More and more often you will come across different abbreviations and abbreviations denoting types of galaxies, came to the conclusion that it is necessary to write a separate article on this topic in parallel and independently, so that if you have any question or misunderstanding about the types of galaxies, you simply refer to this small article.

There are very few types of galaxies. Main 4, with some additions 6. Let's figure it out.

Types of galaxies

Looking at the diagram above, let's go in order, let's figure out what the letter and the number next to it (or another additional letter) mean. Everything will fall into place.

1 Elliptical Galaxies (E)

Type E galaxy (M 49)

elliptical galaxies are oval shaped. They lack a bright central core.

The number that is added after English letter E divides this type into 7 subtypes: E0 - E6. (some sources say there can be 8 subtypes, some 9, doesn't matter). It is determined by a simple formula: E = (a - b) / a, where a is the major axis, b is the minor axis of the ellipsoid. Thus, it is not difficult to understand that E0 is these perfectly round, E6 is oval or oblate.

elliptical galaxies are less than 15% of total number all galaxies. There is no star formation in them, they consist mainly of, yellow and dwarfs.

When observing through a telescope, they are not of great interest, because it will not be possible to consider the details in detail.

2. Spiral galaxies (S)

Galaxy type S (M 33)

The most popular type of galaxy. More than half of all existing galaxies spiral. Our galaxy Milky Way is also spiral.

Because of their "branches" they are the most beautiful and interesting to watch. Most of the stars are located in close proximity to the center. Further, due to rotation, the stars scatter, forming spiral branches.

spiral galaxies are divided into 4 (sometimes 5) subtypes (S0, Sa, Sb and Sc). In S0, the spiral branches are not expressed at all, they have a light core. They are very similar to elliptical galaxies. They are still often taken out in a separate type - lenticular. Such galaxies are no more than 10% of the total. Next come Sa (often just write S), Sb, Sc (sometimes add Sd) depending on the degree of twisting of the branches. The older the additional letter, the less the degree of twisting and the "branches" of the galaxy surround the core less and less.

The "branches" or "arms" of spiral galaxies have many young ones. There are processes of active star formation.

3. Spiral galaxies with a bar (SB)

SBb-type galaxy (M 66)

Spiral galaxies with a bar(or also called “barred”) are of the type of spiral galaxies, but contain the so-called “bar” that passes through the center of the galaxy - its core. Spiral branches (sleeves) diverge from the ends of these bridges. In ordinary spiral galaxies, branches diverge from the core itself. Depending on the degree of twisting of the branches, they are designated as SBa, SBb, SBc. The longer the sleeve, the older the additional letter.

4. Irregular galaxies (Irr)

Irr-type galaxy (NGC 6822)

Irregular galaxies do not have any distinct shape. They have a "torn" structure, the core is not distinguishable.

This type has no more than 5% of the total number of galaxies.

However, even irregular galaxies have two subtypes: Im and IO (or Irr I, Irr II). Im have at least some hint of structure, some symmetry or visible borders. IO is completely chaotic.

5. Galaxies with polar rings

Polar Ring Galaxy (NGC 660)

This type of galaxy stands apart from others. Their feature is that they have two stellar disks that rotate at different angles relative to each other. Many believe that this is possible due to the merger of two galaxies. But scientists still do not have an exact definition of how such galaxies formed.

Majority polar ring galaxies are lenticular galaxies or S0. Although they are rare to find, the sight is memorable.

6. Peculiar galaxies

Peculiar Tadpole Galaxy (PGC 57129)

Based on the definition from Wikipedia:

peculiar galaxy- this is a galaxy that cannot be attributed to a certain class, since it has pronounced individual characteristics. There is no unambiguous definition for this term, the assignment of galaxies to this type can be disputed.

They are unique in their kind. Finding them in the sky is not easy and requires professional telescopes, but what you see looks amazing.

That's all. I hope nothing complicated. Now you know the basic types (classes) of galaxies. And when you get acquainted with astronomy or read articles on my blog, you will not have questions with their definition. And if, suddenly, you forget, immediately refer to this article.

Doctor of Pedagogical Sciences E. LEVITAN.

Classification scheme for galaxies, according to Hubble (1925).

Galaxy NGC 4314 (constellation Aquarius).

Irregular galaxies: on the left - the Large Magellanic Cloud, on the right - the Small Magellanic Cloud.

A huge elliptical galaxy in the constellation Virgo is a radio source Virgo A. It is almost a spherical galaxy. In all likelihood, very active - visible ejection of a bright jet of matter.

Galaxy NGC 4650 A (constellation Centaur). The distance to it is 165 million light years.

The gas nebula (M27), which is located in our Galaxy, but very far from us - at a distance of 1200 light years.

Before you is not a galaxy, but the Tarantula Nebula 30 Doradus - a famous landmark of the Large Magellanic Cloud.

"A long time ago, in a galaxy far, far away..." - these are the words that usually begin the films of the famous series "Star Wars". Do you have any idea how large the number of such "distant, distant" galaxies is? For example, about 250 galaxies that we see as a point brighter than 12 m are known. There are about 50,000 galaxies whose brightness is even weaker - up to 15 m. The number of those that can only be photographed by a very powerful, for example, 6-meter telescope on limit of its capabilities - many billions. With the help of the space telescope, you can see even more of them. Together, these star islands are the Universe - the world of galaxies.

People living on Earth understood this far from immediately. First they had to discover their own planet - the Earth. Then the solar system. Then - our own star island - our Galaxy. We call it the Milky Way.

After some time, astronomers discovered that our Galaxy has neighbors, that the Andromeda Nebula, the Large Magellanic Cloud, the Small Magellanic Cloud and many other foggy spots are no longer our Galaxy, but other, independent star islands.

So man looked beyond the limits of his galaxy. Gradually it became clear that the world of galaxies is not only amazingly large, but also diverse. Galaxies vary greatly in size, appearance and the number of stars included in them, luminosity.

The American astronomer Edwin Hubble (1889-1953) is rightfully considered the founder of extragalactic astronomy, which deals with these issues. He proved that many "nebulae" are actually other galaxies made up of many stars. Studied more than a thousand galaxies, determined the distance to some of them. Among the galaxies, he distinguished three main types: spiral, elliptical and irregular.

Now we know that spiral galaxies occur more often than others. More than half of the galaxies are spiral. These include our Milky Way, and the galaxy in Andromeda (M31), and the galaxy in Triangulum (M33).

Spiral galaxies are very beautiful. In the center is a bright core (a large, dense cluster of stars). Spiral branches emerge from the core, twisting around it. They consist of young stars and clouds of neutral gas, mostly hydrogen. All branches - and there may be one, two or more - lie in a plane coinciding with the plane of rotation of the galaxy. Therefore, the galaxy looks like a flattened disk.

Astronomers for a long time could not understand why galactic spirals, or, as they are also called, arms, do not collapse for so long. There have been many hypotheses on this issue. Now most researchers of galaxies are inclined to believe that galactic spirals are waves of increased density of matter. They are like waves on the surface of water. And those, as you know, do not transfer matter during their movement.

In order for waves to appear on a calm surface of the water, it is enough to throw at least a small stone into the water. The emergence of spiral arms is probably also associated with some kind of push. These could be movements in the very mass of stars inhabiting this galaxy. A connection with the so-called differential rotation and "bursts" during star formation is not ruled out.

Astrophysicists spoke quite confidently that it is precisely in the arms of spiral galaxies that the bulk of newly born stars are concentrated. But then information began to appear that the birth of stars may also occur in the central regions of galaxies (see "Science and Life" No. 10, 1984). It sounded like a sensation. One such discovery was made recently, when the Hubble Space Telescope photographed the galaxy NGC 4314 (photo below).

The galaxies called elliptical, in appearance significantly differ from spiral ones. In photographs, they look like ellipses with varying degrees compression. Among them are lens-like galaxies and near-spherical star systems. There are giants and dwarfs. About a quarter of the brightest galaxies are classified as elliptical. Many of them are characterized by a reddish color. For a long time, astronomers considered this one of the evidence that elliptical galaxies are mostly composed of old (red) stars. Recent observations by the Hubble Space Telescope and the infrared telescope "ISO" refute this view (see "Science and Life" Nos. and ).

Among the elliptical galaxies there are such interesting objects as the spherical galaxy NGC 5128 (the constellation of the Centaur) or M87 (the constellation of Virgo). They attract attention as the most powerful sources of radio emission. A particular mystery of these and several spiral galaxies is their core. What is concentrated in them: supermassive star clusters or black holes? According to some astrophysicists, a sleeping black hole (or several black holes) may have lurked in the center of our Galaxy, shrouded in clouds of opaque interstellar matter, or, for example, in the Large Magellanic Cloud.

Until recently, the only sources of information about the processes taking place in the central regions of our and other galaxies were observations in the radio and X-ray bands. For example, a team of scientists led by Academician R. Sunyaev obtained extremely interesting data on the structure of the center of our Galaxy with the help of the Russian orbital observatories Astron and Granat. Later, in 1997, using the infrared camera of the American Hubble Space Telescope, astrophysicists obtained images of the nucleus of the elliptical galaxy NGC 5128 (Centaur A radio galaxy). It was possible to detect individual details located at a distance of 10 million light years from us (about 100 light years in size). An impressive picture was revealed of a riot of hot gas swirling around some center, possibly a black hole. However, it is possible that the monstrous activity of the nuclei of galaxies like this one is associated with other turbulent events. After all, there are many unusual things in the history of the life of galaxies: they collide, and sometimes even "devour" each other.

Finally, let's turn to the third (according to the Hubble classification) type of galaxies - wrong(or irregular). They are characterized by a chaotic, ragged structure and do not have any definite form.

These are the two relatively small galaxies closest to us - the Magellanic Clouds. These are satellites of the Milky Way. They are visible to the naked eye, however, only in the sky of the southern hemisphere of the Earth.

You probably know that South Pole world is not marked in the sky by any noticeable star (unlike North Pole world, next to which is now located a Ursa Minor - the North Star). The Magellanic Clouds help determine the direction to the South Pole of the world. The Big Cloud, Small Cloud and the South Pole lie at the vertices of an equilateral triangle.

The two galaxies closest to us were named after Ferdinand Magellan in the 16th century at the suggestion of Antonio Pigafetta, who was the chronicler of the famous circumnavigation of the world. In his notes, he noted everything unusual that happened or was observed during the voyage of Magellan. I did not disregard these foggy spots in the starry sky.

Although irregular galaxies are the smallest class of galaxies, their study is very important and fruitful. This is especially true of the Magellanic Clouds, which attract the special attention of astronomers primarily because they are almost next to us. The Large Magellanic Cloud is less than 200 thousand light years away, and the Small Magellanic Cloud is even closer - about 170 thousand light years.

Astrophysicists are constantly discovering something very interesting in these extragalactic worlds: unique observations of a supernova explosion in the Large Magellanic Cloud on February 23, 1987. Or, for example, the Tarantula Nebula, in which last years made many amazing discoveries.

Several decades ago, one of my teachers, Professor B. A. Vorontsov-Velyaminov (1904-1994), made great efforts to draw the attention of his colleagues to interacting galaxies. In those days, this topic seemed exotic to many astronomers, not of particular interest. But now, years later, it became clear that the work of Boris Alexandrovich (and his followers) - studies of interacting galaxies - opened a new, very important page in the history of extragalactic astronomy. And now, not only the most bizarre (and not always understandable) forms of interaction between galaxies, but even "cannibalism" in the world of giant star systems, are no longer exotic to anyone.

"Cannibalism" - the mutual "eating" of galaxies by each other (their merger during close encounters) - is captured in photographs. According to one hypothesis, our Milky Way can become a "cannibal". The basis for this assumption was the discovery in the early 90s of a dwarf galaxy. It has only a few million stars, and it is located at a distance of 50 thousand light years from the Milky Way. This "baby" is not so young: it arose several billion years ago. It is difficult to say how her long life will end. But it is possible that she will someday get close to milky way and he will consume it.

We emphasize once again that the world of galaxies is unusually diverse, amazing and largely unpredictable. And astronomy lovers will be able to follow the news of extragalactic astronomy, which is now rapidly developing. So expect new information, new photos of the most extraordinary galaxies.

Dr. Danny Faulkner

Since their discovery, galaxies have never ceased to amaze the human mind. Many of them are in the form of beautiful spirals. But if they were to rotate for billions of years, would they not lose their distinct spiral arms?

Huge islands of stars called "galaxies" float in pitch-black space. The estimated number of visible galaxies is about 170 billion, and each of them contains billions or even trillions of individual stars. As we contemplate this shimmering wonder, we wonder, “Where did these shining jewels come from?”

In the first chapter of the book of Genesis, we are given an unmistakable answer: on the fourth day the Creator created the stars (Genesis 1:16). Astronomers who deny the history given to us by God cannot find an alternative explanation for the origin of the stars.

One of the main problems for them is the beautiful spiral arms that adorn many galaxies. Simply put, these spirals would have to lose their shape if they existed in ancient universe . But in fact, the presence of spiral arms proves that the universe is very young.

The structure of galaxies

Any reasonable interpretation of the origin of galaxies requires a lengthy explanation. The galaxies are located far apart, and it seems that there is no matter between them. For example, our galaxy, called the Milky Way, is separated from the nearest galaxy of significant size - Andromeda (M 31) - by a distance of two million light years.

Every galaxy has great amount stars. The Milky Way and M 31, which are ordinary galaxies, are made up of about 200 billion stars each, and span 100,000 light-years from edge to edge. Quite interesting is the fact that other smaller galaxies orbit larger galaxies, such as our own and the galaxy M 31.

Galaxies are divided into two main types - spiral and elliptical. Elliptical galaxies, as the name suggests, are shaped like an ellipse. Spiral galaxies, on the other hand, have a dense concentration of stars at the center, called the core, and graceful spiral arms radiating from the core to the outer edge. This gives the galaxy a swirling appearance. Where did this arrangement and diversity come from?

Spirals generate the most controversy among astronomers. Beginning in the 1930s, scientists began to argue about the structure and origin of the spiral arms, and these disputes continue today.

Discovering a young universe

Before dealing with technical difficulties, we must address one common misconception. Many people believe that there are many stars inside the arms of the spiral, but there are practically no stars between the arms. In fact, the grouping of stars between the arms and inside the arm is almost the same.

If so, why do the arms of the spiral appear so bright to the eye? The reason is that there are very hot and bright blue stars in the spiral arm. The light from these stars dominates the visible spectrum, which is why the arms of the spiral stand out so well in photographs. This is especially true of old black and white photographs, which were very sensitive to blue color. In more recent infrared color photographs, the spiral arms do not stand out as much, as the more numerous red stars dominate.

In addition to bright blue stars, there is also a lot of dust and gas in the arms of the spiral. Sometimes dust and gas are concentrated into "clouds" called "nebulae". Astronomers refer to the nebulae and blue stars as "spiral satellites" because they plot the locations of the arms of the spiral.

However, back in the 1930s, astronomers were faced with a problem. The outer stars took longer to complete their orbit than the stars inside the spiral. As the distance from the center of the galaxy increases, the arms of the spiral must become unstable. I.e, after a few rotations, the spiral arms should have dissipated.

Astronomers have been arguing for years about the direction in which spiral arms move, trying to determine whether they are twisting or unwinding. But no matter which view they held, if galaxies were at least ten billion years old, as is commonly assumed, then spiral arms would no longer exist.

Bad Assumptions

By the late 1960s, astronomers seemed to have found the answer to their question. They developed the theory of spiral wave density. According to this concept, the spiral arms behave in interstellar space like sound waves. If some external forces compress interstellar space, clouds of gas and dust appear in the arms of the spiral. In addition, due to the compression of the gas, stars were presumably formed.

According to this world view, some new stars should have become massive blue stars with very short life cycles (a few million years at best). Such stars were very important in confirming this theory, however, since they are supposed to exist for a short time, there is not enough time for the “wave” to move and leave behind blue stars. Therefore, in their theory, they suggested that here the gravity of the galaxy entered the scene and completed the process of collecting material and forming stars.

The details of the spiral wave density theory are difficult to prove, but this worldview still has adamant adherents. By the 1990s, scientists had studied small satellite galaxies and concluded that they could be the very mechanism that maintains the shape of the spiral, but this theory is also quite difficult to prove in detail.

Dark matter?

Behind last decade astronomers have received evidence of the existence of dark matter, which only complicates the overall picture. Dark matter is interesting because it does not emit light, but its total mass far exceeds the total mass of illuminated matter, and its gravity has the greatest influence on the structures of bodies within the galaxy, as well as the entire cosmos.

Evidence suggests that dark matter is in outer layers galaxies. Most astronomers today believe that it is dark matter that helps the spirals of galaxies to support life. However, even the best evidence for the existence of dark matter—a higher rotational speed of the outer layers of galaxies than expected—may only exacerbate, not solve, the problem of the existence of spirals.

Creationists have long argued that spiral arms should not exist in an ancient universe, so the presence of spiral arms indicates a very young age of the universe. However, since most evolutionary astronomers begin their research with the assumption that the universe is billions of years old, they are convinced that there are mechanisms that continue to keep galaxies spiral. If they actually had convincing answers to all these questions, they would stop making new assumptions. Their errors indicate that creationist arguments should not be discounted.

In recent years, another method has been developed. Astronomers have photographed distant galaxies 12 million light-years from Earth. Assuming that there was a "big bang" about 13.7 billion years ago, they believe that these galaxies are the youngest in the universe. They are practically indistinguishable from neighboring (and presumably older) galaxies, and are virtually identical in appearance. In other words, we do not observe evolutionary processes here either.

Based on the theory of recent creation, we can assume that distant galaxies should look almost the same as nearby ones, but the evolutionary model cannot allow this. Let's say it again: God's Word sheds unshakable light on the origin and structure of His great universe.

Dr. Danny Faulkner is Professor of Physics and Astronomy at Lancaster University of South Carolina. He has written numerous articles for astronomical journals and is also the author of the book " A universe created by intelligent design».

Spiral structure of galaxies

Spiral branches (sleeves) - salient feature so-called spiral galaxies, to which ours belongs. The branches contain a relatively small part of all the stars in the galaxy, but they are yavl. one of the most prominent galaxies. formations, because almost all high-luminosity hot stars are concentrated in them. Stars of this type are classified as young, so spiral branches can be considered the place of star formation. In addition to young stars, most of the interstellar gas of the galaxy is concentrated in the arms, from which, according to modern. ideas, and stars are formed. Spiral galaxies are divided into classes according to the nature of the spiral arms and certain other features. In Sa class galaxies (according to the Hubble classification, see ) the branches are relatively thin (200-300 pc) and tightly wound, in Sc class galaxies they are more blurred (diffuse) and steeply removed from the central region. Barred galaxies are close to spiral galaxies; spiral branches usually extend from the ends of the swarm. One of the most common classifications of spiral galaxies belongs to the French. astronomer J. Vaukuler, it is shown in fig. 1. The letters A, B, AB characterize families of spiral galaxies. SA denotes a normal spiral galaxy, SB - with a bar (bar), SAB - transitional forms. In addition to the families, as can be seen from Fig. 1, varieties are taken into account (ring - r, spiral s, mixed - rs).

The gas in spiral arms consists mainly of hydrogen. Usually it is practically non-ionized (neutral hydrogen, HI), but around hot stars the hydrogen is ionized (). The gas often forms dense diffuse nebulae, which also serve as a guide in determining the type of spiral arms. Another sign of branches yavl. scattered in the gas, detected by the absorption it produces. It is visible as a thin dark band along the inner (closer to the center of the galaxy) edge of the spiral branch. In addition, thin stripes crossing the arms (Fig. 2) and separate dark masses are observed in the arms. The concentration of stars that form galaxies. disk, also increases somewhat in the branches, but not as much as the gas concentration.

Stars, gas, and other galactic objects. disks move in orbits close to circular. It has been experimentally established that the angular velocity of this movement as a function of the radius, i.e. , decreases with distance from the center of the galaxy. With this type of rotation, large gas clouds or other extended formations are stretched and become like part of a spiral branch. However, spiral branches could not have arisen in this way. Differential rotation can create structures similar to the observed arms in less than 10 9 years. During several revolutions of the Galaxy, the age of which is more than 10 10 years, such structures should have collapsed, the spatial distribution of hydrogen, dust and hot stars should have become irregular, which is not observed in most cases.

B. Lindblad (Sweden) was the first to put forward the idea that spiral branches could be density waves. In 1964, C. Lin and F. Shu (USA) showed that in galaxies there really can be spiral-shaped density waves rotating with angular velocity (i.e., the shape of the front of such waves is not distorted by the differential rotation of the galactic disk) and propagating along the radius with a certain group velocity v gr. Since there is little gas in the Galaxy (2-5%), the waves propagate through the stellar population, in which they can be excited, and the gas already reacts to the disturbance associated with waves traveling through the system of stars, i.e. its motion in gravity. field of sleeves yavl. non-self-consistent.

Galaxies are the so-called. collisionless star systems, because the time between two successive approaches of the c.-l. stars with another star are 3-4 orders of magnitude greater than the age of the galaxy. Therefore, the possibility of wave propagation in such systems is rather unusual. Here, the elasticity required for the propagation of density waves is due to the Coriolis forces leading to the epicyclic motion of stars, i.e. ultimately - the rotation of the system.

In the wave, the concentration of stars increases slightly (the corresponding change in the gravitational potential is 10-20%). However, the reaction of the interstellar gas even to such a significant change in gravity. The potential of the galaxy is large: accelerating in the field of a spiral wave of stellar density, the gas acquires supersonic speed and is compressed into several. once. This can lead to the emergence of a global shock wave (covering most of the disk) in the interstellar gas. One of the observational manifestations of gas deceleration in a shock wave (the gas catches up with the arms during its galactic motion and then slows down) is yavl. dark bands of dense gas with dust on the inside. edge of the spiral arms (Fig. 2). Compression of gas can serve as a trigger (trigger) for the formation of stars. Indeed, young OB stars and their associations, HII zones, supernova remnants, molecular dark clouds, H 2 O masers, and γ-radiation sources usually serve as indicators of the spiral structure (see ). When interstellar gas flows through spiral arms, a kind of phase transitions can occur in it with the formation of a cloud structure. This sheds light on the origin of coexisting different phases (cold, warm, hot) of the interstellar gas.

The wave theory of the spiral structure of galaxies has been developed in sufficient detail and can be compared quantitatively with observations. However, there are a number of unresolved problems. A regular spiral pattern is observed by no means in all galaxies; a rather irregular structure is often visible, consisting of many short formations, which only "as a whole" form a kind of spiral arms. A regular global spiral pattern is usually observed in galaxies with a bar and in galaxies with "satellites" (Fig. 2). In these cases, the regular structure finds an explanation. Thus, the bar in the center of the galaxy acts as a generator that excites and maintains density waves. A satellite galaxy, as shown by computer calculations, can also excite spiral density waves in the main. galaxy, thanks to the tidal forces that arise here.

Despite the fact that the wave interpretation of the spiral pattern of galaxies is yavl. practically generally accepted, within the framework of the wave theory there are points of view, the final choice between which can only be made by observations. If the Galaxy with all its subsystems is considered as an infinitely thin disk with some cf. stellar velocity dispersion and with a surface density corresponding to the projection of the total density at a given point, and assign the observed galaxy rotation curve to this model, then the geometry of the two-arm pattern turns out to coincide with that observed at 13 km/(spc) for a certain type of density waves. According to another point of view, the type of density waves is determined by the flat subsystem and the dispersion of the velocities of its components, which are much less value taken in the first case. In this case, the geometry of the observed pattern is better described by another type of waves with 24 km/(spc). There are a number of theoretical considerations and observational data that apparently testify in favor of the fact that the second case is realized in the Galaxy. If so, then the Sun is in an exceptional position in the Galaxy, which can have far-reaching consequences for the cosmogony of the solar system and the origin of life in it. Because the galactic the disk rotates differentially, and the spiral arms rotate rigidly, a circle must exist in the Galaxy, on which the angular velocities of the disk and density waves are equal. Such a circle is called corotation (from the English corotation - joint rotation). Her radius R=R C is determined by the condition. Since only one such circle can exist in each spiral galaxy, then, obviously, it is yavl. dedicated. Angular velocity the rotation of the Sun in the Galaxy is 25 km/(jpc), the distance of the Sun to the center of the Galaxy is 10 kpc. If 24 km/(jpc), then, according to the Schmidt model (1965), for example, 10.3 kpc. This means that the galactic the orbit of the solar system is close to a corotation circle and, therefore, is in a special position.

A galaxy is a large formation of stars, gas, dust, which are held together by the force of gravity. These largest compounds in the universe can vary in shape and size. Most of the space objects are part of a particular galaxy. These are stars, planets, satellites, nebulae, black holes and asteroids. Some of the galaxies have a lot of invisible dark energy. Due to the fact that the galaxies are separated by an empty space, they are figuratively called oases in the cosmic desert ..

	elliptical galaxy	spiral galaxy	wrong galaxy
spheroidal component	entire galaxy	There is	Very weak
stellar disk	No or weak	Main component	Main component
Gas and dust disk	Not	There is	There is
spiral branches	None or only near the core	There is	Not
Active cores	Meet	Meet	Not
	20%	55%	5%

Our galaxy

Our closest star, the Sun, is one of the billion stars in the Milky Way galaxy. Looking at the night starry sky, it is hard not to notice a wide band strewn with stars. The ancient Greeks called the cluster of these stars the Galaxy.

If we had the opportunity to look at this star system from the side, we would have noticed an oblate ball, in which there are over 150 billion stars. Our galaxy has dimensions that are hard to imagine in your imagination. A beam of light travels from one side of it to the other for a hundred thousand Earth years! The center of our Galaxy is occupied by the core, from which huge spiral branches filled with stars depart. The distance from the Sun to the nucleus of the Galaxy is 30,000 light years. solar system located on the outskirts milky way.

Stars in the Galaxy, despite the huge accumulation of cosmic bodies, are rare. For example, the distance between the nearest stars is tens of millions of times greater than their diameters. It cannot be said that the stars are scattered randomly in the Universe. Their location depends on the forces of gravity that hold heavenly body in a certain plane. Star systems with their gravitational fields and are called galaxies. In addition to stars, the composition of the galaxy includes gas and interstellar dust.

composition of galaxies.

The universe is also made up of many other galaxies. The closest to us are distant at a distance of 150 thousand light years. You can see them in the sky southern hemisphere in the form of small misty specks. They were first described by a member of the Magellanic expedition around the world of Pigafett. They entered science under the name of the Large and Small Magellanic Clouds.

The closest galaxy to us is the Andromeda Nebula. It has a very large size, so it is visible from the Earth in regular binoculars, and in clear weather - even with the naked eye.

The very structure of the galaxy resembles a giant spiral convex in space. On one of the spiral arms, ¾ of the distance from the center, is the solar system. Everything in the galaxy revolves around the central core and obeys the force of its gravity. In 1962, astronomer Edwin Hubble classified galaxies according to their shape. The scientist divided all galaxies into elliptical, spiral, irregular and barred galaxies.

There are billions of galaxies in the part of the Universe available for astronomical research. Collectively, astronomers call them the Metagalaxy.

Galaxies of the Universe

Galaxies are represented by large groupings of stars, gas, dust, held together by gravity. They can vary greatly in shape and size. Most space objects belong to a galaxy. These are black holes, asteroids, stars with satellites and planets, nebulae, neutron satellites.

Most of the universe's galaxies contain vast amounts of invisible dark energy. Since the space between different galaxies is considered empty, they are often called oases in the void of space. For example, a star called the Sun is one of the billions of stars in the "Milky Way" galaxy in our universe. At ¾ of the distance from the center of this spiral is the solar system. In this galaxy, everything is constantly moving around the central core, which obeys its gravity. However, the core also moves along with the galaxy. At the same time, all galaxies move at superspeeds.
Astronomer Edwin Hubble in 1962 carried out a logical classification of the galaxies of the universe, taking into account their shape. Now galaxies are divided into 4 main groups: elliptical, spiral, galaxies with a bar (bar) and irregular.
What is the largest galaxy in our universe?
The largest galaxy in the universe is the super-giant lenticular galaxy in the Abell 2029 cluster.

spiral galaxies

They are galaxies that in their shape resemble a flat spiral disk with a bright center (core). The Milky Way is a typical spiral galaxy. Spiral galaxies are usually called with the letter S, they are divided into 4 subgroups: Sa, So, Sc and Sb. Galaxies belonging to the So group are distinguished by bright nuclei that do not have spiral arms. As for the Sa galaxies, they are distinguished by dense spiral arms tightly wrapped around the central core. The arms of the Sc and Sb galaxies rarely surround the core.

Spiral galaxies in the Messier catalog

barred galaxies

Barred galaxies are similar to spiral galaxies, but still have one difference. In such galaxies, spirals do not start from the core, but from the bridges. About 1/3 of all galaxies fall into this category. They are usually denoted by the letters SB. In turn, they are divided into 3 subgroups Sbc, SBb, SBa. The difference between these three groups is determined by the shape and length of the bridges, from where, in fact, the arms of the spirals begin.

Messier barred spiral galaxies

elliptical galaxies

The shape of galaxies can vary from perfectly round to elongated ovals. Their distinguishing feature is the absence of a central bright core. They are designated by the letter E and are divided into 6 subgroups (by shape). Such forms are designated from E0 to E7. The former are almost round in shape, while the E7 are characterized by an extremely elongated shape.

Elliptical galaxies in the Messier catalog

Irregular galaxies

They do not have any pronounced structure or shape. Irregular galaxies are usually divided into 2 classes: IO and Im. The most common is the Im class of galaxies (it has only a slight hint of structure). In some cases, spiral remnants are traced. IO belongs to a class of galaxies that are chaotic in shape. Small and Large Magellanic Clouds - a prime example I'm class.

Messier catalog irregular galaxies

Table of characteristics of the main types of galaxies

	elliptical galaxy	spiral galaxy	wrong galaxy
spheroidal component	entire galaxy	There is	Very weak
stellar disk	No or weak	Main component	Main component
Gas and dust disk	Not	There is	There is
spiral branches	None or only near the core	There is	Not
Active cores	Meet	Meet	No
Percentage of the total number of galaxies	20%	55%	5%

Large portrait of galaxies

Not so long ago, astronomers began working on a collaborative project to determine the location of galaxies throughout the universe. Their task is to get a more detailed picture of the general structure and shape of the universe on a large scale. Unfortunately, the scale of the universe is difficult to estimate for understanding by many people. Take at least our galaxy, consisting of more than a hundred billion stars. There are billions more galaxies in the universe. Distant galaxies have been discovered, but we see their light as it was almost 9 billion years ago (we are separated by such a large distance).

Astronomers became aware that most galaxies belonged to a particular group (it became known as a "cluster"). The Milky Way is part of a cluster, which, in turn, consists of forty known galaxies. As a rule, most of these clusters are part of an even larger grouping, which is called superclusters.

Our cluster is part of a supercluster commonly referred to as the Virgo Cluster. Such a massive cluster consists of more than 2 thousand galaxies. At the same time that astronomers mapped the location of these galaxies, superclusters began to take shape. Large superclusters have gathered around what appear to be gigantic bubbles or voids. What kind of structure this is, no one knows yet. We do not understand what can be inside these voids. By assumption, they can be filled with a certain type of dark matter unknown to scientists, or they can have empty space inside. It will be a long time before we know the nature of such voids.

Galactic Computing

Edwin Hubble is the founder of galactic research. He is the first to figure out how to calculate the exact distance to a galaxy. In his research, he relied on the method of pulsating stars, which are better known as Cepheids. The scientist was able to notice the relationship between the period that is needed to complete one pulsation of brightness, and the energy that the star releases. The results of his research were a major breakthrough in the field of galactic research. In addition, he found that there is a correlation between the red spectrum emitted by a galaxy and its distance (the Hubble constant).

Nowadays, astronomers can measure the distance and speed of a galaxy by measuring the amount of redshift in the spectrum. It is known that all galaxies of the Universe move from each other. The further the galaxy is from the Earth, the greater its speed of movement.

To visualize this theory, it is enough to imagine yourself driving a car that moves at a speed of 50 km per hour. A car in front of you is driving faster at 50 km per hour, which indicates that the speed of its movement is 100 km per hour. There is another car in front of him, which is moving faster by another 50 km per hour. Even though the speed of all 3 cars will be 50 km/h different, the first car is actually moving away from you 100 km/h faster. Since the red spectrum indicates the speed of the galaxy moving away from us, the following is obtained: the greater the redshift, the faster the galaxy moves, respectively, and the greater its distance from us.

Now we have new tools to help scientists in their search for new galaxies. Thanks to the Hubble Space Telescope, scientists have been able to see what they could only dream of before. The high power of this telescope provides good visibility of even small details in nearby galaxies and allows you to study more distant ones that have not yet been known to anyone. Currently, new tools for space observation are under development, and in the near future they will help to gain a deeper understanding of the structure of the universe.

Types of galaxies

• spiral galaxies. In shape, they resemble a flat spiral disk with a pronounced center, the so-called core. Our Milky Way galaxy belongs to this category. In this section of the portal site you will find many different articles describing the space objects of our Galaxy.
• Barred galaxies. They resemble spiral ones, only they differ from them in one significant difference. Spirals do not depart from the core, but from the so-called jumpers. This category includes a third of all galaxies in the universe.
• Elliptical galaxies come in a variety of shapes, from perfectly round to oval-shaped. Compared to spiral ones, they lack a central, pronounced core.
• Irregular galaxies do not have a characteristic shape or structure. They cannot be attributed to any of the above types. There are far fewer irregular galaxies in the vastness of the universe.

Astronomers in recent times launched a joint project to identify the location of all galaxies in the universe. Scientists hope to get a better picture of its structure on a large scale. The size of the universe is difficult to estimate for human thinking and understanding. Our galaxy alone is a connection of hundreds of billions of stars. And there are billions of such galaxies. We can see the light from the discovered distant galaxies, but do not even mean that we are looking into the past, because the light beam reaches us for tens of billions of years, such a great distance separates us.

Astronomers also associate most galaxies with certain groups called clusters. Our Milky Way belongs to a cluster of 40 explored galaxies. Such clusters are combined into large groupings called superclusters. The cluster with our galaxy is part of the Virgo supercluster. This giant cluster contains over 2,000 galaxies. As scientists began to map the distribution of these galaxies, superclusters took on certain shapes. Most of the galactic superclusters were surrounded by giant voids. No one knows what might be inside these voids: outer space like interplanetary or new form matter. It will take a long time to solve this riddle.

Interaction of galaxies

No less interesting for scientists is the question of the interaction of galaxies as components space systems. It's no secret that space objects are in constant motion. Galaxies are no exception to this rule. Some of the types of galaxies could cause a collision or merger of two space systems. If you look into how these space objects appear, large-scale changes as a result of their interaction become more understandable. During the collision of two space systems, a huge amount of energy splashes out. The meeting of two galaxies in the vastness of the Universe is an even more probable event than the collision of two stars. The collision of galaxies does not always end in an explosion. A small space system can freely pass by its larger counterpart, changing only slightly its structure.

Thus, formations are formed that are similar in appearance to elongated corridors. Stars and gas zones stand out in their composition, new luminaries often form. There are times when galaxies do not collide, but only lightly touch each other. However, even such an interaction triggers a chain of irreversible processes that lead to huge changes in the structure of both galaxies.

What is the future of our galaxy?

As scientists suggest, it is possible that in the distant future the Milky Way will be able to absorb a tiny satellite system, which is located at a distance of 50 light years from us. Studies show that this satellite has a long life potential, but if it collides with a giant neighbor, it will most likely end its separate existence. Astronomers also predict a collision between the Milky Way and the Andromeda Nebula. Galaxies move towards each other at the speed of light. Before a likely collision, wait about three billion Earth years. However, whether it will actually happen now is hard to argue due to the lack of data on the motion of both space systems.

Description of galaxiesKvant. Space

The portal site will take you to the world of interesting and fascinating space. You will learn the nature of the construction of the Universe, get acquainted with the structure of known large galaxies and their components. By reading articles about our galaxy, some of the phenomena that can be observed in the night sky become more understandable to us.

All galaxies are at a great distance from the Earth. Only three galaxies can be seen with the naked eye: the Large and Small Magellanic Clouds and the Andromeda Nebula. It is impossible to count all galaxies. Scientists suggest that their number is about 100 billion. Spatial arrangement galaxies unevenly - one area can contain a huge number of them, in the second there will not be even a single small galaxy at all. Astronomers failed to separate the image of galaxies from individual stars until the early 1990s. At that time, there were about 30 galaxies with individual stars. All of them were assigned to the Local group. In 1990, a majestic event took place in the development of astronomy as a science - the Hubble telescope was launched into Earth's orbit. It was this technique, as well as new ground-based 10-meter telescopes, that made it possible to see significantly more resolved galaxies.

Today, the "astronomical minds" of the world are puzzling over the role of dark matter in the construction of galaxies, which manifests itself only in gravitational interaction. For example, in some large galaxies it makes up about 90% of the total mass, while dwarf galaxies may not contain it at all.

Evolution of galaxies

Scientists believe that the emergence of galaxies is a natural stage in the evolution of the Universe, which took place under the influence of gravitational forces. Approximately 14 billion years ago, the formation of protoclusters in the primary matter began. Further, under the influence of various dynamic processes, the separation of galactic groups took place. The abundance of galaxy shapes is explained by the variety of initial conditions in their formation.

It takes about 3 billion years to compress a galaxy. Over a given period of time, the gas cloud turns into a star system. Star formation occurs under the influence of gravitational compression gas clouds. After reaching a certain temperature and density in the center of the cloud, sufficient to start thermonuclear reactions, is formed new star. Massive stars are formed from thermonuclear chemical elements larger than helium in mass. These elements create the primary helium-hydrogen environment. During grandiose explosions of supernovae, elements heavier than iron are formed. It follows from this that the galaxy consists of two generations of stars. The first generation are the oldest stars, consisting of helium, hydrogen and a very small amount of heavy elements. Second-generation stars have a more noticeable admixture of heavy elements, since they are formed from a primordial gas enriched in heavy elements.

In modern astronomy, galaxies as cosmic structures are given a separate place. The types of galaxies, the features of their interaction, similarities and differences are studied in detail, and a forecast of their future is made. This area contains many more incomprehensible things that require further study. modern science solved many questions regarding the types of construction of galaxies, but there are also many blank spots associated with the formation of these cosmic systems. The current pace of modernization of research equipment, the development of new methodologies for the study of space bodies give hope for a significant breakthrough in the future. One way or another, galaxies will always be in the center scientific research. And it is based not only on human curiosity. Having received data on the patterns of development of space systems, we will be able to predict the future of our galaxy called the Milky Way.

The most interesting news, scientific, author's articles about the study of galaxies will be provided to you by the portal site. Here you can find breathtaking videos, high-quality images from satellites and telescopes that do not leave you indifferent. Dive into the world of unknown space with us!