Space is difficult arranged system, the elements of which are closely interconnected: planets unite around one star, stars form galaxies, and those form even larger associations, such as the Local Group of Galaxies. Multiplicity is a very common phenomenon in the Universe associated with high gravity. Thanks to it, a center of mass is formed around which both relatively small objects like stars and galaxies and their associations rotate.
The Local Group is believed to be based on three large objects: the Milky Way, the Andromeda Galaxy and the Triangulum Galaxy. By gravitational attraction Their satellites are associated with them, as well as a number of dwarf galaxies, the belonging of which to one of the three systems cannot yet be established. In total, the Local Group of galaxies includes at least fifty large celestial objects, and with the improvement of the quality of technology for astronomical observations, this number is growing.
As already mentioned, multiplicity in is a common occurrence. The Local Group of galaxies is not the largest of these galaxies, although its size is impressive: it is about one megaparsec across (3.8 x 10 19 km). Along with other similar associations, the Local Group is included in the Virgo Supercluster. Its dimensions are difficult to imagine, but its mass has been measured relatively accurately: 2 × 10 45 kg. In total, this association includes about a hundred galactic systems.
It should be noted that the multiplicity does not end there. The Virgo Supercluster, like several others, form the so-called Laniakea. Studying such giant systems has allowed astrophysicists to create a theory of the large-scale structure of the Universe.
Scientists have found that the age of all members of the Local Group is approximately 13 billion years. In addition, the material that forms them has the same composition, which allows us to speak about the common origin of Local Group galaxies. They are not located in any random order: most of them are built around an imaginary line that runs between Milky Way and the Andromeda Nebula.
The largest member of the Local Group of galaxies by size is the Andromeda Nebula: its diameter is 260 thousand light years (2.5 × 10 18 km). In terms of mass, the Milky Way clearly stands out - approximately 6 × 10 42 kg. Along with such large objects, there are also dwarf objects like the SagDEG galaxy, located in the constellation Sagittarius.
Most of the Local Group galaxies are classified as irregular, but there are also spiral ones like the Andromeda Nebula and elliptical ones like the already mentioned SagDEG.
The accuracy of astronomical observations of the Local Group depends on what galaxy we are in. That is why the Milky Way is, on the one hand, the most studied object, and on the other hand, it causes greatest number questions. To date, it has been established that at least 14 objects are satellites of our galaxy, including the Ursa Major, Sagittarius, Sculptor and Leo galaxies.
Of particular note is the SagDEG galaxy in Sagittarius. It is the most distant from the gravitational center of the Local Group. According to calculations, the Earth is separated from this galaxy by 3.2 × 10 19 km.
One of the controversial issues is the connection between the Milky Way and the Magellanic Clouds - two galaxies so close to us that they can be observed with the naked eye from the Southern Hemisphere. For a long time it was believed that they were satellites of our galaxy. In 2006 when using latest technologies it was found that they move much faster than other satellites of the Milky Way. Based on this, it was suggested that they do not have a gravitational connection with our galaxy.
But it is indisputable further fate Magellanic Clouds. Their movement is directed towards the Milky Way, so their absorption by a larger galaxy is inevitable. According to scientists, this will happen after 4 billion years.
In 5 billion years, a similar fate threatens our galaxy, only Andromeda, the largest galaxy of the Local Group, poses a threat to it. The distance to is 2.5 × 10 6 light years. It has 18 satellites, of which, due to their brightness, the most famous are M23 and M110 (catalogue numbers from the 18th century French astronomer Charles Messier).
Although the Andromeda Nebula is the closest galaxy to the Milky Way, observing it is very difficult due to its structure. It is one of the spiral galaxies: it has a pronounced center from which two large spiral arms emerge. However, the Andromeda Nebula is edge-on towards the Earth.
Its significant distance from the Earth significantly complicates the study of both the galaxy itself and its satellites. The number of satellites of the Triangulum Galaxy is controversial. For example, dwarf Andromeda II is located exactly in the middle between the Triangulum and the Nebula. The state of modern observation devices does not allow us to determine which of the two largest members of the Local Group of galaxies this gravitational field belongs to. Most still assume that Andromeda II is associated with Triangulum. But there are also representatives of the opposite point of view, who even propose to rename it Andromeda XXII.
The Triangulum Galaxy also contains one of the exotic objects in the Universe - the black hole M33 X-7, whose mass is 16 times that of the Sun, making it one of the largest known modern science black holes, excluding supermassive ones.
The number of members of the Local Group varies constantly, not only because of the discovery of other galaxies orbiting the same center of mass. Improvements in the quality of astronomical technology have made it possible to establish that objects previously considered galaxies are not actually galaxies.
This applies to a greater extent to spherical galaxies. They contain a large number of stars tied to one gravitational center, and their shape resembles spherical galaxies. Quantitative relationships help to distinguish them: the density of stars in globular clusters is much higher, and the diameter is correspondingly higher. For comparison: in the vicinity of the Sun there is one star per 10 cubic parsecs, while in globular clusters this figure can be 700 and even 7000 times higher.
Palomar 12 in the constellation Capricorn and Palomar 4 in Ursa Major have long been considered dwarf galaxies. Recent studies have shown that they are in fact quite large globular clusters.
Until the second quarter of the 20th century, it was believed that the Milky Way and the Universe were identical concepts. All matter is supposedly located within our galaxy. However, in 1924, Edwin Hubble, using his telescope, recorded several Cepheids - variable stars with a pronounced luminosity period - the distance to which clearly exceeded the size of the Milky Way. Thus, the existence of extragalactic objects was proven. Scientists have begun to think that the Universe is more complex than it previously seemed.
With his discovery, Hubble also proved that the Universe is expanding all the time, and objects are moving away from each other. Improvements in technology brought new discoveries. Thus, it was discovered that the Milky Way has its own satellites, the distances between them were calculated and the prospects for existence were determined. Such discoveries were enough to formulate for the first time the idea of the existence of the Local Group as an impressive association of closely related galaxies and even to suggest that associations of a higher rank may exist, since satellites were also discovered in the closest galaxy to the Milky Way - the Andromeda Nebula. The term “Local Group” itself was first used by the same Hubble. He mentions it in his work on measuring distances to other galaxies.
It can be argued that space exploration has just begun. This also applies to the Local Group. The SagDEG galaxy was discovered relatively recently, but the reason for this is not only its low luminosity, which was not detected by telescopes for a long time, but also the presence in the Universe of matter that does not have visible radiation - the so-called “dark matter”.
In addition, observations are complicated by diffuse interstellar gas (usually hydrogen) and cosmic dust. However, observational technology does not stand still, which allows us to count on new amazing discoveries in the future, as well as on clarifying existing information.
Most galaxies are collected into certain associations - groups, clusters and superclusters. If we build a three-dimensional model of the part of the Universe known to us, it turns out that the distribution of galaxies resembles the structure of a honeycomb or a fishing net - relatively thin “walls” and “fibers” surround large “bubbles” of almost empty space, the so-called voids. Clusters of galaxies are “nodes” of this “grid”. The lowest level of association is the group. Typically, groups consist of a small (no more than 50) number of galaxies of all kinds and have a size from 1 to 2 Mpc. The mass of a group of galaxies, as a rule, does not exceed 13 solar masses, and the individual speed of galaxies in the group is approximately 150 km/s. Clusters are groups of galaxies larger than a group, although there is no clear distinction between these two classes. A cluster may include hundreds or tens of thousands of galaxies. There are many known galaxy clusters; Astronomers still use their catalog, compiled by J. Abel. In turn, clusters of galaxies unite into galactic superclusters. Back in the second half of the 50s of the last century, it was discovered that most of the brightest galaxies visible from Earth form an integral structure, in the center of which is a cluster in the constellation Virgo, and on its periphery is our Local Group of galaxies. This structure was called the Local Supercluster of Galaxies. Local supercluster covers an area in space several tens of megaparsecs in size, which is 10 times the size of the cluster in the constellation Virgo.
LOCAL GALAXIES GROUP is a collection of several dozen nearby galaxies surrounding our star system - the Milky Way galaxy. Members of the Local Group move relative to each other, but are connected by mutual gravity and therefore occupy a long time limited space about 6 million light years in size and exist separately from other similar groups of galaxies. All members of the Local Group are believed to have a common origin and have been coevolving for about 13 billion years.
The Local Group includes more than 50 galaxies. This number is constantly increasing with the discovery of new galaxies. The local group can be divided into several subgroups:
Milky Way Group consists of the giant spiral Milky Way galaxy and its 14 known satellites (as of 2005), which are dwarf and mostly irregular galaxies;
Andromeda group very similar to the Milky Way group: at the center of the group is the giant spiral galaxy Andromeda. Its 18 known (as of 2005) satellites are also mostly dwarf galaxies;
Triangle Group- the Triangulum galaxy and its possible satellites;
Other dwarf galaxies that cannot be classified into any of the above groups.
The diameter of the Local Group is about one megaparsec. The local group is part of a local supercluster - the Virgo supercluster, main role in which the Virgo cluster plays.
Milky Way - the galaxy in which our solar system is located. The galaxy got its name because the Earth is in the plane of the galaxy and therefore it is visible in the sky as a hazy streak (in fact, all the stars visible to the naked eye in the sky lie in the Milky Way). The fact that this haze is a cluster of many stars was proven by Galileo in 1610. Edwin Hubble showed that the Milky Way is just one of many galaxies. The Milky Way is a barred spiral galaxy, 100-120 thousand light-years in diameter and about 1000 light-years thick, containing 200-400 billion stars. It has recently been proven that, on average, all star systems in the Milky Way have at least one planet. The density of stars in the Milky Way drops sharply when moving 40,000 light-years from the center of the galaxy. The reason for this phenomenon is not yet known. The orbital period of the entire galaxy is between 15 and 20 million years. The Milky Way is about 13.2 billion years old, so it is one of the first galaxies. In the center of the galaxy there is a bridge, from which four arms extend (perhaps only two of them are full-fledged arms), consisting of stars, gas and dust, although until the early 90s it was believed that the Milky Way was an ordinary spiral galaxy. At the center of the galaxy is a small but very massive source of powerful radiation, Sagittarius A*. Most likely it is a black hole.
Magellanic Clouds- The Large Magellanic Cloud and the Small Magellanic Cloud are satellite galaxies of the Milky Way. Both Clouds were previously considered irregular galaxies, but subsequently discovered structural features of barred spiral galaxies. They are located relatively close to each other and form a gravitationally bound (double) system. Visible to the naked eye in the southern hemisphere. Both Clouds “float” in a common hydrogen shell.
The Magellanic Clouds are located at high galactic latitudes, so the light from them is little absorbed by the Milky Way, moreover, the plane of the Large Magellanic Cloud is almost perpendicular to the line of sight, so for objects visible nearby it will often be true to say that they are close spatially. These features of the Magellanic Clouds made it possible to study the patterns of distribution of stars and star clusters using their example.
The Magellanic Clouds have a number of features that distinguish them from the Milky Way. For example, star clusters with ages of 10 7 -10 8 years have been discovered there, while clusters in the Milky Way are usually older than 10 9 years.
The Magellanic Clouds were familiar to sailors in the southern hemisphere and were called the "Cape Clouds" in the 15th century. Ferdinand Magellan used them for navigation, as an alternative to the North Star, during his trip around the world in 1519-1521. When, after the death of Magellan, his ship returned to Europe, Antonio Pigafetta (Magellan's companion and official chronicler of the trip) proposed calling the Cape Clouds Magellan's Clouds as a kind of perpetuation of his memory.
Stars are massive luminous balls of gas (plasma). They are formed from a gas-dust environment (mainly hydrogen and helium) as a result of gravitational compression. The temperature of matter in the interior of stars is measured in millions of kelvins, and on their surface - in thousands of kelvins. The energy of the vast majority of stars is released as a result of thermal nuclear reactions the transformation of hydrogen into helium, which occurs during high temperatures in the interior areas. Stars are often called the main bodies of the Universe, since they contain the bulk of luminous matter in nature. It is also noteworthy that stars have negative heat capacity. 3stars are newborn, young, middle-aged and old. New stars are constantly being formed, and old ones are constantly dying. The youngest, called T Tauri stars (after one of the stars in the constellation Taurus), are similar to the Sun, but much younger than it. In fact, they are still in the process of formation and are examples of protostars (primary stars). This variable stars, their luminosity changes, since they have not yet reached a stationary mode of existence. Many Taurus stars have rotating disks of material around them; Powerful winds emanate from such stars. The energy of the matter that falls on the protostar under the influence of gravity is converted into heat. As a result, the temperature inside the protostar increases all the time. When its central part becomes so hot that nuclear fusion begins, the protostar turns into a normal star. Once nuclear reactions begin, the star has a source of energy that can support its existence for a very long time. How long depends on the size of the star at the beginning of this process, but a star the size of our Sun will have enough fuel to survive stable for about 10 billion years. However, it happens that stars much more massive than the Sun last only a few million years; the reason is that they compress their nuclear fuel at a much faster rate. All stars are fundamentally similar to our Sun: they are huge balls of very hot glowing gas, in the very depths of which nuclear energy is generated. But not all stars are exactly like the Sun. The most obvious difference is the color. In addition, stars differ in both brightness and brilliance. How bright a star appears in the sky depends not only on its true luminosity, but also on the distance separating it from us. Taking into account distances, the brightness of stars changes in wide range: from one ten thousandth the brightness of the Sun to the brightness of more than a million Suns. The vast majority of stars appear to be located closer to the dim end of this scale. The Sun, which is in many ways a typical star, is much more luminous than most other stars. With the naked eye you can see very a small amount of weak stars by nature. In the constellations of our sky, the main attention is drawn to the “signal lights” of unusual stars, those that have a very high luminosity. Why do stars vary so much in their brightness? It turns out that this does not depend on the mass of the star. The amount of matter contained in a particular star determines its color and brightness, as well as how the brightness changes over time. The most massive stars are also the hottest and the brightest. They appear white or bluish. Despite their huge size, these stars produce such a colossal amount of energy that all their nuclear fuel reserves burn out in just a few million years. In contrast, stars with low mass are always dim and their color is reddish. They can exist for many billions of years. However, among very bright stars There are reds and oranges in our sky. These include Aldebaran - the eye of the bull in the constellation Taurus, and Antares in Scorpio. These stars have expanded greatly and are now much larger in size than normal red stars. For this reason they are called giants, or even supergiants. Due to their enormous surface area, giants emit immeasurably more energy than normal stars like the Sun, despite the fact that their surface temperature is much lower. The diameter of a red supergiant - for example, Betelgeuse in Orion - is several hundred times greater than the diameter of the Sun. In contrast, the size of a normal red star is typically no more than one-tenth the size of the Sun. In contrast to the giants, they are called "dwarfs". Stars become giants and dwarfs at different stages of their lives, and a giant may eventually become a dwarf when it reaches "old age." A star has two parameters that determine all internal processes - mass and chemical composition. If you set them for a single star, then at any moment in time you can predict all the others physical characteristics stars such as brilliance, spectrum, size, internal structure.
Weight
The mass of a star can only be reliably determined if it is a component of a binary star. In this case, the mass can be calculated using Kepler's generalized third law. But even so, the estimated error ranges from 20% to 60% and largely depends on the error in determining the distance to the star. In all other cases, it is necessary to determine the mass indirectly, for example, from the mass-luminosity relationship. Apparent magnitudes say nothing about the total energy emitted by the star or the brightness of its surface. Indeed, due to differences in distances, a small, relatively cool star, only because of its relatively great proximity to us, can have a significantly lower apparent magnitude (i.e., appear brighter) than a distant hot giant. If the distances to two stars are known, then based on their apparent magnitudes it is easy to find the ratio of the actual light fluxes emitted by them. To do this, it is enough to refer the illumination created by these stars to the standard distance common to all stars. This distance is taken to be 10 parsecs. The magnitude that a star would have if observed from a distance of 10 parsecs is called absolute magnitude. Like visible magnitudes, absolute magnitudes can be visual, photographic, etc.
Another significant characteristic of a star is its radius. The radii of stars vary over a very wide range. There are stars no larger in size than Earth(the so-called “white dwarfs”), there are huge “bubbles” inside which the orbit of Mars could easily fit. It is no coincidence that we called such giant stars “bubbles.” From the fact that stars differ relatively little in their masses, it follows that at a very large radius the average density of matter should be negligibly small. If the average density of solar matter is 1.4 g/cm3, then in such “bubbles” it can be millions of times less than that of air. At the same time, white dwarfs have a huge average density, reaching tens and even hundreds of thousands of grams per cubic centimeter.
Local group of galaxies
The group of galaxies that includes our Milky Way is located on the periphery (at a distance of about 50 million light years from the center) of a giant cluster of galaxies visible in our sky in the constellation Virgo (Virgo Cluster) and consisting of more than 2000 star systems . It is formed at the intersection of two universal fibers of dark matter. It should be noted that this cluster is one of the great many superclusters of star islands that make up the fibrous megastructure of the part of the Universe observed today.
Hypothetical inhabitants of a highly developed civilization located in the center of the Virgo cluster, using powerful telescopes, could observe a close pair of spiral galaxies, indicated by faint hazy lines in the starry sky - this is how our Local Group is visible from there, the light from which would travel to these imaginary observers for 50 million years. About fifty smaller galaxies included in our group are difficult to register from such a huge distance, and conversely, the number of star systems included, according to modern calculations, in the Virgo Cluster does not include a huge number of dwarf galaxies. tick within this supercluster.
The concept of a Local Group used by astronomers can be interpreted as a small town on the outskirts of the country, on the streets of which its own laws apply. Its inhabitants actively interact, determining the present and future of each other, the stronger members of the community organize and subordinate to their will the movement of the weaker ones, and ultimately absorb them (scientists like to call these processes in the life of galaxies cannibalism), exciting in its expanded womb there are active processes of the birth of new generations of stars, planetary systems and, possibly, new organic life.
Similar scenarios describe the birth and development of our Galaxy and the Andromeda Galaxy (M31). The merger of this couple after several billion years is very likely from the point of view of modern science.
With a diameter of about 6 million light years, our Local Group represents the Universe in miniature. Its structure and composition allows us to study in detail the processes of birth, development and structure of all currently known types of galaxies. By studying the stars that form the galaxies in our immediate environment, using the most powerful ground-based and space telescopes, we obtain information about the age of the objects from which they consist. For the most ancient of them, it is 13 billion years old, which is almost equal to the age of the Universe. These are representatives of dwarf stars, in which nuclear combustion occurs extremely slowly. Oxygen, nitrogen, carbon, as well as heavier chemical elements(astrophysicists generally call them “metals”) were formed only during nuclear reactions in the interior of stars. By shedding their shells or flaring up as Supernovae, the stars enriched the surrounding space with the products of their vital activity. Representatives of luminaries of later generations are much richer in heavy elements, and the younger the star, the greater its metallicity, the more recent generation it belongs to. Thus, determining the composition of the stellar population of members of the Local Group of galaxies allows us to draw a conclusion about the age of its members.
Astronomers have received a huge amount of statistical and factual material as a result of the implementation of the GOODS program (Great Observatori-es Origins Deep Survey, which in one of the literary translations sounds like this: “Deep study of the origin of objects in the Universe at the largest observatories”). At present, the most substantiated theory is that the first stars formed from cold dark matter, which makes up 90% of the baryonic matter of the Universe, or more precisely, from giant hydrogen clouds. star clusters and dwarf galaxies, which themselves had a very stormy, bright and explosive youth. Subsequently, from these dwarf galaxies, through their merger and mutual absorption by larger smaller ones, the spiral, elliptical, irregular galaxies that we observe today were formed.
Astronomers believe that our Local Group formed from a cloud of dark matter when the Universe cooled to a temperature of 2000 K, about 13 billion years ago. If we extrapolate the linear dimensions into the past, taking into account changes in the scale of the expanding Universe, then at that time the diameter of the group was 600,000 light years (a quarter of the current distance between the Milky Way and the Andromeda Nebula). Moreover, the sizes of the two largest galaxies should have been smaller, and the members of the Local Group should have been more numerous.
Local scale
In order to understand the scale relationships in our Local Group, Ray Willard, an employee of the Space Telescope Science Institute in Baltimore, proposed the following comparison in his article in the journal Astronomy. Let's imagine our Galaxy as a compact disc (diameter 12 cm), in the center of which a tennis ball is placed. Now imagine the same design, but 1.5 times larger. This will be the Andro-meda Nebula. By placing these two disks at a distance of 3 m, we obtain a model of a galactic pair, and all dwarf galaxies - satellites of our galaxies and more distant members of the group - will fit into a sphere with a radius of 4.5 m.
The oldest globular star clusters and dwarf galaxies collided and merged, forming the core of our Galaxy. In the process of further evolution, a disk with spiral arms was formed. The turbulent past has left behind traces that appear in the form of huge arc-shaped gas and stellar flows that exist in the galactic halo - a very rarefied stellar environment. The size of the Milky Way halo in the scale model adopted above would occupy the volume of a volleyball (according to other estimates, the diameter of a spherical halo is approximately equal to the diameter of the galactic disk).
Only a few of the relict globular clusters have survived to today. Within the Milky Way, they resemble the ruins of ancient castles. The ability to survive depended on their masses and trajectories relative to the disk of the “host” galaxy. Modern observations allow us to conclude that our Galaxy has absorbed, is absorbing and will continue to absorb smaller stellar communities. We wrote about the M12 cluster, which is in the process of destruction due to interaction with the galactic disk as it passes through its plane. Like the face of a child engrossed in eating jam, the face of our Galaxy bears many traces of large-scale meals. The galactic halo contains the remains of swallowed star systems, the disk of the Milky Way is deformed by the passages of satellites - dwarf galaxies. Streams of stars located along the previous trajectories of movement of dwarf satellites around the center of our Galaxy literally rain stars onto the galactic disk.
According to some assumptions, the huge star cloud in the Milky Way, which can be observed in the constellation Sagittarius, represents the “population” of a dwarf galaxy that merged with our stellar island in the distant past. According to Steve Majewski, an employee of the University of Virginia, this is the largest satellite of our Galaxy that ended up in its womb.
The most impressive trace of the Galaxy's turbulent past is the huge flows of cold hydrogen forming arcs spanning 100 arc degrees around the south galactic pole. At the head of these flows are the Large and Small Magellan clouds - the largest satellites of the Milky Way.
Mysteries of the Magellanic Clouds
The most recent studies of the movement of Magellanic clouds, carried out by astronomers Nithya Kallivavalil, Charles Alcock from the Harvard-Smithsonian Center for Astrophysics ( Nitya Kallivayalil, Charles Alcock, Harvard-Smithsonian Center for Astrophysics ) and Roland Van der Marel from the Space Telescope Science Institute ( Roeland van der Marel, Space Telescope Science Institute ), made it possible to clarify the dynamics of the motion of these dwarf galaxies. This dynamics was revised on the basis of refined values of the spatial velocity components of the Small and Large Magellanic clouds.
The greatest difficulty was calculating the velocity component perpendicular to the line of sight. This required several years of meticulous observations (using the Hubble Space Telescope) and calculations. As a result, the authors presented surprising findings at the 209th Conference of the American Astronomical Society. It turned out that the LMC, relative to our Galaxy, has a speed of 378 km/s, while the SMC has a speed of 302 km/s. In both cases, the speeds “turned out to be significantly greater than previously expected. There can be two explanations for this fact:
The mass of the Milky Way is greater than previously thought. Magellanic clouds are not in orbit around the Galaxy and will overcome its gravitational forces in the future.
The difference in cloud speeds (i.e., the speed of their relative movement) is also surprisingly high. This suggests that they are not gravitationally connected to each other. In addition, this explains the fact that they have not merged with each other in the more than ten billion history of the Local Group. Detailed studies of hydrogen flows trailing in trails behind the Magellanic clouds are planned for the future. This will make it possible to clarify the trajectories of their movements relative to each other and relative to our Galaxy.
Laboratory in the backyard
The theory of the development and formation of galaxy clusters unsatisfactorily explains the possibility of the formation of an isolated pair of large galaxies on the periphery of a giant cluster in the constellation Virgo. Scientists consider it a gift from Fate to have such a wonderful representative of spiral galaxies in our immediate surroundings, which is M31, or the Andromeda Nebula. Moreover, nature decreed that the plane of its disk is under optimal angle towards the direction of an observer located on Earth (and on any planet located in our Galaxy). It is this angle of view that allows us to study with maximum care all the components - the core, spiral arms and halo of a huge stellar island.
Like our Galaxy, M31 contains many globular clusters. Some of them are located outside the spiral arms, but move around galactic centers without leaving the halo. The Hubble Space Telescope received an image of the globular star cluster G1, orbiting the center of M31 in an orbit with a radius of 130 thousand light years (the radius of the disk of the Andromeda Nebula is 70 thousand light years). G1, also designated Mayall II, is the brightest globular cluster in the Local Group: it consists of at least 300 thousand old stars. Analysis of this detailed image, obtained in the near infrared in July 1994, allows us to conclude that the cluster contains stars in which helium nuclear burning processes occur, and the temperature and brightness of these stars suggests that it is the same age as our Milky Way and the Local Group as a whole. G1 is unique in that it contains a 10,000 solar mass black hole at its center.
A real miracle is the MZZ, a spiral galaxy in the Triangulum (NGC 598, or Trian-gulum Pinwheel Galaxy). It is half the diameter of the Milky Way and three times the size of the Andromeda Nebula. According to astronomers, over billions of years of close coexistence with M31, it should have collided with it long ago. But for some still unclear reasons this did not happen.
The study of the Local Group - the Universe in miniature - allows scientists to penetrate into many of the secrets of the Universe.
There are black holes of various masses in our environment: in the center of our own Galaxy, in the center of the Andromeda Nebula and the globular clusters M15 and G1. The assumption that the mass of the central black hole should be one ten-thousandth of the mass of the entire galaxy is confirmed by the examples of the mentioned clusters. This makes it possible to identify some fundamental patterns connecting the parameters of black holes and their “mother” galaxies.
Of particular interest is the discovery of hypothetical compact massive non-luminous (invisible) baryonic halo objects that concentrate the light of more distant stars due to the effect of gravitational lensing.
Modern cosmological models, based on long-term observations of the starry sky and on the huge amount of factual material obtained, admit that planets similar to our Earth began to form more than ten billion years ago. Thus, the Universe developed a sufficient amount of time for the emergence of conditions that ensure the formation of high-molecular organic compounds and life, and also, given the colossal number of galaxies and stars, for the emergence of intelligence. No matter how improbable it may be, let us still assume that in our local group, besides us, there is only one highly developed civilization. It is natural to assume that its representatives are interested in the world around them. We can hope that their scientists, having a longer history behind them, have observed the evolution of our group of galaxies, and terrestrial science will eventually be able to obtain this knowledge. Our civilization happened to exist in a relatively calm period of galactic history, which will end in about 2-3 billion years with a grandiose cataclysm - the collision of the Milky Way and the Andromeda Nebula.
True, one important circumstance should be taken into account here. Our Galaxy and M31 are approaching at a speed of 120 km/s, or 3.8 billion km per year, or 400 light years in one billion years (as the distances between their centers decrease, this speed will increase). The radial velocity can be determined quite accurately from the shift of the spectral lines. However, does the velocity vector of relative motion have a tangential component? If it does, and it is large enough, then the collision will not occur at all, at least within the next tens of billions of years. Galaxies will pass each other at enormous speeds, stir up their “hairs” by mutual gravitational influences and continue traveling along elliptical trajectories, closing the colossal arcs of their orbits around general center wt.
It is still possible that the Milky Way and the Andromeda Nebula are on collision courses. It was this assumption that Thomas Cox and Avi Loeb from the Harvard-Smithsonian Center for Astrophysics (TJ. Cox, Avi Loeb, Harvard Smithsonian Center for Astrophysics) based their model on. Having carried out scrupulous calculations, introducing into the equations all currently known parameters and initial conditions, scientists concluded that our star will live until the time when galaxies begin to merge. According to researchers, the first "contact"will take place in 2 billion years. Terrestrial astronomers will observe increasing deformations of the spiral structures of our Galaxy under the influence of gravity of the approaching “stellar monster”. As a result of several oscillatory movements, indicated by the nuclei of galaxies, the population of their stellar disks will increasingly mix, gradually forming a relatively homogeneous body of a giant elliptical galaxy. According to the assumptions of Cox and Loeb, our star, in its extreme old age, will still reach the period of formation of the “final” structure and, if this can console anyone living today, will end up on the periphery of the newly formed stellar island at a distance of 100 thousand light years from its center. Whether this area will be a “life zone” of a new galaxy, in which dynamic and energy parameters will provide conditions favorable for the existence of life on the planets around the stars inhabiting it, is, of course, impossible to say today. Let's hope for the best, for the benefit of our descendants.
As Avi Loeb joked, observing all these enchanting and grandiose changes in the starry sky, future scientists may refer to the lines of his report: “This is my first publication that will be quoted 5 billion years later.”
Computer simulation of the merger of galaxies allows us to trace the development of events: at the first stage of the collision, processes similar to those observed today in the “Mouse” galaxy (NGC 4676) will occur. First, the Milky Way and M31 will come into contact with their peripheral regions. In the process of further, deeper mutual absorption, the pattern will resemble the Antennae galaxies (NGC 4038-4039). Then the nuclei will merge, then perhaps the black holes that exist at the center of each star system will collide. Then jets will appear - ejections of matter into intergalactic space, similar to those observed near the galaxy NGC 5128. The universal catastrophe will most likely end with the formation of one giant elliptical galaxy - an analogue of NGC 1316." All on- Our local group will submit to the gravitational influence of this galaxy, and the appetites of the newly baked monster will be so great that the remaining members of the group will be absorbed by it in a relatively short time (by galactic standards).
Let's not forget that the Local Group, among other things, is moving towards the center of the Virgo cluster at a speed of 3 million light years for every billion years. How would we avoid colliding with something larger (as they say, “don’t hit a pine tree”)... After all, there are clearly more invisible objects hidden from us in the Universe than directly observed! How many years has earthly science been collecting photographic data about the world of galaxies around us? About a hundred? In any case, this is not even a moment, it is just a frozen photograph of the Cosmos. The development of processes within such short periods of time is noticeable only within very small volumes of space. Besides evolution solar system, we can observe the expansion of the shells of novae, supernovae, changes in the interiors of gas and dust clouds under the influence of “hurricane winds” generated by the young stellar inhabitants of these regions of space. To understand the dynamics of such formations as a cluster of galaxies (even if “local” and on the “outskirts” of the solid Virgo cluster) requires at least millennia. Of course, over these millennia we plan to inform our readers about current changes in the surrounding Universe. There must be at least something stable in this world!
Clusters and superclusters of galaxies. Local group. Milky Way Galaxy
The Milky Way Galaxy is part of a family of neighboring galaxies known as Local group and forms with them cluster of galaxies. Our Galaxy is one of the largest in the Local Group. The Andromeda Galaxy, part of the Local Group, is the most distant object visible to the naked eye. The 25 galaxies of the Local Group are scattered over 3 million light years. A cluster of galaxies is held together by gravitational forces. Larger galaxy clusters are the Virgo Cluster (several thousand objects) and the Coma Cluster (about 1000 bright elliptical galaxies and several thousand smaller objects). Our Galaxy and its neighbors in the Local Group are slowly moving towards the Virgo Cluster.
Clusters of galaxies, in turn, are grouped into families. The Local Group of Clusters, known as the Local Supercluster, is a formation that includes both the Local Group and the Virgo Cluster. The center of mass is located in the Virgo Cluster. Another supercluster is located in the constellation Hercules. It is 700 million light years away. Superclusters are separated from each other by giant empty spaces and form a spongy structure in the Universe.
Characteristics of galaxies included in the Local Group
Milky Way Galaxy
Milky Way- this is our Galaxy, consisting of 100 billion stars. Our Galaxy has 4 spiral arms, stars, gas and dust. Within 1000 light years of the galactic center, stars are very densely packed. In the very center of the Galaxy there is a mysterious source of colossal energy. There may be a black hole at the center of the Galaxy. The galaxy is spinning. Its internal parts rotate faster than its external parts. The Galaxy's disk is surrounded by a halo cloud of invisible matter.
9/10 The Milky Way galaxies are invisible. Our neighboring two galaxies - the Large and Small Magellanic Clouds - are attracted by an invisible halo and are absorbed by the Milky Way Galaxy.
Characteristics of the Milky Way Galaxy
* More distant flat component stars have longer orbital periods; those located closer to the center of the star have shorter periods. The central part of the Galaxy rotates like a rigid body.
Subsystems of the Galaxy
Average distance of subsystem objects from the galactic plane, kps; T is the age of the stars included in the subsystem, years; M is the mass of the subsystem (in% of the total mass of the Galaxy); N is the estimated total number of objects.
The galactic core is elliptical in shape, dimensions 4.8? 3.1 kps; number of stars?3·E10 7 .
The central core of the Galaxy is elliptical in shape, dimensions ~ 15? 30 ps; number of stars ~ 3·E10 6.
Nucleolus of the Galaxy - diameter ~ 1 ps; in its center there is a compact object (a black hole with a mass of 108-09 solar masses).
Star clusters (relatively close groups of stars):
scattered - diameter from 1.5 to 15 ps; age from several million to several billion years; the number of stars from several tens to several thousand; belong to the subsystem of the galactic plane;
ball - diameter from 15 to 200 ps; age 8-10 billion years; number of stars 10 5 -10 7 ; belong to the intermediate and extreme spherical subsystems.
The total number of stars in the Galaxy is 1.2-10 11.
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From the book Big Soviet Encyclopedia(GA) of the author TSB From the book Great Soviet Encyclopedia (ML) by the author TSB From the book Great Soviet Encyclopedia (ME) by the author TSB From the book Russian Rock. Small encyclopedia author Bushueva Svetlana From the book The Newest Book of Facts. Volume 1 [Astronomy and astrophysics. Geography and other earth sciences. Biology and Medicine] authorWhat is the Local Group of Galaxies? Our Galaxy (the Milky Way), together with the Andromeda galaxy, is part of a small group of 30–40 galaxies that astronomers call the Local Group of galaxies. The most distant of the Local Group galaxies is farther from the Sun
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