See what "Nearest galaxies" is in other dictionaries. What is the distance to the nearest galaxy

Andromeda is a galaxy also known as M31 and NGC224. It is a spiral formation located at a distance of approximately 780 kp (2.5 million from the 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 of them. Scientists believe that the collision of the Milky Way and the Andromeda galaxy will happen in about 3, 75 billion years, and as a result, a giant elliptical or disk galaxy will be formed. But more on that later. First, let's find out what the "mythical princess" looks like.

The picture shows Andromeda. The galaxy has blue and white stripes. They form rings around it and shelter hot red-hot giant stars. Dark blue-gray bands contrast sharply against these bright rings and show regions where star formation is just beginning in dense cloud cocoons. When viewed in the visible spectrum, Andromeda's rings look more like spiral arms. In the ultraviolet range, these formations rather resemble ring structures. They were previously discovered by the NASA telescope. Astronomers 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.

Moons of Andromeda

Like the Milky Way, Andromeda has a number of dwarf 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 of the galaxies will collide with each other, since the distances between them are very large. About what will actually happen, scientists still have a rather vague idea. But a name has already been invented for the future newborn. Mlekomed - this is the name of the unborn giant galaxy scientists.

Star Collisions

Andromeda is a galaxy with 1 trillion stars (10 12), and the Milky Way - 1 billion (3 * 10 11). However, the chance of a collision of celestial bodies is negligible, since there is a huge distance between them. For example, the nearest star to the Sun, Proxima Centauri, is located at a distance of 4.2 light years (4 * 10 13 km), or 30 million (3 * 10 7) diameters of the Sun. Imagine that our star 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 in breadth for 30 million km. Even the stars in the center of the galaxy (namely, where their largest cluster) are located at intervals of 160 billion (1.6 * 10 11) km. It's like one table tennis ball for every 3.2 km. Therefore, the chance that any two stars will collide during a merger of galaxies is extremely small.

Collision of black holes

The Andromeda Galaxy and the Milky Way have a central Sagittarius A (3.6*10 6 solar masses) and an object inside the P2 cluster of the Galactic Core. These black holes will converge at a point near the center of the newly formed galaxy, transferring orbital energy to the stars, which will move to higher trajectories over time. The above process can take millions of years. When the black holes approach within one light year apart, they will start emitting gravitational waves. Orbital energy will become even more powerful until the fusion is complete. Based on simulation data from 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 erupted outside of Mlecomeda.

Confirmation of the theory

The Andromeda Galaxy is approaching us at a speed of about 110 km per second. Up until 2012, there was no way to know if a collision would occur or not. To conclude that it is almost inevitable, the Hubble Space Telescope helped scientists. After tracking the movements of Andromeda from 2002 to 2010, it was concluded that the collision would 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 indicates 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 - the final merger. However, a collision of M33 with the Milky Way before Andromeda approaches, or our Solar System is thrown out of the Local Group, is ruled out.

The fate of the solar system

Scientists from Harvard argue that the timing of the merging of galaxies will depend on the tangential speed of Andromeda. Based on the calculations, they concluded that there is a 50% chance that during the merger the Solar System will be thrown back to a distance three times the current distance to the center of the Milky Way. It is not known exactly how the Andromeda galaxy will behave. Planet Earth is also under threat. Scientists say there is a 12% chance that we will be thrown out of our former "home" some time after the collision. But this event, most likely, will not produce strong adverse effects on the Solar System, and celestial bodies will not be destroyed.

If we exclude planetary engineering, then by the time the surface of the Earth will be very hot and there will be no water left on it in liquid state and hence life.

Possible side effects

When two spiral galaxies merge, the hydrogen present in their disks contracts. Begins enhanced education new stars. For example, this can be observed in the interacting galaxy NGC 4039, otherwise known as "Antennas". In the event of a merger between Andromeda and the Milky Way, 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 quite likely.

Merging result

The galaxy formed during the merger is tentatively called Mlecomed by scientists. 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 likely. Much will depend on how much gas remains within the Milky Way and Andromeda. In the near future, the rest will merge into one object, and this will mean the beginning of a new evolutionary stage.

Facts about Andromeda

• Andromeda is the largest galaxy in the Local Group. But probably not the most massive. Scientists suggest that more is concentrated in the Milky Way and this is what makes our galaxy more massive.
• Scientists are exploring Andromeda in order to understand the origin and evolution of formations like it, because it is the closest spiral galaxy to us.
• Andromeda looks amazing from Earth. Many even manage to photograph it.
• 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 in the 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 found.
• The Andromeda Galaxy is the most distant object that can be seen with the naked eye. You will need good point visibility and a minimum of bright light.

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

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 is filled with galaxies to the limits where the most powerful telescopes can penetrate. 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 unequivocally proved 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 therefore the nearest "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 and other galaxies has given 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 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. Recently completed similar review of the southern sky using the European Southern Observatory 1 meter Schmidt camera 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; them visible form 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 passage through the center and crossing the disk linear structure (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– spheroid and 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 ( at the bottom) 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 class (or color) and the luminosity of stars different type. 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, brightest stars and the 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 ( outer part each of lines straight, indicating 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", - important characteristic 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 weaker.

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 spectral type A actually consists of a mixture of light from giant stars of spectral types 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 increase 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 corresponds to white color, 0.5 - yellowish, 1.0 - 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 they are shifted 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, the stars and gas in the disk rotate with the same speed in one 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.

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 entity 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 cohabitant. But truth be told, Andromeda is the closest spiral Galaxy, but not the nearest galaxy at all. This distinction falls to the point of forming what is actually within the Milky Way itself, but a dwarf galaxy, which is known by the name 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 away from the solar system.

Prior to its discovery, astronomers believed that the Sagittarius Dwarf Galaxy was the closest galactic formation to our own. At 70,000 light-years from Earth, this galaxy was determined 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 Canis Major dwarf galaxy was discovered by the 2 Micron Panoramic Survey (2MASS), during an astronomical mission that took place between 1997 and 2001.

With the help of telescopes located on the MT. Hopkins Observatory in Arizona (for the Northern Hemisphere) and at the Inter-American Observatory in Chile for the Southern Hemisphere, astronomers have been able to conduct a comprehensive survey of the sky in infrared light, which is not blocked by gas and dust as brutally 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 constellations big dog, as well as several other accompanying structures as part of this type of star, two of which have the appearance of wide, swooning arcs (as seen in the image above).

The abundance of M-class stars is what made the formation easy to spot. These cool, "red dwarfs" aren't very bright compared to other classes of stars, and can't even be seen with the naked eye. However, they shine very brightly in infrared, and in in large numbers appeared.

In addition to its composition, the Galaxy has a near elliptical shape and is believed to contain as many stars as the Sagittarius Dwarf Elliptical Galaxy, the 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 stream was first detected 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 Sagittarius dwarf elliptical galaxies, that the Canis Major dwarf galaxy was discovered.

The current theory is that this galaxy was fused (or swallowed up) into the Milky Way Galaxy. Other globular clusters orbiting the center of the Milky Way as a satellite - that is, either NGC 1851, NGC 1904, NGC 2298 and NGC 2808 - are believed to have been part of the big dog of the dwarf galaxy prior to 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 stars of the canis major dwarf galaxy are technically already part of the Milky Way, it is, by definition, the closest galaxy to us.

Astronomers also believe that canis major dwarf galaxies are pulling apart the gravitational field of the more massive Milky Way galaxy in the process. The main body of the galaxy is already extremely degraded, and this process will continue as it travels around and through our Galaxy. During the accretion is likely to end with a large dog dwarf galaxy deposited 1 billion stars per 200 m0 400 billion, which are already part of the Milky Way.

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

The Andromeda Galaxy (M31) is the closest spiral galaxy to us. Although - gravitationally - it is connected with milky way, this is still not the nearest galaxy - 2 million light-years from us. 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.

The Milky Way - a very characteristic example of its type of galaxy - is so huge that it takes light more than 100,000 years to travel 300,000 kilometers per second across the Galaxy from edge to edge. The Earth and the Sun are located at a distance of about 30 thousand light years from the center of the Milky Way. If we tried to send a message to a hypothetical being living near the center of our galaxy, we would not receive an answer until 60,000 years later. A message sent at the speed of an airplane (600 miles or 1000 kilometers per hour) at the time of the birth of the universe would by now have traveled only half the way to the center of the Galaxy, and the waiting time for a response would have been 70 billion years.

Some galaxies are much larger than ours. The diameters of the largest of them - vast galaxies that emit huge amounts of energy in the form of radio waves, such as the famous object of the southern sky - Centaurus A, are a hundred times larger than the diameter of the Milky Way. On the other hand, there are many relatively small galaxies in the Universe. Dimensions of dwarf elliptical galaxies ( typical representative located in the constellation Draco) are only about 10 thousand light years. Of course, even these inconspicuous objects are almost unimaginably huge: although the galaxy in the constellation Draco can be called a dwarf galaxy, its diameter exceeds 160,000,000,000,000,000 kilometers.

Although space is inhabited by billions of galaxies, they are not at all cramped: the Universe is large enough for galaxies to comfortably fit in it, and there is still a lot of free space. The typical distance between bright galaxies is about 5-10 million light-years; the remaining volume is occupied by dwarf galaxies. However, if we take their sizes into account, it turns out that galaxies are relatively much closer to each other than, for example, stars in the vicinity of the Sun. The diameter of a star is negligible compared to the distance to the nearest neighboring star. The diameter of the Sun is only about 1.5 million kilometers, while the distance to the nearest star to us is 50 million times greater.

In order to imagine the huge distances between galaxies, let's mentally reduce their size to the height of an average person. Then in a typical region of the Universe, "adult" (bright) galaxies will be on average 100 meters apart, and a small number of children will be located between them. The universe would be like a vast baseball field with a lot of space between the players. Only in some places where galaxies gather in close clusters. our scale model The universe is like a city sidewalk, and nowhere would it be anything like a party or a subway car at rush hour. If, however, the stars of a typical galaxy were reduced to the scale of human growth, then the area would turn out to be extremely sparsely populated: the nearest neighbor would live at a distance of 100 thousand kilometers - about a quarter of the distance from the Earth to the Moon.

From these examples, it should be clear that galaxies are quite rarely scattered in the universe and consist mainly of empty space. Even if we take into account the rarefied gas that fills the space between the stars, the average density of matter is still extremely low. The world of galaxies is vast and almost empty.

Galaxies in the universe are not alike. Some of them are even and round, others are flattened, spreading spirals, and some have almost no structure. Astronomers, following the pioneering work of Edwin Hubble published in the 1920s, classify galaxies according to their shape into three main types: elliptical, spiral, and irregular, designated E, S, and Irr, respectively.

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 on different stages time, as 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 in general terms 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