The evolution and structure of galaxies briefly. Structure and evolution of the galaxy. Local group of galaxies. Milky way galaxy
Submitting your good work to the knowledge base is easy. Use the form below
Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.
Posted on http://www.allbest.ru/
Non-state educational institution
higher professional education
ABSTRACT
according to the concept of modern natural science
on the topic: “Evolution and structure of the Galaxy”
Moscow 2013
Introduction
1. Evolution of galaxies
2. Structure of galaxies
3. The structure of our galaxy (Milky Way)
Conclusion
List of used literature
Introduction
At the moment, there is no satisfactory theory of the origin and evolution of galaxies. There are several competing hypotheses to explain this phenomenon, but each has its own serious problems. According to the inflation hypothesis, after the appearance of the first stars in the Universe, the process of their gravitational unification into clusters and then into galaxies began. Recently, this theory has been called into question. Modern telescopes are able to “look” so far that they see objects that existed approximately 400 thousand years after the Big Bang. It was discovered that fully formed galaxies already existed at that time. It is assumed that too little time passed between the emergence of the first stars and the above-mentioned period of development of the Universe, and according to the Big Bang theory, galaxies simply would not have had time to form.
Another common hypothesis is that quantum vibrations constantly occur in a vacuum. They also occurred at the very beginning of the existence of the Universe, when the process of inflationary expansion of the Universe, expansion at superluminal speed, was underway. This means that the quantum fluctuations themselves expanded (from the Latin fluctuatio - oscillation), and to sizes that were perhaps many, many times larger than their initial size. Those of them that existed at the moment of the cessation of inflation remained “inflated” and thus turned out to be the first gravitating inhomogeneities in the Universe. It turns out that matter had about 400 thousand years to undergo gravitational compression around these irregularities and form gas nebulae. And then the process of the emergence of stars and the transformation of nebulae into galaxies began.
1. Evolution of galaxies
The formation of galaxies is considered as a natural stage in the evolution of the Universe, occurring under the influence of gravitational forces. Apparently, about 14 billion years ago, the separation of protoclusters began in the primary substance (proto from Greek - first). In protoclusters, groups of galaxies were separated in the course of various dynamic processes. The variety of galaxy shapes is associated with the variety of initial conditions for the formation of galaxies. The contraction of the galaxy lasts about 3 billion years. During this time, the gas cloud transforms into a star system. Stars are formed by the gravitational compression of clouds of gas. When the center of the compressed cloud reaches densities and temperatures sufficient for efficient flow of thermonuclear reactions, a star is born. In the depths of massive stars, thermonuclear fusion of chemical elements heavier than helium occurs. These elements enter the primary hydrogen-helium environment during stellar explosions or during the quiet outflow of matter with stars. Elements heavier than iron are formed during enormous supernova explosions. Thus, first-generation stars enrich the primary gas with chemical elements heavier than helium. These stars are the oldest and consist of hydrogen, helium and very small amounts of heavy elements. In second-generation stars, the admixture of heavy elements is more noticeable, since they are formed from a primary gas already enriched with heavy elements. The process of star birth occurs with the ongoing compression of the galaxy, so the formation of stars occurs closer and closer to the center of the system, and the closer to the center, the more heavy elements there should be in the stars. This conclusion agrees well with data on the abundance of chemical elements in stars in the halo of our Galaxy and elliptical galaxies. In a rotating galaxy, the stars of the future halo form at an earlier stage of contraction, when the rotation has not yet affected the overall shape of the galaxy.
Evidence of this era in our Galaxy are spherical star clusters. When the compression of the protogalaxy stops, the kinetic energy of the resulting disk stars is equal to the energy of the collective gravitational interaction. At this time, conditions are created for the formation of a spiral structure, and the birth of stars occurs in the spiral branches, in which the gas is quite dense. These are third generation stars. These include our Sun. The reserves of interstellar gas are gradually depleted, and the birth of stars becomes less intense. In a few billion years, when all gas reserves are exhausted, the spiral galaxy will turn into a lenticular galaxy, consisting of faint red stars. Elliptical galaxies are already at this stage: all the gas in them was consumed 10-15 billion years ago. The age of galaxies is approximately the age of the Universe. One of the secrets of astronomy remains the question of what the nuclei of galaxies are. A very important discovery was that some galactic nuclei are active. This discovery was unexpected. Previously, it was believed that the galactic core was nothing more than a cluster of hundreds of millions of stars. It turned out that both the optical and radio emission of some galactic nuclei can change over several months. This means that within a short time, a huge amount of energy is released from the nuclei, hundreds of times greater than that released during a supernova explosion. Such nuclei are called “active”, and the processes occurring in them are called “activity”. In 1963, objects of a new type were discovered located beyond the boundaries of our galaxy. These objects have a star-shaped appearance. Over time, they found out that their luminosity is many tens of times greater than the luminosity of galaxies! The most amazing thing is that their brightness changes. The power of their radiation is thousands of times greater than the power of active nuclei. These objects were called quasars. It is now believed that the nuclei of some galaxies are quasars.
Scientists began to take a serious approach to the problem of galaxy evolution in the mid-1940s. These years were marked by important discoveries in stellar astronomy. It was possible to find out that among star clusters, open and globular, there are young and old, and scientists were even able to estimate their age. It was necessary to carry out a kind of population census in galaxies of different types and compare the results. In which galaxies (elliptical or spiral), in which classes of galaxies are younger or older stars predominant. Such a study would give a clear indication of the direction of evolution of galaxies and would make it possible to clarify the evolutionary meaning of the Hubble classification of galaxies. But first, astronomers needed to figure out the numerical relationship between different types of galaxies. Direct study of photographs taken at the Mount Wilson Observatory allowed Hubble to obtain the following results: elliptical galaxies - 23%, spiral galaxies - 59%, barred spirals - 15%, irregular - 3%.
Astrophysicist Edwin Powell Hubble proposed an interesting classification of galaxies in 1926 and improved it in 1936. This classification is called the “Hubble Tuning Fork.” Until his death in 1953. Hubble improved his system, and after his death, this was done by the American astronomer Allan Rex Samndage, who in 1961 introduced significant innovations to the Hubble system. star dark matter galaxy Milky Way
However, in 1948, astronomer Yuri Nikolaevich Efremov processed data from the galaxy catalog of the American astronomer Harlow Shapley and the NASA Research Center. Ames and came to the following conclusions: elliptical galaxies are on average 4 magnitudes fainter than spiral galaxies in absolute magnitude. Among them there are many dwarf galaxies. If we take this circumstance into account and recalculate the number of galaxies per unit volume, it turns out that there are approximately 100 times more elliptical galaxies than spiral ones. Most spiral galaxies are giant galaxies, most elliptical galaxies are dwarf galaxies. Of course, among both there is a certain spread in size; there are elliptical giant galaxies and spiral dwarfs, but there are very few of both. In 1947, H. Shapley drew attention to the fact that the number of bright supergiants gradually decreases as we move from irregular galaxies to spiral ones, and then to elliptical ones. It turned out that it was the irregular galaxies and galaxies with highly branched branches that were young. H. Shapley then expressed the idea that the transition of galaxies from one class to another does not necessarily occur. It is possible that the galaxies were all formed as we see them, and then only slowly evolved in the direction of smoothing and rounding their shapes. There is probably no unidirectional change in galaxies. H. Shapley drew attention to another important circumstance. Double galaxies are not the result of one galaxy colliding and being captured by another. Spiral galaxies often coexist in such pairs with elliptical ones. Such galactic pairs, in all likelihood, arose together. In this case, it is impossible to assume that they have gone through a significantly different development path. In 1949, Soviet astronomer Boris Vasilyevich Kukarkin drew attention to the existence of not only paired galaxies, but also clusters of galaxies. Meanwhile, the age of a galaxy cluster, judging by celestial mechanics data, cannot exceed 10-12 billion years. Thus, it turned out that galaxies of different shapes formed almost simultaneously in the Metagalaxy. This means that the transition of each galaxy during its existence from one type to another is completely unnecessary.
2. Structure of galaxies
The galamctic (ancient Greek GblboYabt - Milky Way) is a gravitationally bound system of stars, interstellar gas, dust and dark matter. All objects within galaxies participate in motion relative to a common center of mass. Galaxies are extremely distant objects; the distance to the nearest ones is usually measured in megaparsecs, and to distant ones - in units of redshift z. It is precisely because of their distance that only three of them can be distinguished in the sky with the naked eye: the Andromeda nebula (visible in the northern hemisphere), the Large and Small Magellanic Clouds (visible in the southern hemisphere). It was not possible to resolve images of galaxies down to individual stars until the beginning of the 20th century. By the early 1990s, there were no more than 30 galaxies in which individual stars could be seen, and all of them were part of the Local Group. After the launch of the Hubble Space Telescope and the commissioning of 10-meter ground-based telescopes, the number of galaxies in which it was possible to distinguish individual stars increased sharply. One of the unsolved problems in the structure of galaxies is dark matter, which manifests itself only in gravitational interaction. It can make up up to 90% of the total mass of the galaxy, or it can be completely absent, as in dwarf galaxies.
The galaxy consists of a disk, a halo and a corona.
1. Halo (spherical component of the Galaxy). Its stars are concentrated towards the center of the galaxy, and the density of matter, high in the center of the galaxy, falls quite quickly with distance from it.
2. The bulge is the central, densest part of the halo within several thousand light years from the center of the Galaxy.
3. Stellar disk (flat component of the Galaxy). It looks like two plates folded at the edges. The concentration of stars in the disk is much greater than in the halo. The stars inside the disk move in circular trajectories around the center of the Galaxy. The Sun is located in the stellar disk between the spiral arms.
The central, most compact region of the Galaxy is called the core. The core has a high concentration of stars, with thousands of stars in every cubic parsec. At the center of almost every galaxy there is a very massive body - black hole - with such powerful gravity that its density is equal to or greater than the density of atomic nuclei. In fact, each black hole is a small in space, but in terms of mass it is simply a monstrous, furiously rotating core. The name “black hole” is clearly unfortunate, since it is not a hole at all, but a very dense body with powerful gravity - such that even light photons cannot escape from it. And when a black hole accumulates too much mass and kinetic energy of rotation, the balance of mass and kinetic energy is disturbed in it, and then it expels fragments from itself, which (the most massive) become small black holes of the second order, smaller fragments become future stars, when they gather large hydrogen atmospheres from galactic clouds, and small fragments become planets, when the collected hydrogen is not enough to start thermonuclear fusion. I think that galaxies are formed from massive black holes; moreover, the cosmic circulation of matter and energy takes place in galaxies. First, the black hole absorbs matter scattered in the Metagalaxy: at this time, thanks to its gravity, it acts as a “dust and gas sucker.” Hydrogen scattered in the Metagalaxy is concentrated around the black hole, and a spherical accumulation of gas and dust is formed. The rotation of the black hole entrains gas and dust, causing the spherical cloud to flatten, forming a central core and arms. Having accumulated a critical mass, the black hole in the center of the gas and dust cloud begins to eject fragments (fragmentoids), which break away from it with high acceleration, sufficient to be thrown into a circular orbit around the central black hole. In orbit, interacting with gas and dust clouds, these fragmentoids gravitationally capture gas and dust. Large fragmentoids become stars. Black holes, with their gravity, pull in cosmic dust and gas, which, falling onto such holes, become very hot and emit X-rays. When the amount of matter around a black hole becomes scarce, its glow decreases sharply. This is why some galaxies have a bright glow at their center, while others do not. Black holes are like cosmic “killers”: their gravity attracts even photons and radio waves, which is why the black hole itself does not emit and looks like a completely black body. But, probably, periodically the gravitational balance inside black holes is disrupted, and they begin to eject clumps of superdense matter with strong gravity, under the influence of which these clumps take on a spherical shape and begin to attract dust and gas from the surrounding space. From the captured substance, solid, liquid and gaseous shells are formed on these bodies. The more massive the clot of superdense matter (fragmentoid) ejected by the black hole was, the more dust and gas it will collect from the surrounding space (if, of course, this substance is present in the surrounding space). Almost all the molecular matter of the interstellar medium is concentrated in the annular region of the galactic disk (3-7 kpc). The visible radiation from the central regions of the Galaxy is completely hidden from us by thick layers of absorbing matter.
There are three types of galaxies: spiral, elliptical and irregular. Spiral galaxies have a well-defined disk, arms, and halos. At the center is a dense cluster of stars and interstellar matter, and at the very center is a black hole. The arms in spiral galaxies extend from their center and twist to the right or left depending on the rotation of the core and the black hole (more precisely, a superdense body) at its center. At the center of the galactic disk is a spherical condensation called a bulge. The number of branches (arms) can be different: 1, 2, 3,... but most often there are galaxies with only two branches. In galaxies, the halo includes stars and very rarefied gaseous matter that is not included in the spirals or disk. We live in a spiral galaxy called the Milky Way, and on clear days our Galaxy is clearly visible in the night sky as a wide, whitish stripe across the sky. Our Galaxy is visible to us in profile. Globular clusters in the center of galaxies are practically independent of the position of the galactic disk. The arms of galaxies contain a relatively small part of all stars, but almost all hot stars of high luminosity are concentrated in them. Stars of this type are considered young by astronomers, so the spiral arms of galaxies can be considered the place of star formation. Elliptical galaxies are often found in dense clusters of spiral galaxies. They have the shape of an ellipsoid or a ball, and spherical ones are usually larger than ellipsoidal ones. The rotation speed of ellipsoidal galaxies is less than that of spiral galaxies, which is why their disk is not formed. Such galaxies are usually saturated with globular clusters of stars. Elliptical galaxies, astronomers believe, consist of old stars and are almost completely devoid of gas. Irregular galaxies typically have low mass and volume and contain few stars. As a rule, they are satellites of spiral galaxies. They usually have very few globular clusters of stars. Examples of such galaxies are the satellites of the Milky Way - the Large and Small Magellanic clouds. But among the irregular galaxies there are also small elliptical galaxies.
3. The structure of our galaxy (Milky Way)
Milky Way - from lat. via lactea "milk road"
In the Soviet astronomical school, the Milky Way was simply called “our Galaxy” or “the Milky Way system”; The phrase "Milky Way" was used to refer to the visible stars that optically constitute the Milky Way to an observer.
The diameter of the Galaxy is about 30 thousand parsecs (about 100,000 light years, 1 quintillion kilometers) with an estimated average thickness of about 1000 light years. The galaxy contains, according to the lowest estimate, about 200 billion stars (modern estimates range from 200 to 400 billion). The bulk of stars are located in the shape of a flat disk. As of January 2009, the mass of the Galaxy is estimated at 3·10 12 solar masses, or 6·10 42 kg. Most of the Galaxy's mass is contained not in stars and interstellar gas, but in a non-luminous halo of dark matter. It wasn't until the 1980s that astronomers suggested that the Milky Way was a barred spiral galaxy rather than a regular spiral galaxy. This assumption was confirmed in 2005 by the Lyman Spitzer Space Telescope, which showed that the central bar of our galaxy is larger than previously thought. Young stars and star clusters, whose age does not exceed several billion years, are concentrated near the plane of the disk. They form the so-called flat component. Among them there are many bright and hot stars. The gas in the Galaxy's disk is also concentrated mainly near its plane. It is distributed unevenly, forming numerous gas clouds - from giant clouds of heterogeneous structure, over several thousand light years in extent, to small clouds no more than a parsec in size. In the middle part of the Galaxy there is a thickening called a bulge, which is about 8 thousand parsecs in diameter. The center of the galactic core is located in the constellation Sagittarius. The distance from the Sun to the center of the Galaxy is 8.5 kiloparsecs (2.62·10 17 km, or 27,700 light years). In the center of the Galaxy, apparently, there is a supermassive black hole around which, presumably, a black hole of average mass and an orbital period of about 100 years and several thousand relatively small ones rotate. Their combined gravitational effect on neighboring stars causes the latter to move along unusual trajectories. There is an assumption that most galaxies have supermassive black holes at their core. The central regions of the Galaxy are characterized by a strong concentration of stars: each cubic parsec near the center contains many thousands of them. The distances between stars are tens and hundreds of times smaller than in the vicinity of the Sun. As with most other galaxies, the distribution of mass in the Milky Way is such that the orbital speed of most stars in this Galaxy does not depend significantly on their distance from the center. Further from the central bridge to the outer circle, the usual speed of rotation of stars is 210-240 km/s. Thus, such a distribution of speed, not observed in the solar system, where different orbits have different speeds of rotation, is one of the prerequisites for the existence of dark matter. The length of the galactic bar is believed to be about 27,000 light years. This bar passes through the center of the galaxy at an angle of 44 ± 10 degrees to the line between our Sun and the center of the galaxy. It consists primarily of red stars, which are considered very old. The jumper is surrounded by a ring called the "Five Kiloparsec Ring". This ring contains most of the Galaxy's molecular hydrogen and is an active star-forming region in our Galaxy. If observed from the Andromeda Galaxy, the galactic bar of the Milky Way would be a bright part of it.
Our galaxy belongs to the class of spiral galaxies, which means that the Galaxy has spiral arms located in the plane of the disk. The disk is immersed in a spherical halo, and around it is a spherical corona. The solar system is located at a distance of 8.5 thousand parsecs from the galactic center, near the galactic plane (displacement towards North Pole The galaxy is only 10 parsecs away), on the inner edge of an arm called the Orion Arm. This arrangement does not make it possible to observe the shape of the sleeves visually. New data from observations of molecular gas (CO) suggest that our Galaxy has two arms, starting at a bar in the inner part of the Galaxy. In addition, there are a couple more sleeves in the inner part. These arms then transform into a four-arm structure observed in the neutral hydrogen line in the outer parts of the Galaxy. Majority celestial bodies combined into various rotating systems. Thus, the Moon revolves around the Earth, the satellites of the giant planets form their own systems, rich in bodies. For more high level, The Earth and other planets revolve around the Sun. A natural question arose: is the Sun also part of an even larger system? The first systematic study of this issue was carried out in the 18th century by the English astronomer William Herschel. He counted the number of stars in different areas of the sky and discovered that there was big circle(later it was called the galactic equator), which divides the sky into two equal parts and on which the number of stars is greatest. In addition, the closer the part of the sky is to this circle, the more stars there are. Finally it was discovered that it was on this circle that the Milky Way was located. Thanks to this, Herschel guessed that all the stars we observed form a giant star system, which is flattened towards the galactic equator. At first it was assumed that all objects in the Universe are parts of our Galaxy, although Kant also suggested that some nebulae could be galaxies similar to the Milky Way. As early as 1920, the question of the existence of extragalactic objects caused debate (for example, the famous Great Debate between Harlow Shapley and Heber Curtis; the former defended the uniqueness of our Galaxy). Kant's hypothesis was finally proven only in the 1920s, when Edwin Hubble was able to measure the distance to some spiral nebulae and show that, due to their distance, they cannot be part of the Galaxy.
Conclusion
There is a cycle of matter in the Universe, the essence of which is the scattering of matter by supermassive black holes, explosions of novae and supernovae, and then the collection of scattered matter by planets, stars and black holes using their gravity. There was no Big Bang, as a result of which our Universe (Metagalaxy) was born from a singularity. Explosions (and very powerful ones) happen and have happened in the Metagalaxy periodically here and there. The Universe does not pulsate, it simply boils, it is infinite, and we know very little about it and understand even less about it. There is no final theory that explains the Universe and the processes occurring in it, and there never will be. Theories and hypotheses correspond to the level of development of our technology, our science, and the experience that humanity has accumulated at the moment. Therefore, we must treat the accumulated experience as carefully as possible and always put fact above theory. As soon as some science does the opposite, it immediately ceases to be open information system and turns into a new religion. In science the main thing is doubt, and in religion it is faith.
List of used literature:
1. Wikipedia. Access address: http://ru.wikipedia.org/wiki/
2. Agekyan T.A. Stars, Galaxies, Metagalaxy. - M.: Nauka, 1981.
3. Vaucouleurs J. Classification and morphology of galaxies // Structure of stellar systems. Per. with him. - M., 1962.
4. Zeldovich Ya.B. Novikov I.D. The structure and evolution of the Universe, - M.: Nauka, 1975.
5. Levchenko I.V. The many-sided Universe // Discoveries and hypotheses, LLC "Intelligence Media". - September 9 (67), 2007.
6. Novikov I. D., Frolov V. P. Black holes in the Universe // Advances in Physical Sciences. - 2001. - T. 131. No. 3.
Posted on Allbest.ru
Similar documents
Hypothesis about the origin of stars and solar system and the evolution of galaxies. The theory of star formation from gas due to gravitational instability. The concept of thermodynamics of the earth's atmosphere and the stage of convective equilibrium. Transformation of a star into a white dwarf.
abstract, added 08/31/2010
Definition of the concept of entropy and the principles of its increase. Differences between two types of thermodynamic processes - reversible and irreversible. Unity and diversity organic world. The structure and evolution of stars and the Earth. Origin and evolution of galaxies.
test, added 11/17/2011
Formation of the basic principles of cosmological theory - the science of the structure and evolution of the Universe. Characteristics of theories of the origin of the Universe. The Big Bang Theory and the Evolution of the Universe. The structure of the Universe and its models. The essence of the concept of creationism.
presentation, added 11/12/2012
Revolution in natural science, the emergence and further development of the doctrine of the structure of the atom. Composition, structure and time of the megaworld. Quark model of hadrons. Evolution of the Metagalaxy, galaxies and individual stars. Modern picture of the origin of the Universe.
course work, added 07/16/2011
Principles of uncertainty, complementarity, identity in quantum mechanics. Models of the evolution of the Universe. Properties and classification of elementary particles. Evolution of stars. Origin, structure of the Solar system. Development of ideas about the nature of light.
cheat sheet, added 01/15/2009
Structure and evolution of the Universe. Hypotheses of the origin and structure of the Universe. State of space before the Big Bang. Chemical composition stars according to spectral analysis. The structure of a red giant. Black holes, hidden mass, quasars and pulsars.
abstract, added 11/20/2011
The concept of evolution as a process of self-development and complication of matter from its simplest forms up to the appearance of complex ones public entities. Characteristics of the main evolutionary theories. Signs of approaching the point of disaster. Justification of the theory of epigenesis.
presentation, added 12/01/2014
The emergence of the class of amphibians (amphibians) is a major step in the evolution of vertebrates. Structure and characteristics of frogs of the amphibian class. Reptiles, dividing them into groups. The structure of lizards and crocodiles. Specialized structure of snakes and turtles.
test, added 04/24/2009
Study of the evolutionary pattern of the animal world. Studying the Features nervous system diffuse, nodular and stem type. The structure of the brain of arthropods. Development of general motor coordination in cartilaginous fish. Stages of vertebrate brain evolution.
presentation, added 06/18/2016
The concept of open systems introduced by non-classical thermodynamics. Theories, hypotheses and models of the origin of galaxies. Assumptions to explain the expansion of the Universe. " Big bang": its causes and chronology. Stages and consequences of evolution.
The formation and structure of galaxies is the next important question about the origin of the Universe. It is studied not only by cosmology as the science of the Universe, but also cosmogony (Greek. “Goneya” means birth) is a field of science that studies the origin and development of cosmic bodies and their systems (planetary, stellar, galactic cosmogony is distinguished). Cosmology bases its conclusions on the laws of physics, chemistry and geology.
Galaxy are giant clusters of stars and their systems (up to about 10 13 stars), having their own center (core) and different shapes (spherical, spiral, elliptical, oblate or even irregular). The cores of galaxies produce hydrogen, the basic substance of the Universe. The sizes of galaxies range from several tens of light years to 18 million light years. In the part of the Universe visible to us - the Metagalaxy - there are billions of galaxies and in each of them there are billions of stars. All galaxies are moving away from each other, and the speed of this “expansion” increases as the galaxies move away. Galaxies are far from static structures: they change shape and outline, collide and absorb each other. Our Galaxy is currently engulfing the Sagittarius Dwarf Galaxy. In about 5 billion years, a “collision of worlds” will occur. The neighboring galaxies the Milky Way and the Andromeda Nebula are slowly but inevitably moving towards each other at a speed of 500 thousand km/h.
Our galaxy is called the Milky Way and consists of 150 billion stars. We see this cluster of stars on clear nights as a strip of the Milky Way. It consists of a core and several spiral branches. Its dimensions are 100 thousand light years. The age of the Galaxy is about 15 billion years. The closest galaxy to the Milky Way (which a light beam reaches in 2 million years) is the Andromeda Nebula. Most of the stars in our galaxy are concentrated in a giant “disk” in the form of a biconvex lens about 1500 light years thick. Stars and nebulae within the Galaxy move in very complex orbits. First of all, they participate in the rotation of the Galaxy around its axis at a speed of approximately 250 km/s. The Sun is located at a distance of about 30 thousand light years from the center of the galaxy. During its existence, the Sun made approximately 25 revolutions around its axis of rotation.
The process of galaxy formation—as opposed to the formation of stars and the synthesis of elements within them—is not yet well understood. In 1963, at the border of the observable Universe, they discovered quasars(quasi-stellar radio sources) are the most powerful sources of radio emission in the Universe with a luminosity hundreds of times greater than the luminosity of galaxies and sizes tens of times smaller than them. It was assumed that quasars represent the nuclei of new galaxies and, therefore, the process of galaxy formation continues to this day.
The poet asked: “Listen! After all, if the stars light up, does that mean someone needs it?” We know that stars are needed to shine, and our Sun provides the energy necessary for our existence. Why are galaxies needed? It turns out that galaxies are also needed, and the Sun not only provides us with energy. Astronomical observations show that there is a continuous outflow of hydrogen from the nuclei of galaxies. Thus, the nuclei of galaxies are factories for the production of the main building material of the Universe - hydrogen.
Hydrogen, the atom of which consists of one proton in the nucleus and one electron in its orbit, is the simplest “building block” from which more complex atoms are formed in the depths of stars in the process of atomic reactions. Moreover, it turns out that it is no coincidence that stars have different sizes. The greater the mass of a star, the more complex atoms are synthesized in its depths.
Our Sun, like an ordinary star, produces only helium from hydrogen (which is produced by the cores of galaxies); very massive stars produce carbon - the main “building block” of living matter. That's what galaxies and stars are for. What is the Earth for? It produces all the necessary substances for the existence of human life. Why does man exist? Science can't answer this question, but it can make us think about it again.
If someone needs the “ignition” of the stars, then maybe someone needs a person too? Scientific data helps us formulate an idea of our purpose, the meaning of our lives. When answering these questions, turning to the evolution of the Universe means thinking cosmically. Natural science teaches us to think cosmically, while at the same time not breaking away from the reality of our existence.
The question of the formation and structure of galaxies is the next important question of the origin of the Universe. It is studied not only by cosmology, as the science of the Universe - a single whole, but also by cosmogony (Greek “gonea” means birth) - a field of science in which the origin and development of cosmic bodies and their systems are studied (planetary, stellar, galactic cosmogony is distinguished ).
A galaxy is a giant cluster of stars and their systems, having its own center (core) and various, not only spherical, but often spiral, elliptical, oblate or generally irregular shape. There are billions of galaxies, and each of them contains billions of stars.
Our galaxy is called the Milky Way and consists of 150 billion stars. Oka consists of a core and several spiral branches. Its dimensions are 100 thousand light years. Most of the stars in our galaxy are concentrated in a giant “disk” about 1,500 light-years thick. The Sun is located at a distance of about 30 thousand light years from the center of the galaxy.
The closest galaxy to ours (to which the light ray travels 2 million years) is the “Andromeda nebula”. It is named so because it was in the constellation Andromeda that the first extragalactic object was discovered in 1917. Its belonging to another galaxy was proven in 1923 by E. Hubble, who found stars in this object through spectral analysis. Later, stars were discovered in other nebulae.
And in 1963, quasars (quasi-stellar radio sources) were discovered - the most powerful sources of radio emission in the Universe with a luminosity hundreds of times greater than the luminosity of galaxies and sizes tens of times smaller than them. It was assumed that quasars represent the nuclei of new galaxies and, therefore, the process of galaxy formation continues to this day.
Astronomy and space exploration
Stars are studied by astronomy (from the Greek “astron” - star and “nomos” law) - the science of the structure and development of cosmic bodies and their systems. This classical science is experiencing its second youth in the 20th century due to the rapid development of observation technology - its main research method: reflecting telescopes, radiation receivers (antennas), etc. In the USSR in 1974, the Stavropol region a reflector with a mirror diameter of 6 m, collecting light millions of times more than the human eye.
Astronomy studies radio waves, light, infrared, ultraviolet, x-ray radiation and gamma rays. Astronomy is divided into celestial mechanics, radio astronomy, astrophysics and other disciplines.
At present, astrophysics is a part of astronomy that studies physical and chemical phenomena occurring in celestial bodies, their systems and in outer space. Unlike physics, which is based on experiment, astrophysics is based primarily on observations. But in many cases, the conditions in which matter is found in celestial bodies and systems differ from those available to modern laboratories (ultra-high and ultra-low densities, high temperatures, etc.). Thanks to this, astrophysical research leads to the discovery of new physical laws.
The intrinsic significance of astrophysics is determined by the fact that currently the main attention in relativistic cosmology is transferred to the physics of the Universe - the state of matter and physical processes, occurring at different stages of the expansion of the Universe, including the earliest stages.
One of the main methods of astrophysics is spectral analysis. If you miss a beam of white sunlight through a narrow slit, and then through a glass triangular prism, it breaks up into its component colors, and a rainbow color stripe appears on the screen with a gradual transition from red to violet - a continuous spectrum. The red end of the spectrum is formed by the rays that are the least deflected when passing through a prism, the violet end is the most deflected. To everyone chemical element correspond to well-defined spectral lines, which makes it possible to use this method for studying substances.
Unfortunately, short-wave radiation - ultraviolet, x-rays and gamma rays - do not pass through the Earth’s atmosphere, and here science comes to the aid of astronomers, which until recently was considered primarily technical - astronautics (from the Greek “nautike” - the art of navigation) , providing space exploration for the needs of mankind using aircraft.
Cosmonautics studies problems: theories of space flight - calculations of trajectories, etc.; scientific and technical - design of space rockets, engines, on-board control systems, launch facilities, automatic stations and manned spacecraft, scientific instruments, ground-based flight control systems, trajectory measurement services, telemetry, organization and supply of orbital stations, etc.; medical and biological – creation of on-board life support systems, compensation of adverse phenomena in the human body associated with overload, weightlessness, radiation, etc.
The history of astronautics begins with theoretical calculations of man's exit into extraterrestrial space, which were given by K.E. Tsiolkovsky in his work “Investigation of World Spaces with Reactive Instruments” (1903). Work in the field of rocket technology began in the USSR in 1921. The first launches of liquid fuel rockets were carried out in the United States in 1926.
The main milestones in the history of astronautics were: the launch of the first artificial Earth satellite on October 4, 1957, the first manned flight into space on April 12, 1961, the lunar expedition in 1969, the creation of manned orbital stations in low-Earth orbit, and the launch of a reusable spacecraft. Work was carried out in parallel in the USSR and the USA, but in recent years there has been a consolidation of efforts in the field of space exploration. Implemented in 1995 joint project"Mir" - "Shuttle", in which American space shuttle ships were used to deliver astronauts to the Russian orbital station "Mir".
Opportunity to study at orbital stations Cosmic radiation, which is trapped by the Earth's atmosphere, contributes to significant progress in the field of astrophysics.
Structure of the Universe
the universe at its most different levels, from conventionally elementary particles to giant superclusters of galaxies, there is inherent structure. Modern structure The Universe is the result of cosmic evolution, during which galaxies were formed from protogalaxies, stars from protostars, and planets from protoplanetary clouds.
A metagalaxy is a collection of star systems - galaxies, and its structure is determined by their distribution in space, filled with extremely rarefied intergalactic gas and penetrated by intergalactic rays.
According to modern concepts, the Metagalaxy is characterized by a cellular (mesh, porous) structure. These ideas are based on astronomical observational data, which have shown that galaxies are not evenly distributed, but are concentrated near the boundaries of cells, within which there are almost no galaxies. In addition, huge volumes of space have been found (on the order of a million cubic megaparsecs) in which galaxies have not yet been discovered. A spatial model of such a structure can be a piece of pumice, which is heterogeneous in small isolated volumes, but homogeneous in large volumes.
If we take not individual sections of the Metagalaxy, but its large-scale structure as a whole, then it is obvious that in this structure there are no special, distinctive places or directions and the matter is distributed relatively evenly.
The age of the Metagalaxy is close to the age of the Universe, since the formation of its structure occurs in the period following the separation of matter and radiation. According to modern data, the age of the Metagalaxy is estimated at 15 billion years. Scientists believe that, apparently, the age of galaxies that formed at one of the initial stages of the expansion of the Metagalaxy is also close to this.
A galaxy is a giant system consisting of clusters of stars and nebulae, forming a rather complex configuration in space.
Based on their shape, galaxies are conventionally divided into three types: elliptical, spiral and irregular.
Elliptical galaxies have the spatial shape of an ellipsoid with varying degrees of compression. They are the simplest in structure: the distribution of stars uniformly decreases from the center.
Spiral galaxies are presented in a spiral shape, including spiral arms. This is the most numerous type of galaxy, which includes our Galaxy - the Milky Way.
Irregular galaxies do not have a distinct shape and lack a central core.
Some galaxies are characterized by exceptionally powerful radio emission, exceeding visible radiation. These are radio galaxies.
In the structure of “regular” galaxies, one can very simply distinguish a central core and a spherical periphery, presented either in the form of huge spiral branches or in the form of an elliptical disk, including the hottest and bright stars and massive gas clouds.
Galactic nuclei exhibit their activity in different forms: in the continuous outflow of flows of matter; in emissions of gas clumps and gas clouds with a mass of millions of solar masses; in non-thermal radio emission from the perinuclear region.
The oldest stars, whose age is close to the age of the galaxy, are concentrated in the core of the galaxy. Middle-aged and young stars are located in the galactic disk.
Stars and nebulae within a galaxy move in a rather complex way: together with the galaxy, they take part in the expansion of the Universe, in addition, they participate in the rotation of the galaxy around its axis.
Stars. On modern stage During the evolution of the Universe, the matter in it is predominantly in a stellar state. 97% of the matter in our Galaxy is concentrated in stars, which are giant plasma formations of various sizes, temperatures, and with different characteristics of motion. Many, if not most, other galaxies have "stellar matter" that makes up more than 99.9% of their mass.
The age of stars varies over a fairly wide range of values: from 15 billion years, corresponding to the age of the Universe, to hundreds of thousands - the youngest. There are stars that are currently being formed and are in the protostellar stage, i.e. they haven't become real stars yet.
Of great importance is the study of the relationship between stars and the interstellar medium, including the problem continuing education stars from condensing diffuse (scattered) matter.
The birth of stars occurs in gas-dust nebulae under the influence of gravitational, magnetic and other forces, due to which unstable homogeneities are formed and diffuse matter breaks up into a series of condensations. If such condensations persist long enough, then over time they turn into stars. It is important to note that the birth process is not of an individual isolated star, but of stellar associations. The resulting gas bodies are attracted to each other, but do not necessarily combine into one huge body. Instead, they tend to spin relative to each other, and the centrifugal force of this movement counteracts the force of gravity, leading to further concentration. Stars evolve from protostars, giant balls of gas that glow faintly and have a low temperature, to stars, dense plasma bodies with internal temperatures of millions of degrees. Then the process of nuclear transformations begins, described in nuclear physics. The main evolution of matter in the Universe took place and is happening in the depths of stars. It is there that the “melting crucible” is located, which determined the chemical evolution of matter in the Universe.
In the depths of stars, at a temperature of the order of 10 million K, and at a very high density, atoms are in an ionized state: electrons are almost completely or absolutely all separated from their atoms. The remaining nuclei interact with each other, due to which hydrogen, which is abundant in most stars, is converted with the participation of carbon into helium. These and similar nuclear transformations are the source of colossal amounts of energy carried away by stellar radiation.
The enormous energy emitted by stars results from nuclear processes, occurring inside stars. The same forces that are released in an explosion hydrogen bomb, form energy inside the star that allows it to emit light and heat for millions and billions of years due to the transformation of hydrogen into heavier elements, and above all into helium. As a result, at the final stage of evolution, stars turn into inert (“dead”) stars.
Stars do not exist in isolation, but form systems. The simplest star systems - the so-called multiple systems - consist of two, three, four, five or more stars revolving around a common center of gravity. The components of some multiple systems are surrounded by a common shell of diffuse matter, the source of which, apparently, is the stars themselves, which eject it into space in the form of a powerful gas flow.
Stars are also united into even larger groups - star clusters, which can have a “scattered” or “spherical” structure. Open star clusters number several hundred individual stars, globular clusters number many hundreds of thousands.
Associations, or clusters of stars, are also not immutable and eternally existing. After a certain amount of time, estimated in millions of years, they are scattered by the forces of galactic rotation.
The solar system is a group of celestial bodies, very different in size and physical structure. This group includes: the Sun, nine major planets, dozens of planetary satellites, thousands of small planets (asteroids), hundreds of comets and countless meteorite bodies, moving both in swarms and in the form of individual particles. By 1979, 34 moons and 2,000 asteroids were known. All these bodies are united into one system due to the gravitational force of the central body - the Sun. The solar system is an ordered system that has its own structural laws. The unified nature of the solar system is manifested in the fact that all the planets revolve around the sun in the same direction and in almost the same plane. Most of the planets' satellites (their moons) rotate in the same direction and in most cases in the equatorial plane of their planet. The sun, planets, satellites of planets rotate around their axes in the same direction in which they move along their trajectories. The structure of the solar system is also natural: each subsequent planet is approximately twice as far from the Sun as the previous one. Taking into account the laws of the structure of the solar system, its accidental formation seems impossible.
There are also no generally accepted conclusions about the mechanism of planet formation in the Solar System. The solar system is estimated to have formed approximately 5 billion years ago, with the Sun being a second (or even later) generation star. Thus, the Solar System arose from the waste products of stars of previous generations, which accumulated in gas and dust clouds. This circumstance gives grounds to call the solar system a small part of stardust. On the origin of the solar system and its historical evolution science knows less than is necessary to build a theory of planet formation. From the first scientific hypotheses, put forward approximately 250 years ago, to this day it has been proposed large number various models of the origin and development of the Solar system, but none of them has been promoted to the rank of a generally accepted theory. Most of the previously put forward hypotheses are today of only historical interest.
The first theories of the origin of the solar system were put forward by the German philosopher I. Kant and the French mathematician P.S. Laplace. Their theories entered science as a kind of collective cosmogonic hypothesis of Kant-Laplace, although they were developed independently of each other.
According to this hypothesis, the system of planets around the Sun was formed as a result of the forces of attraction and repulsion between particles of scattered matter (nebulae) in rotational motion around the Sun.
The beginning of the next stage in the development of views on the formation of the Solar system was the hypothesis of the English physicist and astrophysicist J.X. Jeans. He suggested that the Sun once collided with another star, as a result of which a stream of gas was torn out of it, which, condensing, transformed into planets. However, given the enormous distance between the stars, such a collision seems completely improbable. A more detailed analysis revealed other shortcomings of this theory.
Modern concepts the origin of the planets of the solar system are based on the fact that it is necessary to take into account not only mechanical forces, but also others, in particular electromagnetic ones. This idea was put forward by the Swedish physicist and astrophysicist H. Alfvén and the English astrophysicist F. Hoyle. It is considered probable that it was electromagnetic forces that played a decisive role in the birth of the Solar System. According to modern ideas, the original gas cloud from which both the Sun and the planets were formed, consisted of ionized gas subject to the influence of electromagnetic forces. After the Sun was formed from a huge gas cloud through concentration, small parts of this cloud remained at a very large distance from it. The gravitational force began to attract the remaining gas to the resulting star - the Sun, but its magnetic field stopped the falling gas at various distances - exactly where the planets are located. Gravitational and magnetic forces influenced the concentration and condensation of the falling gas, and as a result, planets were formed. When the largest planets arose, the same process was repeated on a smaller scale, thus creating satellite systems. Theories of the origin of the Solar system are hypothetical in nature, and it is impossible to unambiguously resolve the issue of their reliability at the present stage of scientific development. In all existing theories There are contradictions and unclear areas.
Conclusion
As can be seen from the above, various approaches, hypotheses and concepts of the origin of the universe have made a huge contribution to the development of astrophysics and naturally scientific knowledge the world around us as a whole.
An important fact is that these models of the universe gave rise to other areas of scientific knowledge, especially related to the evolution of the universe.
The concept " galaxy" V modern language means huge star systems. It comes from the Greek word “milk, milky” and was put into use to designate our star system, which represents a light stripe with a milky tint stretching across the entire sky and is therefore called the “Milky Way”. The number of stars in it is several hundred billion, i.e. about a trillion (10 12). It has the shape of a disk with a thickening in the center.
The diameter of the galaxy's disk is 10 21 m. The arms of the Galaxy have a spiral shape, that is, they diverge in spirals from the core. In one of the arms, at a distance of about 3 × 10 20 m from the core, there is the Sun, located near the plane of symmetry. The most numerous stars in our galaxy are dwarfs (their mass is about 10 times less than the mass of the Sun). In addition to single stars and their satellites (planets), there are double and multiple stars and entire star clusters (the Pleiades). More than 1000 of them have already been discovered. Globular clusters contain red and yellow stars - giants and supergiants. One of the objects in the Galaxy are nebulae, consisting mainly of gas and dust. Interstellar space is filled with fields and tenuous interstellar gas. The galaxy rotates around the center, and the angular and linear velocities change with increasing distance from the center. The linear speed of the Sun around the center of the Galaxy is 250 km/s. The Sun completes its orbit in approximately 290 million years (2×10 8 years).
At the beginning of the twentieth century, it was proven that there are others besides our Galaxy. Galaxies differ sharply in size, number of stars included in them, luminosity, and appearance. They are designated by numbers under which they are listed in catalogues.
Based on their appearance, galaxies are conventionally divided into three types: elliptical, spiral, and irregular.
Almost a quarter of all studied galaxies are elliptical. These are the simplest galaxies in structure.
Spiral galaxies are the most numerous type. It includes the Andromeda nebula (one of the closest galaxies to us), approximately 2.5 million light years away from us.
Irregular galaxies do not have central nuclei; no patterns have yet been discovered in their structure. These are the Large and Small Magellanic Clouds, which are satellites of our Galaxy.
Galaxies, as it turns out, form groups (tens of galaxies) and clusters consisting of hundreds and thousands of galaxies. Discoveries of the late 70s of the twentieth century showed that galaxies in superclusters are distributed unevenly: they are concentrated near the boundaries of cells, i.e. the Universe has a cellular (mesh, porous) structure. On small scales, matter in the Universe is distributed unevenly. On large scales it is homogeneous and isotropic. The metagalaxy is nonstationary. Let us note some features of the expansion of the metagalaxy:
1. Expansion manifests itself only at the level of clusters and superclusters of galaxies. The galaxies themselves are not expanding.
2. There is no center from which expansion occurs.
The question of the formation and structure of galaxies is the next important question of the origin of the Universe. It is studied not only cosmology as a science about the Universe - a single whole, but also cosmogony(Greek “gonos” means birth) is a field of science in which the origin and development of cosmic bodies and their systems are studied (galactic, stellar, planetary cosmogony is distinguished).
How were galaxies and stars formed? The density of matter in the Universe was not the same in different parts, and matter from neighboring areas was attracted to areas of higher density. Areas of high density thus became even denser. The so-called "islands" matter that began to shrink due to its own gravity. Within the islands, separate “mini-islands” with even higher densities were formed. Galaxies were formed from the original islands, and stars were formed from mini-islands. This process was completed within 1 billion years.
Galaxies are giant clusters of stars and their systems, having their own center (core) and various, not only spherical, but often spiral, elliptical, oblate or generally irregular shapes. There are billions of galaxies, and each of them contains billions of stars.
Our galaxy is called Milky Way. The word galaxy itself comes from the Greek. "galaktikos" - milky. They got their name because the cluster of stars resembles a whitish cloud. Our galaxy belongs to the group of spiral galaxies and consists of three parts. 100 billion stars of the galaxy are concentrated in a giant disk about 1,500 light-years thick and approximately 100,000 light-years in diameter. The movement of stars is carried out in almost circular orbits around the center of the galaxy. The Sun is located in the disk at a distance of about 30 thousand light years from the center of the galaxy. The second part of the galaxy is spherical subsystem, which also has about 100 billion stars. But they move along highly elongated orbits, the planes of which pass through the center of the galaxy. The diameter of the spherical subsystem is close to the diameter of the disk. The third, outer, part of the galaxy is called halo. Its size is 10 times larger than the size of the disk and it consists of dark matter, so named because it has no stars and no light comes from it. It cannot be seen, but is recognized by the presence of gravity. The mass of dark matter in the halo is 10 times greater than the total mass of all the stars in the galaxy.
What the dark matter consists of is unclear. There are many assumptions: from elementary particles to dwarf stars. The cosmological environment as a whole consists of four components: 1) dark energy; 2) dark matter; 3) baryons (ordinary matter); 4) radiation. Radiation includes relict radiation (photons), neutrinos and antineutrinos.
Dark energy(or cosmic vacuum) - “this is a state of the cosmic environment that has a constant density in time and everywhere the same in space - and, moreover, in any reference system” 1. Nothing is known about the physical nature of dark energy. Recent observations show that 6-8 billion years ago, slowing expansion gave way to accelerated expansion. The reason is believed to be that earlier 6-8 billion years ago gravity prevailed, and then antigravity. This argues for the presence of dark energy. The cosmic vacuum accounts for 67% of the world's total energy, dark matter - 30%, and ordinary matter - 3%.
The closest galaxy to ours (which the light beam reaches in 2 million years) is the Andromeda Nebula. It is named so because it was in the constellation Andromeda that the first extragalactic object was discovered in 1917. Its belonging to another galaxy was proven in 1924.
E. Hubble, who found stars in this object through spectral analysis. The size of the Andromeda Nebula is comparable to the size of our galaxy. Later other galaxies were discovered.
Galaxies are collected in groups from a few to thousands - clusters of galaxies. Our cluster is called Local group(its dimensions are 60 times the size of the Milky Way). The name of galaxies from the Local Group is the Andromeda Nebula, Triangulum, Large Magellanic Cloud, Small Magellanic Cloud, etc. Clusters are grouped into superclusters. At the center of our supercluster is the Virgo cluster. There are hundreds of billions of galaxies in the Universe.
Galaxies, clusters and superclusters are distributed evenly throughout the Universe. The homogeneity of galaxies means that none of them is the center of the world. In general, there is 1 hydrogen atom for every 10 m of space. Compact massive clumps in the central parts of galaxies are called galactic nuclei.
- Chereptsuk L. M., Chernin L. D. Decree. op. P. 229.
- Right there. P. 233.
Loading...