home Cosmetics Classification of galaxies according to their shapes and appearance. Main types of galaxies (according to E

Classification of galaxies according to their shapes and appearance. Main types of galaxies (according to E

Many facts known today seem so familiar and familiar that it is difficult to imagine how we lived without them before. However, scientific truths for the most part did not arise at the dawn of mankind. This largely concerns knowledge about outer space. The types of nebulae, galaxies, and stars are known to almost everyone today. Meanwhile, the path to modern understanding was quite long. People did not immediately realize that the planet was part solar system, and she is the Galaxies. Types of galaxies began to be studied in astronomy even later, when it was understood that the Milky Way is not alone and the Universe is not limited to it. as well as the general knowledge of space outside the “milk road”, became Edwin Hubble. Thanks to his research, today we know a lot about galaxies.

Types of galaxies in the Universe

Hubble studied nebulae and proved that many of them are formations similar to the Milky Way. Based on the collected material, he described what the galaxy looks like and what types of similar space objects exist. Hubble measured the distances to some of them and proposed its own classification. Scientists still use it today.

He divided all the many systems in the Universe into 3 types: elliptical, spiral and irregular galaxies. Each type is actively studied by astronomers around the world.

The piece of the Universe where the Earth is located, the Milky Way, belongs to the “spiral galaxy” type. Types of galaxies are identified based on differences in their shapes, which affect certain properties of the objects.

Spiral

The types of galaxies are not equally distributed throughout the Universe. According to modern data, spiral-shaped ones are more common than others. In addition to the Milky Way, this type includes the Andromeda Nebula (M31) and the galaxy in (M33). Such objects have an easily recognizable structure. If you look from the side at what such a galaxy looks like, the view from above will resemble concentric circles spreading across the water. Spiral arms radiate from a spherical central bulge called the bulge. The number of such branches varies - from 2 to 10. The entire disk with spiral arms is located inside a rarefied cloud of stars, which in astronomy is called a “halo”. The core of the galaxy is a cluster of stars.

Subtypes

In astronomy, the letter S is used to designate spiral galaxies. They are divided into types depending on the structural design of the arms and features of the general shape:

Galaxy Sa: the arms are tightly twisted, smooth and unshaped, the bulge is bright and extended;

galaxy Sb: the arms are powerful, clear, the bulge is less pronounced;

galaxy Sc: the arms are well developed, have a ragged structure, the bulge is poorly visible.

In addition, some spiral systems have a central, almost straight bridge (called a “bar”). In this case, the letter B (Sba or Sbc) is added to the galaxy designation.

Formation

The formation of spiral galaxies appears to be similar to the appearance of waves from the impact of a stone on the surface of water. According to scientists, some kind of push led to the emergence of the sleeves. The spiral branches themselves represent waves of increased density of matter. The nature of the push can be different, one of the options is movement into stars.

The spiral arms are young stars and neutral gas (the main element is hydrogen). They lie in the plane of rotation of the galaxy, so it resembles a flattened disk. The formation of young stars is also possible at the center of such systems.

Nearest neighbor

The Andromeda Nebula is a spiral galaxy: a view from above reveals several arms emanating from a common center. From Earth, it can be seen with the naked eye as a blurry, foggy spot. Our galaxy's neighbor is somewhat larger in size: 130 thousand light years in diameter.

Although the Andromeda nebula is the closest galaxy to the Milky Way, the distance to it is enormous. It takes light two million years to travel through it. This fact perfectly explains why flights to a neighboring galaxy are so far only possible in science fiction books and films.

Elliptic systems

Let us now consider other types of galaxies. A photo of the elliptical system clearly demonstrates its difference from its spiral counterpart. Such a galaxy has no arms. It looks like an ellipse. Such systems can be compressed to varying degrees, and can be something like a lens or a sphere. There is practically no cold gas found in such galaxies. The most impressive representatives of this type are filled with rarefied hot gas, the temperature of which reaches a million degrees and above.

A distinctive feature of many elliptical galaxies is their reddish tint. For a long time astronomers believed this to be a sign of the antiquity of such systems. They were thought to be mostly made up of old stars. However, research last decades showed the fallacy of this assumption.

Education

For a long time, there was another hypothesis related to elliptical galaxies. They were considered the very first to arise, formed shortly after the Big Bang. Today this theory is considered outdated. German astronomers Alar and Yuri Thumre, as well as the American scientist Francois Schweizer, made a great contribution to its refutation. Their research and discoveries recent years confirm the truth of another hypothesis, the hierarchical model of development. According to it, larger structures were formed from fairly small ones, that is, galaxies did not form immediately. Their appearance was preceded by the formation of star clusters.

According to modern concepts, elliptical systems were formed from spiral-shaped arms as a result of the merger. One of the confirmations of this is a large number of"twisted" galaxies observed in distant areas of space. On the contrary, in the closest regions there is a noticeably higher concentration of elliptical systems, which are quite bright and extended.

Symbols

Elliptical galaxies also received their own designations in astronomy. They use the symbol “E” and numbers from 0 to 6, which indicate the degree of flattening of the system. E0 are galaxies with an almost regular spherical shape, and E6 are the flattest.

Raging Cannonballs

Elliptical galaxies include the systems NGC 5128 from the constellation Centaur and M87, located in Virgo. Their feature is powerful radio emission. Astronomers are primarily interested in the structure of the central part of such galaxies. Observations by Russian scientists and studies by the Hubble telescope show quite high activity in this zone. In 1999, American astronomers obtained data on the core of the elliptical galaxy NGC 5128 (constellation Centaur). There, in constant motion, there are huge masses of hot gas, swirling around the center, possibly a black hole. There is no exact data on the nature of such processes yet.

Irregularly shaped systems

It is also located in the Large Magellanic Cloud. Here scientists have discovered a region of constant star formation. Some of the stars that make up the nebula are only two million years old. In addition, the most impressive star discovered in 2011, RMC 136a1, is also located here. Its mass is 256 solar.

Interaction

The main types of galaxies describe the features of the shape and arrangement of the elements of these cosmic systems. However, no less interesting is the question of their interaction. It's no secret that all space objects are in constant motion. Galaxies are no exception. Types of galaxies, at least some of their representatives, could be formed in the process of merger or collision of two systems.

If we remember what such objects are, it becomes clear how large-scale changes occur during their interaction. During a collision, a colossal amount of energy is released. Interestingly, such events are even more likely in the vastness of space than the meeting of two stars.

However, the “communication” of galaxies does not always end with a collision and explosion. A small system can pass through its large brother, disturbing its structure. This creates formations similar in appearance with long corridors. They consist of stars and gas and often become zones for the formation of new luminaries. Examples of such systems are well known to scientists. One of them is the Cartwheel galaxy in the constellation Sculptor.

In some cases, the systems do not collide, but pass by each other or only slightly touch. However, regardless of the degree of interaction, it leads to serious changes in the structure of both galaxies.

Future

According to scientists’ assumptions, it is possible that after some, quite a long time, the Milky Way will absorb its closest satellite, a relatively recently discovered system, tiny by cosmic standards, located at a distance of 50 light years from us. Research data suggests an impressive lifespan for this satellite, which will likely end as it merges with its larger neighbor.

Collision is a possible future for the Milky Way and the Andromeda Galaxy. Now the huge neighbor is separated from us by about 2.9 million light years. Two galaxies are approaching each other at a speed of 300 km/s. A probable collision, according to scientists, will occur in three billion years. However, today no one knows for sure whether it will happen or whether the galaxies will only slightly touch each other. For forecasting, there is not enough data on the characteristics of the movement of both objects.

Modern astronomy studies in detail such cosmic structures as galaxies: types of galaxies, features of interaction, their differences and similarities, the future. There is still a lot that is unclear in this area and requires additional study. The types of structure of galaxies are known, but there is no precise understanding of many details associated, for example, with their formation. The current pace of improvement of knowledge and technology, however, allows us to hope for significant breakthroughs in the future. In any case, galaxies will not cease to be the center of much research. And this is connected not only with the curiosity inherent in all people. Data about cosmic patterns and life make it possible to predict the future of our piece of the Universe, the Milky Way galaxy.

In 1936, Edwin Hubble proposed a sequence of galaxy evolution that, with minor modifications, remains valid today. According to this classification, there are four main types of galaxies. Sometimes dwarf galaxies are classified as a separate type, but they are not distinguished by anything other than their relatively small size and themselves belong to one or another type in the classical categorization.

©GALEX, JPL-Caltech, NASA

Elliptical galaxy

From the outside it looks like a giant star - a luminous ball with the strongest brightness in the center and dimming towards the edges. Elliptical or spheroidal galaxies are composed almost entirely of old stars, so they always have a yellow or reddish tint. New stars practically do not form in them, since the amount of interstellar gas and dust in them is negligible (although there are exceptions). Elliptical star systems differ from each other only in size and degree of compression. It is by compression that they are classified, from E0 to E7. They make up about a quarter of the number of visible galaxies. According to Hubble's classification, this is the initial stage of galactic evolution.

©NASA/ESA

Spiral galaxy

The most common type, and probably the most beautiful, makes up more than half the number of all known galaxies. Looks like a disc with bright yellow ball in the center, around which dimmer branch-sleeves of a bluish hue are twisted in the form of spirals (due to the presence of special stars - white and blue supergiants).

It differs from elliptical star systems in a number of structural features. Firstly, spiral galaxies have arms where active star formation processes take place. Secondly, there is a stellar disk - a relatively thin layer of matter along the plane of the galaxy, where the bulk of the objects in the system are located, and the stars in which rotate around the center of the disk. Third, the presence of interstellar gas and dust, the environment necessary for the birth of stars, is widely observed. Many spiral galaxies have a kind of bridge (bar) at their center, from the ends of which arms diverge. They are classified by the letter S and differ in the density of the sleeves (Sa-Sd, with a jumper - SBa-SBd).

The average number of sleeves is a couple, but there are more; in some cases the sleeves differ in size. All of them (if they do not survive a galactic collision) are twisted in one direction around the center, where the bulk of the matter is concentrated in the form of a supermassive black hole and a dense spherical cluster of old stars - a bulge.

Both our galaxy, the Milky Way, and the Andromeda Nebula, which we will inevitably encounter in 4 billion years, are both spiral galaxies. The Sun is located between the arms and away from the galactic center, and the speed of its movement is approximately equal to the speed of rotation of the arms; Thus, the solar system avoids regions of active star formation that are dangerous to terrestrial life, where supernovae often erupt.

©NASA

Lenticular galaxy

According to Hubble's classification, it is an intermediate type between elliptical and spiral galaxies (S0). Lenticular star systems have a stellar disk around a central globular bulge cluster, but the arms are relatively small and not very pronounced, and the amount of interstellar gas and dust matter is not enough for the active birth of new stars. The main inhabitants are old large stars, red or yellow in color.

They differ in the amount of interstellar dust and the density of the bridge in the galactic center. They make up approximately 20% of the number of galaxies.

©NASA/ESA

Wrong galaxy

Neither an ellipse nor a spiral, irregular galaxies have either of the common shapes. As a rule, these are star clusters chaotically bound by gravity, sometimes without a clear shape or even a clearly defined center. They make up approximately 5% of galaxies.

Why are they so different from their galactic counterparts? It is very likely that each such star system was once elliptical or spiral, but was disfigured by a collision with another galaxy, or close proximity to it.

They are divided into two main types: those who have at least some semblance of a structure that allows them to be classified as a Hubble sequence (Irr I), and those who do not even have a similarity (Irr II).

Sometimes a third type is distinguished - dwarf irregular galaxies (dl or dIrr). They contain low amounts of heavy elements and large amounts of interstellar gas, making them similar to the protogalaxies of the early Universe. Therefore, the study of this type of irregular galaxies has important to understand the process of galactic evolution.

©NASA/ESA

There are three main types of galaxies: spiral, elliptical and irregular. The first include, for example, the Milky Way and Andromeda. In the center are objects and a black hole, around which a halo of stars and dark matter revolves. Arms branch off from the core. The spiral shape is formed due to the fact that the galaxy does not stop rotating. Many representatives have only one sleeve, but some have three or more.

Table of characteristics of the main types of galaxies

Spiral ones come with or without a jumper. In the first type, the center is crossed by a dense bar of stars. And in the latter, such formation is not observed.

Elliptical galaxies contain the oldest stars and do not have enough dust and gas to create young ones. They may resemble a circle, oval or spiral type in shape, but without sleeves.

About a quarter of the galaxies are irregular groups. They are smaller than spiral ones and sometimes display bizarre shapes. They can be explained by the appearance of new stars or gravitational contact with a neighboring galaxy. Among the incorrect ones are .

There are also many galactic subtypes: Seyfert (fast-moving spirals), bright elliptical supergiants (absorbing others), ring supergiants (without a core), and others.

Send your good work in the knowledge base is simple. 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/

Introduction

1. I. Kant’s theory of disk-shaped galaxies, its development

2. Types of galaxies and their structure

2.1 Spiral

2.2 Elliptical

2.3 Incorrect

3. Modern representations about galaxies

Conclusion

List of used literature

Introduction

From the naive ancient picture of the world, which accepted as reality the apparent equal distance of all stars and located them all on the surface of a crystal sphere, we must move on to knowledge of the true spatial structure of the grandiose star system.

The first thing we strive to establish is the general contours, the general outlines of our stellar system, at least in its roughest outline. This was done even before the distance to the nearest star became known. At first, it was quite correctly assumed for this purpose that the luminosity of all stars is the same and that the difference in their apparent brightness depends solely on their distance from us. We now know that in reality the luminosities of stars vary monstrously, but we also know that there are very few very bright stars and that of the very faint stars only those that are very close to us are visible.

1. TheorydiscoidgalaxiesAND.Kant,herdevelopment

The philosopher I. Kant dealt mainly with natural scientific problems and put forward a number of important hypotheses, including the “nebular” cosmogonic hypothesis, according to which the emergence and evolution of the solar system is deduced from the existence of the “primordial nebula.” At the same time, the philosopher suggested the existence of a large universe of galaxies outside our galaxy.

In 1747, without defending his master's thesis, Kant left Konigsberg for the first time. During this period, Kant wrote a manuscript on astronomy, “Cosmogony or an attempt to explain the origin of the universe, the formation of celestial bodies and the reasons for their movement by the general laws of the development of matter in accordance with Newton’s theory.” The article was written on a competitive topic proposed by the Prussian Academy of Sciences, but the young scientist did not dare to take part in the competition. The article was published only in 1754 after Kant returned to Konigsberg. Somewhat later, at the end of the summer of 1754, Kant published a second article, also devoted to issues of cosmogony - “The question of whether the Earth is aging from a physical point of view.” These two articles were, as it were, a prelude to the cosmogonic treatise, which was soon written. Its final title was "The General Natural History and Theory of the Heavens, or an Attempt to Interpret the Structure and Mechanistic Origin of the Whole Universe, Starting from Newton's Principles." The treatise was published anonymously in 1755, and soon an approving review appeared in one of the Hamburg publications. The work is a unique attempt to combine the inquisitiveness of a naturalist with the tenets of the church familiar from childhood. When starting to present the cosmogonic system, Kant is concerned with one thing: how to reconcile it with faith in God. The philosopher is convinced that there is no contradiction between his hypothesis and traditional religious (Christian) beliefs. However, some similarity of his views with the ideas of the ancient materialists - Democritus and Epicurus is obvious. Like these philosophers, Kant believed that the original state of nature was the general dispersion of primary matter, atoms. He showed how, under the influence of purely mechanistic causes, our solar system could be formed from the initial chaos of material particles. Thus, the philosopher denied God the role of “architect of the universe.” However, he still saw in him the creator of that initially dispersed substance from which (according to the laws of mechanics) the current universe arose. Regarding the Galaxy, Kant argued that it has a clear disk shape.

We see further development of this theory in the following. Let's say you are standing on a high hill above a plain on which clumps of old and young trees are scattered. They are different in height, you do not know the height of each of them. But, looking at them from a hill, you can quite correctly judge the distance to each clump of trees by their apparent size. This way of studying the stellar Universe was proposed by William Herschel. Before him, they were limited to observing the position of stars in the sky and studying the surface of the Moon and planets, and were also keen on studying the movement of members of the solar system.

To clarify the contours of the Universe, Herschel began to count the number of stars of different brilliance visible in the field of view of his telescope in different parts of the sky - in the Milky Way and away from it. He found that the fainter the stars, the faster their number increased as they approached the Milky Way. The Milky Way itself, as Galileo discovered, consists of countless faint stars merging into a continuous shining mass that encircles the entire sky like a ring.

From these calculations, it became clear to Herschel that our star system extends farthest in all directions from us towards the Milky Way in a plane passing through its midline. Since the Milky Way encircles the entire sky, dividing it almost in half, then, obviously, our Solar system is located near this plane (near the galactic plane, as it is called).

However, Herschel accepted that with his gigantic telescope he penetrated to the boundaries of our stellar system, consisting of stars located seemingly evenly in space.

The founder of the Pulkovo Observatory, V. Ya. Struve, in 1847 revised Herschel’s calculations and, having studied the distribution of stars, proved the fallacy of such conclusions. Struve established that in space the stars are not evenly distributed, but are condensed towards the plane of the Milky Way, that our Sun does not at all occupy a central position in this stellar system and that Herschel’s largest telescopes have not yet reached its boundaries, and therefore it is premature to talk about its shape . Herschel believed that he seemed to be sitting with his telescope in the center of a regularly located grove, from which he surveyed all its edges, and Struve proved that Herschel was sitting somewhere in a huge forest, full of thickets and thin spots, from where the edges of the forest were still far from visible .

The farther from the plane of the Milky Way, the fewer faint stars are visible there and the smaller the distance in these directions the star system stretches. In general, our star system, called the Galaxy, occupies a space that resembles a lens or lentil. It is flattened, thickest in the middle and thinner towards the edges. If we could see it “from above” or “from below”, it would have, roughly speaking, the appearance of a circle (not a ring!). From the “side” it would look like a spindle. But what are the dimensions of this “spindle”? Is the arrangement of stars in it uniform?

The answer is given by a simple examination of the Milky Way, which entirely consists of a pile of star clouds. Some clouds are brighter and have more stars (such as in the constellations Sagittarius and Cygnus), while others are poorer in stars.

The visible raggedness of the Milky Way is also created by the uneven distribution of clouds of cosmic dust, dark nebulae of different densities, absorbing the light of the stars located behind them. But even taking this into account, our stellar Universe is heterogeneous. The galaxy consists of star clouds. The solar system is in one of them, called the Local System. The most powerful clouds of stars are in the direction of the constellation Sagittarius; there the Milky Way is brightest. It is least bright in the opposite part of the sky.

From this it is easy to conclude that the Solar System is not located in the center of the Galaxy, which is visible from us in the direction of the constellation Sagittarius. This means that the Milky Way is a picture visible to us who are inside the Galaxy, near its plane, but far from its center.

In the middle of the Galaxy is its core, which, by analogy with the cores of other stellar systems, should have the appearance of a slightly oblate ellipsoid of rotation. We are located a little further than 25,000 light years from it. In the core of the Galaxy there are no hot supergiants and diffuse gas nebulae excited by them to glow. There is no dust there either, but there is neutral hydrogen in it, which, for an as yet unclear reason, spreads from there into the plane of the Galaxy at a speed of about 50 km/sec. The core is probably surrounded by a rapidly rotating ring of neutral hydrogen. The main radiation of the core is apparently created by orange giant stars (not supergiants) of spectral class K and many dwarf stars of class M. Individually, they are not visible, and this conclusion is based on an analysis of the total color and spectrum of the core. In general rough terms, the shape of the Galaxy is similar to a lentil or a thin lens, in the middle of which there is a thicker and brighter core. This core should have appeared very bright if it had not been concealed and obscured by the absorption of light in the masses of cosmic dust.

2. KindsgalaxiesAndtheirstructure

The shapes of galaxies are diverse.

Most galaxies belong to several main types (according to their characteristic external signs, and small differences in galaxies help to subdivide these types into separate subtypes).

2 .1 Spiralgalaxies

spiral elliptical galaxy star

In 1845, the English astronomer Lord Ross (William Parsons), using a telescope with a 180-centimeter metal mirror, discovered a whole class of “spiral nebulae,” the most striking example of which was the nebula in the constellation Canes Venatici (M 51 according to Messier’s catalog III). The nature of these nebulae was established only in the first half of the 20th century. At that time, intensive research was carried out to determine the size of our Galaxy - the Milky Way - and the distances to some nebulae that were able to be resolved into stars. The conclusions were contradictory both in assessing the distance to nebulae and in determining the scale of the Galaxy. Some researchers took stellar nebulae far beyond the boundaries of our Galaxy and called them “island universes”; others (and these were the majority), on the contrary, included these nebulae as part of the Milky Way.

Everything fell into place when in the 20s. Cepheids were discovered in nearby spiral nebulae, which made it possible to estimate the distances to them.

Cepheids are stars of variable luminosity, so named after the first star of this type discovered in the constellation Cepheus. The brightness of Cepheids changes periodically, and the less frequently a star flares, the greater the luminosity it reaches at maximum brightness. Cepheid periods vary from hours to months. By measuring the pulsation period of a star and its brightness at maximum, you can determine the distance to it.

Refinement of the Cepheid distance scale in 1952 doubled all intergalactic distances. With the new scale, the sizes of nearby spiral nebulae became comparable to the sizes of the Milky Way, and sometimes even exceeded them. Thus, the latest evidence was obtained that spiral nebulae are huge star systems comparable to our Galaxy and millions of light years away from it. Since then they began to be called galaxies.

Spiral galaxies resemble a lentil or a lenticular lens in appearance. On the galactic disk there is a noticeable spiral pattern of 2 or more (up to 10) branches or arms twisted in one direction, extending from the center of the galaxy. The spiral arms contain many young bright stars and luminous gas clouds heated by them. The disk is immersed in a rarefied, weakly luminous spheroidal cloud of stars - a halo. Half of all observed galaxies belong to this class. They are designated by the letter S. The stars and gas in them revolve around the center of the galaxy, and with different angular speeds at different distances from the center.

Just looking at a photograph of a spiral galaxy evokes admiration and wonder: how could such a system of stars arise? What force collects and holds stars in spiral branches? Why are the brightest, most massive, and therefore short-lived stars in the spiral arms, while between the arms are mostly faint, long-lived stars? Why does the galaxy look like two saucers with their edges next to each other? Why is there a spherical “bulge” (bulge) formed by low-mass yellow and red stars at the center of edge-on galaxies? And many more similar questions can be asked if you delve into the depths of the creation of the world and the universe. And the more answers scientists receive, the more questions they face. So it was and so it will be. But we can try to answer some of them using the materials that we have.

The flat, disc-shaped shape is due to rotation. During the formation of the galaxy, centrifugal forces prevented the compression of the protogalactic cloud or system of gas clouds in the direction perpendicular to the axis of rotation. As a result, the gas concentrated towards a certain plane - this is how rotating disks of spiral galaxies were formed. The disk did not rotate as a single solid body (for example, a wheel): the period of revolution of the stars along the edges of the disk is much longer than in the inner parts.

Astronomers had to put a lot of effort into understanding the reason for other observed properties of spiral galaxies. Domestic science made a significant contribution to the study of their nature. This is how we imagine the nature of the spiral arms of galaxies today.

All the stars inhabiting the galaxy interact gravitationally, resulting in the creation of a common gravitational field of the galaxy. There are several known reasons why, when a massive disk rotates, regular compactions of matter arise, spreading like waves on the surface of water. In galaxies they have the shape of spirals, which is due to the nature of the rotation of the disk. In the spiral branches, an increase in the density of both stars and interstellar matter - dust and gas - is observed. Increased gas density accelerates the formation and subsequent compression of gas clouds and thereby stimulates the birth of new stars. Therefore, spiral arms are sites of intense star formation.

Spiral branches are density waves traveling along a rotating disk. Therefore, after some time, a star born in a spiral ends up outside it. The brightest and most massive stars have a very short lifespan; they burn out before they have time to leave the spiral branch. Less massive stars live long and live out their lives in the interspiral space of the disk.

The low-mass yellow and red stars that make up the bulge are much older than the stars concentrated in the spiral arms. These stars were born before the galactic disk formed. Having arisen in the center of the protogalactic cloud, they could no longer be involved in compression towards the plane of the galaxy and therefore form a spherical structure.

The galaxy's bulge and disk are embedded in a massive halo. Some researchers suggest that the bulk of the halo mass lies not in stars, but in non-luminous (hidden) matter, consisting either of bodies with a mass intermediate between the masses of stars and planets, or of elementary particles, the existence of which is predicted by theorists, but which have yet to be discovered . The problem of the nature of this substance - the hidden mass - is now occupying the minds of many scientists, and its solution may provide the key to the nature of matter in the Universe as a whole.

In this photograph of the strikingly beautiful galaxy M 51, called the Whirlpool in the constellation Canes Venatici, a small satellite galaxy is visible at the end of one of the spiral arms. It orbits the mother galaxy. It was possible to build a computer model of the formation of this system. It is assumed that a small galaxy, flying close to a large one, led to strong gravitational (tidal) disturbances of its disk. As a result, a spiral-shaped density wave is created in the disk of a large galaxy. Stars born in the spiral arms make the arms appear bright and clear.

2. 2 Ellipticalgalaxies

Elliptical galaxies make up 25% of the total number of high-luminosity galaxies. They are usually denoted by the letter E (elliptical), to which a number from 0 to 6 is added, corresponding to the degree of flattening of the system (E0 - “spherical” galaxies, E6 - the most “oblate”). Elliptical galaxies are reddish in color because they are composed primarily of old stars.

There is almost no cold gas in such systems, but the most massive of them are filled with very rarefied hot gas, with a temperature of more than a million degrees. The emission spectrum of these galaxies shows that the stars in them move with almost equal probability in all directions, and they rotate slowly. The density of stars per unit volume increases towards the center and smoothly decreases from the center to the edge.

There are no blue-white giants or supergiants. There is no dust matter, which in those galaxies in which it is present is visible as dark stripes against the continuous background of the stars of the galaxy. Therefore, externally, elliptical galaxies differ from each other mainly in one feature - greater or lesser compression. Hubble proposed that the compression indicator be considered a value that can be calculated by knowing the major and minor axis of its ellipse. If the galaxy has the shape of a ball, then its compression value is zero, since the major and minor axes of the ellipse are equal. If the major axis is significantly larger than the minor axis, then a different class, the maximum class in this system is 10. These data are written as follows: E0, E7, where E is a class (elliptic), the number is a subclass. In addition, elliptical galaxies can differ greatly in size from each other. The formation of new stars has practically not occurred over the past 10 billion years.

Lenticular galaxies are an intermediate type between spiral and elliptical. They have a halo and disk, but no spiral arms. Such galaxies are designated S0.

The fraction of elliptical galaxies in total number galaxies in the observable part of the universe - about 13%.

The closest elliptical galaxy to us is a dwarf galaxy in the constellation Sculptor (ESO 351-30, subclass - dE0 or dSph, radius - 1505 light years)

2.3 Incorrectgalaxies

Incorrectgalaxies-- these are galaxies that do not fit into the Hubble sequence. They exhibit neither a spiral nor an elliptical structure. Most often, such galaxies have a chaotic shape without a pronounced core and spiral branches. As a percentage, they make up one quarter of all galaxies. Most irregular galaxies in the past were spiral or elliptical, but were deformed by gravitational forces.

There are two large types of irregular galaxies:

§ Irregular galaxies of the first type ( IrrI) are irregular galaxies that have hints of structure, which, however, are not enough to assign them to the Hubble sequence. There are two subtypes of such galaxies - those exhibiting a similar spiral structure ( Sm), and with the absence of such ( Im).

§ Irregular galaxies of the second type ( IrrII) are galaxies that do not have any features in their structure that allow them to be attributed to the Hubble sequence.

The third subtype of irregular galaxies are the so-called dwarf irregular galaxies, designated as dI or dIrrs. This type of galaxy is now considered an important link in understanding the overall evolution of galaxies. This is because they tend to have low metal content and extremely high gas content and are therefore implied to be similar to the earliest galaxies to fill the Universe. This type of galaxy may represent a local (and therefore most modern) version of the faint blue galaxies discovered by the Hubble Ultra Deep Field mission.

Some irregular galaxies are small spiral galaxies destroyed by the tidal forces of larger companions.

In the past, the Large and Small Magellanic Clouds were thought to be irregular galaxies. However, they were later discovered to have a helical structure with a bar. Therefore, these galaxies were reclassified as SBm, the fourth type of barred spiral galaxy.

3. ModernrepresentationOgalaxies

Galaxies have become the subject of cosmogonic research since the 20s of the twentieth century, when their actual nature was reliably established and it turned out that they were not nebulae, i.e. not clouds of gas and dust located near us, but huge star worlds lying at very great distances from us. All modern cosmology is based on one fundamental idea - the idea of gravitational instability, dating back to Newton. Matter cannot remain uniformly dispersed in space, because the mutual attraction of all particles of matter tends to create in it concentrations of certain scales and masses. In the early Universe, gravitational instability intensified initially very weak irregularities in the distribution and movement of matter and at a certain epoch led to the emergence of strong inhomogeneities: “pancakes” - protoclusters. The boundaries of these compaction layers were shock waves, at the fronts of which the initially non-rotational, irrotational motion of matter acquired vorticity. The disintegration of layers into separate condensations also occurred, apparently due to gravitational instability, and this gave rise to protogalaxies. Many of them turned out to be rapidly rotating due to the swirling state of the substance from which they were formed. Fragmentation of protogalactic clouds as a result of their gravitational instability led to the emergence of the first stars, and the clouds turned into star systems - galaxies. Those of them that had rapid rotation acquired a two-component structure because of this - a more or less spherical halo and a disk were formed in them, in which spiral arms arose, where the birth of Protogalaxy stars, whose rotation was slower, still continues or completely absent, turned into elliptical or irregular galaxies. In parallel with this process, the formation of a large-scale structure of the Universe took place - superclusters of galaxies arose, which, connecting with their edges, formed a kind of cells or honeycombs; they have been recognized in recent years.

Subsequent observations showed that the described classification is not sufficient to systematize the entire variety of forms and properties of galaxies. Thus, galaxies were discovered that occupy, in a sense, an intermediate position between spiral and elliptical galaxies (denoted So). These galaxies have a huge central clump and a surrounding flat disk, but no spiral arms. In the 60s of the twentieth century, numerous finger-shaped and disk-shaped galaxies were discovered with all gradations of the abundance of hot stars and dust. Back in the 30s of the twentieth century, elliptical dwarf galaxies were discovered in the constellations Furnace and Sculptor with extremely low surface brightness, so low that these, one of the closest galaxies to us, even in their central part are hardly visible against the sky. On the other hand, in the early 60s of the twentieth century, many distant compact galaxies were discovered, of which the most distant in appearance are indistinguishable from stars even in the strongest telescopes. They differ from stars in their spectrum, in which bright emission lines are visible with enormous redshifts, corresponding to such great distances that even the brightest single stars cannot be seen. Unlike ordinary distant galaxies, which appear reddish due to a combination of their true spectral energy distribution and redshift, the most compact galaxies (also called quasi-stellar galaxies) are bluish in color. As a rule, these objects are hundreds of times brighter than ordinary supergiant galaxies, but there are also fainter ones. Radio emission of a non-thermal nature has been detected in many galaxies, arising, according to the theory of the Russian astronomer I.S. Shklovsky, when electrons and heavier charged particles moving at speeds close to the speed of light are decelerated in a magnetic field (the so-called synchotron radiation). Particles achieve such speeds as a result of grandiose explosions inside galaxies.

Compact, distant galaxies that emit powerful non-thermal radio emissions are called N-galaxies.

Star-shaped sources with such radio emission are called quasars (quasi-stellar radio sources), and galaxies with powerful radio emission and having noticeable angular dimensions are called radio galaxies. All these objects are extremely far from us, which makes them difficult to study. Radio galaxies, which have particularly powerful non-thermal radio emission, have a predominantly elliptical shape; spiral ones are also found.

Radio galaxies are galaxies whose cores are in the process of decay. The ejected dense parts continue to fragment, possibly forming new galaxies - sisters, or satellites of galaxies of lower mass. At the same time, the speed of dispersion of fragments can reach enormous values. Research has shown that many groups and even clusters of galaxies are disintegrating: their members are moving indefinitely away from each other, as if they were all generated by an explosion.

Supergiant galaxies have luminosities 10 times greater than the luminosity of the Sun, quasars are on average another 100 times brighter; The faintest of the known galaxies - dwarfs - are comparable to ordinary globular star clusters in our galaxy. Their luminosity is about 10 times the luminosity of the sun.

The sizes of galaxies are very diverse and range from tens of parsecs to tens of thousands of parsecs.

The space between galaxies, especially within galaxy clusters, appears to sometimes contain cosmic dust. Radio telescopes do not detect a noticeable amount of neutral hydrogen in them, but cosmic rays penetrate through it in the same way as in electromagnetic radiation.

The galaxy consists of many stars of various types, as well as star clusters and associations, gas and dust nebulae, and individual atoms and particles scattered in interstellar space. Most of them occupy a lens-shaped volume with a diameter of about 30 and a thickness of about 4 kiloparsecs (about 100 thousand and 12 thousand light years, respectively). The smaller part fills an almost spherical volume with a radius of about 15 kiloparsecs (about 50 thousand light years).

All components of the galaxy are connected into a single dynamic system rotating around a minor axis of symmetry. To an earthly observer located inside the galaxy, it appears in the form of the Milky Way (hence its name - “Galaxy”) and the entire multitude of individual stars visible in the sky.

Stars and interstellar gas and dust matter fill the volume of the galaxy unevenly: they are most concentrated near the plane perpendicular to the axis of rotation of the galaxy and the component plane of its symmetry (the so-called galactic plane). Near the line of intersection of this plane with the celestial sphere (galactic equator), the Milky Way is visible, the middle line of which is almost a large circle, since the Solar system is located not far from this plane. The Milky Way is a collection of a huge number of stars merging into a wide whitish stripe; however, the stars projected in the sky nearby are removed from each other in space at enormous distances, excluding their collisions, despite the fact that they move at high speeds (tens and hundreds of km/sec) in the direction of the poles of the galaxy (its North Pole located in the constellation Coma Berenices). Total There are an estimated 100 billion stars in the galaxy.

Interstellar matter is also scattered in space unevenly, concentrating mainly near the galactic plane in the form of globules, individual clouds and nebulae (from 5 to 20 - 30 parsecs in diameter), their complexes or amorphous diffuse formations. Particularly powerful dark nebulae that are relatively close to us appear to the naked eye as dark clearings. irregular shapes against the background of the strip of the Milky Way; Their lack of stars is a result of light being absorbed by these non-luminous dust clouds. Many interstellar clouds are illuminated by high-luminosity stars close to them and appear as bright nebulae, since they glow either by reflected light (if they consist of cosmic dust grains) or as a result of the excitation of atoms and their subsequent emission of energy (if the nebulae are gaseous).

Conclusion

Our days are rightfully called the golden age of astrophysics - remarkable and most often unexpected discoveries in the world of stars are now following one after another. The solar system has become Lately the subject of direct experimental, and not just observational studies. Interplanetary flights space stations, orbital laboratories, expeditions to the Moon brought a lot of new specific knowledge about the Earth, near-Earth space, planets, the Sun and galaxies. We live in an era of amazing scientific discoveries and great achievements. The most incredible fantasies unexpectedly quickly come true. For a long time, people have dreamed of unraveling the secrets of the Galaxies scattered in the boundless expanses of the Universe. One can only be amazed at how quickly science puts forward various hypotheses and immediately refutes them. However, astronomy does not stand still: new methods of observation are emerging and old ones are being modernized. With the invention of radio telescopes, for example, astronomers can “look” at distances that are still in the 40s. years of the twentieth century seemed inaccessible. However, one must clearly imagine the enormous magnitude of this path and the colossal difficulties that still lie ahead on the path to the stars.

Listusedliterature

1. Zelmanova A.L. "Metagalaxy and the Universe". M., 2000.

2. About the systems of the galaxy / M. B. Sizov. - M.: Prometheus, 2009. - 16 p.

3. Origin and evolution of the Earth and other planets of the Solar system / A. A. Marakushev. - M.: Science, - 204 p.

4. Physical model of the Universe / B. P. Ivanov. - St. Petersburg: Politekhnika, 2000. - 312 p.

5. Evolution of the solar system: Transl. from English / H. Alven, G. Arrhenius. - M.: Mir, - 511 p.

Posted on Allbest.ru

Diagnostics and diseases. Medicines from A to Z