How many galaxies in the universe is known to modern man? Types of galaxies in the universe

Galaxy (Late Greek Galaktikos - milky, milky, from Greek gala - milk)

the vast star system to which the Sun belongs, and therefore our entire planetary system, together with the Earth. G. consists of many stars 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 lenticular volume with a diameter of about 30 and a thickness of about 4 kiloparsec. (respectively, about 100 thousand and 12 thousand light years). A smaller part fills an almost spherical volume with a radius of about 15 kiloparsec (about 50 thousand light years). All components of the hydrodynamic system are linked into a single dynamic system that rotates around a minor axis of symmetry. To an earthly observer who is inside the G., it appears in the form of the Milky Way (hence its name - "G.") and the whole multitude of individual stars visible in the sky. In this regard, G. is also called the system of the Milky Way. Unlike all other galaxies (See Galaxies) , the one to which the Sun belongs is sometimes called "our Galaxy" (the term is always written with a capital letter).

Stars and interstellar gas and dust fill the volume of the galaxy unevenly: they are most concentrated near the plane perpendicular to the axis of rotation of the galaxy and which is its plane of symmetry (the so-called galactic plane). Near the line of intersection of this plane with the celestial sphere (the galactic equator (See Galactic equator)) and see the Milky Way middle line which is almost big circle, because the solar system is not far from this plane. The Milky Way is a cluster of a huge number of stars merging into a wide whitish band; however, the stars projected nearby in the sky are far from each other in space at great distances, excluding their collisions, despite the fact that they move at high speeds (tens and hundreds km/s) in different directions. The lowest density of the distribution of stars in space (spatial density) is observed in the direction of the planet's poles (its north pole is in the constellation Coma Berenices). The total number of stars in G. is estimated at 100 billion.

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

The total mass of galaxies, including all stars and interstellar matter, is estimated at 10 11 solar masses, i.e., about 10 44 G. As the results of detailed studies show, the structure of the galaxy is similar to the structure of a large galaxy in the constellation Andromeda, a galaxy in the constellation Coma Veronica, etc. However, being inside the galaxy, we cannot see its entire structure as a whole, which makes it difficult to study it.

The stellar nature of the Milky Way was first discovered by G. Galileo in 1610, but a consistent study of the structure of the Milky Way began only at the end of the 18th century, when V. Herschel, using his "scoop method", calculated the number of stars visible in his telescope in various directions. Based on the results of these observations, he suggested that the observed stars form a giant oblate system. V. Ya. Struve discovered (1847) that the number of stars per unit volume increases with approach to the galactic plane, that interstellar space is not perfectly transparent, and the Sun is not located at the center of G. In 1859, M. A. Kovalsky pointed out a probable axial rotation of the entire gyratory system. The first more or less substantiated estimates of the dimensions of the horn were made by the German astronomer H. Zeliger and the Dutch astronomer J. Kaptein in the first quarter of the 20th century. Zeliger, admitting an uneven distribution of stars in space and their different luminosities, concluded that surfaces of the same stellar density are ellipsoids of revolution with a contraction of 1:5. However, due to the disregard for the distorting effect of interstellar absorption of stellar light, many of the first conclusions were erroneous; in particular, the dimensions of the city turned out to be exaggerated. When determining the position of the Sun (Earth) in the city, most researchers attributed it to the center of the city, main reason which was also ignoring the effect of light absorption. This view was also supported by the vitality of the geocentric and anthropocentric world view. In the 20s. 20th century The American astronomer H. Shapley finally proved the non-central position of the Sun in H., while determining the direction to the center of H. (in the constellation Sagittarius).

In the mid 20s. 20th century G. Strömberg (USA), studying the laws of motion of the Sun relative to various groups of stars, discovered the so-called. the asymmetry of stellar movements, which provided factual material for substantiating many conclusions about the complexity of the structure G. Shved. the astronomer B. Lindblad (20s of the 20th century), studying the dynamics and structure of gyroscopes on the basis of an analysis of the velocities of stars, discovered the complexity of the structure of gyros and the fundamental difference in the spatial velocities of the stars inhabiting different parts of the gyrus, although they are all connected into a single system symmetrical with respect to the galactic plane. In 1927, the Dutch astronomer J. Oort, on the basis of a statistical study of the radial velocities and proper motions of stars, proved the existence of gyratory rotation around its own minor axis. It turned out that the internal, closer to the center, parts of the G. rotate faster than the external ones. At the distance of the Sun from the center of G. (10 kiloparsec) this speed is about 250 km/s; the period of a complete revolution is about 180 million years.

Proof of interstellar absorption of stellar light (1930, Soviet astronomer B. A. Vorontsov-Velyaminov, American astronomer R. Trumpler), his quantitative estimates and accounting made it possible to clarify the distances to individual galactic objects and the dimensions of the planet, and laid the foundation for revealing the details of its structure. Numerous studies of the spatial distribution of stars of various types (the Soviet astronomer P. P. Parenago and others), the proper motions of stars (the early work of S. K. Kostinsky at the Pulkovo Observatory, the American astronomer V. Bos, and others), the motion of the Sun in space, as well as the movements of stellar streams (by the Soviet astronomer V. G. Fesenkov, the Dutch astronomer A. Blau, etc.), the study of the galactic gravitational field, etc. made it possible to discover, on the one hand, many general patterns, and on the other hand, a great variety in kinematic, physical and structural characteristics of individual components of G.

In the 30s and subsequent years of the 20th century. Soviet astronomical observatories have made significant progress in the field of astronomical research. Important results have been obtained: in the field of the dynamics of stellar systems; in observations and compilation of numerous catalogs of the parameters of stars and other galactic objects; in the development of new views on the nature of the interstellar medium; in the development of new theories and methods that made it possible to carry out quantitative estimates of the parameters characterizing absorption in galactic space; in elucidating the connections between stars and interstellar matter. In selected regions of the Milky Way, according to the plan of G. A. Shain (USSR) and according to the comprehensive plan of P. P. Parenago, photometry and spectral classification of tens of thousands of stars were carried out. Great value In order to understand the processes of development, astrology had the discovery of stellar associations (see stellar associations). Advances in the Soviet science of variable stars played an important role in the study of galaxies. Comparison of their physical features and morphological characteristics with age and spatial parameters made it possible to solve a number of problems of the structure and nature of G. Studies by Soviet and American astronomers made it obvious complex structure G. It turned out that various parts G. correspond to various, well-defined elements of their composition. In 1948, as a result of observations in infrared rays, Soviet researchers obtained for the first time an image of the G nucleus. 20th century showed that our G. has spiral arms. The study of astronomy, its structure, and development is primarily the subject of three branches of astronomy: stellar astronomy, astrometry, and astrophysics. All these sections have played a major role in refining and detailing our ideas about gravitation. The development of radio astronomy, which has obtained much new information about gravitation, has been of great importance for the study of gravitation. hydrogen, study their movements, find out common features internal structure G.

By the beginning of the 70s. 20th century as a result of studies carried out in the USSR and abroad, the following idea of ​​​​g. has developed. , The thickness of the layer located along the plane of the galactic equator, inside which the majority of stars and the bulk of the interstellar matter is located, is 400-500 parsec. The spatial density of stars in it is such that one star falls on a volume equal to a cube with an edge of 2 parsec. In the vicinity of the Sun, the density is somewhat less. It increases significantly as it approaches the center of G., which, when observed from the Earth, is visible in the constellation Sagittarius. Consequently, the distribution of stars is characterized by a concentration both toward the planetary plane and toward its center. The total mass of interstellar gas in G. is about 0.05 the mass of all stars, and its average density near the plane of the equator does not exceed 10 -25 or 10 -24 g/cm 3. Interstellar dust, consisting of solid particles, the radii of which are of the order of 10 -4 -10 -5 cm, in its mass is about 100 times less than the mass of gas. Due to its negligible mass, dust does not affect the dynamics of gravity, but nevertheless noticeably affects the visible structure of gravity, scattering the light of stars passing through its medium. The core of G., being immersed in relatively dense masses of interstellar matter, is not easily accessible optical observations, but radio astronomical observations indicate the activity of the nucleus, the presence in it of large masses of matter and energy sources.

G. has a pronounced subsystem structure; There are three subsystems: flat, intermediate and spherical. The flat subsystem is characterized by the presence of young hot stars, variable stars such as long-period Cepheids, stellar associations, open star clusters, and gas and dust matter. All of them are concentrated near the galactic plane in the form of an equatorial disk (thickness is 1/20 of the galactic diameter). Average age The stellar population of the disk is about 3 billion years. The yellow and red dwarf and giant stars, which occupy a volume in the form of a strongly oblate ellipsoid, are less concentrated towards the galvanic plane. All subdwarfs, yellow and red giants, variable stars such as short-period Cepheids and globular star clusters form a spherical component (sometimes called a halo), filling a spherical volume (with an average diameter exceeding 30 thousand km). parsec, i.e. 100 thousand light years) with sharp drop density in the direction from the central regions to the periphery. Its age is more than 5 billion years. Objects of different components differ from each other also in the speed of movement, and chemical composition. The stars of the flat component have high velocities of motion relative to the center of the galaxy, and they are richer in metals. This indicates that stars of different types belonging to different subsystems were formed under different initial conditions and in various areas space occupied by galactic matter. The entire galactic system is immersed in a vast gaseous mass, which is sometimes called the galactic corona (See Galactic corona). Spiral branches propagate from the central region of the galaxy along the galactic plane, which, going around the nucleus and branching, gradually expand, losing brightness. A spiral structure that turned out to be very characteristic property galaxies at some stage of their evolution, G. is similar to many other stellar systems of the same type as it, which have the same stellar composition. Apparently, gravitational forces and magnetohydrodynamic phenomena play a role in the development of the spiral structure, while it is also influenced by the features of rotation G. Star formation occurs along the spiral branches and they are inhabited by the youngest galactic objects.

Questions of the evolution of geometry as a whole or of its individual constituent elements are of great ideological significance. For a long time, the view of the simultaneous formation of all stars and other G objects dominated. Such a view was associated with the recognition of the simultaneous origin of all galaxies at one point in the Universe and their subsequent "scattering" in different sides from her. However, detailed studies based on numerous observations led to the conclusion (by the Soviet astronomer V. A. Ambartsumyan) that the process of star formation continues in the present epoch.

The problem of the origin and development of stars in galaxies is a fundamental problem. There are two main but opposite points of view on the formation of stars. According to the first of these, stars are formed from gaseous matter, which is scattered in significant amounts in the galaxy and observed by optical and radio astronomical methods. The gaseous substance, where its mass and density reach a sufficiently large value, is compressed and compacted under the influence of its own attraction, forming a cold ball. In the process of further compression, the temperature inside it, however, rises to several million degrees; this is sufficient for the occurrence of thermonuclear reactions, which, together with the processes of radiation, determine the further evolution of this ball-star. According to the second point of view, stars are formed from some superdense matter. Superdense matter of this kind has not yet been discovered and its properties are unknown, but the fact that in the observable Universe the processes of outflow of masses from stars, fission and decay of systems are observed in many cases, while the processes of formation of stars from interstellar matter are not observed, speaks in favor of the second point vision.

It is assumed that the gas as a whole developed in the process of condensation of a primary gas cloud rich in hydrogen; the stars formed in this process are observed in our epoch as stars of the spherical component, poor in metals and having the greatest age. The primary gas cloud, continuing to shrink under the influence of gravitational forces, was enriched in metals due to the ejection of matter from the interiors of previously formed stars, in which intranuclear reactions had been going on for many hundreds of millions of years and hydrogen was turning into heavier elements. For this reason, the later "generation" of stars that formed the G disk turned out to be richer in metals. This concept explains the observed distribution of stellar velocities and the stratification of the latter into subsystems. However, there are many inconsistencies in this picture. The idea developed by a number of Soviet astronomers about the role of powerful explosive repulsive forces hidden in the interior of galaxies in the evolution of galaxies can shed new light on the problem of the development of G.

Cm. ill.

Lit.: Parenago P. P., Course of stellar astronomy, 3rd ed., M., 1954; Bok B. J. and Bok P. F., Milky Way, trans. from English, M., 1959; Course of astrophysics and stellar astronomy, vol. 2, M., 1962; Bakulin P. I., Kononovich E. V., Moroz V. I., Course of General Astronomy, M., 1966.

E. K. Kharadze.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

Synonyms:

See what "Galaxy" is in other dictionaries:

GALAXY, huge cluster stars, dust and gas. An example is our own galaxy. According to Edwin Hubble's 1925 classification, there are three main types of galaxies. Elliptical galaxies (E) are round or ... ... Scientific and technical encyclopedic dictionary

Galaxy- Galaxy. Schematic representation of the Galaxy (edge-on view). GALAXY, star system (spiral galaxy) to which the Sun belongs (to distinguish it from other galaxies, it is written with a capital letter). The galaxy contains at least 1011 stars ... ... Illustrated Encyclopedic Dictionary

GALAXY, star system (spiral galaxy) to which the Sun belongs (to distinguish it from other galaxies, it is written with a capital letter). The galaxy contains at least 1011 stars (a total mass of 1011 solar masses), interstellar matter (gas and dust, ... ... Modern Encyclopedia

- (from Greek galaktikos milky) star system (spiral galaxy) to which the Sun belongs. The galaxy contains at least 1011 stars (with a total mass of 1011 solar masses), interstellar matter (gas and dust, the mass of which is several ... ... Big Encyclopedic Dictionary

GALAXY, and, wives. Giant star system. Our G. (the one to which the Sun belongs). other galaxies. | adj. galactic, oh, oh. Galactic nebulae. Dictionary Ozhegov. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 ... Explanatory dictionary of Ozhegov

The universe is huge and fascinating. It is difficult to imagine how small the Earth is compared to the abyss of space. According to the most cautious assumptions of astronomers, there are 100 billion galaxies, and the Milky Way is just one of them. As for the Earth, there are 17 billion such planets in the Milky Way alone... and that's not counting others that are radically different from our planet. And among the galaxies that have become known to scientists today, there are very unusual ones.

1. Messier 82

Messier 82 or simply M82 is a galaxy five times brighter than the Milky Way. This is due to the very rapid process of the birth of young stars in it - they appear 10 times more often than in our galaxy. The red plumes emanating from the center of the galaxy are glowing hydrogen ejected from the center of M82.

2. Sunflower Galaxy

Formally known as Messier 63, this galaxy has been nicknamed the Sunflower because it looks like it stepped out of a Vincent van Gogh painting. Its bright, sinuous "petals" are made up of newly formed blue-white giant stars.

3. MACS J0717

MACS J0717 is one of the strangest galaxies known to scientists. Technically, this is not a single stellar object, but a cluster of galaxies - MACS J0717 was formed when four other galaxies collided. Moreover, the collision process has been going on for more than 13 million years.

4. Messier 74

If Santa Claus had a favorite galaxy, it would clearly be Messier 74. It is often remembered by astronomers during the Christmas holidays, because the galaxy is very similar to the Christmas wreath.

5. Baby Boom Galaxy

Located about 12.2 billion light-years from Earth, the baby boom galaxy was discovered in 2008. She got her nickname due to the fact that new stars are born incredibly quickly in her - about every 2 hours. For example, in the Milky Way, a new star appears on average every 36 days.

6 Milky Way

Our Milky Way Galaxy (which contains the Solar System, and, accordingly, the Earth) is indeed one of the most remarkable galaxies known to scientists in the Universe. It contains at least 100 billion planets and about 200-400 billion stars, some of which are among the oldest in the known universe.

7. IDCS 1426

Thanks to the cluster of galaxies IDCS 1426, today you can see what the Universe used to be two-thirds younger than it is now. IDCS 1426 is the most massive cluster of galaxies in the early universe, with a mass of about 500 trillion suns. The bright blue core of a galaxy of gas is the result of a collision of galaxies in this cluster.

8. I Zwicky 18

The dwarf blue galaxy I Zwicky 18 is the youngest known galaxy. She is only 500 million years old (the age of the Milky Way is 12 billion years) and is essentially in the state of an embryo. This is a giant cloud of cold hydrogen and helium.

9. NGC 6744

NGC 6744 is a large spiral galaxy that is (according to astronomers) one of the most similar to our Milky Way. The galaxy, located about 30 million light-years from Earth, has an elongated core and spiral arms that are surprisingly identical to the Milky Way.

10 NGC 6872

The galaxy, known as NGC 6872, is the second largest spiral galaxy ever discovered by scientists. Many regions of active star formation have been found in it. Since NGC 6872 has practically no free hydrogen left for star formation, it "sucks" it from the neighboring galaxy IC 4970.

11. MACS J0416

Found 4.3 billion light-years from Earth, the MACS J0416 galaxy looks more like some kind of light show at a fancy disco. In fact, behind the bright purple and pink flowers hides an event of colossal scale - a collision of two clusters of galaxies.

12. M60 and NGC 4647 - a galactic pair

Although gravitational forces pull most galaxies towards each other, there is no evidence that this is happening to neighboring Messier 60 and NGC 4647. There is also no evidence that they are moving away from each other. Like a couple living together for a long time, these two galaxies race side by side through cold and dark space.

13. Messier 81

Located near Messier 25, Messier 81 is a spiral galaxy with a supermassive black hole at its center, with a mass 70 million times that of the Sun. M81 is home to many short lived but very hot blue stars. The gravitational interaction with M82 has led to plumes of hydrogen gas stretching between both galaxies.

About 600 million years ago, the galaxies NGC 4038 and NGC 4039 crashed into each other, starting to massively exchange stars and galactic matter. because of appearance these galaxies are called antennae.

15. Sombrero Galaxy

The Sombrero Galaxy is one of the most popular among amateur astronomers. It got its name from the fact that, thanks to its bright core and large central bulge, it looks like this headdress.

16.2MASX J16270254+4328340

This blurry galaxy in all the pictures is known for its rather complicated name 2MASX J16270254 + 4328340. As a result of the merger of two galaxies, a "fine fog consisting of millions of stars" was formed. This "fog" is thought to be slowly dissipating as the galaxy's lifespan expires.

17. NGC 5793

Not too strange (although very beautiful) at first glance, the spiral galaxy NGC 5793 is better known for its rare phenomenon: masers. People are familiar with lasers that emit light in the visible region of the spectrum, but few people know about masers that emit light in the microwave range.

18. Triangulum Galaxy

This photo shows the nebula NGC 604, located in one of the spiral arms of the Messier 33 galaxy. More than 200 very hot stars heat the ionized hydrogen in this nebula, which causes it to fluoresce.

19. NGC 2685

NGC 2685, also sometimes referred to as a spiral galaxy, lies in the constellation Ursa Major. One of the first polar ring galaxies to be found, NGC 2685 has an outer ring of gas and stars orbiting the galaxy's poles, making it one of the rarest galaxies. Scientists still don't know what causes these polar rings to form.

20. Messier 94

Messier 94 looks like a terrible hurricane that was removed from orbit on Earth. This galaxy is surrounded by bright blue rings of actively forming stars.

21. Pandora Cluster

Formally known as Abell 2744, this galaxy has been nicknamed the Pandora Cluster because of its range of strange phenomena resulting from the collision of several smaller clusters of galaxies. It's a real chaos.

22. NGC 5408

What looks more like a colorful birthday cake in the pictures is an irregular galaxy in the constellation Centaurus. It is notable for the fact that it emits super-powerful X-rays.

23. Whirlpool Galaxy

The Whirlpool Galaxy, officially known as M51a or NGC 5194, is large enough and close enough to the Milky Way to be visible in the night sky even with binoculars. It was the first spiral galaxy to be classified and is of particular interest to scientists due to its interaction with the dwarf galaxy NGC 5195.

24. SDSS J1038+4849

The galaxy cluster SDSS J1038+4849 is one of the most attractive clusters ever found by astronomers. It looks like a real smiley in space. The eyes and nose are galaxies, and the curved line of the "mouth" is due to the effects of gravitational lensing.

25. NGC3314a and NGC3314b

Although these two galaxies look like they are colliding, they are actually optical illusion. There are tens of millions of light years between them.

We have a magnificent observatory in the city. And I loved to disappear there in my school years. The workers were loyal to me and fed my curiosity, shared the nuances of work and interesting astronomical facts. I remember that time with great fondness.

The emergence of galaxies

What is a galaxy? It's one of the fundamental concepts. I remember how they took me around the observatory museum and told me about it. What shortly after the Big Bang galaxies began to form as stars were born and gravitationally attracted to each other in sheets of gas caused by small fluctuations in the density of matter in the young universe. Then the stars began to form protogalaxies. It was very hard to imagine. But it felt like something unthinkable, grandiose.

In fact, now I understand what the galaxy is collection of stars and planets, a huge amount of gas and dust that are held together by gravity. And all the heavenly bodies revolve around the central object. Just dry facts. And then it was practically magic.

How galaxies are classified

There, in the observatory, there were huge models of various types of galaxies. It turns out that most of the bright galaxies nearby are spiral. They differ in shape and size, interact with each other, sometimes crash into each other and merge, sometimes tearing each other apart. In general, all galaxies are divided into four main types:

•  spiral galaxies;
• galaxies with jumper;
• elliptical;
• irregular galaxies.

Spiral galaxy emerges when stars inside a protogalaxy are born at different intervals. The gas between developing stars is collapsing, and as a result, gravitational differences govern the stars, dust, and gas of the protogalaxy. This movement causes everything to rotate, and differences in gravity lead to the appearance of spiral arms.

When I look at the sky, I constantly mentally fly away to the stars and see in my imagination all this splendor. Stars gather into galaxies. Galaxies - into groups of galaxies, and these groups - into clusters.

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Many kids love Milky Way bars. And my grandson is no exception. Knowing the Basics of English language, he understands that milky means milky, and way means the way, the road. But recently he learned that the creators meant by this name not a trip along the roads with milk chocolate, but the name of our Galaxy "Milky Way". And then a hail of questions rained down:

1. why our Galaxy called " Milky Way»?
2. what Galaxy generally?
3. if there is our Galaxy, so there are not ours galaxies?

I will try to answer these questions. I think that the answers may be useful to you in communicating with your children and grandchildren.

Origin of the name "Milky Way"

The beauty of the night sky, the celestial objects and phenomena themselves have attracted the attention of people since time immemorial. But astronomical knowledge, which has taken shape in science, has come down to us from scientists Ancient Greece(Hellas). So, for example, the picture of the world Ptolemy dominated Europe for 14 centuries. But among the ancient Greeks themselves, ideas about the world around were intertwined with their religious ideas and myths. Name "Milky Way" comes from Hellenic legends.

When the boy was born who was to become a mighty hero Hercules he was placed on the bed of the sleeping supreme goddess Hera for him to drink it breast milk and became immortal. But Hera woke up and pushed the mortal baby away, while her milk splashed across the sky, forming a whitish sparkling strip that crosses the entire celestial sphere. So, according to the ideas of the Hellenes, "Milky (Milky) Way".

Our Galaxy

"Galaxy", translated from ancient Greek, means "Milky Way". Of course, in our time, no one would even think of believing in such an explanation for the appearance of this amazing object in our sky. So what is Galaxy in fact?

We understand that life on Earth can only exist thanks to the radiation of light and heat from a huge cosmic object called sun. This fireball could contain 1,300,000 Earth-sized planets. But it looks like the size of a soccer ball, because it is very far from us. It turns out that all the stars in our sky are nothing but the same luminaries, somewhat different in temperature, size and age. It's just that they are all removed from us at colossal cosmic distances, which is why they look like burning sparks.

Stars in the universe are not distributed randomly. They are collected by the forces of attraction into stellar associations, which, due to rotation, take the form of a disk thickened in the center. They are called galaxies. The star formation to which our Sun belongs is called "Milky Way". We see it from the side, which is why it sparkles with a whitish stripe across the sky. Almost all objects observed in the starry sky also enter our galaxy.

Other galaxies

Ferdinand Magellan used whitish nebulae in the 15th century for navigation in the Southern Hemisphere, later named Magellanic Clouds.

Another such luminous little cloud ( Andromeda's nebula) back in the 10th century, a Persian astronomer observed As-Sufi.

Only in the 19th century, scientists armed with sophisticated optical equipment were able to prove that these objects are located outside of our galaxies and, just like "Milky Way", are huge star clusters. These are the others closest to us, Galaxies. And there are billions of them.

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When I was in the 7th (!) grade, I argued with my desk mate about which is bigger: the galaxy or the universe. Now I am very ashamed of this argument. Thankfully, I've learned a lot more about the universe since then.

What is a galaxy

The galaxy is not a measure of the division of the universe, as some people (mostly children) mistakenly believe. It's just a collection of stars, gas, dust, dark matter, planets, held together by the gravitational field and moving relative to the center of mass.

This is how not only planets and satellites move, but even the galaxy itself. Our galaxy is no exception, and we are now moving at great speed towards the center of the Universe.

Some of the galaxies can be seen from our planet even without the help of a telescope. Unfortunately, there are only 4 of them:

• Andromeda (visible in the Northern Hemisphere);
• Large and Small Magellanic Clouds (these are 2 galaxies, visible in the Southern Hemisphere);
• M33 in the constellation of the triangle (Northern Hemisphere).

It will be interesting to know that our galaxy is spiral, that is, it has arms, our solar system is located on the inner edge of one of them (Orion's arm), due to this location in the galaxy, we cannot see part of the arm through a telescope, for example .

What are groups of galaxies

In fact, there are very few lonely galaxies in the universe. About 96% are galactic associations. Very often in such clusters of galaxies there is one that is much larger than the others (dominant), and it is she who attracts the rest with her gravitational field. Over time, the largest galaxies absorb smaller ones, increasing their size.

Our galaxy is not alone either, it belongs to the local group of galaxies and dominates it along with Andromeda. The exact number of galaxies in our group is unknown, it is assumed that there are about 43 of them.

The dimensions of the universe itself are colossal, but it is also finite, there is absolutely nothing beyond 13.7 billion light years. But even the greatest minds of mankind find it difficult to answer the question of what this “nothing” is.

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I've been interested in astronomy for quite a long time, and I've studied everything! Films, books, pictures, articles, now it can be easily found, and I will try to answer your question here with the help of my knowledge. :) Space is fraught with many dangers and mysteries, and there is hardly a better place for us than the Earth. But let's take a look, shall we?

Our place in space

Everyone can well imagine our home planet, if you go higher into space, then there will be our solar system. It includes:

• 8 planets(they are all so different, beautiful and fraught with riddles that only, perhaps, have to be unraveled).
• the main star is a yellow dwarf Sun(did you know that this huge body, containing 1352418 of our planets, is called yellow dwarf? It turns out that there are stars much larger than our Sun!).
• well, where without stardust, meteorites and asteroids.
• we are surrounded Kuiper Belt- "remnants" from the formation of the solar system.

So...

We are leaving our solar system, but how many are around?! Can't count, billions planets, stars unimaginable in size clouds of gas, dust, energy... All this was formed due to the attraction to each other of this all by the forces gravity. All this (our galaxy) revolves around supermassive black hole. This object has not been studied at all, because according to modern concepts, a black hole is nothing does not radiate, but only "sucks" objects into itself, literally dissolving them.

But do not be afraid, we are far from it. The picture shows white patches- places with a lower temperature, but not all are clogged with planets and stars, there are dark areas- lots are empty.

Look at this photo:

Lots of lights, but it's really millions of galaxies, in our time, astronomers can observe them, but there are boundaries. The level of development of technology does not allow us to look further, we can only observe where we can look.

"... You can endlessly look at three things: fire, water and the starry sky." This classical statement belongs to the category of axioms and does not require proof. But if water and fire cause people to different situations different emotions, then at the sight of a huge starry tent, as a rule, everyone has the same feelings - admiration, peace and understanding of how small all our problems are compared to the sparkling and boundless world spread overhead.

Thanks to the knowledge gained back in school, we understand that we see individual stars above us, like our Sun, entire star systems, our Galaxy, the Universe, in the end. However, despite enough high level education of modern man, many do not quite correctly understand how the galaxy differs from the universe. Let's try to deal with this issue, especially since it is completely simple.

Galaxy, our starry home

Clusters of stellar systems connected by gravitational forces are called a galaxy. This is the most primitive description this phenomenon, but at the same time most accurately reflecting its essence. Galaxies may not be very large, consisting of several billion stars, but they can also be gigantic monsters, including trillions of stars.

An example is the dwarf galaxy Small Magellanic Cloud (1.5 billion stars) and a mega-formation - a spiral galaxy with a faceless name NGC 6872. It is difficult to calculate the exact number of stars in it due to its gigantic size, but the fact that the count goes into trillions is beyond doubt.

To more clearly imagine the immensity of this monster, you can compare it with our great space homeland - milky way(the solar system is in this galaxy):

• the size of the Milky Way is 100-120 thousand light years in diameter, and it is also considered far from being a small formation;
• a flyby of the galaxy NGC 6872 along the same route will take no less than 500 thousand light years.

By the way, many galaxies are also interconnected by gravity and live (rotate) in the same rhythm. In our cluster of galaxies, in addition to us, there are Andromeda (diameter 200 thousand light years), Triangulum galaxies (50 thousand light years) and a number of satellite formations, the so-called dwarf galaxies.

So, with galaxies sorted out a bit. Now, in order to understand what is the difference between a galaxy and the universe, we should talk about the universe itself.

The Universe… The Unfathomable Abyss

Briefly: the universe is a boundless volume of space filled with stars, star systems, galaxies, black holes, emptiness, etc. And, quite possibly, there are many more different objects and phenomena in it, about which modern science doesn't even suspect. All this diversity is in constant motion and lives its own, sometimes incomprehensible life for us.

When you look at the night sky, it seems that it is simply crammed with stars. Pictures taken with powerful telescope in the Hubble world seem to confirm this impression. Yes, and the latest research by astronomers shows that there are at least 100-200 billion galaxies in the universe, and according to some sources, more than 500 billion. However, in reality, all these star clusters are infinitely lonely in a boundless universe. Often they are separated by such vast distances that the human mind is simply unable to imagine them.

The Universe was formed after the Big Bang and, accordingly, has its own age, although it has no boundaries. According to the latest data, the age of the foremother of everything that exists in space is estimated at 13.75 ± 0.13 billion years. True, many serious scientists believe that the Universe is eternal, that it has always existed, and there were no Big Bangs at all. However, let's leave scientific disputes to "specially trained people" and move on to the main point of our article.

Comparison

Now let's bring together everything that we learned from the previous material. Let's try to determine the differences between these two objects. They are few, but they are significant enough.

In the table, we have identified the main, in our opinion, points that show what is the difference between the galaxy and the universe. Figuratively speaking, the universe can be imagined as a kind of extravagant house, consisting of blocks, each of which differs from its neighbor in its weight, size, and even physical properties(in theory). However, despite such "confusion", the whole structure looks surprisingly harmonious and durable. It is subject to uniform, "universal" laws, unshakable and eternal.

The article tells about what galaxies are, how they formed, what they include and what is their approximate number in the observable zone of the Universe.

Ancient times

Since time immemorial, people have been attracted by the starry sky. Unable to understand or establish the nature of the stars and the moon, people often attributed mystical or divine meaning, and our companion was even worshipped. Gradually, with the development of astronomy as a science and the first primitive telescopes, it became clear that our planet is not at all the only one, and it revolves around the Sun along with others.

Gradually, with the improvement of observation instruments and the development of astronomy, it became clear to scientists: the stars are also someone's "suns", and their planets almost certainly revolve around them. Unfortunately, they are so far away that there is no way to test this in practice. At least for now. And clusters of planets and star systems form galaxies. So what are galaxies? What do they include and how many are there? In this we will understand.

Definition

First, we need to remember the general structure of our Universe. There are celestial bodies - these are planets, satellites, asteroids, comets and in general everything that was not created by man and that is in space. Usually, under the influence of gravity of more massive objects, they revolve around them in their orbits, for example, like the Moon around the Earth. Those, in turn, “fly” around even more massive bodies, for example, the Sun. It's called a star system. So what are galaxies?

And galaxies are clusters of stars and star systems that, in turn, rotate around a common center of mass. Simply put, this is a great variety of planetary systems, stars, dark matter, interstellar gas, meteorites, dwarf planets and asteroids, which, under the influence of mutual gravity, have come together and rotate around the center of mass. So we sorted out what a galaxy is, the definition became clear. But how many are there? And what are they?

Milky Way

Our galaxy, which contains the Earth, the Sun and other celestial bodies, is called the Milky Way.

Highly for a long time, until the end of the 20th century, technology did not allow seeing individual stars in alien galaxies - the resolution of telescopes was not enough, and digital image processing methods were far from ideal. But then everything changed, and by the 90s of the last century, scientists could observe more than 30 star clusters, in which it was possible to make out individual luminaries.

The form

They also differ in their shape. There are elliptical, spiral disc, lenticular, dwarf, irregular, etc. For example, our galaxy is spiral, with separate "sleeves". Unfortunately, in the study of others, scientists have made very little progress, however, as in the study of ours. It's all about vast distances, as well as accumulations of interstellar dust that absorbs light. It is because of it that we do not see most of the stars, otherwise the night would not be much different from the day.

Quantity

When children are told about galaxies, they are most often interested in the question of quantity. And it is difficult to answer in such a way as to satisfy children's curiosity. Of course, you can name a certain number, but it will not be true. Our Universe is infinite, and moreover, it is constantly expanding, somewhere the formation of new stars, planetary systems is taking place, and it is impossible to find its boundary. This means that the number of galaxies is incalculable.

As already mentioned, due to dust, we see only a tiny part of the Universe, and the approximate number of galaxies in it is more than 100 billion. And, unfortunately, it is impossible to reach even the closest ones now.

Traffic

Oddly enough, not only planets move around stars or satellites with comets and meteorites, but also galaxies. This movement is not as noticeable as, for example, the Earth around the Sun. The speed depends on the mass, the density of the interstellar gas and other things.

Now we figured out what a galaxy is, and how many of them, we also found out. At the moment, the only way to study them is observation through terrestrial or orbital telescopes, both in the visible light spectrum, and in infrared or X-ray. The most famous such telescope is called the Hubble, launched into Earth orbit in 1990.

Now we have finally figured out what galaxies are.