Largest galaxy closest to the Milky Way. Sizes and distances of galaxies

Divided into social groups, our Milky Way galaxy will belong to a strong "middle class". So, it belongs to the most common type of galaxy, but at the same time it is not average in size or mass. There are more galaxies that are smaller than the Milky Way than those that are larger than it. Our "star island" also has at least 14 satellites - other dwarf galaxies. They are doomed to circle the Milky Way until they are consumed by it, or fly away from an intergalactic collision. Well, so far this is the only place where life certainly exists - that is, we are with you.

But still the Milky Way remains the most mysterious galaxy in the Universe: being on the very edge of the "star island", we see only a part of its billions of stars. And the galaxy is completely invisible - it is covered with dense sleeves of stars, gas and dust. The facts and secrets of the Milky Way will be discussed today.

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 number 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 to the most distant galaxies registered by telescopes - billions of light years. The study of galaxies is one of the most ambitious tasks of astronomy.

History reference. The brightest and closest outer 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 as early as 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 with the help of 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, and .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 unambiguously proven mainly due to the work of American astronomers G. Curtis (1872-1942) and E. Hubble (1889-1953). They proved that the distances to the brightest, and hence the closest "white nebulae" are much larger than the size of our galaxy. Between 1924 and 1936, Hubble pushed the frontier of galaxy exploration from nearby systems to the limits 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 its speed. This relationship, Hubble's law, has become the observational basis of modern cosmology. After the end of World War II, an active study of galaxies began with the help of new large telescopes with electronic light amplifiers, automatic measuring machines and computers. The detection of radio emission from our own and other galaxies provided a new opportunity for studying 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 made it possible to detect X-ray emission from the nuclei of active galaxies and clusters of galaxies.

Rice. 1. Classification of galaxies according to Hubble

The first catalog of "nebulae" was published in 1782 by the French astronomer C. Messier (1730-1817). This list includes both star clusters and gaseous nebulae in our Galaxy, as well as extragalactic objects. Messier object numbers are still in use 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 objects were added to these objects, and J. Dreyer (1852–1926) in 1888 published 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. So, the Andromeda Nebula is designated either M 31 or NGC 224. A separate list of 1249 galaxies brighter than the 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 has been substantially expanded by the first (1964), second (1976), and third (1991) editions. Reference catalog of bright galaxies J. de Vaucouleurs with employees. 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 the 15th magnitude. A similar survey of the southern sky was recently completed using the 1-meter Schmidt camera of the European Southern Observatory in Chile and the British 1.2-meter Schmidt camera in Australia.

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

Classification. There are galaxies of various shapes, sizes and luminosities; some of them are isolated, but most have neighbors or satellites that exert a 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. It was later refined by Hubble and Shapley, then by Sandage, and finally by Vaucouleur. All galaxies in it are divided into 4 types: elliptical, lenticular, spiral and irregular.

Elliptical(E) galaxies have the shape of ellipses in photographs without sharp boundaries and clear details. Their brightness increases towards the center. These are rotating ellipsoids made up of old stars; their apparent shape depends on the orientation to the observer's line of sight. When viewed from the edge, 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-like structures like the rings of Saturn. Viewed edge-on, lenticular galaxies look 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, but the galaxy type can be determined from the relative brightness of the bulge and disk.

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

Wrong(I) galaxies are of two main types: Magellanic type, i.e. type of the Magellanic Clouds, continuing the sequence of spirals from sm before Im, and non-magellanic type I 0, which have chaotic dark dust lanes over a spheroidal or disk structure such as a lenticular or early spiral structure.

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

Types L and S are divided into two families and two species 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 are in series 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. BASIC FAMILIES AND TYPES OF SPIRALS on the 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 types 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 that are visible near the Sun, but 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 the G5 to K5 class, subgiants, and probably subdwarfs; it contains planetary nebulae and outbursts of novae (Fig. 3). On fig. Figure 4 shows the relationship between the spectral classes (or color) of stars and their luminosity in different populations.

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

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

Initially, elliptical galaxies were thought to contain only Population II, and irregular galaxies only Population I. However, it turned out that galaxies usually contain a mixture of two stellar populations in different proportions. A detailed population analysis is only possible for a few nearby galaxies, but measurements of the color and spectrum of distant systems show that the difference in their stellar populations may be more significant than Baade thought.

Distance. The measurement of distances to distant galaxies is based on the absolute distance scale to the stars of our Galaxy. It is installed in several ways. The most fundamental is the method of trigonometric parallaxes, which operates up to distances of 300 sv. years. Other methods are indirect and statistical; they are based on the study of proper motions, radial velocities, brightness, color and spectrum of stars. Based on them, the absolute values ​​of the New and variables of the RR Lyrae 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 the 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 know 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, the distances are estimated with low accuracy by their redshift ( see below: The nature of the redshift).

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 (shown is the logarithm of surface brightness depending on the fourth root of the reduced radius ( r/r e) 1/4 , where r is the distance from the center, and r e is the effective radius containing half of the total luminosity of the galaxy); b– lenticular galaxy NGC 1553; in- three normal spiral galaxies (the outer part of each of the lines is straight, which indicates an exponential dependence of luminosity on distance).

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

Spirals are very diverse, their structure is complex, and there is no single law for the distribution of their luminosity. However, it seems that in 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 high as it seems when looking at photographs of galaxies. The arms add no more than 20% to the luminosity of the disk in blue rays and much less in red ones. The contribution to the luminosity from the bulge decreases from Sa to SD(Fig. 5, in).

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 it.

For galaxies selected up to a certain limiting visible magnitude, the luminosity function of each type separately from E before sc almost Gaussian (bell-shaped) with an 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 grows 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 some limiting visible value; b is a full sample in a certain large amount of space. Note the vast majority of dwarf systems with M B< -16.

The size. Since the stellar density and luminosity of galaxies gradually fall outward, the question of their size actually rests on the capabilities of the telescope, on its ability to distinguish the faint glow of the outer regions of the galaxy against the background of the glow of the night sky. Modern technology makes it possible to register regions of galaxies with a brightness of less than 1% of the brightness of the sky; this is about a million times lower than the brightness of the nuclei of galaxies. According to this isophote (lines of equal brightness), the diameters of galaxies range from several thousand light-years in dwarf systems to hundreds of thousands in 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 Nebulae, obtained at the Potsdam Observatory in 1899 by J. Scheiner (1858–1913), resembles the spectrum of the Sun with its absorption lines. The mass study of the spectra of galaxies began with the creation of "fast" spectrographs with low dispersion (200–400 /mm); Later, the use of electronic image intensifiers made it possible to increase the dispersion to 20–100/mm. Morgan's observations at the 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. class spectra 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 elliptic systems have spectra G and K. True, later it turned out that the radiation of galaxies of the spectral type A actually consists of a mixture of light from giant stars of spectral classes B and K.

In addition to absorption lines, many galaxies show emission lines, like the emission nebulae of the Milky Way. Usually these are hydrogen lines of the Balmer series, for example, H  on the  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 enhanced 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 galaxies with very broad lines of hydrogen in their nuclei, indicating their high activity. The luminosity of these nuclei and their spectra change with 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. the 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 is white, 0.5 is yellowish, and 1.0 is reddish.

With detailed photometry, it usually turns out that the color of the galaxy changes from the core to the edge, which indicates a change in the stellar composition. Most galaxies are bluer in the outer regions than in the core; this is much more noticeable in spirals than in ellipticals, since their disks contain many young blue stars. Irregular galaxies, usually devoid of 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: the lines from the regions of the galaxy approaching us are shifted to the violet part of the spectrum, and from the receding regions - to the red (Fig. 7). According to the Doppler formula, the relative change in the wavelength of the line is   / = V r /c, where c is the speed of light, and V r is the 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. Usually the disk rotation speed reaches its maximum value ( V M) at some distance from the center ( r M), and then decreases (Fig. 8). Our Galaxy V M= 230 km/s at distance r M= 40 thousand St. years from the center:

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

Rice. 8. GALAXY ROTATION CURVE. Rotational speed V r reaches its maximum value V M in the 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, 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, it is possible to understand which edge of the galaxy is closer to us, we can find out the direction of twisting of the spiral arms: in all the studied galaxies they are lagging behind, i.e., moving away from the center, the arm bends in the direction opposite to the direction rotation.

An analysis of the rotation curve makes it possible to determine the mass of the galaxy. In the simplest case, equating the gravitational force to the centrifugal force, we obtain the mass of the galaxy inside the star's orbit: M = rV r 2 /G, where G is the gravitational constant. An analysis of the motion of peripheral stars makes it possible 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 ratio M/L they have almost the same and for the luminosity in blue rays is equal M/L 5 in units of mass and luminosity of the Sun.

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

radio emission The Milky Way was discovered by K. Jansky in 1931. The first radio map of the Milky Way was received 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 the synchrotron radiation of interstellar electrons moving almost at the speed of light in a weak interstellar magnetic field. In 1950, continuous radiation at a wavelength of 1.9 m was discovered by R. Brown and C. 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 radiate in the radio range hardly one millionth of their optical power. 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 Cygnus A radio galaxy, this ratio is close to unity. Only a few years after the discovery of this powerful radio source, it was possible to find a faint galaxy associated with it. Many weak radio sources, probably associated with distant galaxies, have not yet been identified with optical objects.

What is the distance to the nearest galaxy? March 12th, 2013

Scientists for the first time were able to measure the exact distance to the nearest galaxy from us. This dwarf galaxy is known as Large Magellanic Cloud. It is located at a distance of 163 thousand light years from us, or 49.97 kiloparsecs, to be exact.

Galaxy Large Magellanic Cloud slowly floats in outer space, bypassing our galaxy Milky Way around like the moon revolves around the earth.

Huge clouds of gas around the galaxy are slowly dissipating, resulting in the formation of new stars that illuminate interstellar space with their light, creating bright colorful cosmic landscapes. These landscapes were photographed by a space telescope Hubble.

The small galaxy Large Magellanic Cloud includes the Tarantula Nebula - the brightest stellar cradle in space in our neighborhood - it has been seen signs of the formation of new stars.

Scientists were able to do the calculations by observing rare, close pairs of stars known as eclipsing binary stars. These pairs of stars are gravitationally bound together, and when one of the stars outshines the other, as seen by an observer from Earth, the overall brightness of the system decreases.

If you compare the brightness of the stars, you can calculate the exact distance to them with incredible accuracy in this way.

Determining the exact distance to space objects is very important for understanding the size and age of our Universe. So far, the question remains open: what is the size of our Universe, none of the scientists can say for sure yet.

Once astronomers have been able to achieve such accuracy in determining distances in space, they will be able to look at more distant objects and, ultimately, will be able to calculate the size of the universe.

Also, new features will allow us to more accurately determine the expansion rate of our Universe, as well as more accurately calculate Hubble constant. This coefficient was named after Edwin P. Hubble, the American astronomer who proved in 1929 that our universe has been constantly expanding since the very beginning of its existence.

distance between galaxies

The Large Magellanic Cloud Galaxy is the closest dwarf galaxy from us, but the largest galaxy in size is considered to be our neighbor Andromeda spiral galaxy, which is located at a distance of about 2.52 million light years from us.

The distance between our galaxy and the Andromeda galaxy is gradually shrinking. They are approaching each other at a speed of about 100-140 kilometers per second, although they will meet very soon, or rather, in 3-4 billion years.

Perhaps this is what the night sky will look like to an earthly observer in a few billion years.

The distances between galaxies, therefore, can be very different at different stages of time, since they are constantly in dynamics.

The scale of the universe

The visible Universe has an incredible diameter, which is billions, and maybe tens of billions of light years. Many of the objects that we can see with telescopes are no longer there or look completely different because the light traveled before them for an incredibly long time.

The proposed series of illustrations will help you to imagine at least in general terms the scale of our universe.

The solar system with its largest objects (planets and dwarf planets)

Sun (center) and nearest stars

The Milky Way galaxy showing the group of star systems closest to the solar system

A group of nearby galaxies, including more than 50 galaxies, the number of which is constantly increasing as new ones are discovered.

Local supercluster of galaxies (Virgo Supercluster). Size - about 200 million light years

Group of superclusters of galaxies

Visible Universe

The science

Scientists for the first time were able to measure the exact distance to our nearest galaxy. This dwarf galaxy is known as Large Magellanic Cloud. It is located at a distance from us 163 thousand light years or 49.97 kiloparsecs to be exact.

Galaxy Large Magellanic Cloud slowly floats in outer space, bypassing our galaxy Milky Way around like The moon revolves around the earth.

Huge clouds of gas in the region of the galaxy are slowly dissipating, resulting in the formation of new stars, which illuminate interstellar space with their light, creating bright colorful space landscapes. These landscapes were photographed by a space telescope Hubble.

Small galaxy Large Magellanic Cloud includes tarantula nebula- the brightest stellar cradle in space in our neighborhood - signs of the formation of new stars.

Scientists were able to do the calculations by observing rare, close pairs of stars known as eclipsing binary stars. These pairs of stars are gravitationally connected to each other, and when one of the stars outshines the other, as seen by an observer from Earth, the overall brightness of the system decreases.

If you compare the brightness of the stars, you can calculate the exact distance to them with incredible accuracy in this way.

Determining the exact distance to space objects is very important for understanding the size and age of our Universe. While the question remains open: how big is our universe No scientist can say for sure yet.

After astronomers managed to achieve such accuracy in determining distances in space, they will be able to deal with more distant objects and eventually be able to calculate the size of the universe.

Also, new features will allow us to more accurately determine the expansion rate of our Universe, as well as more accurately calculate Hubble constant. This ratio was named after Edwin P. Hubble, an American astronomer who in 1929 proved that our The universe has been constantly expanding since the very beginning of its existence..

distance between galaxies

The Large Magellanic Cloud is the closest galaxy to us. dwarf galaxy, but a large galaxy - our neighbor is considered Andromeda spiral galaxy, which is located at a distance of about 2.52 million light years.

The distance between our galaxy and the Andromeda galaxy is gradually decreasing. They approach each other at a speed of about 100-140 kilometers per second, although they will meet very soon, or rather, through 3-4 billion years.

Perhaps this is what the night sky will look like to an earthly observer in a few billion years.

The distances between galaxies are thus can be very different at different stages of time, as they are constantly in dynamics.

The scale of the universe

The visible universe has incredible diameter, which is billions, and maybe tens of billions of light years. Many of the objects that we can see with telescopes are no longer there or look completely different because the light traveled before them for an incredibly long time.

The proposed series of illustrations will help you to imagine at least in general terms the scale of our universe.

The solar system with its largest objects (planets and dwarf planets)

Sun (center) and nearest stars

The Milky Way galaxy showing the group of star systems closest to the solar system

A group of nearby galaxies, including more than 50 galaxies, the number of which is constantly increasing as new ones are discovered.

Local supercluster of galaxies (Virgo Supercluster). Size - about 200 million light years

Group of superclusters of galaxies

Visible Universe

Understanding how and when galaxies, stars and planets could appear, scientists have come close to unraveling one of the main mysteries of the Universe. they argue that as a result of the big bang - and, as we already know, it happened 15-20 billion years ago (see "Science and Life" No.) - exactly such material arose from which celestial bodies and their clusters could subsequently form .

Planetary gas nebula Ring in the constellation Lyra.

The Crab Nebula in the constellation Taurus.

The Great Nebula of Orion.

The Pleiades star cluster in the constellation Taurus.

The Andromeda Nebula is one of the closest neighbors of our galaxy.

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

An elliptical galaxy in the constellation Centaurus with a broad dust lane. It is sometimes called 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. In this huge galactic carousel, not only stars are spinning. There are also foggy spots, or nebulae. There aren't many of them visible to the naked eye. Another thing, 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 that are made of gas and are illuminated by stars. Often they are round in shape, for which they are called planetary. Many of these nebulae were formed as a result of the evolution of aged massive stars. An example of the "foggy remnant" of a supernova (we'll tell you more about what it is) is the Crab Nebula in the constellation Taurus. This crab-like nebula is quite young. It is known that she was born in 1054. There are nebulae and much older, their age is tens and hundreds of thousands of years.

Planetary nebulae and remnants of once exploding 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 up. Such, for example, is the nebula that is visible in the constellation of Orion, it is called the Great Nebula of Orion.

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 hard to imagine that this is not a cloud of gas, but hundreds and thousands of stars. There are also more “rich” clusters of hundreds of thousands or even millions of stars! Such stellar "balls" are called globular star clusters. A whole retinue of such "balls" surrounds the Milky Way.

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

Our most famous galactic neighbor is the Andromeda Nebula in the constellation Andromeda. When viewed with the naked eye, it looks like a hazy patch. And in photographs taken with large telescopes, the Andromeda Nebula appears as a beautiful galaxy. Through a telescope, we see not only many of its constituent stars, but also 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 spiral galaxy to us and the largest known spiral galaxy. A beam of light goes from it to the Earth "only" about two million light years. So, if we wanted to greet the "Andromedans" by signaling them with a bright spotlight, they would know about our efforts in almost two million years! And the answer from them would have come to us after the same time, that is, back and forth - about four million years. This example helps to imagine how far the Andromeda Nebula is from our planet.

In the 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, planets - satellites of the Sun or the Moon - a satellite of the Earth. Satellites of galaxies are also galaxies, only "small", consisting of millions of stars.

There are satellites in our galaxy. There are several dozen of them, and two of them are visible to the naked eye in the sky of the Southern Hemisphere of the Earth. Europeans first saw them during the circumnavigation of Magellan. 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 takes only 170,000 years to reach us. Until recently, this galaxy was considered the closest satellite of the Milky Way. But recently, astronomers have discovered satellites and closer, however, they are much smaller than the Magellanic Clouds, and are not visible to the naked eye.

Examining the "portraits" of some galaxies, astronomers found that among them there are dissimilar to 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 scatter one from the other in all directions. To understand how this happens, you can use a balloon and do the simplest experiment with it.

Use ink, felt-tip pen or paint to draw small circles or squiggles to represent galaxies on the balloon. When you start to inflate the balloon, the drawn "galaxies" will diverge farther and farther from one another. 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 unlike our solar system, which was born in our galaxy. Recently, astronomers have already discovered about 300 planets moving around other stars.