed, and the Earth’s mantle arose from lighter compounds. Silicon became the basis for the formation of continents, and the lightest chemical compounds formed the oceans and atmosphere of the Earth. The earth's atmosphere initially contained a lot of hydrogen, helium and hydrogen-containing compounds such as methane, ammonia, and water vapor.

The lunar phase lasted 400 million years from 4.2 to 3.8 billion years ago. In this case, the cooling of the molten substance of the outer sphere of the Earth led to the formation of a thin primary crust. At the same time, the formation of the granite layer of the continental crust took place. The continents are composed of rocks containing 65-70% silica and significant amounts of potassium and sodium. The ocean floor is lined with basalts - rocks containing 45-50% Si0 2 and rich in magnesium and iron. Continents are built with less dense material than the ocean floors.

II. Geological history - this is the period of development of the Earth as a planet as a whole, especially its crust and natural environment. After cooling earth's surface to a temperature below 100°C, a huge mass of liquid water formed on it, which was not a simple accumulation of motionless waters, but those in active global circulation. The earth has largest mass of the terrestrial planets and therefore has the greatest internal energy - radiogenic, gravitational.

Due to the greenhouse effect, the surface temperature increases, instead of -23°C it became +15°C. If this had not happened, then in the natural environment liquid water would not be 95% of the total amount in the hydrosphere, but many times less.

The sun supplies the Earth with the heat necessary to maintain its temperature in a suitable range. It should be kept in mind that small change Just a few percent of the amount of heat the Earth receives from the Sun will lead to dramatic changes in the Earth's climate. The earth's atmosphere plays extremely important role in maintaining temperature within acceptable limits. It acts like a blanket, preventing the temperature from rising too much during the day and the temperature from dropping too much at night.

2. Composition of the Solar System and its features

.1 Structure of the Solar System

The main patterns observed in the structure, movement, properties of the Solar system:

1. The orbits of all planets (except for the orbit of Pluto) lie practically in the same plane, almost coinciding with the plane of the solar equator.
2. All planets revolve around the Sun in almost circular orbits in the same direction, coinciding with the direction of rotation of the Sun around its axis.
3. The direction of axial rotation of the planets (with the exception of Venus and Uranus) coincides with the direction of their revolution around the Sun.
4. The total mass of the planets is 750 times less than the mass of the Sun (almost 99.9% of the mass of the Solar system falls on the Sun), but they account for 98% of the total angular momentum of the entire Solar system.
5. The planets are divided into two groups, which differ sharply in structure and physical properties - terrestrial planets and giant planets.

The main part of the solar system is made up of planets.

The planets that are closest to the Sun (Mercury, Venus, Earth, Mars) are very different from the next four. They are called terrestrial planets because, like Earth, they are made of solid rock. Jupiter, Saturn, Uranus and Neptune are called giant planets and are composed mainly of hydrogen.

Ceres is the name of the large asteroid, whose diameter is about 1000 km.

These are blocks with diameters that do not exceed several kilometers in size. Most of asteroids orbit the sun in a wide “asteroid belt” that lies between Mars and Jupiter. The orbits of some asteroids extend far beyond this belt, and sometimes come close to Earth.

These asteroids cannot be seen with the naked eye because their sizes are too small and they are very far away from us. But other debris - such as comets - can be visible in the night sky due to their bright shine.

Comets are celestial bodies that are composed of ice, solid particles and dust. Most of the time, the comet moves in the far reaches of our solar system and is invisible to the human eye, but when it approaches the Sun, it begins to glow. This occurs under the influence of solar heat.

Meteorites are large meteoroid bodies that reach the earth's surface. Due to the collision of huge meteorites with the Earth in the distant past, huge craters were formed on its surface. Almost a million tons of meteorite dust settle on Earth every year.

2.2 Terrestrial planets

To the number general patterns development of the terrestrial planets include the following:

.All planets originated from a single gas and dust cloud (nebula).

1. Approximately 4.5 billion years ago, under the influence of rapid accumulation of thermal energy, the outer shell of the planets underwent complete melting.
2. As a result of the cooling of the outer layers of the lithosphere, a crust was formed. At the early stage of the existence of planets, differentiation of their substance into a core, mantle and crust occurred.
3. The outer region of the planets developed individually. The most important condition here is the presence or absence of an atmosphere and hydrosphere on the planet.

Mercury is the planet closest to the Sun in the solar system. The distance from Mercury to the Sun is only 58 million km. Mercury is a bright star, but it is not so easy to see it in the sky. Being close to the Sun, Mercury is always visible to us not far from solar disk. Therefore, it can only be seen on those days when it moves away from the Sun at its greatest distance. It was established that Mercury has a highly rarefied gas shell, consisting mainly of helium. This atmosphere is in dynamic equilibrium: each helium atom stays in it for about 200 days, after which it leaves the planet, and another particle from the plasma takes its place solar wind. Mercury is much closer to the Sun than the Earth. Therefore, the Sun shines on it and warms 7 times stronger than ours. On the day side of Mercury it is terribly hot, the temperature there rises to 400 ABOUT above zero. But always on the night side severe frost, which probably goes up to 200 ABOUT below zero. One half of it is a hot rock desert, and the other half is an icy desert covered with frozen gases.

Venus is the second closest planet to the Sun, almost the same size as Earth, and its mass is more than 80% of Earth's mass. For these reasons, Venus is called the twin or sister of the Earth. However, the surface and atmosphere of these two planets are completely different. On Earth there are rivers, lakes, oceans and the atmosphere that we breathe. Venus - scorching hot planet with a dense atmosphere that would be fatal to humans. Venus receives more than twice as much from the Sun more light and heat than the Earth, with shadow side on Venus frost prevails more than 20 degrees below zero, since the sun's rays do not reach here. The planet has a very dense, deep and cloudy atmosphere, making it impossible to see the surface of the planet. The planet has no satellites. The temperature is about 750 K over the entire surface both day and night. The reason for such a high temperature near the surface of Venus is the greenhouse effect: the sun's rays easily pass through the clouds of its atmosphere and heat the surface of the planet, but thermal infrared radiation the surface itself exits through the atmosphere back into space with great difficulty. The atmosphere of Venus consists mainly of carbon dioxide (CO 2) - 97%. Hydrochloric and hydrofluoric acid were found in the form of small impurities. During the day, the planet's surface is illuminated by diffuse sunlight with approximately the same intensity as on a cloudy day on Earth. A lot of lightning has been seen on Venus at night. Venus is covered with hard rocks. Hot lava circulates beneath them, tension-inducing thin surface layer. Lava constantly erupts from holes and fractures in solid rock.

On the surface of Venus, rock rich in potassium, uranium and thorium was discovered, which in terrestrial conditions corresponds to the composition of secondary volcanic rocks. Thus, the surface rocks of Venus turned out to be the same as those on the Moon, Mercury and Mars, erupted igneous rocks of basic composition.

ABOUT internal structure Little is known about Venus. It probably has a metal core occupying 50% of the radius. But magnetic field the planet does not due to its very slow rotation.

Earth is the third planet from the Sun in the solar system. The shape of the Earth is close to an ellipsoid, flattened at the poles and stretched in the equatorial zone. Earth's surface area 510.2 million km ², of which approximately 70.8% occurs in the World Ocean. Land makes up 29.2% respectively and forms six continents and islands. Mountains occupy over 1/3 of the land surface.

Thanks to its unique conditions, the Earth became the place where organic life arose and developed. About 3.5 billion years ago, conditions favorable for the emergence of life arose. Homo sapiens (Homo sapiens) appeared as a species approximately half a million years ago.

The period of revolution around the Sun is 365 days, with daily rotation - 23 hours 56 minutes. The Earth's rotation axis is located at an angle of 66.5º .

The Earth's atmosphere consists of 78% nitrogen and 21% oxygen. Our planet is surrounded by a vast atmosphere. According to temperature, the composition and physical properties of the atmosphere can be divided into different layers. The troposphere is the region lying between the Earth's surface and an altitude of 11 km. This is a fairly thick and dense layer containing most of the water vapor in the air. Almost everything takes place in it atmospheric phenomena, which are of direct interest to the inhabitants of the Earth. The troposphere contains clouds, precipitation, etc. The layer separating the troposphere from the next atmospheric layer, the stratosphere, is called the tropopause. This is an area of ​​very low temperatures.

Moon - natural satellite Earth and the celestial body closest to us. The average distance to the Moon is 384,000 kilometers, the diameter of the Moon is about 3,476 km. Not being protected by the atmosphere, the surface of the Moon heats up to +110 C during the day, and cools down to -120 ° C at night. The origin of the Moon is the subject of a number of hypotheses. One of them is based on the theories of Jeans and Lyapunov - the Earth rotated very quickly and threw off part of its matter, the other - on the Earth’s capture of a passing celestial body. The most plausible hypothesis is that the Earth collided with a planet whose mass corresponds to the mass of Mars, which occurred at a high angle, as a result of which a huge ring of debris was formed, which formed the basis for the Moon. It was formed near the Sun due to the earliest pre-metallic condensates at high temperatures.

Mars is the fourth planet of the solar system. It's almost double in diameter smaller than Earth and Venus. The average distance from the Sun is 1.52 AU. It has two satellites - Phobos and Deimos.

The planet is shrouded gas shell- an atmosphere that is less dense than the earth's. Its composition resembles the atmosphere of Venus and contains 95.3% carbon dioxide mixed with 2.7% nitrogen.

average temperature on Mars is significantly lower than on Earth, about -40° C. At the most favorable conditions in summer, on the daytime half of the planet, the air warms up to 20° C. But winter night frost can reach -125° C. Such sudden temperature changes are caused by the fact that the thin atmosphere of Mars is not able to retain heat for a long time. They blow over the surface of the planet strong winds, the speed of which reaches 100 m/s.

There is very little water vapor in the atmosphere of Mars, but at low pressure and temperature it is in a state close to saturation and often collects in clouds. The Martian sky in clear weather has a pinkish color, which is explained by scattering sunlight on specks of dust and the haze is illuminated by the orange surface of the planet.

The surface of Mars, at first glance, resembles the moon. However, in reality its relief is very diverse. Over the course of Mars' long geological history, its surface has been altered by volcanic eruptions.

.3 Giant planets

The giant planets are the four planets of the solar system: Jupiter, Saturn, Uranus, Neptune. These planets, which have a number of similar physical characteristics, also called the outer planets.

Unlike the terrestrial planets, they are all gas planets and have significantly large sizes and masses, lower densities, powerful atmospheres, rapid rotation, as well as rings (while terrestrial planets do not have those) and big amount satellites.

The giant planets rotate very quickly around their axes; It takes Jupiter less than 10 hours to complete one revolution. Moreover, the equatorial zones of the giant planets rotate faster than the polar ones.

The giant planets are far from the Sun, and regardless of the nature of the seasons, they are always dominated by low temperatures. There are no seasons at all on Jupiter, since the axis of this planet is almost perpendicular to the plane of its orbit.

Giant planets are distinguished by a large number of satellites; Jupiter has so far found 16 of them, Saturn - 17, Uranus - 16, and only Neptune - 8. A remarkable feature of the giant planets is the rings, which are open not only on Saturn, but also on Jupiter, Uranus and Neptune.

The most important feature of the structure of giant planets is that these planets do not have solid surfaces, since they consist mainly of hydrogen and helium. In the upper layers of the hydrogen-helium atmosphere of Jupiter, chemical compounds, hydrocarbons (ethane, acetylene), as well as various compounds containing phosphorus and sulfur are found in the form of impurities, coloring the details of the atmosphere in red-brown and yellow colors. Thus, in their chemical composition, the giant planets differ sharply from the terrestrial planets.

Unlike the terrestrial planets, which have a crust, mantle and core, on Jupiter the gaseous hydrogen that is part of the atmosphere passes into the liquid and then into the solid (metallic) phase. The appearance of such unusual states of aggregation hydrogen is associated with a sharp increase in pressure as one dives deeper.

The giant planets account for 99.5% of the total mass of the solar system (excluding the Sun). Of the four giant planets, the best studied is Jupiter, the largest and closest planet of this group to the Sun. It is 11 times larger than 3 Earth in diameter and 300 times larger in mass. The period of its revolution around the Sun is almost 12 years.

Since the giant planets are very far from the Sun, their temperature (at least above their clouds) is very low: on Jupiter - 145 ° C, on Saturn - 180 ° C, on Uranus and Neptune even lower.

The average density of Jupiter is 1.3 g/cm3, Uranus is 1.5 g/cm3, Neptune is 1.7 g/cm3, and Saturn is even 0.7 g/cm3, that is, less than the density of water. Low density and abundance of hydrogen distinguish giant planets from the rest.

The only formation of its kind in the solar system is a flat ring several kilometers thick surrounding Saturn. It is located in the plane of the planet's equator, which is inclined to the plane of its orbit by 27°. Therefore, during the 30-year revolution of Saturn around the Sun, the ring is visible to us either quite open, or exactly edge-on, when it can be seen as a thin line only in large telescopes. The width of this ring is such that, if it were solid, the globe could roll along it.

Conclusion

Thus, there are two theories of the origin of the Universe: the theory of a stable state, according to which matter, energy, space and time have always existed, and the theory of the Big Bang, which states that the Universe, which appears to be an infinitesimal hot blob, suddenly exploded, resulting in the appearance of clouds matter from which galaxies subsequently emerged.

Wide use received three points of view on the process of planet formation: 1) the planets were formed from the same gas and dust cloud as the Sun (I. Kant); 2) the cloud from which the planets were formed is captured by the Sun during its revolution around the center of the Galaxy (O.Yu. Shmidt); 3) this cloud separated from the Sun during its evolution
(P. Laplace, D. Jeans, etc.). The existence of the Earth is divided into 2 periods: early history and geological history. The early history of the Earth is represented by such stages of development as: the birth phase, the phase of melting of the outer sphere and the phase of the primary crust ( lunar phase). Geological history - this is the period of development of the Earth as a planet as a whole, especially its crust and natural environment. The geological history of the Earth is characterized by the emergence of the atmosphere and the transition of water vapor into liquid water; The evolution of the biosphere is the process of development of the organic world, starting with the simplest cells of the Archean period, and ending with the emergence of mammals in the Cenozoic period.

The process of the birth of the Earth had its own characteristics. Approximately 4.6-3.9 billion years ago, it was intensively bombarded with interplanetary debris and meteorites. The primary substance was compressed under the influence of gravity and took the shape of a ball, the depths of which heated up.

Mixing processes took place, chemical reactions took place, lighter rocks were squeezed out from the depths to the surface and formed the earth's crust, heavy rocks remained inside. The heating was accompanied by violent volcanic activity, vapors and gases burst out.

The planets are located in the following order from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto.

Terrestrial planets have a solid shell, unlike giant planets, which have a gaseous shell. Giant planets several times more planets earthly group. Giant planets have a low average density compared to other planets. Terrestrial planets have a crust, mantle and core, while on Jupiter the gaseous hydrogen included in the atmosphere turns first into liquid, then into solid metal phase. The appearance of such aggregate states of hydrogen is associated with a sharp increase in pressure as one dives into depth. Giant planets also have powerful atmospheres and rings.

Bibliography

1.Gromov A.N. Amazing solar system. M.: Eksmo, 2012. -470 p. With. 12-15, 239-241, 252-254, 267-270.

2.Guseikhanov M.K. Concepts modern natural science: Textbook. M.: "Dashkov and Co", 2007. - 540 p. With. 309, 310-312, 317-319, 315-316.

.Dubnischeva T.Ya. Concepts of modern natural science: tutorial for university students. M.: "Academy", 2006. - 608 p. With. 379, 380

.Characteristics of giant planets: #"justify">. Structure of the Solar System: http://o-planete.ru/zemlya-i-vselennaya/stroenie-solnetchnoy-sistem.html

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On the scale of space, planets are just grains of sand, playing an insignificant role in the grandiose picture of development natural processes. However, these are the most diverse and complex objects in the Universe. None of the other types of celestial bodies exhibit a similar interaction of astronomical, geological, chemical and biological processes. In no other place in space can life as we know it originate. In the last decade alone, astronomers have discovered more than 200 planets.

The formation of planets, long considered calm and stationary process, actually turned out to be quite chaotic.

The amazing diversity of masses, sizes, compositions and orbits has led many to wonder about their origins. In the 1970s the formation of planets was considered orderly, deterministic process— a conveyor belt on which amorphous gas-dust disks are transformed into copies of the Solar System. But we now know that this is a chaotic process, with a different outcome for each system. The born planets survived the chaos of competing mechanisms of formation and destruction. Many objects died, burned in the fire of their star, or were thrown into interstellar space. Our Earth may have long-lost twins now wandering in dark and cold space.

The science of planet formation lies at the intersection of astrophysics, planetary science, statistical mechanics and nonlinear dynamics. In general, planetary scientists are developing two main directions. According to the theory of sequential accretion, tiny dust particles stick together to form large clumps. If such a block attracts a lot of gas, it turns into a gas giant like Jupiter, and if not, into a rocky planet like Earth. The main disadvantages of this theory are the slowness of the process and the possibility of gas dispersal before planet formation.

Another scenario (gravitational instability theory) states that gas giants form through sudden collapse, leading to the destruction of the primordial gas and dust cloud. This process replicates the formation of stars in miniature. But this hypothesis is very controversial, since it assumes the presence of strong instability, which may not occur. In addition, astronomers have discovered that the most massive planets and the least massive stars are separated by “emptiness” (there are simply no bodies of intermediate mass). Such a “failure” indicates that planets are not just low-mass stars, but objects of a completely different origin.

Although scientists continue to debate, most believe the successive accretion scenario is more likely. In this article I will rely specifically on it.

1. The interstellar cloud is shrinking

Time: 0 ( starting point process of planet formation)

Our Solar System is located in a Galaxy where there are about 100 billion stars and clouds of dust and gas, mostly the remains of stars of previous generations. IN in this case dust is just microscopic particles of water ice, iron and other solids, condensed in the outer, cool layers of the star and thrown into outer space. If clouds are cold and dense enough, they begin to compress under the influence of gravity, forming clusters of stars. Such a process can last from 100 thousand to several million years.

Each star is surrounded by a disk of remaining material, enough to form planets. Young disks mainly contain hydrogen and helium. In their hot inner regions, dust particles evaporate, and in the cold and rarefied outer layers, dust particles persist and grow as steam condenses on them.

Astronomers have discovered many young stars surrounded by such disks. Stars between 1 and 3 million years old have gaseous disks, while those that have existed for more than 10 million years have weak, gas-poor disks, as gas is “blown” out of it either by the newborn star itself or by neighboring stars. bright stars. This time range is precisely the era of planet formation. The mass of heavy elements in such disks is comparable to the mass of these elements in the planets of the Solar system: quite strong argument in defense of the fact that planets form from such disks.

Result: the newborn star is surrounded by gas and tiny (micron-sized) dust particles.

Balls of cosmic dust

Even the giant planets began as humble bodies—micron-sized grains of dust (the ashes of long-dead stars) floating in a rotating disk of gas. As it moves away from the newborn star, the temperature of the gas drops, passing through the “ice line”, beyond which the water freezes. In our solar system, this boundary separates the inner rocky planets from the outer gas giants.

1. Particles collide, stick together and grow.
2. Small particles are carried away by the gas, but those larger than a millimeter are slowed down and move in a spiral towards the star.
3. At the ice line, conditions are such that the friction force changes direction. Particles tend to stick together and easily combine into larger bodies - planetesimals.

2. The disk acquires structure

Time: about 1 million years

Dust particles in the protoplanetary disk, moving chaotically along with gas flows, collide with each other and sometimes stick together, sometimes collapse. Dust grains absorb starlight and re-emit it at long wavelengths. infrared range, transferring heat to the darkest inner areas of the disk. The temperature, density and pressure of the gas generally decrease with distance from the star. Due to the balance of pressure, gravity and centrifugal force, the speed of rotation of the gas around the star is less than that of free body at the same distance.

As a result, dust grains larger than a few millimeters in size are ahead of the gas, so the headwind slows them down and forces them to spiral down towards the star. The larger these particles become, the faster they move downward. Meter-sized chunks can halve their distance from a star in just 1,000 years.

As the particles approach the star, they heat up, and gradually water and other substances with low boiling points, called volatiles, evaporate. The distance at which this occurs - the so-called "ice line" - is 2-4 astronomical units s (a.e.). In the Solar System, this is exactly a cross between the orbits of Mars and Jupiter (the radius of the Earth’s orbit is 1 AU). The ice line divides the planetary system into an inner region devoid of volatiles and containing solids, and the outer one, rich in volatile substances and containing ice bodies.

At the ice line itself, water molecules evaporated from dust grains accumulate, which serves as a trigger for a whole cascade of phenomena. In this region, a gap occurs in the gas parameters, and a pressure jump occurs. The balance of forces causes the gas to accelerate its movement around the central star. As a result, particles falling here are influenced not by a headwind, but by a tailwind, pushing them forward and stopping their migration into the disk. And as particles continue to flow from its outer layers, the line of ice turns into a stripe of ice accumulation.

As particles accumulate, they collide and grow. Some of them break through the ice line and continue migrating inward; when heated, they become covered with liquid mud and complex molecules, which makes them stickier. Some areas become so filled with dust that mutual gravitational attraction particles accelerates their growth.

Gradually, dust grains gather into kilometer-sized bodies called planetesimals, which, in the last stage of planet formation, rake up almost all the primordial dust. It is difficult to see the planetesimals themselves in forming planetary systems, but astronomers can guess about their existence from the debris of their collisions (see: Ardila D. Invisible planetary systems // VMN, No. 7, 2004).

Result: many kilometer-long “building blocks” called planetesimals.

The rise of the oligarchs

The billions of kilometer-long planetesimals formed in stage 2 then assemble into Moon- or Earth-sized bodies called embryos. A small number of them dominate in their orbital zones. These "oligarchs" among the embryos are fighting for the remaining substance

3. The embryos of planets are formed

Time: from 1 to 10 million years

The cratered surfaces of Mercury, the Moon, and asteroids leave no doubt that planetary systems are like shooting ranges during their formation. Mutual collisions of planetesimals can stimulate both their growth and destruction. The balance between coagulation and fragmentation results in a size distribution in which small bodies primarily account for the surface area of ​​the system and large bodies determine its mass. The orbits of bodies around a star may initially be elliptical, but over time, deceleration in the gas and mutual collisions turn the orbits into circular ones.

Initially, body growth occurs due to random collisions. But the larger the planetesimal becomes, the stronger its gravity, the more intensely it absorbs its low-mass neighbors. When the masses of planetesimals become comparable to the mass of the Moon, their gravity increases so much that they shake the surrounding bodies and deflect them to the sides even before the collision. This limits their growth. This is how “oligarchs” arise - embryos of planets with comparable masses, competing with each other for the remaining planetesimals.

The feeding zone of each embryo is a narrow strip along its orbit. Growth stops when the embryo absorbs most of the planetesimals from its zone. Elementary geometry shows that the size of the zone and the duration of absorption increase with distance from the star. At a distance of 1 AU embryos reach a mass of 0.1 Earth masses within 100 thousand years. At a distance of 5 AU they reach four Earth masses in a few million years. The seeds can become even larger near the ice line or at the edges of disk breaks where planetesimals are concentrated.

The growth of "oligarchs" fills the system with a surplus of bodies striving to become planets, but only a few succeed. In our solar system, although the planets are distributed according to large space, but they are as close to each other as possible. If another planet with the mass of the Earth is placed between the terrestrial planets, it will throw the entire system out of balance. The same can be said about other known planetary systems. If you see a cup of coffee filled to the brim, you can be almost sure that someone overfilled it and spilled some liquid; It is unlikely that you can fill the container to the brim without spilling a drop. It is just as likely that planetary systems have more matter at the beginning of their lives than at the end. Some objects are thrown out of the system before it reaches equilibrium. Astronomers have already observed free-flying planets in young star clusters.

Result:“oligarchs” are the embryos of planets with masses ranging from the mass of the Moon to the mass of the Earth.

A giant leap for a planetary system

Formation of such gas giant, like Jupiter, is the most important moment in the history of the planetary system. If such a planet has formed, it begins to control the entire system. But for this to happen, the embryo must collect gas faster than it spirals toward the center.

The formation of a giant planet is hampered by the waves it excites in the surrounding gas. The action of these waves is not balanced, slows down the planet and causes its migration towards the star.

The planet attracts gas, but it cannot settle until it cools. And during this time it can spiral quite close to the star. A giant planet may not form in all systems

4. A gas giant is born

Time: from 1 to 10 million years

Jupiter probably began with an embryo comparable in size to Earth, and then accumulated about 300 more Earth-sized masses of gas. This impressive growth is due to various competing mechanisms. The gravity of the nucleus attracts gas from the disk, but the gas contracting towards the nucleus releases energy and must cool in order to settle. Consequently, the growth rate is limited by the possibility of cooling. If it occurs too slowly, the star may blow gas back into the disk before the embryo forms a dense atmosphere around itself. The bottleneck in heat removal is the transfer of radiation through the outer layers of the growing atmosphere. The heat flow there is determined by the opacity of the gas (mainly depending on its composition) and the temperature gradient (depending on the initial mass of the embryo).

Early models showed that a planetary embryo would need to have a mass of at least 10 Earth masses to cool quickly enough. Such a large specimen can only grow near the ice line, where a lot of material had previously accumulated. Perhaps that is why Jupiter is located just behind this line. Large nuclei can form in any other place if the disk contains more material than planetary scientists usually assume. Astronomers have already observed many stars, the disks around which are several times denser than previously assumed. For a large sample, heat transfer does not seem to be a serious problem.

Another factor that complicates the birth of gas giants is the movement of the embryo in a spiral towards the star. In a process called Type I migration, the embryo excites waves in the gas disk, which in turn exert a gravitational influence on its orbital motion. The waves follow the planet, just as its wake follows a boat. The gas on the outer side of the orbit rotates slower than the embryo and pulls it back, slowing down its movement. And the gas inside the orbit rotates faster and pulls forward, accelerating it. The outer region is larger, so it wins the battle and causes the embryo to lose energy and sink towards the center of the orbit by several astronomical units per million years. This migration usually stops at the ice line. Here the oncoming gas wind turns into a tailwind and begins to push the embryo forward, compensating for its braking. Perhaps this is also why Jupiter is exactly where it is.

The growth of the embryo, its migration, and the loss of gas from the disk occur at almost the same rate. Which process wins depends on luck. It is possible that several generations of embryos will go through the migration process without being able to complete their growth. Behind them, new batches of planetesimals move from the outer regions of the disk towards its center, and this is repeated until a gas giant is eventually formed, or until all the gas is dissolved and the gas giant can no longer form. Astronomers have discovered Jupiter-like planets in about 10% of the Sun-like stars studied. The cores of such planets may be rare embryos surviving from many generations - the last of the Mohicans.

The outcome of all these processes depends on the initial composition of the substance. About a third of stars rich in heavy elements have planets like Jupiter. Perhaps such stars had dense disks, which allowed the formation of massive embryos that did not have problems with heat removal. And, on the contrary, planets rarely form around stars poor in heavy elements.

At some point, the mass of the planet begins to grow monstrously quickly: in 1000 years, a planet like Jupiter acquires half of its final mass. At the same time, it generates so much heat that it shines almost like the Sun. The process stabilizes when the planet becomes so massive that it turns Type I migration on its head. Instead of the disk changing the planet's orbit, the planet itself begins to change the movement of gas in the disk. The gas inside the planet's orbit rotates faster than her, therefore its attraction slows down the gas, forcing it to fall towards the star, i.e., away from the planet. Gas outside the planet’s orbit rotates more slowly, so the planet accelerates it, forcing it to move outward, again away from the planet. Thus, the planet creates a rupture in the disk and destroys the reserve building material. Gas tries to fill it, but computer models show that the planet wins the battle if, at a distance of 5 AU. its mass exceeds the mass of Jupiter.

This critical mass depends on the era. The earlier a planet forms, the greater its growth will be, since there is still a lot of gas in the disk. Saturn has less mass than Jupiter simply because it formed several million years later. Astronomers have discovered a shortage of planets with masses ranging from 20 Earth masses (this is the mass of Neptune) to 100 Earth masses (the mass of Saturn). This could be the key to reconstructing the picture of evolution.

Result: A planet the size of Jupiter (or lack thereof).

5. The gas giant is becoming restless

Time: from 1 to 3 million years

Oddly enough, many of the extrasolar planets discovered in the last ten years orbit their star at very close distances, much closer than Mercury orbits the Sun. These so-called “hot Jupiters” did not form where they are now because the orbital feeding zone would be too small to supply the necessary material. Perhaps their existence requires a three-stage sequence of events, which for some reason was not realized in our Solar System.

First, a gas giant must form in the inner part of a planetary system, near the ice line, while there is still enough gas in the disk. But for this to happen, the disk must contain a lot of solid matter.

Secondly, the giant planet must move to its current location. Type I migration cannot provide this, since it acts on the embryos even before they have accumulated a lot of gas. But type II migration is also possible. The forming giant creates a rupture in the disk and restricts the flow of gas through its orbit. In this case, it must fight the tendency of turbulent gas to spread into adjacent areas of the disk. Gas will never stop leaking into the rift, and its diffusion toward the central star will cause the planet to lose orbital energy. This process is quite slow: it takes several million years for the planet to move several astronomical units. Therefore, a planet must begin to form in the inner part of the system if it is to eventually enter orbit near the star. As this and other planets move inward, they push remaining planetesimals and embryos ahead of them, perhaps creating "hot Earths" in orbits even closer to the star.

Third, something must stop the motion before the planet falls onto the star. This could be the magnetic field of the star, clearing the space near the star from gas, and without gas the movement stops. Perhaps the planet excites tides on the star, and they, in turn, slow down the fall of the planet. But these limiters may not work in all systems, so many planets may continue to move towards the star.

Result: a giant planet in a close orbit (“hot Jupiter”).

How to hug a star

In many systems, a giant planet forms and begins to spiral toward the star. This happens because the gas in the disk loses energy due to internal friction and settles towards the star, dragging the planet with it, which eventually ends up so close to the star that it stabilizes its orbit

6. Other giant planets appear

Time: from 2 to 10 million years

If one gas giant manages to form, then it contributes to the birth of the next giants. Many, and perhaps most, known giant planets have twins of comparable mass. In the solar system, Jupiter helped Saturn form faster than it would have happened without its help. In addition, he “lent a helping hand” to Uranus and Neptune, without which they would not have reached their current mass. At their distance from the Sun, the process of formation without outside help would proceed very slowly: the disk would dissolve even before the planets had time to gain mass.

The first gas giant proves useful for several reasons. At the outer edge of the gap it creates, the substance is concentrated, in general, for the same reason as at the ice line: the pressure difference causes the gas to accelerate and act as favourable wind on dust grains and planetesimals, stopping their migration from the outer regions of the disk. In addition, the gravity of the first gas giant often throws its neighboring planetesimals into the outer region of the system, where new planets are formed from them.

The second generation of planets is formed from the material collected for them by the first gas giant. In this case, pace is of great importance: even a small delay in time can significantly change the result. In the case of Uranus and Neptune, the accumulation of planetesimals was excessive. The embryo became too large, 10-20 Earth masses, which delayed the onset of gas accretion until there was almost no gas left in the disk. The formation of these bodies was completed when they gained only two Earth masses of gas. But these are no longer gas giants, but ice giants, which may turn out to be the most common type.

The gravitational fields of the second generation planets increase chaos in the system. If these bodies formed too close, their interactions with each other and with the gas disk could throw them into higher elliptical orbits. In the Solar System, the planets have almost circular orbits and are sufficiently distant from each other, which reduces their mutual influence. But in other planetary systems, the orbits are usually elliptical. In some systems they are resonant, that is, the orbital periods are related as small integers. It is unlikely that this was incorporated during formation, but it could have arisen during the migration of planets, when gradually the mutual gravitational influence tied them to each other. The difference between such systems and the Solar System could be determined by different initial gas distributions.

Most stars are born in clusters, and more than half of them are binaries. Planets may form outside the plane of orbital motion of stars; in this case, the gravity of a neighboring star quickly rearranges and distorts the orbits of the planets, forming not such flat systems as our Solar system, but spherical ones, reminiscent of a swarm of bees around a hive.

Result: company of giant planets.

Addition to the family

The first gas giant creates the conditions for the birth of the next. The strip cleared by him acts like a fortress moat, which cannot be overcome by the substance moving from the outside to the center of the disk. It collects on the outside of the gap, where new planets form from it.

7. Earth-like planets form

Time: from 10 to 100 million years

Planetary scientists believe that Earth-like planets are more common than giant planets. While the birth of a gas giant requires a precise balance of competing processes, the formation of a rocky planet must be much more complex.

Before the discovery of extrasolar Earth-like planets, we relied only on data about the Solar System. The four terrestrial planets - Mercury, Venus, Earth and Mars - are mainly composed of substances with high temperature boiling, such as iron and silicate rocks. This indicates that they formed inside the ice line and did not migrate noticeably. At such distances from the star, planetary embryos can grow in a gaseous disk up to 0.1 Earth masses, i.e. no more than Mercury. For further growth, the orbits of the embryos need to intersect, then they will collide and merge. The conditions for this arise after the evaporation of gas from the disk: under the influence of mutual disturbances over several million years, the orbits of the nuclei are stretched into ellipses and begin to intersect.

Much more difficult to explain is how the system stabilizes itself again, and how the terrestrial planets ended up in their current nearly circular orbits. A small amount of remaining gas could provide this, but such gas should have prevented the initial “looseness” of the orbits of the embryos. Perhaps, when the planets are almost formed, there is still a decent swarm of planetesimals. Over the next 100 million years, the planets sweep away some of these planetesimals and deflect the remaining ones towards the Sun. The planets transfer their erratic motion to the doomed planetesimals and move into circular or nearly circular orbits.

Another idea is that the long-term influence of Jupiter's gravity causes the forming terrestrial planets to migrate, moving them into areas with fresh material. This influence should be greater in resonant orbits, which gradually shifted inward as Jupiter descended toward its present orbit. Radioisotope measurements indicate that asteroids formed first (4 million years after the formation of the Sun), then Mars (10 million years later), and later Earth (50 million years later): as if a wave raised by Jupiter passed through the solar system. If it had not encountered obstacles, it would have moved all the terrestrial planets towards the orbit of Mercury. How did they manage to avoid such a sad fate? Perhaps they had already become too massive, and Jupiter could not move them much, or perhaps strong impacts threw them out of Jupiter’s zone of influence.

Note that many planetary scientists do not consider the role of Jupiter to be decisive in the formation rocky planets. Most sun-like stars do not have Jupiter-like planets, but they do have dusty disks around them. This means that there are planetesimals and embryos of planets there, from which objects like the Earth can form. The main question that observers must answer in the next decade is how many systems have Earths but no Jupiters.

The most important era for our planet was the period between 30 and 100 million years after the formation of the Sun, when an embryo the size of Mars crashed into the proto-Earth and generated a huge amount of debris from which the Moon was formed. So a strong beat, of course, scattered a huge amount of matter throughout the solar system; therefore, Earth-like planets in other systems may also have satellites. This strong blow was supposed to disrupt the Earth's primary atmosphere. Its present-day atmosphere largely arose from gas trapped in planetesimals. The Earth was formed from them, and later this gas came out during volcanic eruptions.

Result: terrestrial planets.

Explanation of non-circular motion

In the inner solar system, planetary embryos cannot grow by capturing gas, so they must merge with each other. To do this, their orbits must intersect, which means something must disrupt their initially circular motion.

When embryos form, their circular or nearly circular orbits do not intersect.

The gravitational interaction of the embryos with each other and with the giant planet disturbs the orbits.

The embryos unite into an earth-type planet. It returns to a circular orbit, mixing the remaining gas and scattering the remaining planetesimals.

8. Clearance operations begin

Time: from 50 million to 1 billion years

At this point, the planetary system was almost formed. Several more minor processes continue: the disintegration of the surrounding star cluster, which is capable of destabilizing the orbits of planets with its gravity; internal instability that occurs after a star finally collapses its disk of gas; and finally the continued dispersal of the remaining planetesimals by the giant planet. In the Solar System, Uranus and Neptune eject planetesimals outward, into the Kuiper belt, or towards the Sun. And Jupiter, with its powerful gravity, sends them to the Oort cloud, to the very edge of the region gravitational influence Sun. The Oort cloud may contain about 100 Earth masses of material. From time to time, planetesimals from the Kuiper belt or Oort cloud approach the Sun, forming comets.

By scattering planetesimals, the planets themselves migrate a little, and this may explain the synchronization of the orbits of Pluto and Neptune. It is possible that Saturn's orbit was once closer to Jupiter, but then moved away from it. This is probably related to the so-called late bombardment epoch - a period of very intense collisions with the Moon (and, apparently, with the Earth), which began 800 million years after the formation of the Sun. In some systems, grandiose collisions of formed planets can occur at a late stage of development.

Result: The end of the formation of planets and comets.

Messengers from the past

Meteorites are not just space rocks, but space fossils. According to planetary scientists, these are the only tangible evidence of the birth of the Solar System. It is believed that these are pieces of asteroids, which are fragments of planetesimals that never participated in the formation of planets and remained frozen forever. The composition of meteorites reflects everything that happened to their parent bodies. It is amazing that they show traces of the long-standing gravitational influence of Jupiter.

Iron and stony meteorites apparently formed in planetesimals that experienced melting, causing the iron to separate from the silicates. Heavy iron sank to the core, and light silicates accumulated in the outer layers. Scientists believe the heating was caused by the decay radioactive isotope aluminum-26, which has a half-life of 700 thousand years. A supernova explosion or a nearby star could “infect” the protosolar cloud with this isotope, as a result of which it entered in large quantities into the first generation of planetesimals of the Solar System.

However, iron and stone meteorites are rare. Most contain chondrules - small millimeter-sized grains. These meteorites - chondrites - arose before planetesimals and never experienced melting. It appears that most of the asteroids are not associated with the first generation of planetesimals, which were most likely ejected from the system by Jupiter's influence. Planetologists have calculated that the region of the current asteroid belt previously contained a thousand times more matter than it does now. Particles that escaped Jupiter's clutches or later entered the asteroid belt coalesced into new planetesimals, but by then they had little aluminum-26 left in them, so they never melted. The isotopic composition of chondrites shows that they formed approximately 2 million years after the formation of the Solar System began.

The glassy structure of some chondrules indicates that before they entered planetesimals, they were sharply heated, melted, and then quickly cooled. The waves that drove Jupiter's early orbital migration must have turned into shock waves and could have caused this sudden heating.

There is no single plan

Before the era of discovery of extrasolar planets, we could only study the Solar System. Although this allowed us to understand the microphysics the most important processes, we had no idea about the ways of development of other systems. The amazing diversity of planets discovered over the past decade has significantly expanded the horizon of our knowledge. We are beginning to understand that extrasolar planets are the last surviving generation of protoplanets that have experienced formation, migration, destruction, and continuous dynamic evolution. The relative order in our solar system cannot be a reflection of any general plan.

From trying to figure out how our solar system was formed in the distant past, theorists have turned to research that makes it possible to make predictions about the properties of as yet undiscovered systems that may be discovered in the near future. Until now, observers have noticed only planets with masses on the order of that of Jupiter near sun-like stars. Armed with a new generation of instruments, they will be able to search for Earth-like objects, which, in accordance with the theory of successive accretion, should be widespread. Planetary scientists are just beginning to realize how diverse the worlds are in the Universe.

Translation: V. G. Surdin

Additional literature:
1) Towards a Deterministic Model of Planetary Formation. S.Ida and D.N.C. Lin in Astrophysical Journal, Vol. 604, No. 1, pages 388-413; March 2004.
2) Planet Formation: Theory, Observation, and Experiments. Edited by Hubert Klahr and Wolfgang Brandner. Cambridge University Press, 2006.
3) Alven H., Arrhenius G. Evolution of the Solar System. M.: Mir, 1979.
4) Vityazev A.V., Pechernikova G.V., Safronov V.S. Terrestrial planets: Origin and early evolution. M.: Nauka, 1990.

Take a felt-tip pen and draw several “galaxies” on a balloon different shapes. When the balloon is dry, start inflating it and you will see how the “galaxies” scatter. How bigger ball swells, the further they run away from each other. The same thing happens in the Universe. This is one of the models proposed by scientists to illustrate the expansion of the Universe.

Billions of years ago, the solar system began its formation with the formation of a gas and dust cloud. The center of the system is the Sun, around which a huge number of other objects move under the force of gravity - planets, asteroids, comets, meteorites and a lot of cosmic dust. The Sun is so massive that it essentially makes up most of the mass of the entire system.

Structure of the Solar System

There are eight planets in total in the solar system. The so-called terrestrial planets - Mercury, Venus, Earth and Mars are inner planets, in contrast to the four giant planets, which are separated by the asteroid belt - Jupiter, Saturn, Uranus and Neptune. Terrestrial planets are mostly composed of rocky matter, while the outer planets are mostly gas planets. Moreover, the latter are many times larger and more massive.

Why exactly the huge asteroid belt formed between the inner and outer planets still remains a mystery, but scientists agree that if it weren’t for gravitational fields Jupiter - then perhaps they would have united into a planet. But there are a lot of guesses on this matter; some even believe that the asteroid belt was formed due to a collision of the planet with some other celestial body.

Although the structure of the solar system has seemingly already been studied, scientists are still making amendments, for example, in 2005, an amendment was adopted in the definition of “what is a planet” due to which Pluto ceased to be a planet and began to be called a dwarf planet, of which the solar system has quite a few a lot of.

Location of planets in the solar system

The planets in the Solar System are arranged according to the following scheme:

Sun > Mercury > Venus > Earth > Mars > Asteroid Belt > Jupiter > Saturn > Uranus > Neptune

Origin of the Solar System

The most popular theory is that, like most galaxies, planets and stars, our system was formed after the Big Bang that occurred 15 billion years ago. The huge amount of matter that escaped gradually cooled and cosmic bodies were formed, including our galaxy. It is not known for certain as a result of what processes, but about 5 billion years ago, clots of matter from dust and gas, as a result of the force of gravity, began to compress and spin around each other. At the center of this action the Sun was formed. But inside this vortex, other parts began to unite, forming “seals”, which later became planets.

But still, the origin of the solar system has not yet been reliably studied, because there are some mysteries and inconsistencies in scientists’ theories, for example, it is not entirely clear why Venus rotates in the opposite direction, relative to other planets. On this score, there are hypotheses that she collided with her companion and he changed the direction of her movement, but there is no convincing evidence of this.

Solar system video presentation:

(now that about 100 planetary systems have been discovered, it is customary to talk not about the Solar, but about the planetary system) began to be decided about 200 years ago, when two outstanding scientists - the philosopher I. Kant, the mathematician and astronomer P. Laplace almost simultaneously formulated the first scientific hypotheses its origin. It must be said that the hypotheses themselves and the discussion around them and other hypotheses (for example, J. Jean-sa) were completely speculative. Only in the 50s. XX century Enough data was collected to allow the formulation of a modern hypothesis.

A comprehensive hypothesis about the origin of the planetary system, which would explain in detail such issues as the difference in the chemical and isotopic compositions of the planets and their atmospheres, does not yet exist. At the same time, modern ideas about the origin of the planetary system quite confidently interpret such issues as the division of planets into two groups, the main differences in chemical composition, and the dynamic history of the planetary system.

Planet formation occurs very quickly; Thus, it took about 100,000,000 years to form the Earth. Calculations carried out in recent years have shown that modern hypothesis The formation of planets is quite well substantiated.

Particle sticking together

In the formed protoplanetary disk, particles began to coalesce. Adhesion is ensured by the structure of the particles. They are carbon, silicate or iron dust particles on which a snow (water, methane, etc.) “coat” grows. The speed of rotation of dust grains around the Sun was quite high (this is the Keplerian speed of tens of kilometers per second), but the relative speeds were very small, and during collisions the particles stuck together into small lumps. Material from the site

The appearance of planets

Very quickly, the forces of attraction began to play a decisive role in the increase in lumps. This led to the fact that the growth rate of the resulting aggregates is proportional to their mass to approximately the fifth power. As a result, one large body remained in each orbit - future planet and, perhaps, several more bodies of much smaller mass that became its satellites.

Bombing planets

At the very last stage, it was no longer particles that fell on the Earth and other planets, but bodies of asteroid sizes. They contributed to the compaction of matter, heating of the subsoil and the appearance on their surfaces of traces in the form of seas and craters. This period is

University: not specified

Introduction 3

Origin of the Solar System 4

Evolution of the Solar System 6

Conclusion 9

References 10

Introduction

The branch of astronomy that studies the origin and development of celestial bodies is called cosmogony. Cosmogony studies the processes of changing the forms of cosmic matter, leading to the formation of individual celestial bodies and their systems, and the direction of their subsequent evolution. Cosmogonic research also leads to the solution of such problems as the emergence chemical elements And cosmic rays, the appearance of magnetic fields and sources of radio emission.

The solution of cosmogonic problems is associated with great difficulties, since the emergence and development of celestial bodies occurs so slowly that it is impossible to trace these processes through direct observations; The timing of cosmic events is so long that the entire history of astronomy in comparison with their duration seems like an instant. Therefore, cosmogony from the comparison of simultaneously observed physical properties of celestial bodies establishes character traits successive stages of their development.

The insufficiency of factual data leads to the need to formalize the results of cosmogonic research in the form of hypotheses, i.e. scientific assumptions based on observations, theoretical calculations and basic laws of nature. Further development a hypothesis shows to what extent it corresponds to the laws of nature and quantification the facts she predicted.

Astronomers of the past have proposed many theories about the formation of the Solar System, and in the 1940s, Soviet astronomer Otto Schmidt proposed that the Sun, rotating around the center of the Galaxy, captured a cloud of dust. From the substance of this huge cold dust cloud, cold dense preplanetary bodies - planetesimals - were formed.

Origin of the Solar System

Age of the most ancient rocks found in the samples lunar soil and meteorites, is approximately 4.5 billion years. Calculations of the age of the Sun gave a close value - 5 billion years. It is generally accepted that all the bodies that currently make up the Solar System were formed approximately 4.5-5 billion years ago.

According to the most developed hypothesis, they were all formed as a result of the evolution of a huge cold gas and dust cloud. This hypothesis explains quite well many features of the structure of the Solar system, in particular, the significant differences between the two groups of planets.

Over the course of several billion years, the cloud itself and its constituent substances changed significantly. The particles that made up this cloud revolved around the Sun in a variety of orbits.

As a result of some collisions, particles were destroyed, while in others they were combined into larger ones. Larger clumps of matter arose - the embryos of future planets and other bodies.

The meteorite “bombardment” of the planets can also be considered confirmation of these ideas - in fact, it is a continuation of the process that led to their formation in the past. At present, when there is less and less meteorite matter left in interplanetary space, this process is much less intense than in the past. initial stages formation of planets.

At the same time, a redistribution of matter and its differentiation occurred in the cloud. Under the influence of strong heating, gases evaporated from the vicinity of the Sun (mainly the most common in the Universe - hydrogen and helium) and only solid, refractory particles remained. From this substance the Earth, its satellite the Moon, and other terrestrial planets were formed.

During the formation of planets and later over billions of years, processes of melting, crystallization, oxidation and others took place in their interiors and on the surface. physical and chemical processes. This led to a significant change in the original composition and structure of the matter from which all currently existing bodies of the Solar System are formed.

Far from the Sun, at the periphery of the cloud, these volatile substances froze onto dust particles. The relative content of hydrogen and helium turned out to be increased. From this substance, giant planets were formed, the size and mass of which significantly exceed the terrestrial planets. After all, the volume of the peripheral parts of the cloud was greater, and therefore the mass of the substance from which the planets far from the Sun were formed was greater.

Data on the nature and chemical composition of satellites giant planets received in last years by using spacecraft, became another confirmation of the validity of modern ideas about the origin of the bodies of the Solar System. In conditions when hydrogen and helium, which went to the periphery of the protoplanetary cloud, became part of the giant planets, their satellites turned out to be similar to the Moon and the terrestrial planets.

However, not all of the matter in the protoplanetary cloud became part of the planets and their satellites. Many clots of its matter remained both inside the planetary system in the form of asteroids and even smaller bodies, and outside it in the form of comet nuclei.

Evolution of the Solar System

Theoretically, the planets formed along with the Sun at approximately the same time and were in a plasma state. one system formed during gravitational interactions who currently support it. Subsequently, the planets, as less energy-intensive systems, quickly switched to the processes of nuclear and molecular fusion, crust formation and information evolution.

The process of cooling and loss of energy began from the periphery of the system. Distant planets cooled earlier, matter passed into a molecular state, and a crust formed. Here, an external information factor in the form of cosmic radiation is connected to the energy conditioning of processes. Here is what V.I. Vernadsky wrote in 1965: ... in the history of planet Earth, we are continuously, really confronted with the energetic and material manifestation of the Milky Way - in the form of cosmic matter - meteorites and dust (which was often taken into account by geologists) and material-energetic, invisible to the eye and consciously by man, imperceptible penetrating cosmic radiation. Another authoritative researcher of the last century, Hess, proved in 1933 that these radiations - flows - are constantly brought to our planet, into its biosphere elementary particles, causing ionization of air, the importance of which in energy earth's shells paramount.

The formation of the planet's crust is an energy-information interaction, after which the planetary system is included in the process of galactic information exchange. The next quantum of energy loss by the planetary system is replaced by an increase in the level of information that conserves energy. Biopolymers, under increased external information influence, form complex molecular conglomerates, the development of which leads to the appearance of a living cell and organic life. The role of external factors in the origin of life has long been discussed by scientists. One of the first versions was put forward by Arrhenius (1859-1927) that among the cosmic dust scattered in the vacuum there should be countless spores - the embryos of living matter that come from the planets, terrestrial planets, and they are caught again in the course of time. Another version was the transfer of living beings using meteorites. Without rejecting these versions, we are inclined to believe that the main transmission is not just material, but material-informational, wave and field influences.

As with any energy-informational structure, the Solar System is characterized by an increase in the information level of the organization of matter as the energy potential of the system decreases. There is no doubt that during the cooling process distant planets the overall energy potential of the Solar System was higher than it is now, so the information level of life on the distant planets was certainly lower than what we observe now on Earth.

The growth of the level of information interactions in the Solar System increased as the overall energy level of the system fell. Reception external information distant planets occurred with the corresponding interaction of the internal energy level system and external information level. At that time, the galactic system of energy-information exchange was just coming into balance. Further, as the Solar System and the entire Universe developed, the energy-information exchange was enriched with information of a higher level, the energy potential of both individual information atoms (which is the Solar System) and the entire galaxy decreased.

Returning to the Solar System, it should be noted that most likely the evolution of distant planets took place in a shorter period of time, since their cooling rate was higher. At the same time, the high energy potential of the solar system did not allow them to reach equilibrium. All these factors certainly did not contribute information development these systems. Therefore, their development quickly reached its information peak, i.e. such an evolutionary state of the system when dense physical matter that binds energy is no longer capable of keeping the system from energy decay. This is the state of the energy minimum of the entire system. The processes of disintegration of the highest levels of matter organization begin with the release of energy.

On the scale of the Solar System, decay processes take a very long time; all six cooling planets of the Solar System (Pluto, Neptune, Uranus, Saturn, Jupiter, Mars) are in a state of molecular decay, a constant decrease in the energy level of the transition of energy into a physical vacuum. Subsequently, the processes of molecular decay turn into nuclear decay, internuclear distances are reduced, and superdense matter is formed. At these stages of decomposition, it is released into the vacuum maximum amount energy.

Conclusion

According to modern ideas, the formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant interstellar molecular cloud. Most of the matter ended up in the gravitational center of collapse with the subsequent formation of a star—the Sun. The matter that did not fall into the center formed a protoplanetary disk rotating around it, from which the planets, their satellites, asteroids and other small bodies of the Solar System were subsequently formed.

Hypothesis about the formation of the Solar system from a gas and dust cloud - nebular hypothesis- was originally proposed in the 18th century by Emmanuel Swedenborg, Immanuel Kant and Pierre-Simon Laplace. Subsequently, its development took place with the participation of many scientific disciplines, including astronomy, physics, geology and planetary science. With the beginning space age in the 1950s, and with the discovery of extrasolar planets (exoplanets) in the 1990s, the model has undergone multiple tests and improvements to explain new data and observations.

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