The starry sky has attracted the eyes of people since ancient times. The best minds of all peoples tried to comprehend our place in the Universe, to imagine and justify its structure. Scientific progress made it possible to move in the study of the vast expanses of space from romantic and religious constructions to logically verified theories based on numerous factual material. Now any student has an idea of ​​​​how our Galaxy looks like according to latest research who, why and when gave her such a poetic name and what is her supposed future.

origin of name

The expression "the Milky Way galaxy" is, in fact, a tautology. Galactikos roughly translated from ancient Greek means "milk". So the inhabitants of the Peloponnese called the cluster of stars in the night sky, attributing its origin to the quick-tempered Hera: the goddess did not want to feed Hercules, the illegitimate son of Zeus, and splashed her breast milk in anger. Drops and formed a star track, visible on clear nights. Centuries later, scientists discovered that the observed luminaries are only a tiny fraction of the existing ones. celestial bodies. They gave the name of the Galaxy or the Milky Way system to the space of the Universe, in which our planet is also located. After confirming the assumption of the existence of other similar formations in space, the first term became universal for them.

Inside view

Scientific knowledge about the structure of the part of the universe, including the solar system, took little from the ancient Greeks. The understanding of what our Galaxy looks like has evolved from the spherical universe of Aristotle to modern theories, in which there is a place for black holes and dark matter.

The fact that the Earth is an element of the Milky Way system imposes certain restrictions on those who are trying to figure out what shape our Galaxy has. An unequivocal answer to this question requires an outside perspective, and long distance from the object of observation. Now science is deprived of such an opportunity. A kind of substitute for an outside observer is the collection of data on the structure of the Galaxy and their correlation with the parameters of other space systems available for study.

The collected information allows us to say with confidence that our Galaxy has the shape of a disk with a thickening (bulge) in the middle and spiral arms diverging from the center. The latter contain the most bright stars systems. The disk is over 100,000 light-years across.

Structure

The center of the Galaxy is hidden by interstellar dust, which makes it difficult to study the system. The methods of radio astronomy help to cope with the problem. Waves of a certain length easily overcome any obstacles and allow you to get such a desired image. Our Galaxy, according to the data obtained, has an inhomogeneous structure.

It is possible to distinguish two bound friend with another element: the halo and the disc proper. The first subsystem has the following characteristics:

• in shape it is a sphere;

• its center is considered to be the bulge;
• the highest concentration of stars in the halo is characteristic of its middle part, with approaching the edges, the density strongly decreases;
• the rotation of this zone of the galaxy is rather slow;
• the halo mostly contains old stars with a relatively small mass;
• a significant space of the subsystem is filled with dark matter.

The galactic disk in terms of the density of stars greatly exceeds the halo. In the sleeves there are young and even just emerging

Center and core

"Heart" Milky Way is located in Without studying it, it is difficult to fully understand what our Galaxy is like. The name "core" in scientific papers either refers only to the central region only a few parsecs in diameter, or includes the bulge and gas ring, which is considered the birthplace of stars. In what follows, the first version of the term will be used.

Hardly penetrates into the center of the Milky Way visible light: It's colliding with a lot of cosmic dust obscuring what our Galaxy looks like. Photos and images taken in the infrared range greatly expand the knowledge of astronomers about the nucleus.

Data on the features of radiation in the central part of the Galaxy led scientists to the idea that there is a black hole in the core of the nucleus. Its mass is more than 2.5 million times the mass of the Sun. Around this object, according to researchers, another, but less impressive in its parameters, black hole rotates. Modern knowledge about the features of the structure of the cosmos suggests that such objects are located in the central part of most galaxies.

Light and darkness

The joint influence of black holes on the movement of stars makes its own adjustments to how our Galaxy looks: it leads to specific changes in orbits that are not typical for cosmic bodies, for example, near the solar system. The study of these trajectories and the ratio of motion velocities with distance from the center of the Galaxy formed the basis of the currently actively developing theory of dark matter. Its nature is still shrouded in mystery. The presence of dark matter, presumably constituting the vast majority of all matter in the Universe, is registered only by the effect of gravity on orbits.

If we dispel all the cosmic dust that the core hides from us, a striking picture opens up. Despite the concentration, this part of the universe is full of light emitted by a huge number of stars. There are hundreds of times more of them per unit of space than near the Sun. Approximately ten billion of them form a galactic bar, also called a bar, of an unusual shape.

space nut

The study of the center of the system in the long-wavelength range made it possible to obtain a detailed infrared image. Our Galaxy, as it turned out, in the core has a structure resembling a peanut in a shell. This "nut" is the jumper, which includes more than 20 million red giants (bright, but less hot stars).

Spiral arms of the Milky Way diverge from the ends of the bar.

The work associated with the discovery of a “peanut” at the center of a star system not only shed light on what our galaxy is in terms of structure, but also helped to understand how it evolved. Initially, in the space of space there was an ordinary disk, in which a jumper formed over time. Under the influence of internal processes, the bar changed its shape and began to look like a walnut.

Our house on the space map

Active star formation occurs both in the bar and in the spiral arms that our Galaxy has. They were named after the constellations where branches of the branches were discovered: the arms of Perseus, Cygnus, Centaurus, Sagittarius and Orion. Near the latter (at a distance of at least 28 thousand light years from the nucleus) and is located solar system. This area has certain characteristics, according to experts, that made possible the emergence of life on Earth.

The galaxy and our solar system rotate with it. The patterns of motion of the individual components do not coincide in this case. Big number stars are sometimes part of the spiral branches, then separated from them. Only the luminaries lying on the boundary of the corotation circle do not make such "journeys". These include the Sun, protected from the powerful processes that are constantly taking place in the arms. Even a slight shift would negate all other advantages for the development of organisms on our planet.

Sky in diamonds

The sun is just one of many similar bodies that fill our galaxy. Stars, single or grouped, total number exceed 400 billion according to the latest data. Proxima Centauri, closest to us, is part of a system of three stars, along with slightly more distant Alpha Centauri A and Alpha Centauri B. The brightest point in the night sky, Sirius A, is located in its luminosity, according to various sources, exceeds the solar in 17-23 times. Sirius is also not alone, he is accompanied by a satellite bearing a similar name, but labeled B.

Children often begin to get acquainted with what our Galaxy looks like by searching the sky for the North Star or Alpha Ursa Minor. It owes its popularity to its position above the North Pole of the Earth. In terms of luminosity, Polaris significantly exceeds Sirius (almost two thousand times brighter than the Sun), but it cannot challenge the rights of Alpha Big Dog for the title of the brightest because of the distance from Earth (estimated from 300 to 465 light years).

Types of luminaries

Stars differ not only in luminosity and distance from the observer. Each is assigned a certain value (the corresponding parameter of the Sun is taken as a unit), the degree of surface heating, color.

The most impressive sizes are supergiants. The highest concentration of a substance per unit volume is neutron stars. The color characteristic is inextricably linked with temperature:

• reds are the coldest;
• heating the surface to 6,000º, like that of the Sun, gives rise to a yellow tint;
• white and blue luminaries have a temperature of more than 10,000º.

The luminosity of a star can change and reach a maximum shortly before its collapse. Supernova explosions make a huge contribution to understanding what our galaxy looks like. The photographs of this process taken by telescopes are amazing.
The data collected on their basis helped to reconstruct the process that led to the flare and to predict the fate of a number of cosmic bodies.

Future of the Milky Way

Our Galaxy and other galaxies are constantly in motion and interacting. Astronomers have found that the Milky Way has repeatedly swallowed up its neighbors. Similar processes are expected in the future. Over time, it will include the Magellanic Cloud and a number of dwarf systems. The most impressive event is expected in 3-5 billion years. This will be a collision with the only neighbor that is visible from Earth to the naked eye. As a result, the Milky Way will become an elliptical galaxy.

The endless expanses of space are amazing. It is difficult for the layman to realize the magnitude of not only the Milky Way or the entire Universe, but even the Earth. However, thanks to the achievements of science, we can imagine at least approximately what a part of the grandiose world we are.

Galaxy is a huge rotating star system. In addition to our Galaxy, there are a great many others, diverse both in appearance and in physical characteristics.

Large galaxies are usually separated from each other in space by distances of several megaparsecs. Parsec(Russian abbreviation: pc; international abbreviation: pc) is a non-systemic unit of distance measurement common in astronomy. 1pc=3.2616 light year . Small galaxies are often located near giant galaxies and are their satellites. This image shows spiral galaxy NGC 4414 in the constellation Coma Berenices, about 17,000 parsecs in diameter, about 20 megaparsecs from Earth.

Can other galaxies be seen with the naked eye?

Yes, you can. But only those closest to us. These are three galaxies: the Large and Small Magellanic Clouds and the Andromeda Nebula. With great difficulty, you can see the Triangulum galaxy and the Bode galaxy. Other galaxies can be seen with a telescope as hazy spots of various shapes - these are extremely distant objects. Even the distance to the nearest of them is usually measured in megaparsecs.

How many galaxies are there?

It is impossible to name the exact number. But images of deep space taken in the early 1990s by the Hubble Space Telescope clearly show that there are hundreds of billions of galaxies. There are galaxies with their own names, for example, the names of galaxies already given in this article, as well as the Spindle, Tadpole, Antennas, Mice, Sunflower, Cigar, Fireworks, Sculptor, Sleeping Beauty, etc. galaxies. Some galaxies are indicated only by letters and numbers: galaxy M82 , galaxy M102, galaxy NGC 3314A, etc.

As mentioned above, galaxies are diverse in shape: among them are spherical elliptical galaxies, disk spiral galaxies, galaxies with a bar (bar), dwarf, irregular, etc. Their mass varies from 107 to 1012 solar masses. Compare: the mass of our Milky Way galaxy is 2 1011 solar masses. The diameter of galaxies is also varied: from 16 to 800 thousand light years. Compare: the diameter of our galaxy is about 100,000 light years.

The structure of galaxies

We already know that a galaxy is a giant gravitationally bound system of stars and star clusters, interstellar gas and dust, and dark matter. We also know that dark matter is not available for direct observation by modern means of astronomy, because does not emit electromagnetic or neutrino radiation for intensity observations and does not absorb them. Therefore, it is one of the unsolved problems of the structure of galaxies. It can make up to 90% of the total mass of the galaxy, or it can be completely absent, as in some dwarf galaxies.
In space, galaxies are unevenly distributed: in one area there may be a whole group of nearby galaxies, but you can not find even a single, even the smallest galaxy (the so-called voids).

Classification of galaxies

Currently, the classification introduced by Hubble is used. It is based on appearance galaxies and divides them into three classes: elliptical, spiral and irregular. Part of this classification includes physical differences.
Elliptical (type E) have the shape of an ellipsoid. The spatial density of stars in them decreases uniformly from the center to the periphery. Most of them are almost devoid of interstellar gas, so there is no formation of young stars, they are composed of old stars like the Sun. Their rotation occurs at a low speed (less than 100 km / s.). But it is among the elliptical galaxies that the most massive galaxies are found.

Spiral (type S) consist, as it were, of two subsystems: spherical and disk. The first resembles an elliptical galaxy, the disk galaxy is highly compressed and contains, in addition to old ones, young stars and interstellar gas and dust. Disk stars and gas clouds revolve around the center of the galaxy at a speed of 150-300 km/sec. The denser clouds of gas and young stars are concentrated in the spiral arms that come out either from the core or from the ends of the bright bridge (bar) that crosses the core. This is our Milky Way galaxy. The Andromeda Nebula also belongs to the spiral galaxy.

Incorrect (type Ir) have a relatively small mass and size, are characterized by a ragged structure - this is due to the presence of several centers of star formation. Magellanic clouds are one of these types of galaxies.
There are more intermediate types of galaxies: lenticular, dwarf, compact, radio galaxies (with intense radio emission), Seyfert (spiral, in the nuclei of which active processes are observed).
Large galaxies are found in pairs or groups: for example, Local group of galaxies. There are interacting galaxies discovered by astronomer B.A. Vorontsov-Velyaminov - close groups in which galaxies almost touch each other or even penetrate each other. The shape of such galaxies is strongly distorted.

clusters of galaxies(associations of several hundred galaxies) are usually spherical or ellipsoidal in shape. The closest cluster of galaxies to us is located in the constellation Virgo, it is the center of the Local Supercluster of galaxies - a system that unites several clusters of galaxies, including the Local Group. Superclusters(thousands of galaxies) are usually flat or cigar-shaped. As astronomers have established, galaxies scatter, i.e. distances between clusters and superclusters are constantly increasing. It has to do with the expansion of the universe.
Our Galaxy is one of the galaxies of the Local Group, dominating it together with Andromeda. More than 40 galaxies are located in the Local Group with a diameter of about 1 megaparsec. The Local Group itself is part of the Virgo supercluster, in which the main role is played by the Virgo cluster, in which our Galaxy is not included.

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 so that he drank her 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 on starry sky are also part of 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.

A galaxy is a system of stars, star clusters, interstellar gas and dust, bound together by gravity and dark matter. There are several main types of classification of galaxies: elliptical, spiral, lenticular and irregular galaxies.

The spiral galaxy M83, also known as the South Pinwheel in the constellation Hydra, is 15 million light years away. NASA photo from the Hubble telescope.

The elliptical galaxy M60, consisting of old stars in the center, and the spiral galaxy NGC 4647, consisting of new bright blue stars, gas and dust. NASA photo from the Hubble telescope.

Irregular galaxy NGC 55, located at a distance of 6 million light years from Earth. Photo by Robert Gendler

Back in the early twentieth century, scientists did not know about the existence of other galaxies. And although the first galaxies were already known, they were attributed to our native galaxy the Milky Way and were called nebulae. Assumptions that these nebulae could be separate star systems already existed, but still did not stand up to criticism. This was facilitated by the imperfection of observation tools.

In 1922, when there were discussions about the distance to the spiral nebulae, Ernst Epik (an astronomer originally from Estonia) calculated the distance to the Andromeda Nebula. The data he received is 0.6 of the current data, which is even more accurate than that of Edwin Hubble. In 1924, Hubble used the largest telescope at the time, 254 centimeters in diameter. He also calculated the distance to Andromeda. The distance was 3 times less than the current data, but still so large that Andromeda simply could not be part of the Milky Way. Thus, Andromeda became a separate galaxy. This discovery forever changed mankind's understanding of the universe. Now it contained not just one Milky Way galaxy, but an infinite number of other worlds. Edwin Hubble also created a type classification of galaxies that astronomers use to this day.

Where do galaxies come from?

To date, there is a unanimous scientific opinion on the question “how are galaxies formed?” still no. Using the most powerful computers, scientists have not been able to build a model that fully describes the formation of galaxies. According to the generally accepted Big Bang theory, the early universe was filled with a dense cloud of hydrogen and helium. From this "cloud" under the influence of dark matter, and then gravity, the first stars began to form.

When did the first stars appear?

Some calculations suggest that the first stars could have formed as early as 30 million years after the Big Bang. According to other sources, this figure reaches 100 million. Computer models show that the first luminaries formed mainly at once, several at a time, up to a hundred. It's all about the action of gravity, when the gas twisted into huge disks. And in these large disks, separate smaller seals formed, which subsequently turned into separate stars. The first stars in the young universe were truly colossal. This was facilitated by the abundance building material who was everywhere.

Computer model of the formation of stars from a gas cloud.

Together with the first star clusters, under the influence of gravity, the gas, together with the already formed stars and clusters of stars, began to form the first galaxies. The first galaxies contained up to a billion stars and, according to the current classification, they would be classified as dwarf galaxies. Do not forget that there were many such galaxies and their concentration in space was much higher. Over time, they interacted with each other, collapsing and merging, thereby forming new larger galaxies. This has been happening for 13 billion years. The consequence of such transformations is today's Universe, which we can observe.

The most ancient and distant galaxies

Advanced space exploration technologies have given us a glimpse into the most ancient times in the universe. Since the speed of light is finite, the distance that it travels in a certain period of time is also finite. Distances in space are usually measured in light years. One light year is equal to the distance that light travels in one year, which is approximately equal to 9.5 trillion kilometers. For example, when you look at the Sun, you see it as it was, because it takes that long for light to reach the Earth. And the deeper we look into space, the more ancient objects we observe. To date, the oldest and most distant known galaxies are:

z8 GND 5296 in the constellation Ursa Major. Light from it flew to us for 13.1 billion years. It formed when the universe was 700 million years old. NASA photo from the Hubble telescope.

MACS0647-JD in the constellation Giraffe. It took light 13.3 billion years to travel and it formed when the universe was 420 million years old. The diameter of the galaxy is 600 light years (for comparison, the diameter of the Milky Way is 100,000 light years). NASA photo from the Hubble and Spitzer telescopes

Galaxy UDFy-38135539 in the constellation Furnace. Its light traveled its distance to us in 13.1 billion years. NASA photo from the Hubble telescope.

The closest galaxies

galaxies in ancient times they were formed in comparative proximity to each other. Under the influence of gravity, they form clusters of galaxies. One of these clusters is called the Local Group, which includes our Milky Way. The Local Group consists of Andromeda (200,000 light-years across) with its satellites, the Milky Way (100,000 light-years across) with its satellites, and the Triangulum Galaxy (50,000 light-years across) with its possible satellites and several dwarf galaxies. , which are not satellites, but also included in the local group.

It is the Andromeda galaxy that is our closest neighbor. It is located at a distance of 2.5 million light years from the Milky Way. To the Triangulum galaxy, the second farthest from us - 2.7 million light years. The local group of galaxies also includes dwarf galaxies: satellites of the Milky Way and Andromeda and other independent dwarf galaxies. In total, the Local Group consists of 50 galaxies. Examples of such galaxies are:

Large Magellanic Cloud. Photo by astrophotographer Marco Lorenzi. For a more detailed image of hydrogen clouds (red), the photo was taken using a filter.

- a dwarf galaxy, a satellite of the Milky Way, the distance to it is 163,000 light years. LMC is the brightest galaxy, a satellite of the Milky Way. BMO can be found in the constellation Dorado, which is in southern hemisphere. Under conditions of good visibility, it is visible to the naked eye. The galaxy has 30 billion stars.

Small Magellanic Cloud and two globular star clusters. The left globular star cluster, 47 Tucanae, is located 13,000 light-years from Earth. At the bottom right, NGC 362 is 27,700 light-years away.

The Small Magellanic Cloud is a dwarf galaxy, a satellite of the Milky Way, a distance of 197,000 light years, located in the constellation Toucan and has 1.5 billion stars.

Sagittarius or SagDIG is a dwarf irregular galaxy belonging to the local group, located in the constellation Sagittarius at a distance of 3.4 million light years. NASA photo from the Hubble telescope.

The Furnace Galaxy is a dwarf galaxy, a satellite of the Milky Way, a distance of 460,000 light years, located in the constellation Furnace. There are 6 globular star clusters in this galaxy. It is noteworthy that the largest of the clusters, NGC 1049, was discovered by John Herschel in 1835, before the galaxy itself was discovered in 1938. Photo by the European Space Agency.

A dwarf galaxy in the constellation Sculptor is a satellite of the Milky Way, a distance of 290,000 light years and others.

The location of galaxies in the vicinity of the Milky Way

The local group, in turn, is part of a much larger local supercluster of galaxies. The diameter of the local supercluster is 200 million light years and contains 30,000 galaxies. The center is the cluster of galaxies in Virgo, the largest in the supercluster and has about 1.5-2 thousand gravitationally bound galaxies. But these are only our closest neighbors. The observable Universe is much larger and today it includes more than 500 billion galaxies.

Metagalaxy is the observable Universe.

To an observer from the Earth, the Universe appears as a ball with our planet in the center. According to currently available astronomical methods of study, the cosmological horizon (the visible Universe) is considered to be a ball with a diameter of 93 billion light years. Despite the fact that since the Big Bang the Universe has only 13 billion years, it is constantly expanding. Galaxies in the Universe are not evenly distributed, and are clusters. The Universe can be represented as a sponge, where the molecules of this sponge are galaxies lining up in structures called filaments (threads) with relatively empty cavities - voids. Compared to a sponge, these are air bubbles.

In this photo, each point of light is a galaxy. Large clusters of galaxies are visible, as well as voids.

The largest galaxies

And finally, a few words about the size of galaxies. We have already talked about the smallest representatives of star systems. These are dwarf galaxies, of which there are a huge number. Their sizes can vary from 2,000 light-years in diameter to several billion stars.

But there are also opposites. The largest galaxies began their life path from dwarf galaxies. They formed, apparently, in such regions of the Universe, where the concentration of galaxies was much higher. These dwarf galaxies, under the influence of gravity, collided with the same small galaxies, as a result of which they increased in size. And the more massive the galaxy became, the greater the force of attraction it possessed, increasing the power of absorption. To date, the largest known galaxies are dozens of times larger than our Milky Way.

For comparison, the Milky Way has a diameter of 100,000 light years. This is the average for all known spiral galaxies.

Andromeda, photo: Martin Pugh
Andromeda is the closest galaxy to us with a diameter of 200,000 light years.

M87, photo: Robert Gendler
M87 is a giant elliptical galaxy in the constellation Virgo, with a diameter of 300,000 light years. The distance to the Earth is 60 million light years. It is the largest galaxy in the nearest outer space.

NGC 6872 is the largest known spiral galaxy. Located in the constellation Peacock at a distance of 212 million light years and has a diameter of 522,000 light years.

A2261-BCG is a giant elliptical galaxy at the center of the Abel 2261 galaxy cluster. It has trillions of stars and is over a million light-years across. This galaxy is also known for having the largest nucleus ever observed. Its size is 10,000 light years, which is a tenth of our entire galaxy. Located at a distance of 3 billion light years.

Galaxy

Galaxies are huge rotating cities of stars. There are at least 100 billion galaxies in the universe, separated by unimaginable distances of almost empty space. Without a telescope from Earth, only three galaxies and part our own Milky Way Galaxy. Two of them are called the Magellanic Clouds. They got this name in honor of the Portuguese navigator Ferdinand Magellan. When Magellan's ships sailed the southern seas in 1519, the crew saw two dimly glowing galaxies in the sky. They brought the news of this with them to Europe.

closest galaxies to earth

Galaxy Magellanic Clouds

The Magellanic Clouds really look like two small clouds - soft and solid. These two small galaxies orbit the larger Milky Way. So the Magellanic Clouds are our closest neighbor. How small are these galaxies? One of them contains 15 billion suns, the other only about 5 billion. For comparison, we can say that there are about 200 billion stars in our Galaxy.

The third galaxy that can be seen with the naked eye is the Andromeda Nebula. It is a spiral galaxy similar to the Milky Way. The Andromeda Nebula is 2.2 million light-years away.. A light year is the distance that light travels in one year at 300,000 kilometers per second. For the year it turns out about 9.6 trillion kilometers. This means that the Andromeda Nebula is 21120000000000000000 kilometers away, and that it takes 2.2 million years for light to travel from the Andromeda Nebula to the Earth, and it also follows that we see the galaxy as it was 2.2 million years ago.

When we look at the Andromeda Nebula or the Magellanic Clouds with the naked eye, we do not see individual stars. One can only see a spot glowing with a dim light with indistinctly defined edges - the combined light of millions and millions of suns. In addition to the three galaxies considered, a part of the Milky Way can be seen in the night sky. The mealy white streak of stars that crosses the sky is part of the disk of our Galaxy. The ancient Greeks believed that the white stripe was a trickle of milk from the breast of the goddess Hera. In Greek, the word for "milk" is "ha-la". That's where the word "galaxy" comes from.

Other galaxies, visible only through a telescope, have very interesting and unusual names. There is a tiny Sculptor galaxy. In the sky there is a Dragon, Tongs, Leo 1 and Leo 2, Sextan, Pegasus, Wagon and Sombrero.

Names of galaxies

True, there are so many galaxies (inabout a universe of about 100 billion galaxies) that there are not enough names for everyone, perhaps. Therefore, each galaxy has an alphanumeric designation. In the 18th century, French astronomer Charles Monsieur compiled a list of unidentified luminous celestial bodies. The list included about 100 objects, among them were several galaxies. He assigned numbers to each object: M1, M2, and so on (so The Andromeda Nebula is M31.).

Later astronomers developed more extensive and detailed catalogs of galaxies and other cosmic objects: constellations and nebulae. So many galaxies only have numbers in the New General Catalog or in the Index Catalog. In these catalogs, the Andromeda Nebula is listed as NGG224.

The word "galaxy" comes from Greek word "gala", which means milk.