A galaxy neighboring ours. The Andromeda Galaxy and the Milky Way: moving towards each other

Scientists have known for some time that the Milky Way Galaxy is not the only one in the Universe. In addition to our galaxy, which is part of the Local Group - a collection of 54 galaxies and dwarf galaxies - we are also part of a larger formation, also known as the Virgo Cluster of Galaxies. So, we can say that the Milky Way has many neighbors.

Of these, most people believe that the Andromeda Galaxy is our closest galactic neighbor. But in truth, Andromeda is the closest spiral Galaxy, but not the nearest Galaxy at all. This distinction falls to the formation of what is actually within the Milky Way itself, a dwarf Galaxy that is known as Canis Major Gnome Galax (aka. Canis Major).

This star formation is located about 42,000 light-years from the galactic center and only 25,000 light-years from our solar system. This puts it closer to us than the center of our own galaxy, which is 30,000 light-years from the solar system.

Before its discovery, astronomers believed that the Sagittarius Dwarf Galaxy was the closest galactic formation in our own. At 70,000 light-years from Earth, this Galaxy was identified in 1994 to be closer to us than the Large Magellanic Cloud, a dwarf galaxy 180,000 light-years away that previously held the title of our nearest neighbor.

That all changed in 2003, when the dwarf galaxy Canis Major was discovered by the Two Micron Survey Survey (2MASS), an astronomical mission that took place between 1997 and 2001.

Using telescopes located on MT. Hopkins Observatory in Arizona (for the Northern Hemisphere) and at the Inter-American Observatory in Chile in the Southern Hemisphere, astronomers were able to conduct a comprehensive survey of the sky in infrared light, which is not blocked by gas and dust as severely as visible light.

Because of this technique, astronomers have been able to detect a very significant density of class M giant stars in the sky occupied by the constellation Canis Major, as well as several other associated structures within this type of star, two of which have the appearance of wide, swooning arcs (as seen in the image above ).

The prevalence of M-class stars is what made the formation easy to detect. These cool, “red dwarfs” are not very bright compared to other classes of stars, and cannot even be seen with the naked eye. However, they shine very brightly in the infrared, and appeared in large numbers.

In addition to its composition, the Galaxy has a nearly elliptical shape and is believed to contain as many stars as the Sagittarius dwarf elliptical Galaxy, a previous contender for the closest Galaxy to our location in the Milky Way.

In addition to the dwarf galaxy, a long string of stars is visible trailing behind it. This complex, ring structure - sometimes called the Monoceros ring - warps around the galaxy three times. The shower was first discovered in the early 21st century by astronomers conducting the Sloan Digital Sky Survey.

It was during the investigation of this ring of stars, and closely spaced groups of globular clusters similar to those associated with the Sagittarius Dwarf Elliptical Galaxy, that the Canis Major Dwarf Galaxy was discovered.

The current theory is that this galaxy was fused (or absorbed) into the Milky Way Galaxy. Other globular clusters orbiting the center of the Milky Way as a satellite - that is, or NGC 1851, NGC 1904, NGC 2298 and NGC 2808 - are believed to have been part of the Canis Major Dwarf Galaxy before its accretion.

The discovery of this galaxy, and subsequent analysis of the stars associated with it, provides some support for the current theory that galaxies can grow in size by swallowing their smaller neighbors. The Milky Way became what it is now, eating up other galaxies like a big dog, and it continues to do so today. And since the Canis Major Dwarf Galaxy stars are technically already part of the Milky Way, it is by definition the closest Galaxy to us.

Astronomers also believe that the big dog dwarf galaxies are in the process being pulled away by the gravitational field of the more massive Milky Way galaxy. The main body of the galaxy is already extremely degraded, and this process will continue, traveling around and throughout our Galaxy. During accretion, it will likely end with the Great Canis Dwarf Galaxy storing 1 billion of the 200 to 400 billion stars that are already part of the Milky Way.

Before its discovery in 2003, it was the Sagittarius dwarf elliptical galaxy, which held the position of the closest galaxy to our own. 75,000 light years away. This dwarf galaxy, which consists of four globular clusters that measure about 10,000 light-years in diameter, was discovered in 1994. Before this, the Large Magellanic Cloud was thought to be our closest neighbor.

The Andromeda Galaxy (M31) is the closest spiral galaxy to us. Although - gravitationally - it is connected to the Milky Way, it is still not the nearest Galaxy - 2 million light years away. Andromeda is currently approaching our galaxy at a speed of about 110 kilometers per second. In about 4 billion years, the Andromeda Galaxy is expected to merge to form a single Super Galaxy.

Fixing its gaze on the stars, humanity has long wanted to find out what is there - in the abyss of space, what laws are there and whether there are intelligent beings. We live in the 21st century, this is a time when space flights are an ordinary part of our lives, of course, people do not yet fly on spaceships, like on airplanes on Earth, but reports of the launches and landings of all kinds of research probes are already quite commonplace. So far, only the Moon, our satellite, has become the first and only extraterrestrial object where a person has set foot; the next stage will be the landing of a person on Mars. But in this article we will not talk about the “red planet” or even the nearest star, we will discuss the curious question of what is the distance to the nearest galaxy. Although from a technical point of view such long flights are not feasible at the moment, it is still interesting to know the approximate timing of the “journey”.

If you read our article about that, you will understand that moving a spaceship to a nearby galaxy is something unimaginable. With today's technologies, it is very difficult to fly, let alone to a galaxy, to a star. However, this seems impossible if we rely on the classical laws of physics (you cannot exceed the speed of light) and the technology of burning fuel in engines, no matter how advanced they are. First, let's talk about the distance between our galaxy and the nearest one so that you understand the enormous scale of the hypothetical journey.

Distances to nearby galaxies

We live in a galaxy called the Milky Way, which has a spiral structure and contains approximately 400 billion stars. Light travels the distance from one end to the other in about one hundred thousand years. The closest to ours is the Andromeda galaxy, which also has a spiral structure, but is more massive, containing approximately one trillion stars. The two galaxies are gradually approaching each other at a speed of 100-150 kilometers per second; in four billion years they will “merge” into a single whole. If after so many years people still live on Earth, they will not notice any transformations other than a gradual change in the starry sky, because... distances between stars, then the chances of collision are very small.

The distance to the nearest galaxy is approximately 2.5 million light years, i.e. Light from the Andromeda Galaxy takes 2.5 million years to reach the Milky Way.

There is also a “mini-galaxy”, which was called the “Large Magellanic Cloud”, it is small in size and is gradually decreasing; the Magellanic Cloud will not collide with our galaxy, because has a different trajectory. The distance to this galaxy is approximately 163 thousand light years, it is the closest to us, but because of its size, scientists prefer to call the Andromeda galaxy closest to us.

To fly to Andromeda on the fastest and most modern spaceship built to date, it will take as much as 46 billion years! It’s easier to “wait” until she herself flies to the Milky Way “in just” 4 billion years.

High-speed "dead end"

As you understand from this article, it is “problematic” for even light to reach the nearest galaxy; intergalactic distances are enormous. Humanity needs to look for other ways to move in outer space than “standard” fuel engines. Of course, at this stage of our development we need to “dig” in this direction; the development of high-speed engines will help us quickly explore the vastness of our solar system; man will be able to set foot not only on Mars, but also on other planets, for example, Titan, the satellite of Saturn, which is already has long been of interest to scientists.

Perhaps, on an improved spaceship, people will be able to fly even to Proxima Centauri, the closest star to us, and if humanity learns to reach the speed of light, then it will be possible to fly to nearby stars in years, not millennia. If we talk about intergalactic flights, then we need to look for completely different ways of moving in space.

Possible ways to overcome huge distances

Scientists have long been trying to understand the nature of “” - massive objects with such strong gravity that even light cannot escape from their depths; scientists suggest that the supergravity of such “holes” can break through the “fabric” of space and open paths to some other points of our Universe. Even if this is true, the method of traveling through black holes has several disadvantages, the main one of which is “unplanned” movement, i.e. people on a spaceship will not be able to choose a point in the Universe where they want to go, they will fly to where the hole “wants”.

Also, such a journey can become one-way, because... the hole may collapse or change its properties. In addition, strong gravity can affect not only space, but also time, i.e. the astronauts will fly as if into the future, for them time will flow as usual, but on Earth years or even centuries may pass before their return (this paradox is well shown in the recent film “Interstellar”).

Scientists involved in quantum mechanics have discovered an amazing fact: it turns out that the speed of light is not the limit of movement in the Universe, at the micro level there are particles that appear for an instant at one point in space, and then disappear and appear in another, the distance for them has no meanings.

“String theory” states that our world has a multidimensional structure (11 dimensions), perhaps by understanding these principles, we will learn to move to any distance. The spaceship will not even need to fly anywhere and accelerate, while standing still, it will be able, with the help of some kind of gravitational generator, to collapse space, thereby getting to any point.

The power of scientific progress

The scientific world should pay more attention to the microcosm, because perhaps this is where the answers to the questions of rapid movement throughout the Universe lie; without revolutionary discoveries in this area, humanity will not be able to overcome large cosmic distances. Fortunately, for these studies, a powerful particle accelerator was built - the Large Hadron Collider, which will help scientists understand the world of elementary particles.

We hope that in this article we have talked in detail about the distance to the nearest galaxy; we are sure that sooner or later a person will learn to overcome distances of millions of light years, perhaps then we will meet our “brothers” in mind, although the author of these lines believes that this will happen sooner. You can write a separate treatise on the meaning and consequences of the meeting; this, as they say, is “another story.”

GALAXIES, “extragalactic nebulae” or “island universes,” are giant star systems that also contain interstellar gas and dust. The solar system is part of our Galaxy - the Milky Way. All outer space, to the extent that the most powerful telescopes can penetrate, is filled with galaxies. Astronomers count at least a billion of them. The nearest galaxy is located at a distance of about 1 million light years from us. years (10 19 km), and the most distant galaxies recorded by telescopes are billions of light years away. The study of galaxies is one of the most ambitious tasks in astronomy.

Historical reference. The brightest and closest external galaxies to us - the Magellanic Clouds - are visible to the naked eye in the southern hemisphere of the sky and were known to the Arabs back in the 11th century, as well as the brightest galaxy in the northern hemisphere - the Great Nebula in Andromeda. With the rediscovery of this nebula in 1612 using a telescope by the German astronomer S. Marius (1570–1624), the scientific study of galaxies, nebulae and star clusters began. Many nebulae were discovered by various astronomers in the 17th and 18th centuries; then they were considered clouds of luminous gas.

The idea of ​​star systems beyond the Galaxy was first discussed by philosophers and astronomers of the 18th century: E. Swedenborg (1688–1772) in Sweden, T. Wright (1711–1786) in England, I. Kant (1724–1804) in Prussia, I. .Lambert (1728–1777) in Alsace and W. Herschel (1738–1822) in England. However, only in the first quarter of the 20th century. the existence of “island Universes” was unequivocally proven mainly thanks to the work of American astronomers G. Curtis (1872–1942) and E. Hubble (1889–1953). They proved that the distances to the brightest, and therefore the closest, “white nebulae” significantly exceed the size of our Galaxy. During the period from 1924 to 1936, Hubble pushed the frontier of galaxy research from nearby systems to the limit of the 2.5-meter telescope at Mount Wilson Observatory, i.e. up to several hundred million light years.

In 1929, Hubble discovered the relationship between the distance to a galaxy and the speed of its movement. This relationship, Hubble's law, has become the observational basis of modern cosmology. After the end of World War II, active study of galaxies began with the help of new large telescopes with electronic light amplifiers, automatic measuring machines and computers. The discovery of radio emission from our and other galaxies provided a new opportunity to study the Universe and led to the discovery of radio galaxies, quasars and other manifestations of activity in the nuclei of galaxies. Extra-atmospheric observations from geophysical rockets and satellites have made it possible to detect X-ray emission from the nuclei of active galaxies and galaxy clusters.

Rice. 1. Classification of galaxies according to Hubble

The first catalog of “nebulae” was published in 1782 by the French astronomer Charles Messier (1730–1817). This list includes both star clusters and gaseous nebulae of our Galaxy, as well as extragalactic objects. Messier object numbers are still used today; for example, Messier 31 (M 31) is the famous Andromeda Nebula, the nearest large galaxy observed in the constellation Andromeda.

A systematic survey of the sky, begun by W. Herschel in 1783, led him to the discovery of several thousand nebulae in the northern sky. This work was continued by his son J. Herschel (1792–1871), who made observations in the Southern Hemisphere at the Cape of Good Hope (1834–1838) and published in 1864 General directory 5 thousand nebulae and star clusters. In the second half of the 19th century. newly discovered ones were added to these objects, and J. Dreyer (1852–1926) published in 1888 New shared directory (New General Catalog – NGC), including 7814 objects. With the publication in 1895 and 1908 of two additional Directory index(IC) the number of discovered nebulae and star clusters exceeded 13 thousand. The designation according to the NGC and IC catalogs has since become generally accepted. Thus, the Andromeda Nebula is designated either M 31 or NGC 224. A separate list of 1249 galaxies brighter than 13th magnitude, based on a photographic survey of the sky, was compiled by H. Shapley and A. Ames from the Harvard Observatory in 1932.

This work was significantly expanded by the first (1964), second (1976) and third (1991) editions Abstract catalog of bright galaxies J. de Vaucouleurs and colleagues. More extensive, but less detailed catalogs based on viewing photographic sky survey plates were published in the 1960s by F. Zwicky (1898–1974) in the USA and B.A. Vorontsov-Velyaminov (1904–1994) in the USSR. They contain approx. 30 thousand galaxies up to 15th magnitude. A similar survey of the southern sky was recently completed using the European Southern Observatory's 1-meter Schmidt Camera in Chile and the UK's 1.2-meter Schmidt Camera in Australia.

There are too many galaxies fainter than magnitude 15 to make a list of them. In 1967, the results of a count of galaxies brighter than 19th magnitude (north of declination 20) carried out by C. Schein and K. Virtanen using plates of the 50-cm astrograph of the Lick Observatory were published. There were approx. such galaxies. 2 million, not counting those that are hidden from us by the wide dust strip of the Milky Way. And back in 1936, Hubble at the Mount Wilson Observatory counted the number of galaxies up to 21st magnitude in several small areas distributed evenly across the celestial sphere (north of declination 30). According to these data, in the entire sky there are more than 20 million galaxies brighter than 21st magnitude.

Classification. There are galaxies of various shapes, sizes and luminosities; some are isolated, but most have neighbors or satellites that exert gravitational influence on them. As a rule, galaxies are quiet, but active ones are often found. In 1925, Hubble proposed a classification of galaxies based on their appearance. Later it was refined by Hubble and Shapley, then Sandage and finally Vaucouleurs. All galaxies in it are divided into 4 types: elliptical, lenticular, spiral and irregular.

Elliptical(E) galaxies in photographs have the shape of ellipses without sharp boundaries and clear details. Their brightness increases towards the center. These are rotating ellipsoids consisting of old stars; their apparent shape depends on the orientation to the observer's line of sight. When observed edge-on, the ratio of the lengths of the short and long axes of the ellipse reaches  5/10 (denoted E5).

Rice. 2. Elliptical Galaxy ESO 325-G004

Lenticular(L or S 0) galaxies are similar to elliptical ones, but, in addition to the spheroidal component, they have a thin, rapidly rotating equatorial disk, sometimes with ring-shaped structures like the rings of Saturn. Observed edge-on, lenticular galaxies appear more compressed than elliptical ones: the ratio of their axes reaches 2/10.

Rice. 2. The Spindle Galaxy (NGC 5866), a lenticular galaxy in the constellation Draco.

Spiral(S) galaxies also consist of two components - spheroidal and flat, but with a more or less developed spiral structure in the disk. Along the sequence of subtypes Sa, Sb, Sc, Sd(from “early” to “late” spirals), the spiral arms become thicker, more complex and less twisted, and the spheroid (central condensation, or bulge) decreases. Edge-on spiral galaxies do not have spiral arms visible, but the type of galaxy can be determined by the relative brightness of the bulge and disk.

Rice. 2. An example of a spiral galaxy, the Pinwheel Galaxy (Messier 101 or NGC 5457)

Incorrect(I) galaxies are of two main types: Magellanic type, i.e. type Magellanic Clouds, continuing the sequence of spirals from Sm before Im, and non-Magellan type I 0, having chaotic dark dust lanes on top of a spheroidal or disk structure such as a lenticular or early spiral.

Rice. 2. NGC 1427A, an example of an irregular galaxy.

Types L And S fall into two families and two types depending on the presence or absence of a linear structure passing through the center and intersecting the disk ( bar), as well as a centrally symmetric ring.

Rice. 2. Computer model of the Milky Way galaxy.

Rice. 1. NGC 1300, an example of a barred spiral galaxy.

Rice. 1. THREE-DIMENSIONAL CLASSIFICATION OF GALAXIES. Main types: E, L, S, I located sequentially from E before Im; families of ordinary A and crossed B; kind s And r. The circular diagrams below are a cross-section of the main configuration in the region of spiral and lenticular galaxies.

Rice. 2. MAIN FAMILIES AND TYPES OF SPIRALS at the cross section of the main configuration in the area Sb.

There are other classification schemes for galaxies based on finer morphological details, but an objective classification based on photometric, kinematic and radio measurements has not yet been developed.

Compound. Two structural components - a spheroid and a disk - reflect the difference in the stellar population of galaxies, discovered in 1944 by the German astronomer W. Baade (1893–1960).

Population I, present in irregular galaxies and spiral arms, contains blue giants and supergiants of spectral classes O and B, red supergiants of classes K and M, and interstellar gas and dust with bright regions of ionized hydrogen. It also contains low-mass main sequence stars, which are visible near the Sun but are indistinguishable in distant galaxies.

Population II, present in elliptical and lenticular galaxies, as well as in the central regions of spirals and in globular clusters, contains red giants from class G5 to K5, subgiants and probably subdwarfs; Planetary nebulae are found in it and outbursts of novae are observed (Fig. 3). In Fig. Figure 4 shows the relationship between the spectral types (or colors) of stars and their luminosities for different populations.

Rice. 3. STAR POPULATIONS. A photograph of the spiral galaxy, the Andromeda Nebula, shows that blue giants and supergiants of Population I are concentrated in its disk, and the central part consists of red Population II stars. The satellites of the Andromeda Nebula are also visible: galaxy NGC 205 ( at the bottom) and M 32 ( top left). The brightest stars in this photo belong to our Galaxy.

Rice. 4. HERZSPRUNG-RUSSELL DIAGRAM, which shows the relationship between the spectral type (or color) and luminosity of stars of different types. I: young Population I stars, typical of spiral arms. II: aged stars of Population I; III: old Population II stars, typical of globular clusters and elliptical galaxies.

It was initially thought that elliptical galaxies contained only Population II, and irregular galaxies only Population I. However, it turned out that galaxies usually contain a mixture of the two stellar populations in different proportions. Detailed population analyzes are only possible for a few nearby galaxies, but measurements of the color and spectrum of distant systems indicate that the difference in their stellar populations may be greater than Baade thought.

Distance. Measuring distances to distant galaxies is based on the absolute scale of distances to the stars of our Galaxy. It is installed in several ways. The most fundamental is the method of trigonometric parallaxes, valid up to distances of 300 sv. years. The remaining methods are indirect and statistical; they are based on the study of the proper motions, radial velocities, brightness, color and spectrum of stars. On their basis, the absolute values ​​of New and variables of the RR Lyra type and  Cepheus, which become the primary indicators of the distance to the nearest galaxies where they are visible. Globular clusters, the brightest stars and emission nebulae of these galaxies become secondary indicators and make it possible to determine distances to more distant galaxies. Finally, the diameters and luminosities of the galaxies themselves are used as tertiary indicators. As a measure of distance, astronomers usually use the difference between the apparent magnitude of an object m and its absolute magnitude M; this value ( m–M) is called the “apparent distance modulus”. To find out the true distance, it must be corrected for light absorption by interstellar dust. In this case, the error usually reaches 10–20%.

The extragalactic distance scale is revised from time to time, which means that other parameters of galaxies that depend on distance also change. In table 1 shows the most accurate distances to the nearest groups of galaxies today. To more distant galaxies, billions of light years away, distances are estimated with low accuracy based on their redshift ( see below: The nature of redshift).

Table 1. DISTANCES TO THE NEAREST GALAXIES, THEIR GROUPS AND CLUSTERS
Galaxy or group	Apparent distance module (m–M )	Distance, million light years
Large Magellanic Cloud
Small Magellanic Cloud
Andromeda group (M 31)
Sculptor's Group
Group B. Ursa (M 81)
Cluster in Virgo
Cluster in the Furnace

Luminosity. Measuring the surface brightness of a galaxy gives the total luminosity of its stars per unit area. The change in surface luminosity with distance from the center characterizes the structure of the galaxy. Elliptic systems, as the most regular and symmetrical, have been studied in more detail than others; in general, they are described by a single luminosity law (Fig. 5, A):

Rice. 5. LUMINOSITY DISTRIBUTION OF GALAXIES. A– elliptical galaxies (the logarithm of the surface brightness is shown depending on the fourth root of the reduced radius ( r/r e) 1/4, where r– distance from the center, and r e is the effective radius, within which half of the total luminosity of the galaxy is contained); b– lenticular galaxy NGC 1553; V– three normal spiral galaxies (the outer part of each line is straight, indicating an exponential dependence of luminosity on distance).

Data on lenticular systems are not as complete. Their luminosity profiles (Fig. 5, b) differ from the profiles of elliptical galaxies and have three main regions: the core, the lens and the envelope. These systems appear to be intermediate between elliptical and spiral.

Spirals are very diverse, their structure is complex, and there is no single law for the distribution of their luminosity. However, it seems that for simple spirals far from the core, the surface luminosity of the disk decreases exponentially towards the periphery. Measurements show that the luminosity of the spiral arms is not as great as it appears when looking at photographs of galaxies. The arms add no more than 20% to the luminosity of the disk in blue light and significantly less in red light. The contribution to the luminosity from the bulge decreases from Sa To Sd(Fig. 5, V).

By measuring the apparent magnitude of the galaxy m and determining its distance modulus ( m–M), calculate the absolute value M. The brightest galaxies, excluding quasars, M 22, i.e. their luminosity is almost 100 billion times greater than that of the Sun. And the smallest galaxies M10, i.e. luminosity approx. 10 6 solar. Distribution of the number of galaxies by M, called the “luminosity function,” is an important characteristic of the galactic population of the Universe, but it is not easy to accurately determine.

For galaxies selected to a certain limiting visible magnitude, the luminosity function of each type separately from E before Sc almost Gaussian (bell-shaped) with average absolute value in blue rays M m= 18.5 and dispersion  0.8 (Fig. 6). But late-type galaxies from Sd before Im and elliptical dwarfs are fainter.

For a complete sample of galaxies in a given volume of space, for example in a cluster, the luminosity function increases steeply with decreasing luminosity, i.e. the number of dwarf galaxies is many times greater than the number of giant ones

Rice. 6. GALAXY LUMINOSITY FUNCTION. A– the sample is brighter than a certain limiting visible value; b– a complete sample in a certain large volume of space. Note the overwhelming number of dwarf systems with M B< -16.

Size. Since the stellar density and luminosity of galaxies gradually decay outward, the question of their size actually rests on the capabilities of the telescope, on its ability to highlight the faint glow of the outer regions of the galaxy against the glow of the night sky. Modern technology makes it possible to record regions of galaxies with a brightness of less than 1% of the sky brightness; this is about a million times lower than the brightness of galactic nuclei. According to this isophote (line of equal brightness), the diameters of galaxies range from several thousand light years for dwarf systems to hundreds of thousands for giant ones. As a rule, the diameters of galaxies correlate well with their absolute luminosity.

Spectral class and color. The first spectrogram of the galaxy - the Andromeda Nebula, obtained at the Potsdam Observatory in 1899 by Yu. Scheiner (1858–1913), with its absorption lines resembles the spectrum of the Sun. Massive research into the spectra of galaxies began with the creation of “fast” spectrographs with low dispersion (200–400 /mm); later, the use of electronic image brightness amplifiers made it possible to increase the dispersion to 20–100/mm. Morgan's observations at Yerkes Observatory showed that, despite the complex stellar composition of galaxies, their spectra are usually close to the spectra of stars of a certain class from A before K, and there is a noticeable correlation between the spectrum and the morphological type of the galaxy. As a rule, the class spectrum A have irregular galaxies Im and spirals Sm And Sd. Spectra class A–F at the spirals Sd And Sc. Transfer from Sc To Sb accompanied by a change in the spectrum from F To F–G, and the spirals Sb And Sa, lenticular and elliptical systems have spectra G And K. True, it later turned out that the radiation of galaxies of the spectral class A actually consists of a mixture of light from giant stars of spectral classes B And K.

In addition to absorption lines, many galaxies have visible emission lines, like the emission nebulae of the Milky Way. Typically these are hydrogen lines of the Balmer series, for example, H  on  6563, doublets of ionized nitrogen (N II) on  6548 and 6583 and sulfur (S II) on  6717 and 6731, ionized oxygen (O II) on  3726 and 3729 and doubly ionized oxygen (O III) on  4959 and 5007. The intensity of the emission lines usually correlates with the amount of gas and supergiant stars in the disks of galaxies: these lines are absent or very weak in elliptical and lenticular galaxies, but are strengthened in spiral and irregular ones - from Sa To Im. In addition, the intensity of the emission lines of elements heavier than hydrogen (N, O, S) and, probably, the relative abundance of these elements decrease from the core to the periphery of disk galaxies. Some galaxies have unusually strong emission lines in their cores. In 1943, K. Seifert discovered a special type of galaxy with very broad hydrogen lines in the cores, indicating their high activity. The luminosity of these nuclei and their spectra change over time. In general, the nuclei of Seyfert galaxies are similar to quasars, although not as powerful.

Along the morphological sequence of galaxies, the integral index of their color changes ( B–V), i.e. difference between the magnitude of a galaxy in blue B and yellow V rays The average color index of the main types of galaxies is as follows:

On this scale, 0.0 corresponds to white, 0.5 to yellowish, and 1.0 to reddish.

Detailed photometry usually reveals that the color of a galaxy varies from core to edge, indicating a change in stellar composition. Most galaxies are bluer in their outer regions than in their cores; This is much more noticeable in spirals than in ellipticals, since their disks contain many young blue stars. Irregular galaxies, which usually lack a nucleus, are often bluer in the center than at the edge.

Rotation and mass. The rotation of the galaxy around an axis passing through the center leads to a change in the wavelength of the lines in its spectrum: lines from regions of the galaxy approaching us shift to the violet part of the spectrum, and from receding regions to the red (Fig. 7). According to the Doppler formula, the relative change in line wavelength is   / = V r /c, Where c is the speed of light, and V r– radial velocity, i.e. source velocity component along the line of sight. The periods of revolution of stars around the centers of galaxies are hundreds of millions of years, and the speeds of their orbital motion reach 300 km/s. Typically, the disk rotation speed reaches its maximum value ( V M) at some distance from the center ( r M), and then decreases (Fig. 8). Near our Galaxy V M= 230 km/s at a distance r M= 40 thousand St. years from the center:

Rice. 7. SPECTRAL LINES OF THE GALAXY, rotating around an axis N, when the spectrograph slit is oriented along the axis ab. Line from the receding edge of the galaxy ( b) is deflected towards the red side (R), and from the approaching edge ( a) – to ultraviolet (UV).

Rice. 8. GALAXY ROTATION CURVE. Rotational speed V r reaches maximum value V M at a distance R M from the center of the galaxy and then slowly decreases.

The absorption lines and emission lines in the spectra of galaxies have the same shape, therefore, the stars and gas in the disk rotate at the same speed in the same direction. When, by the location of dark dust lanes in the disk, we can understand which edge of the galaxy is closer to us, we can find out the direction of twist of the spiral arms: in all the studied galaxies they are lagging, i.e., moving away from the center, the arm bends in the direction opposite to the direction rotation.

Analysis of the rotation curve allows us to determine the mass of the galaxy. In the simplest case, equating the force of gravity to the centrifugal force, we obtain the mass of the galaxy inside the orbit of the star: M = rV r 2 /G, Where G– constant of gravity. Analysis of the motion of peripheral stars allows one to estimate the total mass. Our Galaxy has a mass of approx. 210 11 solar masses, for the Andromeda Nebula 410 11 , for the Large Magellanic Cloud – 1510 9 . The masses of disk galaxies are approximately proportional to their luminosity ( L), so the relation M/L they have almost the same and for luminosity in blue rays equal M/L 5 in units of solar mass and luminosity.

The mass of a spheroidal galaxy can be estimated in the same way, taking instead of the disk rotation speed the speed of chaotic motion of stars in the galaxy (  v), which is measured by the width of spectral lines and is called velocity dispersion: M  R v 2 /G, Where R– radius of the galaxy (virial theorem). The velocity dispersion of stars in elliptical galaxies is usually from 50 to 300 km/s, and the masses from 10 9 solar masses in dwarf systems to 10 12 in giant ones.

Radio emissions The Milky Way was discovered by K. Jansky in 1931. The first radio map of the Milky Way was obtained by G. Reber in 1945. This radiation comes in a wide range of wavelengths  or frequencies  = c/ , from several megahertz (   100 m) up to tens of gigahertz (   1 cm), and is called “continuous”. Several physical processes are responsible for it, the most important of which is synchrotron radiation from interstellar electrons moving almost at the speed of light in a weak interstellar magnetic field. In 1950, continuous emission at a wavelength of 1.9 m was discovered by R. Brown and K. Hazard (Jodrell Bank, England) from the Andromeda Nebula, and then from many other galaxies. Normal galaxies, like ours or M 31, are weak sources of radio waves. They emit barely one millionth of their optical power in the radio range. But in some unusual galaxies this radiation is much stronger. The nearest “radio galaxies” Virgo A (M 87), Centaur A (NGC 5128) and Perseus A (NGC 1275) have a radio luminosity of 10 –4 10 –3 of the optical one. And for rare objects, such as the radio galaxy Cygnus A, this ratio is close to unity. Only a few years after the discovery of this powerful radio source was it possible to find a faint galaxy associated with it. Many faint radio sources, probably associated with distant galaxies, have not yet been identified with optical objects.

By understanding how and when galaxies, stars and planets could have appeared, scientists are closer to solving one of the main mysteries of the Universe. they claim that as a result of the big bang - and it, as we already know, occurred 15-20 billion years ago (see “Science and Life” No.) - exactly the kind of material arose from which celestial bodies and their clusters could subsequently be formed .

Planetary gas nebula Ring in the constellation Lyra.

The Crab Nebula in the constellation Taurus.

Great Orion Nebula.

The Pleiades star cluster in the constellation Taurus.

The Andromeda nebula is one of the closest neighbors of our Galaxy.

The satellites of our Galaxy are galactic clusters of stars: the Small (above) and Large Magellanic Clouds.

An elliptical galaxy in the constellation Centaurus with a wide dust lane. It is sometimes called the Cigar.

One of the largest spiral galaxies visible from Earth through powerful telescopes.

Science and life // Illustrations

Our Galaxy - the Milky Way - has billions of stars, and they all move around its center. It's not just the stars that spin in this huge galactic carousel. There are also foggy spots, or nebulae. Not many of them are visible to the naked eye. It’s a different matter if you look at the starry sky through binoculars or a telescope. What kind of cosmic fog will we see? Distant small groups of stars that cannot be seen individually, or something completely, completely different?

Today, astronomers know what a particular nebula is. It turned out that they are completely different. There are nebulae consisting of gas, they are illuminated by stars. They are often round in shape, which is why they are called planetary. Many of these nebulae were formed by the evolution of aging massive stars. An example of a “foggy remnant” of a supernova (we’ll tell you what it is later) is the Crab Nebula in the constellation Taurus. This crab-shaped nebula is quite young. It is known for sure that she was born in 1054. There are nebulae that are much older, their age is tens and hundreds of thousands of years.

Planetary nebulae and remnants of once-exploded supernovae could be called monument nebulae. But other nebulae are also known, in which stars do not go out, but, on the contrary, are born and grow. Such, for example, is the nebula that is visible in the constellation Orion, it is called the Great Orion Nebula.

Nebulae, which are clusters of stars, turned out to be completely different from them. The Pleiades cluster is clearly visible to the naked eye in the constellation Taurus. Looking at it, it is difficult to imagine that this is not a cloud of gas, but hundreds and thousands of stars. There are also “richer” clusters of hundreds of thousands, or even millions of stars! Such stellar “balls” are called globular star clusters. A whole retinue of such “tangles” surrounds the Milky Way.

Most of the star clusters and nebulae visible from Earth, although located at very large distances from us, still belong to our Galaxy. Meanwhile, there are very distant nebulous spots that turned out to be not star clusters or nebulae, but entire galaxies!

Our most famous galactic neighbor is the Andromeda nebula in the constellation Andromeda. When viewed with the naked eye, it appears as a hazy blur. And in photographs taken with large telescopes, the Andromeda nebula appears as a beautiful galaxy. Through a telescope, we see not only the many stars that make it up, but also the stellar branches emerging from the center, which are called “spirals” or “sleeves.” In size, our neighbor is even larger than the Milky Way, its diameter is about 130 thousand light years.

The Andromeda Nebula is the closest and largest known spiral galaxy. The beam of light goes from it to the Earth “only” about two million light years. So, if we wanted to greet the “Andromedans” by honking at them with a bright spotlight, they would find out about our efforts almost two million years later! And the answer from them would come to us after the same time, that is, back and forth - approximately four million years. This example helps to imagine how far the Andromeda nebula is from our planet.

In photographs of the Andromeda nebula, not only the galaxy itself, but also some of its satellites are clearly visible. Of course, the satellites of the galaxy are not at all the same as, for example, the planets - satellites of the Sun or the Moon - a satellite of the Earth. Satellites of galaxies are also galaxies, only “small” ones, consisting of millions of stars.

Our Galaxy also has satellites. There are several dozen of them, and two of them are visible to the naked eye in the sky of the Earth’s Southern Hemisphere. Europeans first saw them during Magellan's trip around the world. They thought they were some kind of clouds and named them the Large Magellanic Cloud and the Small Magellanic Cloud.

The satellites of our Galaxy are, of course, closer to Earth than the Andromeda nebula. Light from the Large Magellanic Cloud reaches us in just 170 thousand years. Until recently, this galaxy was considered the closest satellite of the Milky Way. But recently, astronomers have discovered satellites that are closer, although they are much smaller than the Magellanic Clouds and are not visible to the naked eye.

Looking at the “portraits” of some galaxies, astronomers discovered that among them there are ones that are unlike the Milky Way in structure and shape. There are also many such galaxies - these are both beautiful galaxies and completely shapeless galaxies, similar, for example, to the Magellanic Clouds.

Less than a hundred years have passed since astronomers made an amazing discovery: distant galaxies are scattering from one another in all directions. To understand how this happens, you can use a balloon and do a simple experiment with it.

Using ink, a felt-tip pen, or paint, draw small circles or squiggles to represent galaxies on the ball. As you begin to inflate the balloon, the drawn “galaxies” will move further and further away from each other. This is what happens in the Universe.

Galaxies rush, stars are born, live and die in them. And not only stars, but also planets, because in the Universe there are probably many star systems, similar and dissimilar to our Solar system, which was born in our Galaxy. Recently, astronomers have already discovered about 300 planets moving around other stars.

Andromeda is a galaxy also popular as M31 and NGC224. This is a spiral formation located at a distance of approximately 780 kp (2.5 million light years) from Earth.

Andromeda is the galaxy closest to the Milky Way. It is named after the mythical princess of the same name. Observations in 2006 led to the conclusion that there are about a trillion stars here - at least twice as many as in the Milky Way, where there are about 200 - 400 billion. Scientists believe that the collision of the Milky Way and the Andromeda galaxy will happen in about 3.75 billion years, and eventually a huge elliptical or disk galaxy will be formed. But more on that later. First, let’s find out what a “mythical princess” looks like.

The picture shows Andromeda. The galaxy has white and blue stripes. They form rings around it and cover the hot, red-hot huge stars. The dark blue-gray bands contrast sharply with these bright rings and show areas where star formation is just beginning in dense cloud cocoons. When observed in the visible part of the spectrum, Andromeda's rings look more like spiral arms. In the ultraviolet spectrum, these formations rather resemble ring structures. They were previously discovered by a NASA telescope. Astrologers believe that these rings indicate the formation of a galaxy as a result of a collision with a neighboring one more than 200 million years ago.

Like the Milky Way, Andromeda has a number of miniature satellites, 14 of which have already been discovered. The most famous are M32 and M110. Of course, it is unlikely that the stars of each galaxy will collide together, since the distances between them are very vast. Scientists still have rather vague ideas about what will happen in reality. But a name has already been invented for the future newborn. Mammoth - this is what scientists call the still unborn huge galaxy.

Star collisions

Andromeda is a galaxy with 1 trillion stars (1012), and the Milky Way has 1 billion (3*1011). However, the chance of a collision between celestial bodies is negligible, since there is a huge distance between them. For example, the closest star to the Sun, Proxima Centauri, is located at a distance of 4.2 light years (4*1013 km), or 30 million (3*107) diameters of the Sun. Imagine that our luminary is a table tennis ball. Then Proxima Centauri will look like a pea, located at a distance of 1100 km from it, and the Milky Way itself will extend 30 million km in width. Even the stars in the center of the galaxy (and specifically there their largest cluster) are located at intervals of 160 billion (1.6 * 1011) km. That's like one table tennis ball for every 3.2 km. Therefore, the chance that any two stars will collide during a galaxy merger is extremely small.

Black hole collision

The Andromeda Galaxy and the Milky Way have central supermassive black holes: Sagittarius A (3.6 * 106 solar masses) and an object inside the P2 cluster of the Galactic Core. These black holes will converge on one point near the center of the newly formed galaxy, transferring orbital energy to the stars, which will eventually move to higher trajectories. The above process can take millions of years. When the black holes come within one light year of each other, they will begin to emit gravitational waves. The orbital energy will become even more powerful until the merger is complete. Based on modeling data carried out in 2006, the Earth may first be thrown almost to the very center of the newly formed galaxy, then pass near one of the black holes and be ejected beyond the boundaries of the Milky Way.

Confirmation of the theory

The Andromeda Galaxy is approaching us at a speed of approximately 110 km per second. Right up until 2012, there was no way to know whether a collision would occur or not. The Hubble Space Telescope helped scientists conclude that it was almost inevitable. After tracking the movements of Andromeda from 2002 to 2010, it was concluded that the collision will occur in about 4 billion years.

Similar phenomena are widespread in space. For example, Andromeda is believed to have interacted with at least one galaxy in the past. And some dwarf galaxies, such as SagDEG, continue to collide with the Milky Way, creating a single formation.

Research also shows that M33, or the Triangulum Galaxy, the third largest and brightest member of the Local Group, will also participate in this event. Its most likely fate will be the entry into orbit of the object formed after the merger, and in the distant future - final unification. However, a collision of M33 with the Milky Way before Andromeda approaches, or our Solar System is thrown beyond the boundaries of the Local Group, is excluded.

Fate of the Solar System

Scientists from Harvard claim that the timing of the galaxy merger will depend on the tangential speed of Andromeda. Based on the calculations, it was concluded that there is a 50% chance that during the merger the Solar System will be thrown back to a distance three times greater than the current one to the center of the Milky Way. It is not clear exactly how the Andromeda galaxy will behave. Planet Earth is also under threat. Scientists say there is a 12% chance that some time after the collision we will be thrown back beyond the borders of our former “home”. But this event will most likely not have major adverse effects on the Solar System, and celestial bodies will not be destroyed.

If we exclude planetary engineering, then by the time the galaxies collide, the surface of the Earth will become very hot and there will be no water left on it in a watery state, and therefore no life.

Possible side effects

When two spiral galaxies merge, the hydrogen present in their disks is compressed. The intensive formation of new stars begins. For example, this can be observed in the interacting galaxy NGC 4039, otherwise known as the Antennae Galaxy. If Andromeda and the Milky Way merge, it is believed that there will be little gas left on their disks. Star formation will not be as intense, although the birth of a quasar is entirely possible.

Merger result

Scientists tentatively call the galaxy formed during the merger Milcomeda. The simulation result shows that the resulting object will have an elliptical shape. Its center will have a lower density of stars than modern elliptical galaxies. But a disk form is also possible. Much will depend on how much gas remains within the Milky Way and Andromeda. In the near future, the remaining galaxies of the Local Group will merge into one object, and this will mark the beginning of a new evolutionary stage.

Facts about Andromeda

Andromeda is the largest Galaxy in the Local Group. But perhaps not the most massive. Scientists suggest that there is more dark matter concentrated in the Milky Way, and this is what makes our galaxy more massive. Scientists will study Andromeda in order to understand the origin and evolution of formations similar to it, because it is the closest spiral galaxy to us. Andromeda looks amazing from Earth. Many even manage to photograph her. Andromeda has a very dense galactic core. Not only are huge stars located at its center, but there is also at least one supermassive black hole hidden at its core. Its spiral arms were bent as a result of gravitational interaction with two neighboring galaxies: M32 and M110. There are at least 450 globular star clusters orbiting inside Andromeda. Among them are some of the densest that have been discovered. The Andromeda Galaxy is the most distant object that can be seen with the naked eye. You'll need a good vantage point and minimal bright light.

In conclusion, I would like to advise readers to raise their gaze to the starry sky more often. It stores a lot of new and unknown things. Find some free time to observe space on the weekend. The Andromeda Galaxy in the sky is a sight to behold.