Galaxy is a huge rotating star system. In addition to our Galaxy, there is a great variety of others, various in appearance as well as 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.

The universe contains many more galaxies than previously thought, and that's not a small difference, according to a study in the upcoming Astrophysical Journal, there would be 2,000 billion galaxies, ten times more than previously thought. But a team of researchers led by Christopher Conselis of the University of Nottingham used data from the Tovar study, but with Hubble's observations increased the result by a factor of ten.

Unfortunately, 90% of the galaxies present are not visible with existing telescopes. They are too faint or far away to be observed. So they discovered how galaxies aggregate over time, merging and therefore decreasing in density.

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.

Therefore, their distribution throughout the history of the universe is not uniform. Exist statistical distributions how many objects there are, the score was made based on them. from the satellite he will watch the Italian cities, he will see the biggest ones like Rome and Milan, but not the small countries. The same thing happens, for example, for Andromeda: two large spiral circus galaxies born from dozens of much smaller galaxies.

Satellite galaxies can contain several million stars, while the Milky Way contains about 100 billion. "Message: We struggle to see these little ones near our home, not to mention those small and distant billions of light years." very small objects are very large, but still "gross stars are in the great galaxies we can see". The new data is a step forward in understanding the origin of galaxies and the nature of dark matter: Interesting, Fontana emphasizes, because these data tell us about the birth of galaxies.

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.

This is one of the important pieces of the puzzle, once, in the history of the universe, there were many and few, and over time they merged together to give life to larger ones. Attention, this does not change the estimate of how much dark matter is used to explain the dynamics of the universe, but the kind of dark matter that it is made of. These data have great importance for the number of small galaxies.

It would be important to see how the smallest galaxies can understand what dark matter is, the astrophysicist concludes, but for this we must wait for the James Webb telescope. Where does all the starlight go? The question to the poetic appearance is more of a paradox, to which the study gives the following answer: if there are so many galaxies in every corner of the sky, why do we see it so dark? The answer lies in the characteristics of starlight modified from redshift due to the expansion of the universe and the absorption of light by intergalactic powders in "dark" regions of the sky.

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.

Many so-called nebulae, when resolved by our telescopes, appear as swarms of various stars. Some are spiral-shaped; others are ellipsoidal or shapeless. Today they are more correctly called "galaxies". They are outside our star system and are excellent systems in their own right; therefore they are called "extragalactic". With binoculars or a small telescope, it looks like an ellipsoidal haze. The Andromeda Nebula is similar to the galaxy to which our solar system belongs.

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 not even a single, even the smallest galaxy (the so-called voids) can be found.

It is about 2 million light years and about a thousand light years. Observers in southern hemisphere are familiar with the Magellanic Clouds, which are irregularly shaped galaxies and lie about 1,000 light-years from Earth. Extragalactic nebulae are of considerable size, which can match and exceed the Milky Way. Our galaxy has large clouds of gas and cosmic dust called "diffuse" or "galactic" nebulae. Some are dark, others are bright. Among the dark nebulae we see some that are found in the constellations of the Southern Cross, Cepheus, Cygnus and Scorpio.

Classification of galaxies

Currently, the classification introduced by Hubble is used. It is based on the appearance of 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.

They look like black holes, irregular in the sky; they actually hide the stars behind them. Diffuse nebulae are usually less dense than the air that remains in a container in which a vacuum is created in a laboratory. Their gases and their cosmic dust could be the materials with which new stars will form. These nebulae shine because they reflect light from nearby stars or because they are hot, like fluorescent flashes excited by starlight. So-called planetary nebulae, a very common type, are masses of gas ejected by a star during a cataclysmic change.

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.

The gas forms a winding or "shell" around the star. This envelope may be ring-like, as in Lyra's annular nebula. Among the widely distributed nebulae, the amateur can observe the Crab Nebula in Taurus, the Great Node in Dorado, and the Lagoon in Sagittarius. Messier listed so many nebula bodies that are now considered globular clusters.

Modern lists of Messier bodies classify them according to current criteria. You can only resolve galaxies in single stars with long exposure photographs taken by large telescopes. Most nebulae can only be observed on clear, dark and moonless nights. The Magellanic Clouds and the great nebulae of Andromeda and Orion are bright enough to be observed in all conditions; but the darker the sky, the better the observation. These large nebulae are easy to find, but for others you may need an atlas.

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.

Determine the exact location of the nebula by referring to nearby bright stars. find the nebula using your coordinates. Spiral nebulae seen from the front may appear to be circular clouds. If you are inclined, compared to our gaze, they appear oval, if we see them from the side, you can see the red-hot mass in the middle of the bicuspid lenticular structure. The apparent shape of any nebula depends on its position relative to our line of sight. Diffuse nebulae can appear as glowing veils.

The Crab Nebula, in Taurus, resembles a thin spray of light. A planetary nebula, like a lyre or Aquarius, can appear as a luminous cloud-like ring. These are not just the opening words of each episode of the Star Wars saga, but what you will see in these photos. The light from the most distant and ancient galaxies in the universe takes millions of years to reach us. We see them today as they were when there were no traces of man on Earth, so take a look at the eyes with the most distant galaxies of the known universe: even better than the movie.

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.

At 28 million light-years, we find one of the celestial objects favored by amateur astronomers around the world: a cutaway galaxy similar in appearance to a Mexican hat and the size of 800 billion suns. The interior of this 50,000 light-year-long celestial object contains a supermassive black hole.

Located at an "astronomical" distance of 45 million light-years, this pair of interacting galaxies is still the closest known colliding duo of galaxies. Their interaction lasted hundreds of thousands of years and led to the emergence of regions of intense star formation. A similar scene could be repeated in three billion years to get closer to reality: even the Milky Way and Andromeda are on a collision course and promise to collide and pierce each other to finally form a unique elliptical galaxy of considerable size.

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.

It's the closest on the list: it's "only" 11.5 million light-years away and takes its name from the oblong shape that "observation" indicates. The stellar children's activity, together with the spectacle of gaseous emissions that we observe, should last 100 million years. The celestial "rose" we catch from 350 million light years away.

At 27 million light-years from Earth, it is one of the brightest galaxies in the sky and is also visible with simple binoculars. Its enormous arms span 170,000 light-years, twice the size of the Milky Way, so large that its gravitational attraction distorts the shape of many nearby galaxies.

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.

This bright blue object is a dwarf galaxy 59 million light-years away: irregularly shaped, much smaller than the Milky Way, and has long been younger than it really is. While observations made 40 years ago suggested that the galaxy formed several billion years after the surrounding galaxies, more recent Hubble studies have shown that the celestial object simply had an abnormal stellar rhythm: slow at the beginning, more intense when we see it .

You are witnessing a show that was 230 million years ago, but no less fascinating: a supermassive black hole hidden in the center of this distant galaxy is causing intense radiation x-rays, which make it fall into Seyfert's classification of galaxies, galaxies from extraordinarily active and brilliant nuclei equipped with central "engines".

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.

It is 15 million light years and is clearly visible even with binoculars. We see it in person, and we can appreciate its strong star-forming regions, such as those we see in this close-up, where red stands for "newborn" stars, some of which have been formed over millions of years. This dwarf galaxy, 54 million light-years away, has a concentration 140 million times that of our Sun, making the small galaxy one of the densest systems in the known universe.

The loneliest of the group, even if not the most distant, is the so-called Lost Space Galaxy, a galaxy that does not belong to a cluster and is therefore gravitationally isolated. It is located at a distance of 18 million light-years from Earth, in a region of the Cosmos called "Empty Local", an area adjacent to our local group in which several galaxies and nebulae are found.

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 disk 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

The "heart" of the 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 relationship between the velocities of motion and the 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 like in structure, but also helped to understand how it developed. 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 according to the latest data, exceed 400 billion. 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.