The hypothesis of the formation of the solar system from a gas and dust cloud - the nebular hypothesis - was originally proposed in the 18th century by Emmanuel Swedenborg, Immanuel Kant and Pierre-Simon Laplace. In the future, its development took place with the participation of many scientific disciplines, including astronomy, physics, geology and planetary science. With the advent of the space age in the 1950s, as well as the discovery of planets outside the solar system in the 1990s (), this model has undergone multiple tests and improvements to explain new data and observations.
According to the currently accepted hypothesis, 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 gas and dust cloud. In general terms, this process can be described as follows:
- The trigger mechanism for the gravitational collapse was a small (spontaneous) compaction of the matter of the gas and dust cloud (possible reasons for which could be both the natural dynamics of the cloud, and the passage of a shock wave from an explosion through the matter of the cloud, etc.), which became the center of gravitational attraction for the surrounding matter - the center gravitational collapse. The cloud already contained not only primordial hydrogen and helium, but also numerous heavy elements (metallicity) left over from the stars of previous generations. In addition, the collapsing cloud had some initial angular momentum.
- In the process of gravitational compression, the size of the gas and dust cloud decreased and, due to the law of conservation of angular momentum, the speed of rotation of the cloud increased. Due to the rotation, the compression rates of the clouds parallel and perpendicular to the axis of rotation differed, which led to the flattening of the cloud and the formation of a characteristic disk.
- As a consequence of compression, the density and intensity of collisions of matter particles with each other increased, as a result of which the temperature of the matter continuously increased as it was compressed. The central regions of the disk were heated most strongly.
- Upon reaching a temperature of several thousand kelvins, the central region of the disk began to glow - a protostar formed. The cloud matter continued to fall onto the protostar, increasing the pressure and temperature at the center. The outer regions of the disk remained relatively cold. Due to hydrodynamic instabilities, separate seals began to develop in them, which became local gravitational centers for the formation of planets from the substance of the protoplanetary disk.
- When the temperature in the center of the protostar reached millions of kelvins, the reaction of thermonuclear fusion of helium from hydrogen began in the central region. The protostar has evolved into an ordinary main sequence star. In the outer region of the disk, large clusters formed planets revolving around the central star in approximately the same plane and in the same direction.
Subsequent evolution
It used to be believed that all the planets were formed approximately in the orbits where they are now, but at the end of the 20th - beginning of the 21st century, this point of view changed radically. It is now believed that at the dawn of its existence, the solar system looked completely different from what it looks like now. According to modern concepts, the outer Solar System was much more compact in size than it is now, it was much closer to the Sun, and in the inner Solar System, in addition to the celestial bodies that have survived to this day, there were other objects no smaller than .
terrestrial planets
Giant collision of two celestial bodies, possibly giving rise to the Earth's satellite Moon
At the end of the planetary epoch, the inner solar system was inhabited by 50-100 protoplanets ranging in size from lunar to Martian. Further growth in the size of celestial bodies was due to collisions and mergers of these protoplanets with each other. So, for example, as a result of one of the collisions, Mercury lost most of its mantle, while as a result of another, the so-called. giant collision (possibly with the hypothetical planet Theia), a satellite was born. This phase of collisions continued for about 100 million years until the 4 massive celestial bodies known today remained in orbit.
One of the unsolved problems of this model is the fact that it cannot explain how the initial orbits of protoplanetary objects, which had to have a high eccentricity in order to collide with each other, could as a result give rise to stable and close to circular orbits of the remaining four planets. According to one hypothesis, these planets were formed at a time when interplanetary space still contained a significant amount of gas and dust material, which, due to friction, reduced the energy of the planets and made their orbits smoother. However, this same gas was supposed to prevent the occurrence of a large elongation in the original orbits of the protoplanets. Another hypothesis suggests that the correction of the orbits of the inner planets occurred not due to interaction with gas, but due to interaction with the remaining smaller bodies of the system. As large bodies passed through a cloud of small objects, the latter, due to the gravitational influence, were drawn into regions with a higher density, and thus created “gravitational ridges” on the path of the large planets. The increasing gravitational influence of these "ridges", according to this hypothesis, caused the planets to slow down and enter a more rounded orbit.
asteroid belt
The outer boundary of the inner solar system is located between 2 and 4 AU. from the Sun and represents . Hypotheses about the existence of a planet between and (for example, the hypothetical planet Phaethon) were put forward, but in the end were not confirmed, which at the early stages of the formation of the solar system collapsed so that asteroids that formed the asteroid belt became its fragments. According to modern views, there was no single protoplanet-source of asteroids. The asteroid belt originally contained enough matter to form 2-3 Earth-sized planets. This area contained a large number of planetosimals, which stuck together, forming ever larger objects. As a result of these mergers, about 20-30 protoplanets with sizes from lunar to Martian were formed in the asteroid belt. However, since the time when the planet Jupiter was formed in relative proximity to the belt, the evolution of this region has taken a different path. Powerful orbital resonances with Jupiter and , as well as gravitational interactions with more massive protoplanets in this area, destroyed already formed planetozimals. Getting into the resonance area when passing nearby a giant planet, planetosimals received additional acceleration, crashed into neighboring celestial bodies and were crushed instead of smoothly merging.
As Jupiter migrated to the center of the system, the resulting perturbations became more and more pronounced. As a result of these resonances, planetozimals changed the eccentricity and inclination of their orbits and were even thrown out of the asteroid belt. Some of the massive protoplanets were also thrown out of the asteroid belt by Jupiter, while other protoplanets likely migrated into the inner solar system, where they played the final role in increasing the mass of the few remaining terrestrial planets. During this period of depletion, the influence of the giant planets and massive protoplanets caused the asteroid belt to "thin" to only 1% of the Earth's mass, which was mainly small planetozimals. This value, however, is 10-20 times greater than the current value of the mass of the asteroid belt, which is now 1/2000 of the mass of the Earth. It is believed that the second period of depletion, which brought the mass of the asteroid belt to its current values, began when Jupiter and Saturn entered a 2:1 orbital resonance.
It is likely that the period of giant collisions in the history of the inner solar system played an important role in obtaining the Earth's water reserves (~6·10 21 kg). The fact is that water is too volatile a substance to occur naturally during the formation of the Earth. Most likely, it was brought to Earth from the outer, colder regions of the solar system. Perhaps it was the protoplanets and planetozimals thrown out by Jupiter outside the asteroid belt that brought water to Earth. Other candidates for the role of the main deliverers of water are also the main asteroid belt, discovered in 2006, while comets from the Kuiper belt and other remote regions supposedly brought no more than 6% of water to Earth.
planetary migration
According to the nebular hypothesis, the two outer planets of the solar system are in the "wrong" place. and , the "ice giants" of the solar system, are located in a region where the reduced density of the material of the nebula and long orbital periods made the formation of such planets a very unlikely event. It is believed that these two planets originally formed in orbits near Jupiter and Saturn, where there was much more building material, and only after hundreds of millions of years migrated to their modern positions.
Simulation showing the positions of the outer planets and the Kuiper belt: a) Before the 2:1 orbital resonance of Jupiter and Saturn b) Scattering of ancient Kuiper belt objects around the Solar System after Neptune's orbital shift c) After Jupiter ejected Kuiper belt objects out of the system
Planetary migration is able to explain the existence and properties of the outer regions of the solar system. Beyond Neptune, the solar system contains the Kuiper belt, and , which are open clusters of small icy bodies and give rise to most of the comets observed in the solar system. Now the Kuiper belt is located at a distance of 30-55 AU. from the Sun, the scattered disk begins at 100 AU. from the Sun, and the Oort cloud is 50,000 AU. from the central light. However, in the past, the Kuiper Belt was much denser and closer to the Sun. Its outer edge was at about 30 AU. from the Sun, while its inner edge was located directly behind the orbits of Uranus and Neptune, which in turn were also closer to the Sun (approximately 15-20 AU) and, moreover, located in the opposite order: Uranus was farther from the Sun than Neptune.
After the formation of the solar system, the orbits of all the giant planets continued to slowly change under the influence of interactions with a large number of remaining planetosimals. After 500-600 million years (4 billion years ago), Jupiter and Saturn entered a 2:1 orbital resonance; Saturn made one revolution around the Sun in exactly the time for which Jupiter made 2 revolutions. This resonance created a gravitational pressure on the outer planets, causing Neptune to escape the orbit of Uranus and crash into the ancient Kuiper belt. For the same reason, the planets began to throw the icy planetozimals surrounding them into the interior of the solar system, while they themselves began to move away outward. This process continued in a similar way: under the influence of resonance, planetozimals were thrown into the interior of the system by each subsequent planet that they met on their way, and the orbits of the planets themselves moved further and further away. This process continued until the planetosimals entered the zone of direct influence of Jupiter, after which the huge gravity of this planet sent them into highly elliptical orbits or even threw them out of the solar system. This work, in turn, slightly shifted Jupiter's orbit inward. Objects ejected by Jupiter into highly elliptical orbits formed the Oort cloud, while bodies ejected by migrating Neptune formed the modern Kuiper belt and scattered disk. This scenario explains why the scattered disk and the Kuiper belt have a low mass. Some of the ejected objects, including , eventually entered into gravitational resonance with the orbit of Neptune. Gradually friction with the scattered disk made the orbits of Neptune and Uranus smooth again.
There is also a hypothesis about the fifth gas giant, which underwent radical migration and was pushed out during the formation of the modern image of the solar system to its distant outskirts (which became the hypothetical planet Tyukhe or another "Planet X") or even beyond it (becoming an orphan planet).
Confirmation of the theory of a massive planet beyond the orbit of Neptune was found by Konstantin Batygin and Michael Brown on January 20, 2016, based on the orbits of six trans-Neptunian objects. Its mass used in the calculations was approximately 10 Earth masses, and the revolution around the Sun presumably took from 10,000 to 20,000 Earth years.
It is believed that, unlike the outer planets, the inner bodies of the system did not undergo significant migrations, since after a period of giant collisions their orbits remained stable.
Late heavy bombardment
The gravitational breakup of the ancient asteroid belt probably started the heavy bombardment period about 4 billion years ago, 500-600 million years after the formation of the solar system. This period lasted several hundred million years, and its consequences are still visible on the surface of geologically inactive bodies of the solar system, such as the Moon or Mercury, in the form of numerous impact craters. And the oldest evidence of life on Earth dates back to 3.8 billion years ago - almost immediately after the end of the late heavy bombardment period.
Giant collisions are a normal (albeit rare lately) part of the evolution of the solar system. Evidence of this is the collision of comet Shoemaker-Levy with Jupiter in 1994, the fall of a celestial body on Jupiter in 2009, and a meteorite crater in Arizona. This suggests that the process of accretion in the solar system is not yet complete, and therefore poses a danger to life on Earth.
Formation of satellites
Natural satellites formed around most of the planets in the solar system, as well as many other bodies. There are three main mechanisms for their formation:
- formation from a circumplanetary disk (in the case of gas giants)
- formation from fragments of the collision (in the case of a sufficiently large collision at a small angle)
- capture of a flying object
Jupiter and Saturn have many satellites, such as , and , which probably formed from disks around these giant planets in the same way that these planets themselves formed from a disk around the young Sun. This is indicated by their large size and proximity to the planet. These properties are impossible for satellites acquired by capture, and the gaseous structure of the planets makes impossible the hypothesis of the formation of moons by the collision of a planet with another body.
Future
Astronomers estimate that the solar system will not undergo extreme changes until the Sun runs out of hydrogen fuel. This milestone will initiate the transition of the Sun from the main sequence of the Hertzsprung-Russell diagram into phase. However, even in the phase of the main sequence of a star, the solar system continues to evolve.
Long term sustainability
The solar system is a chaotic system in which the orbits of the planets are unpredictable over a very long period of time. One example of this unpredictability is the Neptune-Pluto system, which is in a 3:2 orbital resonance. Despite the fact that the resonance itself will remain stable, it is impossible to predict with any approximation the position of Pluto in its orbit for more than 10-20 million years (Lyapunov time). Another example is the tilt of the Earth's axis of rotation, which, due to friction within the Earth's mantle caused by tidal interactions with the Moon, cannot be calculated from some point between 1.5 and 4.5 billion years in the future.
The orbits of the outer planets are chaotic on large time scales: their Lyapunov time is 2-230 million years. Not only does this mean that the position of the planet in orbit from this point in the future cannot be determined with any approximation, but the orbits themselves can change in extreme ways. The chaos of the system can manifest itself most strongly in a change in the eccentricity of the orbit, in which the orbits of the planets become more or less elliptical.
The solar system is stable in the sense that no planet can collide with another or be thrown out of the system in the next few billion years. However, beyond this time frame, for example, within 5 billion years, the eccentricity of the orbit of Mars can grow to a value of 0.2, which will lead to the intersection of the orbits of Mars and the Earth, and hence to a real threat of a collision. In the same period of time, the eccentricity of Mercury's orbit may increase even more, and subsequently a close passage near may throw Mercury out of the solar system, or put it on a collision course with Venus itself or with the Earth.
Satellites and rings of planets
The evolution of lunar systems of planets is determined by tidal interactions between the bodies of the system. Due to the difference in the gravitational force acting on the planet from the side of the satellite, in its different regions (more distant regions are attracted weaker, while closer ones are stronger), the shape of the planet changes - it seems to be slightly stretched in the direction of the satellite. If the direction of the satellite's revolution around the planet coincides with the direction of the planet's rotation, and at the same time the planet rotates faster than the satellite, then this "tidal hillock" of the planet will constantly "run away" forward in relation to the satellite. In this situation, the angular momentum of the planet's rotation will be transferred to the satellite. This will lead to the fact that the satellite will receive energy and gradually move away from the planet, while the planet will lose energy and rotate more and more slowly.
The Earth and Moon are an example of such a configuration. The rotation of the Moon is tidally fixed with respect to the Earth: the period of the Moon's revolution around the Earth (currently about 29 days) coincides with the period of the Moon's rotation around its axis, and therefore the Moon is always turned to the Earth by the same side. The moon is gradually moving away from the earth, while the rotation of the earth is gradually slowing down. In 50 billion years, if they survive the expansion of the Sun, the Earth and Moon will become tidally locked to each other. They will enter the so-called spin-orbit resonance, in which the Moon will revolve around the Earth in 47 days, the period of rotation of both bodies around its axis will be the same, and each of the celestial bodies will always be visible only from one side for its partner.
Other examples of this configuration are the systems of Jupiter's Galilean satellites, as well as most of Saturn's large moons.
Neptune and its moon Triton, photographed during the flyby of the Voyager 2 mission. In the future, this satellite is likely to be torn apart by tidal forces, giving rise to a new ring around the planet.
A different scenario awaits systems in which the satellite moves around the planet faster than it rotates around itself, or in which the satellite moves in the opposite direction of the planet's rotation. In such cases, the tidal deformation of the planet constantly lags behind the position of the satellite. This reverses the direction of transfer of angular momentum between bodies. which in turn will lead to an acceleration of the planet's rotation and a reduction in the satellite's orbit. Over time, the satellite will spiral towards the planet until at some point it either falls to the surface or atmosphere of the planet, or is torn apart by tidal forces, thus giving rise to a planetary ring. Such a fate awaits the satellite of Mars (in 30-50 million years), the satellite of Neptune (in 3.6 billion years), and Jupiter, and at least 16 small moons of Uranus and Neptune. The satellite of Uranus may even collide with the neighboring moon.
And finally, in the third type of configuration, the planet and the satellite are tidally fixed with respect to each other. In this case, the “tidal hillock” is always located exactly under the satellite, there is no transfer of angular momentum, and, as a result, the orbital period does not change. An example of such a configuration is Pluto and.
University: not specified
Introduction 3
Origin of the Solar System 4
Solar System Evolution 6
Conclusion 9
References 10
Introduction
The branch of astronomy that studies the origin and development of celestial bodies is called cosmogony. Cosmogony explores 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. Cosmic research also leads to the solution of such problems as the emergence of 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 the course of cosmic events is so long that the entire history of astronomy, in comparison with their duration, seems to be an instant. Therefore, cosmogony, by comparing the simultaneously observed physical properties of celestial bodies, establishes the characteristic features of the successive stages of their development.
The lack of actual data leads to the need to formalize the results of cosmogonic studies in the form of hypotheses, i.e. scientific assumptions based on observations, theoretical calculations and basic laws of nature. The further development of the hypothesis shows to what extent it corresponds to the laws of nature and to the quantitative assessment of the facts predicted by it.
Astronomers of the past offered many theories for the formation of the solar system, and in the 40s of the twentieth century, Soviet astronomer Otto Schmidt suggested that the Sun, revolving around the center of the Galaxy, captured a cloud of dust. From the substance of this huge cold dust cloud formed cold dense pre-planetary bodies - planetesimals.
Origin of the solar system
The oldest rocks found in lunar soil samples and meteorites are about 4.5 billion years old. 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 formed about 4.5-5 billion years ago.
According to the most developed hypothesis, they 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 matter changed significantly. The particles that made up this cloud revolved around the Sun in a variety of orbits.
As a result of some collisions, the particles were destroyed, while in others they were combined into larger ones. Larger clots of matter arose - the embryos of future planets and other bodies.
The meteorite "bombardment" of the planets can also be considered a confirmation of these ideas - in fact, it is a continuation of the process that led to their formation in the past. At present, when less and less meteorite matter remains in the interplanetary space, this process is much less intense than at the initial stages of planet formation.
At the same time, redistribution of matter and its differentiation took place in the cloud. Under the influence of strong heating, gases escaped from the vicinity of the Sun (mostly the most common in the Universe - hydrogen and helium) and only solid refractory particles remained. From this substance, the Earth, its satellite - the Moon, as well as other planets of the terrestrial group were formed.
During the formation of the planets and later for billions of years, processes of melting, crystallization, oxidation and other physical and chemical processes took place in their depths and on the surface. This led to a significant change in the original composition and structure of the matter from which all the currently existing bodies of the solar system are formed.
Far from the Sun, at the periphery of the cloud, these volatiles 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 planets of the terrestrial group. After all, the volume of the peripheral parts of the cloud was larger, and therefore, the mass of the substance from which the planets far from the Sun were formed was also larger.
Data on the nature and chemical composition of the satellites of the giant planets, obtained in recent years with the help of spacecraft, have become another confirmation of the validity of modern ideas about the origin of the bodies of the solar system. Under conditions when hydrogen and helium, which had gone 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 the matter of the protoplanetary cloud was included in the composition 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 together with the Sun at approximately the same time and were in a plasma state. The unified system was formed during the gravitational interactions that support it at the present time. In the future, the planets, as less energy-intensive systems, quickly switched to the processes of nuclear and molecular fusion, the formation of the crust and information evolution.
The process of cooling, energy loss began from the periphery of the system. Distant planets cooled earlier, matter passed into a molecular state, and the formation of the crust took place. Here, an external information factor in the form of cosmic radiation is connected to the energy conditionality of the processes. Here is what V. I. Vernadsky wrote in 1965: ... in the history of the planet Earth - we continuously, really encounter the energy and material manifestation of the Milky Way - in the form of cosmic matter - meteorites and dust (which is often taken into account by geologists) and material and energy, invisible to the eye and consciously by a person not felt by penetrating cosmic radiations. Another authoritative researcher of the last century, Hess, in 1933 proved that these radiations - streams - constantly bring elementary particles to our planet, into its biosphere, causing air ionization, the importance of which in the energy of the earth's shells is 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 saves 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 an external factor 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 vacuum there should be countless spores - the germs of living matter that come from planets, terrestrial planets, and fall on them again in the course of time. Another version was the transfer of living beings with the help of 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 for any energy-information structure, the solar system is characterized by an increase in the information level of the organization of matter with a drop in the energy potential of the system. Undoubtedly, during the cooling of distant planets, the total energy potential of the solar system was higher than now, so the information level of life of distant planets was, of course, lower than what we are currently observing on Earth.
The growth of the level of information interactions in the solar system increased as the overall energy level of the system fell. The reception of external information by distant planets occurred with the corresponding interaction of the internal energy level of the system and the 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 time, since their cooling rate was higher. At the same time, the high energy potential of the solar system did not allow them to come to equilibrium. All these factors, of course, did not contribute to the information development of these systems. Therefore, their development quickly reached its informational peak, i.e. such an evolutionary state of the system, when dense physical matter that binds energy is no longer able to keep the system from energy decay. This is the state of the energy minimum of the whole system. The processes of disintegration of the higher levels of the organization of matter 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 energy transition into physical vacuum. In the future, the processes of molecular decay turn into nuclear decay, internuclear distances are reduced, and superdense matter is formed. At these stages of decay, the maximum amount of energy is released into the vacuum.
Conclusion
According to modern concepts, 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 the collapse, followed by the formation of a star - the Sun. The substance 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.
The hypothesis of the formation of the solar system from a gas and dust cloud - the nebular hypothesis - was originally proposed in the 18th century by Emmanuel Swedenborg, Immanuel Kant and Pierre-Simon Laplace. In the future, its development took place with the participation of many scientific disciplines, including astronomy, physics, geology and planetary science. With the advent of the space age in the 1950s, and with the discovery of planets outside the solar system (exoplanets) in the 1990s, this model has been subjected to multiple tests and improvements to explain new data and observations.
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(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 - philosopher I. Kant, mathematician and astronomer P. Laplace almost simultaneously formulated the first scientific hypotheses of its origin. It must be said that the hypotheses themselves and the discussion around them and other hypotheses (for example, J. Jeans) were of a completely speculative nature. Only in the 50s. 20th 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 composition of the planets and their atmospheres, does not exist to date. At the same time, modern ideas about the origin of the planetary system quite confidently interpret such issues as the division of the planets into two groups, the main differences in the chemical composition, and the dynamic history of the planetary system.
The formation of planets is very fast; thus, it took about 100,000,000 years to form the Earth. Calculations carried out in recent years have shown that the modern hypothesis of the formation of planets is quite well substantiated.
Clumping of particles
In the formed protoplanetary disk, the coalescence of particles began. Sticking is provided by the structure of the particles. They are carbon, silicate or iron dust particles, on which a snow (water, methane, etc.) "fur coat" grows. The speed of dust grains around the Sun was quite high (this is the Keplerian speed, which is tens of kilometers per second), but the relative velocities are very small, and during collisions the particles stick together into small lumps. material from the site
The appearance of the planets
Very quickly, attractive forces began to play a decisive role in the increase in lumps. This led to the fact that the growth rate of the formed aggregates is proportional to their mass approximately to the fifth power. As a result, one large body remained in each orbit - the future planet and, possibly, several more bodies of much smaller mass, which became its satellites.
planetary bombardment
At the very last stage, it was no longer particles that fell to the Earth and other planets, but bodies of asteroid sizes. They contributed to the compaction of matter, the heating of the bowels and the appearance of traces on their surfaces in the form of seas and craters. This period is
By now, many hypotheses about the origin of the solar system are known, including those proposed independently by the German philosopher I. Kant (1724-1804) and the French mathematician and physicist P. Laplace (1749-1827). The point of view of I. Kant was the evolutionary development of a cold dusty nebula, during which the central massive body, the Sun, first arose, and then the planets were born. P. Laplace considered the original nebula to be gaseous and very hot, in a state of rapid rotation. Compressing under the influence of the force of universal gravitation, the nebula rotated faster and faster due to the law of conservation of angular momentum. Under the action of large centrifugal forces arising from the rapid rotation in the equatorial belt, rings were successively separated from it, turning into planets as a result of cooling and condensation. Thus, according to the theory of P. Laplace, the planets formed before the Sun. Despite such a difference between the two hypotheses under consideration, they both come from the same idea - the solar system arose as a result of the natural development of the nebula. And so this idea is sometimes called the Kant-Laplace hypothesis. However, this idea had to be abandoned due to many mathematical contradictions, and was replaced by several "tidal theories".
The most famous theory was put forward by Sir James Jeans, a famous popularizer of astronomy in the years between the First and Second World Wars. (He was also a leading astrophysicist, and it was only towards the end of his career that he turned to writing books for beginners.)
Rice. 1. Tidal theory of Jeans. A star passes near the Sun, stretching
from it a substance (Fig. A and B); planets are formed from this material (Fig. C)
According to Jeans, the planetary matter was "pulled out" from the Sun by a nearby star, and then disintegrated into separate parts, forming planets. At the same time, the largest planets (Saturn and Jupiter) are located in the center of the planetary system, where there was once a thickened part of the cigar-shaped nebula.
If this were indeed the case, then planetary systems would be extremely rare, since the stars are separated from each other by enormous distances, and it is quite possible that our planetary system could claim to be the only one in the Galaxy. But mathematicians attacked again, and eventually tidal theory joined gaseous Laplace rings in the wastebasket of science. one
2. Modern theory of the origin of the solar system
According to modern concepts, the planets of the solar system formed from a cold gas and dust cloud that surrounded the Sun billions of years ago. This point of view is most consistently reflected in the hypothesis of the Russian scientist, Academician O.Yu. Schmidt (1891-1956), who showed that the problems of cosmology can be solved by the concerted efforts of astronomy and the Earth sciences, primarily geography, geology, and geochemistry. At the heart of the hypothesis O.Yu. Schmidt is the idea of the formation of planets by combining solids and dust particles. The gas and dust cloud that emerged near the Sun initially consisted of 98% hydrogen and helium. The remaining elements condensed into dust particles. The chaotic movement of gas in the cloud quickly ceased: it was replaced by the calm movement of the cloud around the Sun.
Dust particles are concentrated in the central plane, forming a layer of increased density. When the density of the layer reached a certain critical value, its own gravitation began to "compete" with the gravitation of the Sun. The dust layer turned out to be unstable and disintegrated into separate dust clots. Colliding with each other, they formed many continuous dense bodies. The largest of them acquired almost circular orbits and in their growth began to overtake other bodies, becoming potential embryos of future planets. Like more massive bodies, neoplasms attached to themselves the remaining matter of the gas and dust cloud. In the end, nine large planets formed, the movement of which in orbits remains stable for billions of years.
Taking into account the physical characteristics, all the planets are divided into two groups. One of them consists of relatively small terrestrial planets - Mercury, Venus, Earth and Mars. Their substance is distinguished by a relatively high density: on average, about 5.5 g / cm 3, which is 5.5 times higher than the density of water. The other group is made up of the giant planets: Jupiter, Saturn, Uranus and Neptune. These planets have huge masses. Thus, the mass of Uranus is equal to 15 Earth masses, and Jupiter is 318. The giant planets consist mainly of hydrogen and helium, and the average density of their matter is close to the density of water. Apparently, these planets do not have a solid surface similar to the surface of the terrestrial planets. A special place is occupied by the ninth planet - Pluto, discovered in March 1930. In size, it is closer to the terrestrial planets. Not so long ago it was discovered that Pluto is a double planet: it consists of a central body and a very large satellite. Both celestial bodies revolve around a common center of mass.
In the process of planet formation, their division into two groups is due to the fact that in parts of the cloud far from the Sun, the temperature was low and all substances, except hydrogen and helium, formed solid particles. Among them, methane, ammonia and water prevailed, which determined the composition of Uranus and Neptune. The composition of the most massive planets - Jupiter and Saturn, in addition, turned out to be a significant amount of gases. In the region of the terrestrial planets, the temperature was much higher, and all volatile substances (including methane and ammonia) remained in a gaseous state, and, therefore, were not included in the composition of the planets. The planets of this group were formed mainly from silicates and metals. 2
The first geocentric model of the universe was proposed by the mathematician Alexander Ptolemy in 150 AD. His model was accepted by Christian theologians and, in fact, canonized - elevated to the rank of absolute truths. According to this model, the stationary Earth occupies the central position in the Universe, and the Sun, Moon, planets and stars revolve around it in different spheres. However, similar ideas were put forward much earlier by the ancient Greek philosopher Aristotle (384–322 BC). He argued that the Earth is the center of the universe. And these ideas of Aristotle paralyzed the minds of thinkers for one and a half thousand years, which was largely facilitated by the Christian Church, which canonized them.
Nicolaus Copernicus was the first who was able to refute Claudius Ptolemy and scientifically prove that the Earth is not the center of the Universe. He placed the Sun at the center of the universe and created a heliocentric model of the universe. Fearing the persecution of the church, Copernicus gave his work to print shortly before his death. His system was published after the death of the great scientist. However, the church anathematized him and the book and officially banned it.
A supporter of the Copernican doctrine was Galileo Gallilei, who first used a telescope to study the starry sky and saw that the Universe is much larger than previously thought, and that there are satellites around the planets, which, like the planets around the Sun, revolve around their planets. Gallileo experimentally studied the laws of motion. But the church staged a persecution of the scientist and inflicted on him the court of the Inquisition. Galileo was afraid of torture and the fate of Giordano Bruno and officially renounced his teachings. But leaving the court, he allegedly muttered: "And yet it (the Earth) is spinning."
Giordano Bruno went further than Copernicus and Galileo: he created the doctrine that the stars are like the Sun, that planets also move in orbits around the stars. Moreover, he argued that there are many inhabited worlds in the Universe, that besides man, there are other thinking beings in the Universe. For this, Giordano was condemned by the Christian Church and burned at the stake, and his teaching was anathematized.
Giordano Bruno had an extraordinary memory, they said that he was able to recite by heart 26 thousand articles of canon and civil law, 6 thousand passages from the Bible and a thousand poems by Ovid. Thanks to this gift, he was received at the courts of the dukes and kings of Europe, where he discussed mathematics, astronomy, and philosophy with great pleasure. Bruno advocated a religion of love for all people without exception. He charmed with his oratorical talent and knowledge. Bruno traveled all over Europe. King Henry III made him extraordinary professor at the Sorbonne.
The physical studies of Descartes relate mainly to mechanics, optics, and the general structure of the universe. He believed that the Universe is entirely filled with moving matter and is self-sufficient in its manifestations. Descartes did not recognize indivisible atoms and emptiness and sharply criticized the atomists, both ancient and contemporary. In addition to ordinary matter, he singled out an extensive class of invisible subtle matters, with the help of which he tried to explain the action of heat, gravity, electricity and magnetism. Descartes introduced the concept of momentum, formulated the law of conservation of momentum. Studied the laws of light propagation - reflection and refraction. He owns the idea of ether as a carrier of light, the explanation of the rainbow. Descartes derived the law of refraction of light at the boundary of two different media, which made it possible to improve optical instruments, including telescopes.
Hypotheses about the origin of the solar system
Many researchers have tried to solve the problem of the origin of the solar system. The first scientific hypothesis for the formation of the solar system was proposed in 1644 by Rene Descartes. According to her, the solar system was formed from the primary nebula, which had the shape of a disk and consisted of gas and dust. In 1745, Buffon suggested that the matter from which the planets were formed was torn away from the Sun by some large comet or other star passing too close. Philosopher I. Kant and mathematician P. Laplace at the end of the 19th century proposed their hypotheses, the essence of which is that stars and planets were formed from cosmic dust by gradual compression of the original gas-dust nebula.
The hypotheses of Kant and Laplace differed. Kant proceeded from the evolutionary development of a cold dusty nebula, during which the central massive body first arose - the future Sun, and then the planets. According to Laplace, the original nebula was gaseous and hot and rotated rapidly. Compressing under the influence of the force of universal gravitation, it rotated faster and faster. Due to centrifugal forces in the equatorial belt, rings were successively separated from it. Subsequently, these rings condensed, and the planets turned out. According to Laplace, the planets formed before the Sun. Despite the significant difference between these hypotheses, they are combined into one: the solar system arose as a result of the natural development of a gas-dust nebula as a result of condensation. The hypothesis of Kant and Laplace failed to cope with the unusual distribution of the angular momentum of the solar system between the central body - the Sun and the planets. The angular momentum is the "reserve of rotation" of the system. This rotation is made up of the orbital motion of the planets and rotation around their axes of the Sun and planets. The Jeans hypothesis (early 20th century) explains the formation of the solar system by chance, considering it to be the rarest phenomenon. The substance from which the planets later formed was ejected from a rather "old" Sun during the accidental passage of a certain star near it. Thanks to tidal forces acting from the side of the incident star, a jet of gas was ejected from the surface layers of the Sun. This jet remained in the sphere of gravity of the Sun. In the future, the jet condensed and turned out to be planets. If Jeans' hypothesis were correct, then there would be much fewer planetary systems in the Galaxy. Therefore, the Jeans hypothesis should be rejected. In addition, it is also unable to explain the distribution of angular momentum in the solar system. Lyman Spitzer's calculations showed that the substance of a jet ejected from a star should dissipate in the surrounding space, and its condensation will not occur. The latest version of the Jeans hypothesis, developed by Woolfson, suggests that the gas jet from which the planets were formed was ejected not from the Sun, but from a huge loose star flying past (10 times the radius of the current Earth's orbit) and a relatively small mass. Calculations show that if planetary systems were formed in this way, then there would be very few of them in the Galaxy (one planetary system per 100,000 stars). The discoveries of planets around many stars finally buried the Jeans-Wulfson hypothesis.
It turned out that the lion's share of the angular momentum of the solar system is concentrated in the orbital motion of the giant planets Jupiter and Saturn. From the point of view of the Laplace hypothesis, this is completely incomprehensible. When a ring separated from a rapidly rotating nebula, the layers of the nebula, from which the Sun subsequently condensed, had, per unit mass, approximately the same angular momentum as the substance of the separated ring. Thus, the total total angular momentum of the planets must be much less than that of the "proto-sun". Therefore, the main conclusion from the hypothesis of Kant and Laplace contradicts the actual distribution of angular momentum between the Sun and the planets.
H. Alven, saving the hypothesis of Kant and Laplace, suggested that once the Sun had a very strong electromagnetic field. The nebula surrounding the star consisted of neutral atoms. Under the action of radiation and collisions, the atoms became ionized. The ions fell into traps from magnetic field lines and were carried away after the rotating luminary. Gradually, the Sun lost its rotational moment, transferring it to a gas cloud. The weakness of the proposed hypothesis was that the atoms of the lightest elements should have been ionized closer to the Sun, while the atoms of heavy elements - further. This means that the planets closest to the Sun would have to consist of hydrogen and helium, and the more distant planets of iron and nickel. The facts say otherwise. To overcome this difficulty, astronomer F. Hoyle suggested that the Sun originated in the depths of the nebula. It rotated rapidly, and the nebula became more and more flat, turning into a disk. Gradually, the disk also began to accelerate, and the Sun slowed down. The angular momentum in this case passed to the disk. Then planets formed in the disk. But it is impossible to imagine the deceleration of the Sun without the intervention of some third force. The difficulty and contradiction of Hoyle's hypothesis is that it is not easy to imagine how the excess hydrogen and helium could have "sorted out" in the original gaseous disk from which the planets formed, since the chemical composition of the planets is clearly different from that of the Sun; secondly, it is not entirely clear how the light gases left the solar system (the evaporation process proposed by Hoyle runs into considerable difficulties). The main difficulty of Hoyle's hypothesis is the requirement for a too strong magnetic field for the "proto-sun", which sharply contradicts modern astrophysical concepts.
Otto Yulievich Schmidt (1891-1956) in 1937. Portrait of Nesterov. Photo from the site: http://territa.ru/ |
In 1944, O. Yu. Schmidt proposed a hypothesis according to which the planetary system was formed from matter captured from a gas-dust nebula through which the Sun once passed, which even then had an almost "modern" appearance. There is no difficulty with torque in this hypothesis. Beginning in 1961, this hypothesis was developed by the English cosmogonist Littleton. It should be noted that in order for the Sun to capture a sufficient amount of matter, its velocity relative to the nebula must be very small, of the order of one hundred meters per second. Simply put, the Sun must be stuck in this cloud and move with it. In this hypothesis, the formation of planets is not associated with the process of star formation. But this hypothesis does not answer the question: where, when and how did the Sun form? Modern cosmic physics assumes (although it is not clear why?) that a gas, when its mass and density reaches a certain value, under the influence of its own attraction is compressed and compacted, forming a cold gas ball. The assumption of spontaneous compression of the gas cloud is very frivolous. Such compression is not observed anywhere in nature, and cannot be. But this hypothesis asserts that, as a result of continued compression, the temperature of the gas ball must rise, since the potential energy of particles in the field of attraction of the gas ball supposedly decreases as they approach the center. |
The temperature of the cloud at that time was -220°C. At first, the cloud was homogeneous, and then clumps began to appear in it ( but why, the hypothesis does not explain; A. G.), mainly due to gravitational contraction ( but what compresses gas and dust? A. G.). As a result, the matter in the cloud began to heat up and differentiate by separating chemical elements and their compounds in the gravity field ( but what created this gravity field? A. G.). So, the astrophysicist L. Spitzer showed that if the mass of a cloud is 10–20 thousand times greater than the mass of the Sun, and the density of matter in it is more than 20 atoms per cubic cm, then such a cloud begins to shrink under the influence of its own mass. ( But such dense clouds have not been found in the Galaxy.).
But how does such a cloud form by itself? How does it compress to such pressure? Gas can only be compressed when cooled. In this case, it first turns into a liquid, and then goes into a solid phase. When such a solid is heated, it evaporates and turns back into a cloud. So, for example, comets behave as they approach the Sun. They evaporate and lose mass. Astrophysicists suggest that the Protosun with a protoplanetary cloud formed about 6 billion years ago. The matter in the protoplanetary cloud was distributed evenly at first, and then began to cluster in separate areas, from which stars later formed. But this hypothesis does not explain in any way why clusters and clusters began to form in a homogeneous protoplanetary cloud. But if we assume that, contrary to the laws of physics, the gas cloud became a ball, and the ball shrunk into a star, then it is impossible to explain the energy source of this star, which allows it to radiate particles and electromagnetic waves. After all, before the thermonuclear reaction begins, the temperature in the bowels of the cloud-star must rise to at least 20 million degrees Kelvin. If another non-gravitational source of energy does not appear, then the process of radiation as a result of star compression will quickly lead to the exhaustion of energy, and such a star will evaporate and again turn into a loose cloud, but will not shine. However, the compression process, contrary to all the laws of physics, leads to the fact that the central regions of the star are heated to very high temperatures, the pressure in them becomes so high that a thermonuclear fusion reaction of hydrogen nuclei from helium nuclei begins. In this case, a lot of energy is released, which heats up the gas ball. Thermonuclear fusion requires a temperature of several tens of millions of degrees. The period during which a star, shrinking from a gas cloud, reaches a state when thermonuclear reactions begin to operate in its central regions is called the contraction period. After all the hydrogen in the star turns into helium, it will reach the stage of a red giant - it will expand. ( It is completely incomprehensible why, when cooling, the star will suddenly expand, and not contract.). Further, the hypothesis states that now the star, which already consists of helium, will shrink. From this contraction, the temperature at its center will increase to 100 million degrees or more. ( A very frivolous assumption!) Then another thermonuclear reaction will begin - the formation of carbon nuclei from helium nuclei. This reaction will also be accompanied by mass loss and release of radiation energy. The temperature of the star will rise again, causing the compression of the star to stop. This hypothesis of the origin of stars from gaseous matter meets with serious difficulties: there is too little hydrogen in the Galaxy, only about 2% of its total mass. If stars really formed from gas, then star formation in the Galaxy would have to end quickly. Meanwhile, in galaxies, including ours, new young stars appear - blue giants and supergiants.
The nebular hypotheses of Kant and Laplace have a significant drawback: they do not explain why the Sun and the planets distributed the momentum (momentum of momentum) so unevenly among themselves: the Sun accounts for about 2% of the momentum, and the planets account for about 98%, although the total mass of all the planets is 750 times less than the mass of the Sun.
Schmidt proceeds in his hypothesis from the different origin of the Sun and the planets. But to be consistent to the end, one would have to assume that not only the Sun and the planets arose separately, but all the planets also have a separate origin, since they also have a different specific moment of momentum (amount of motion per unit mass). If the specific moment of momentum of the Earth is taken as 1, then the planets of the solar system will have the following specific moments of momentum (Levin B.S. Origin of the Earth and planets):
Those parts of the protoplanetary gas-dust cloud, which once allegedly met with the Sun, were captured by it into its orbit. And these parts of the cloud, if only the latter did not rotate (if the cloud rotated, it, apparently, should have dissipated even before meeting the Sun under the influence of centrifugal force in interstellar space), should have absolutely the same specific moment of momentum, since they Before capture, they moved in the same direction and had the same speed. And the planets, too, would have to have the same specific angular momentum if they had come about according to Schmidt's hypothesis.
The third part of the satellites of the planets of the solar system has the direction of circulation opposite to the solar system. This is one of the largest satellites of Neptune Triton in the solar system, then Saturn's satellite Phoebe, four outer small satellites of Jupiter and five satellites of Uranus. According to Schmidt's hypothesis, all the bodies of the solar system must rotate in the same direction and in the same plane.
Half of the planets of the solar system have large inclinations of the equatorial plane to the plane of their orbit (more than 23° for the Earth, Mars, Saturn and Neptune, and for Uranus the inclination is 98°). If the planets were formed from one cloud, they would have the same inclination of their orbits to the plane of the equator of the Sun and would not have the inclination of the planes of their equators to the plane of their orbits.
If stars really formed from gas, then in the Galaxy one could already detect noticeably compacted gas clouds, gradually turning into stars. But there are no such clusters in stellar associations. There are no transitional stages from gas clouds to stars. But there are regions in the Galaxy from which "finished" stars are ejected, and in the Metagalaxy - even whole "finished" galaxies.
According to the laws of mechanics, a gas-dust cloud with a significant rotational moment simply cannot exist and cannot turn into a single slowly rotating star like the Sun. The stratification of such a cloud rotating by itself into rings is also impossible. It is no coincidence that the rotation of stars in the Galaxy around the center occurs at an order of magnitude greater speed than the rotation of the gaseous disk of the Galaxy, which, by the way, consists not of rings, but of sleeves. Thus, the existing hypotheses of the formation of stars and planets, except for the hypothesis of V. Ambartsumyan, are very far from the truth.
Viktor Amazaspovich Ambartsumian and Jan Hendrik Oort in Byurakan (Armenia) in 1966. Photo from the website: http://www.ambartsumian.ru/Despite the fact that scientists are building fairly accurate models of black holes and neutron stars, there is no theory that could explain the origin of the solar system and all of its currently known features. The theory of the origin of the solar system must explain all known facts and must not contradict the laws of dynamics and modern physics. In addition, consequences must be derived from this theory that would be confirmed by future discoveries: the theory must not only explain, but also predict. All the hypotheses put forward so far have been refuted or remained unproven with a rigorous application of physical theory.
The oldest rocks of the earth's crust solidified 4 billion years ago. It is believed that the Earth itself was formed 4.6 billion years ago. The measurement of the time that has passed since the Earth has cooled is based on traces of lead, helium and other elements left in the rocks after the decay of radioactive elements. The study of meteorites and samples of lunar soil shows that their age in the solid state does not exceed the age of the Earth. It is assumed that the entire solar system has the same age.
A satisfactory theory of the origin of the solar system must first of all take into account the existence of planets, satellites, asteroids and comets. It must explain the location of the planets, the shape of their orbits, the inclination of the axes and the speed of rotation and movement along the orbit, it must explain the distribution of the angular momentum among the planets. So far, there is no such theory, and we can only talk about creating hypotheses.
