Includes the Galaxy and galaxies close to it that form unified system. The local group of galaxies includes St. 20 known galaxies, the distances to which do not exceed approximately 1 Mpc, including the Magellanic Clouds and... ...
local group of galaxies- includes the Galaxy and galaxies close to it, which form a single system. The local group of galaxies includes over 20 known galaxies, the distances to which do not exceed approximately 1 Mpc, including the Magellanic Clouds and... ... encyclopedic Dictionary
Local group of galaxies- a set of nearby galaxies, the distances to which do not exceed approximately 1 million pc (about 3 million light years). Consists of two large groups and there are only about 30 members of dwarf galaxies scattered among them. In one of the groups... ... Great Soviet Encyclopedia
LOCAL GALAXIES GROUP- includes the Galaxy and galaxies close to it, which form a single system. M. g. g. include St. 20 known galaxies, the distances to which do not exceed approximately 1 Mpc, include the Magellanic Clouds and the Andromeda Nebula...
Local group of galaxies- a set of nearby galaxies together with our Galaxy... Astronomical Dictionary
Local group- Galaxies of the Local Group Local group galaxies a gravitationally bound group of galaxies that includes galaxies Milky Way, the Andromeda galaxy (M31) and the Triangulum galaxy ... Wikipedia
galaxy cluster encyclopedic Dictionary
CLUSTER OF GALAXIES- a collection of relatively closely spaced galaxies connected into a single system by gravitational forces. More than 3,000 galaxy clusters are known, numbering from several tens to several thousand members. One of the galaxy clusters is... ... Big Encyclopedic Dictionary
CLUSTER OF GALAXIES- a collection of relatively closely spaced galaxies connected into a single system by gravitational forces. More than 3000 S. years are known, numbering from several. tens to several thousand members. One of the galaxies is, apparently, the Local Group of galaxies... Natural science. encyclopedic Dictionary
List of nearby galaxies- The following is a list of known galaxies within 3.6 megaparsecs (11.7 million light years) of Earth in order of distance from Earth (see note below). 3.6 Mpc is the distance to the center of the nearest two large groups of galaxies: Groups ... ... Wikipedia
Local Group of Galaxies
The MW subgroup has a linear size of about 140 kpc, and the radial velocity dispersion of galaxies in it is 68 km/s.
- As can be seen from Table 1, dwarf diffuse (spheroidal) galaxies of the Sculptor dSph type make up more than half of the objects in the subgroup of our Galaxy.
- With the exception of the most distant dwarf galaxies NGC 6822 +SagittariusDIG and Tucana (which may be unrelated satellites of the Galaxy), all other galaxies have tidal index> 0, i.e. are gravitationally connected, so that the subgroup occupies a volume in space, the boundaries of which can be represented by an ellipsoid with the axial ratio Z:Y:X=8:3:1. Together with clouds of neutral hydrogen from Magellanic Stream this structure should be called a polar ellipsoid rather than a polar ring.
- Spheroidal dwarf galaxy Leo-I at a distance of 0.27 Mpc (Lee et. al., 1993) has a radial velocity of +176 km/s (Zaritsky et. al., 1989) relative to the Galactic center, which is significantly greater than the parabolic velocity of 118 km/s. According to the scenario described in Byrd et.al. (1994) the Leo-I galaxy was thrown out of the neighborhood M31 when galaxies M31 And Milky Way moved away from each other.
- The distribution of spheroidal and irregular satellites shows no noticeable segregation with distance from our Galaxy.
- Judging by the average radial velocity of the satellites +19±20 km/s, the Milky Way subgroup is not experiencing significant compression or expansion.
Subgroup M31
 |
| Subgroups of the Community Group |
The Andromeda nebula galaxy system, visible from the outside, is grouped around its main galaxy M31, containing the closest galaxies with high surface brightness M32 and M110, as well as fainter and more distant NGC147 and NGC185, very faint systems And I, And II, And III .
In the summer of 1998, two groups of observers(I.D. Karachentsev and V.E. Karachentseva; T. Armandroff, J. Davies and G. Jacoby) at least 3 more dwarf spheroidal galaxies were discovered - possibly distant members of the subgroup M31(one of these galaxies was discovered independently by both groups): Pegasus DEG (And VI), Cassiopea Dw and And V. The third largest galaxy in the Local Group, M33 (Triangulum), which may or may not be a distant gravitationally bound companion to M31, itself has a dwarf companion LGS 3.
- Satellites of the galaxy Andromeda form a flat system with an axial ratio of 5:2:1. Its semimajor axis and the major (polar) axis of the Milky Way subgroup form an angle of about 57 o.
- Morphological segregation in the subgroup is clearly visible. All seven closest satellites M31 have types E and Sph, while only spiral and irregular galaxies are found on the periphery.
- As noted by Arp (1982), the radial velocity distribution of satellites M31 highly asymmetrical. Using our criterion for galaxy membership the difference in radial velocities decreases compared to Arp to +46±29 km/s. However, if we consider total weight M31 more; let's say To=3.0 instead of 2.5, then into the zone of influence M31 Other galaxies will also be included (WLM, Pegasus and NGC 404), which increase the asymmetry to +70 km/s.
- The asymmetry of radial velocities decreases significantly if we consider the system relative to the center of mass M31+M33. This may serve as an argument in favor of the fact that the main mass of this subgroup lies in its members, and is not distributed throughout the entire volume of the group.
- Number of satellites located in the North and South of M31 somewhat asymmetrical. If this is due to the absorption of radiation by our Galaxy, then we should expect the discovery of new members of the subgroup near the galaxy IC 10. The validity of this assumption has been shown quite recently.
Galaxies NGC3109, Antlia,Sextans A And Sextans B, apparently, form a separate subgroup with V r=+114+-12 km/s, which is located outside the so-called “zero Local Group distance” of 1.7 Mpc from the Local Group centroid (van den Bergh, 1999).
Other members cannot be classified as any main subgroup and move completely isolated in the gravitational field of members of giant groups. The substructures in the group are probably not stable. Observations and calculations suggest that the groups are very dynamic and have changed significantly in the past: the galaxies around the large elliptical galaxy Maffei 1 were likely once members of the group of our galaxy.
All of the above shows that the MG is not isolated, but is in gravitational interaction and exchange of members with the nearest surrounding groups of galaxies. Particularly noticeable is the interaction with:
- group IC342/Maffei, which, in addition to the giant elliptical galaxy, also contains the smaller Maffei 2, and interacts with the complex around IC 342. It is strongly absorbed by dust, as it is located near the equatorial plane of the Milky Way.
- group Sculptor"a or South Pole group(with members located around the South Galactic Poles), dominated by galaxy NGC 253
- group M83
| Galaxy | Alto. Name | RA (2000.0) | Dec (2000.0) | Type | V_r | Dist. | Diam. | V B tot | A B |
|---|---|---|---|---|---|---|---|---|---|
| WLM | DDO221 | 00:01:58 | -15:27:51 | IB(s)m IV-V | - 116 | 950 | 11.5x4.0 | 11.03 | 0.09 |
| IC 10 | UGC192 | 00:20:24 | +59:17:30 | IBM? | -344 | 660 | 6.3x5.1 | 11.80 | |
| Cetus | dSph | 775 | |||||||
| NGC 147 | DDO 3 | 00:33:12 | +48:30:29 | dE5 pec | -193 | 660 | 13.2x7.8 | 10.47 | 0.70 |
| And III | A0032+36 | 00:35:17 | +36:30:31 | dSph | 760 | 4.5x3.0 | 15.00 | 0.19 | |
| NGC 185 | UGC396 | 00:38:58 | +48:20:12 | dE3 pec + Sy | -202 | 620 | 11.7x10.0 | 10.10 | 0.78 |
| NGC205 | M 110 | 00:40:22 | +41:41:26 | E5 pec | - 241 | 725 | 21.9x11.0 | 8.92 | 0.14 |
| M32 | NGC 221 | 00:42:42 | +40:51:52 | E2 (cE2) | -205 | 725 | 8.7x6.5 | 9.03 | 0.31 |
| M31 | NGC 224 | 00:42:44 | +41:16:09 | SA(s)b Liner | -300 | 725 | 190x60 | 4.36 | 0.10 |
| And I | A0043+37 | 00:45:44 | +38:00:23 | dE3 pec ? | 810 | 2.5x2.5 | 13.6 | 0.20 | |
| SMC | NGC292 | 00:52:45 | -72:49:43 | SB(s)m pec | +158 | 58 | 320x185 | 2.7 | 0.17 |
| Scl dw Irr | E349-G31 | 00:08:13 | -34:34:42 | dIBm | +207 | 1.1x0.9 | 15.48 | ||
| Scl dSph | E351-G30 | 01:00:09 | -33:42:33 | dE3 pec | +110 | 84 | 39.8x30.9 | 10.50 | |
| LGS 3 | Psc dw | 01:03:53 | +21:53:05 | dIr/dSph | -277 | 810 | 2x2 | 18.00 | 0.10 |
| IC1613 | DDO 8 | 01:04:54 | +02:08:00 | IAB(s)m V | -234 | 720 | 16.2x14.5 | 9.88 | 0.02 |
| And V | 01:10:17 | +47:37:41 | dSph | 810 | |||||
| And II | 01:16:11 | +33:21:43 | E? | 680 | 3.6x2.52 | 13.5 | 0.14 | ||
| M33 | NGC 598 | 01:33:51 | +30:39:37 | SA(s)cd II-III | -179 | 795 | 70.8x41.7 | 6.27 | 0.18 |
| Phe dw | E245-G07 | 01:51:06 | -44:26:41 | IAm | +56 | 417 | 4.9x4.1 | 13.07 | |
| For dw | E356-G04 | 02:39:59 | -34:26:57 | dE4 | +53 | 140 | 17.0x12.6 | 9.04 | |
| LMC | E056-G115 | 05:23:34 | -69:45:22 | SB(s)m | +278 | 55 | 645x550 | 0.9 | 0.25 |
| Car dw | E206-G220 | 06:41:37 | -50:57:58 | dE3 | +229 | 100 | 23.4x15.5 | 22.14 | 0.10 |
| Leo A | DDO 69 | 09:59:24 | +30:44:42 | IBm V | +20 | 690 | 5.1x3.1 | 12.92 | 0.07 |
| Sex B | DDO 70 | 10:00:00 | +05:19:42 | Im+ IV-V | +301 | 1370 | 5.1x3.5 | 11.85 | 0.05 |
| NGC 3109 | DDO 236 | 10:03:07 | -26:09:32 | SB(s)m | +403 | 1260 | 19.1x3.7 | 10.39 | 0.14 |
| Antlia | A1001-27 | 10:01.8* | -27:05* | dE3 | +361 | 1320 | 1 | ||
| Leo I | Regulus G. | 10:08:27 | +12:18:27 | dE3 | +168 | 270 | 9.8x7.4 | 11.8 | 0.09 |
| Sex A | DDO 75 | 10:11:06 | -04:42:28 | IBm+ V | +324 | 1420 | 5.9x4.9 | 11.86 | 0.06 |
| Sex dw | 10:13:03 | -01:36:53 | dE3 | +230 | 87 | 0.07 | |||
| Leo II | DDO 93 | 11:13:29 | +22:09:17 | dE0 pec | +90 | 215 | 12.0x11.0 | 12.6 | 0.00 |
| GR 8 | DDO 155 | 12:58:39 | +14:13:02 | I'm V | +214 | 1700 | 1.1x1.0 | 14.68 | 0.04 |
| E269-G70 | 13:10.6* | -43:07* | -8 | ||||||
| IC 4247 | 13:24.0* | -30:06* | +274 | ||||||
| UMi dw | DDO 199 | 15:09:11 | +67:12:52 | dE4 | -209 | 60 | 30.2x19.1 | 11.9 | 0.04 |
| Dra dw | DDO 208 | 17:20:19 | +57:54:48 | dE0 pec | -281 | 76 | 35.5x24.4 | 10.9 | 0.08 |
| Milky Way | 17:45.6 | -28:56 | SAB(s)bc I-II ? | 0 | 10 | 30 | |||
| SagDEG | 18:55 | -30:30 | dE7 | 24 | |||||
Local group of galaxies
The group of galaxies, which includes our Milky Way, is located on the periphery (at a distance of about 50 million light years from the center) giant cluster 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 foggy 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, active processes of the birth of new generations of stars, planetary systems and, perhaps, 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 dwarf stars, nuclear combustion in which 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 reads like this: “Deep study of the origin of objects in the Universe on largest observatories"). At present, the most substantiated theory is that the first stars, star clusters and dwarf gases were formed from cold dark matter, which makes up 90% of the baryonic matter of the Universe, or more precisely, from giant hydrogen clouds. 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 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
To understand the scale relationships in our Local Group, Ray Willard, Associate Scientific Institute space telescope in Baltimore (Ray Willard, Space Telescope Science Institute), in his article in the journal Astronomy, offered the following comparison. 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 progress 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 diameter 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 has decreed that the plane of its disk is at an optimal angle to the direction towards the 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 there is, besides us, 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 displacement spectral lines. However, does the velocity vector have relative motion 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 luminary in its old age will still last until 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 . Will this area be a "life zone" new galaxy, in which the dynamic and energy parameters will provide conditions favorable for the existence of life on the planets around the stars inhabiting it, 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 will collide. star system. 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!
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.
Composition of the group
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 in the quality of technology for astronomical observations this number is growing.
Virgo Supercluster
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.
Types of galaxies that form the Local Group
Scientists have found that the age of all members of the Local Group is approximately 13 billion years. In addition, the substance that forms them has the same composition, which allows us to talk about common origin galaxies of the Local Group. They are not located in any random order: most of them are built around an imaginary line that runs between the 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.
Milky Way subgroup
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 raises the greatest number of 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.
Milky Way and Magellanic Clouds
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 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 the further fate of the Magellanic Clouds is indisputable. 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.
Andromeda Nebula and its satellites
In 5 billion years, a similar fate threatens our galaxy, only Andromeda poses a threat to it - largest galaxy Local group. 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 nearest galaxy to the Milky Way, observing it is greatly complicated 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 problem of globular clusters
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 balls. 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.
Dwarf galaxies for a long time were considered Palomar 12 in the constellation Capricorn and Palomar 4 in Ursa Major. Recent studies have shown that they are in fact quite large globular clusters.
History and difficulties of studying the Local Group of galaxies
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.
The Local Group lies approximately on the line connecting the Milky Way and the Andromeda Galaxy. The local group can be divided into several subgroups:
- Milky Way subgroup consists of the giant spiral Milky Way galaxy and its 14 known satellites (as of 2005), which are dwarf and mostly irregular galaxies;
- Andromeda subgroup quite similar to the Milky Way subgroup: at the center of the subgroup is the giant spiral galaxy Andromeda. Its 18 known (as of 2005) satellites are also mostly dwarf galaxies;
- Triangle subgroup - the Triangulum galaxy and its possible satellites;
- other dwarf galaxies that cannot be classified into any of the indicated subgroups.
The diameter of the Local Group is on the order of one megaparsec. Along with a number of other small groups of galaxies, the Local Group is part of the Local Sheet - a flat cloud of galaxies with a radius of about 7 Mpc (23 million light years) and a thickness of 1.5 Mpc (5 million light years), which, in turn, is part of the Local Supercluster of Galaxies (Virgo Supercluster), in which the Virgo Cluster plays a major role.
Galaxies of the Local Group
| Name | Subgroup | Type | Constellation | Note |
|---|---|---|---|---|
| Spiral galaxies | ||||
| Milky Way | Milky Way | SBbc | All constellations | Second in size. Possibly less massive than Andromeda. |
| Andromeda Galaxy (M31, NGC 224) | Andromeda | SA(s)b | Andromeda | Largest in size. Possibly the most massive member of the group. |
| Triangulum Galaxy (M33, NGC 598) | Triangle | SAc | Triangle | |
| Elliptical galaxies | ||||
| M110 (NGC 205) | Andromeda | E6p | Andromeda | satellite of the Andromeda galaxy |
| M32 (NGC 221) | Andromeda | E2 | Andromeda | satellite of the Andromeda galaxy |
| Irregular galaxies | ||||
| Wolf-Landmark-Melotte (WLM, DDO 221) | Ir+ | Whale | ||
| IC 10 | KBm or Ir+ | Cassiopeia | ||
| Small Magellanic Cloud (SMC, NGC 292) | Milky Way | SB(s)m pec | Toucan | |
| Canis Major Dwarf Dwarf Galaxy | Milky Way | Irr | Big Dog | satellite of the Milky Way galaxy |
| Pisces (LGS3) | Triangle | Irr | Fish | Possible satellite of the Triangulum galaxy (but definitely part of the Triangulum subgroup) |
| IC 1613 (UGC 668) | IAB(s)m V | Whale | ||
| Phoenix Dwarf Galaxy (PGC 6830) | Irr | Phoenix | ||
| Large Magellanic Cloud (LMC) | Milky Way | Irr/SB(s)m | Golden Fish | satellite of the Milky Way galaxy |
| Leo A (Leo III) | IBm V | a lion | ||
| Sextant B (UGC 5373) | Ir+IV-V | Sextant | ||
| NGC 3109 | Ir+IV-V | Hydra | ||
| Sextant A (UGCA 205) | Ir+V | Sextant | ||
| Dwarf elliptical galaxies | ||||
| NGC 147 (DDO 3) | Andromeda | dE5 pec | Cassiopeia | satellite of the Andromeda galaxy |
| SagDIG (Sagittarius Dwarf Irregular Galaxy) | IB(s)m V | Sagittarius | Farthest from the center of mass of the Local Group | |
| NGC 6822 (Barnard's Galaxy) | IB(s)m IV-V | Sagittarius | ||
| Pegasus Dwarf Irregular Galaxy (DDO 216) | Irr | Pegasus | ||
| Dwarf spheroidal galaxies | ||||
| Bootes I | dSph | Bootes | ||
| Whale | dSph/E4 | Whale | ||
| Hounds I and Hounds II | dSph | Hound Dogs | ||
| Andromeda III | dE2 | Andromeda | satellite of the Andromeda galaxy | |
| NGC 185 | Andromeda | dE3 pec | Cassiopeia | satellite of the Andromeda galaxy |
| Andromeda I | Andromeda | dE3 pec | Andromeda | satellite of the Andromeda galaxy |
| Sculptor (E351-G30) | Milky Way | dE3 | Sculptor | satellite of the Milky Way galaxy |
| Andromeda V | Andromeda | dSph | Andromeda | satellite of the Andromeda galaxy |
| Andromeda II | Andromeda | dE0 | Andromeda | satellite of the Andromeda galaxy |
| Oven (E356-G04) | Milky Way | dSph/E2 | Bake | satellite of the Milky Way galaxy |
| Carina Dwarf Galaxy (E206-G220) | Milky Way | dE3 | Keel | satellite of the Milky Way galaxy |
| Antlia Dwarf | dE3 | Pump | ||
| Leo I (DDO 74) | Milky Way | dE3 | a lion | satellite of the Milky Way galaxy |
| Sextant | Milky Way | dE3 | Sextant I | satellite of the Milky Way galaxy |
| Leo II (Leo B) | Milky Way | dE0 pec | a lion | satellite of the Milky Way galaxy |
| Ursa Minor | Milky Way | dE4 | Ursa Minor | satellite of the Milky Way galaxy |
| Dwarf Galaxy in Draco (DDO 208) | Milky Way | dE0 pec | The Dragon | satellite of the Milky Way galaxy |
| SagDEG (Sagittarius Dwarf Elliptical Galaxy) | Milky Way | dSph/E7 | Sagittarius | satellite of the Milky Way galaxy |
| Tucana Dwarf | dE5 | Toucan | ||
| Cassiopeia (Andromeda VII) | Andromeda | dSph | Cassiopeia | satellite of the Andromeda galaxy |
| Pegasus Dwarf Spheroidal Galaxy (Andromeda VI) | Andromeda | dSph | Pegasus | satellite of the Andromeda galaxy |
| Ursa Major I and Ursa Major II | Milky Way | dSph | Big Dipper | satellite of the Milky Way galaxy |
| The type is not precisely defined | ||||
| Virgo Flow | dSph (remnant)? | Virgo | In the process of merging with the Milky Way | |
| Willman 1 | ? | Big Dipper | possibly a globular star cluster | |
| Andromeda IV | Irr? | Andromeda | maybe not a galaxy | |
| UGC-A 86 (0355+66) | Irr, dE or S0 | Giraffe | ||
| UGC-A 92 (EGB0427+63) | Irr or S0 | Giraffe | ||
| Possibly not members of the Local Group | ||||
| GR 8 (DDO 155) | I'm V | Virgo | ||
| IC 5152 | IAB(s)m IV | Indian | ||
| NGC 55 | SB(s)m | Sculptor | ||
| Aquarius (DDO 210) | I'm V | Aquarius | ||
| NGC 404 | E0 or SA(s)0 − | Andromeda | ||
| NGC 1569 | Irp+ III-IV | Giraffe | ||
| NGC 1560 (IC 2062) | Sd | Giraffe | ||
| Giraffe A | Irr | Giraffe | ||
| Argo Dwarf | Irr | Keel | ||
| UKS 2318-420 (PGC 71145) | Irr | Crane | ||
| UKS 2323-326 | Irr | Sculptor | ||
| UGC 9128 (DDO 187) | IRP+ | Bootes | ||
| Palomar 12 (Capricornus Dwarf) | Capricorn | Globular star cluster | ||
| Palomar 4 (originally identified as a UMa I dwarf galaxy) | Big Dipper | Globular star cluster, previously defined as a galaxy | ||
| Sextant C | Sextant | |||
Diagram
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Notes
Links
- Igor Drozdovsky.(Russian) . astronet.ru. Retrieved March 31, 2009. .
- (English) (inaccessible link - story) . www.atlasoftheuniverse.com (06/05/2007). Retrieved April 10, 2009. .
- (English) . www.atlasoftheuniverse.com. Retrieved April 10, 2009. .
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Excerpt characterizing the Local Group
He looked at her intently.-Are you talking about Nikolushka? - he said.
Princess Marya, crying, bowed her head affirmatively.
“Marie, you know Evan...” but he suddenly fell silent.
- What are you saying?
- Nothing. There’s no need to cry here,” he said, looking at her with the same cold gaze.
When Princess Marya began to cry, he realized that she was crying that Nikolushka would be left without a father. WITH with great effort Above himself, he tried to return back to life and was transported to their point of view.
“Yes, they must find it pathetic! - he thought. “How simple it is!”
“The birds of the air neither sow nor reap, but your father feeds them,” he said to himself and wanted to say the same to the princess. “But no, they will understand it in their own way, they will not understand! What they cannot understand is that all these feelings that they value are all ours, all these thoughts that seem so important to us are that they are not needed. We can't understand each other." - And he fell silent.
Prince Andrei's little son was seven years old. He could barely read, he didn't know anything. He experienced a lot after this day, acquiring knowledge, observation, and experience; but if he had then possessed all these later acquired abilities, he could not have understood better, more deeply the full meaning of that scene that he saw between his father, Princess Marya and Natasha than he understood it now. He understood everything and, without crying, left the room, silently approached Natasha, who followed him out, and shyly looked at her with thoughtful, beautiful eyes; raised, ruddy upper lip he trembled, he leaned his head against her and began to cry.
From that day on, he avoided Desalles, avoided the countess who was caressing him, and either sat alone or timidly approached Princess Marya and Natasha, whom he seemed to love even more than his aunt, and quietly and shyly caressed them.
Princess Marya, leaving Prince Andrei, fully understood everything that Natasha’s face told her. She no longer spoke to Natasha about the hope of saving his life. She alternated with her at his sofa and did not cry anymore, but prayed incessantly, turning her soul to that eternal, incomprehensible, whose presence was now so palpable over the dying man.
Prince Andrei not only knew that he would die, but he felt that he was dying, that he was already half dead. He experienced a consciousness of alienation from everything earthly and a joyful and strange lightness of being. He, without haste and without worry, awaited what lay ahead of him. That formidable, eternal, unknown and distant, the presence of which he never ceased to feel throughout his entire life, was now close to him and - due to the strange lightness of being that he experienced - almost understandable and felt.
Before, he was afraid of the end. He experienced this terrible, painful feeling of fear of death, of the end, twice, and now he no longer understood it.
The first time he experienced this feeling was when a grenade was spinning like a top in front of him and he looked at the stubble, at the bushes, at the sky and knew that death was in front of him. When he woke up after the wound and in his soul, instantly, as if freed from the oppression of life that held him back, this flower of love, eternal, free, independent of this life, blossomed, he was no longer afraid of death and did not think about it.
The more he, in those hours of suffering solitude and semi-delirium that he spent after his wound, thought about the new beginning that was open to him eternal love Moreover, without feeling it himself, he renounced earthly life. Everything, to love everyone, to always sacrifice oneself for love, meant not loving anyone, meant not living this earthly life. And the more he was imbued with this principle of love, the more he renounced life and the more completely he destroyed that terrible barrier that, without love, stands between life and death. When, at first, he remembered that he had to die, he said to himself: well, so much the better.
But after that night in Mytishchi, when the one he desired appeared in front of him in a semi-delirium, and when he, pressing her hand to his lips, cried quiet, joyful tears, love for one woman imperceptibly crept into his heart and again tied him to life. Both joyful and anxious thoughts began to come to him. Remembering that moment at the dressing station when he saw Kuragin, he now could not return to that feeling: he was tormented by the question of whether he was alive? And he didn't dare ask this.
His illness took its own physical course, but what Natasha called: this happened to him happened to him two days before Princess Marya’s arrival. This was the last moral struggle between life and death, in which death won. It was the unexpected consciousness that he still valued the life that seemed to him in love for Natasha, and the last, subdued fit of horror in front of the unknown.
It was in the evening. He was, as usual after dinner, in a slight feverish state, and his thoughts were extremely clear. Sonya was sitting at the table. He dozed off. Suddenly a feeling of happiness overwhelmed him.
“Oh, she came in!” - he thought.
Indeed, sitting in Sonya’s place was Natasha, who had just entered with silent steps.
Since she began following him, he had always experienced this physical sensation of her closeness. She sat on an armchair, sideways to him, blocking the light of the candle from him, and knitted a stocking. (She learned to knit stockings since Prince Andrei told her that no one knows how to take care of the sick like old nannies who knit stockings, and that there is something soothing in knitting a stocking.) Thin fingers she was quickly moved by the occasionally colliding spokes, and the pensive profile of her downcast face was clearly visible to him. She made a movement and the ball rolled off her lap. She shuddered, looked back at him and, shielding the candle with her hand, with a careful, flexible and precise movement she bent, raised the ball and sat down in her previous position.
He looked at her without moving, and saw that after her movement she needed to take a deep breath, but she did not dare to do this and carefully took a breath.
In the Trinity Lavra they talked about the past, and he told her that if he were alive, he would forever thank God for his wound, which brought him back to her; but since then they never spoke about the future.
“Could it or could it not have happened? - he thought now, looking at her and listening to the light steel sound of the knitting needles. - Was it really only then that fate brought me so strangely together with her that I might die?.. Was the truth of life revealed to me only so that I could live in a lie? I love her more than anything in the world. But what should I do if I love her? - he said, and he suddenly groaned involuntarily, according to the habit that he acquired during his suffering.
Hearing this sound, Natasha put down the stocking, leaned closer to him and suddenly, noticing him glowing eyes, walked up to him with a light step and bent down.
- You are not asleep?
- No, I’ve been looking at you for a long time; I felt it when you came in. No one like you, but gives me that soft silence... that light. I just want to cry with joy.
Natasha moved closer to him. Her face shone with rapturous joy.
- Natasha, I love you too much. More than anything else.
- And I? “She turned away for a moment. - Why too much? - she said.
- Why too much?.. Well, what do you think, how do you feel in your soul, in your whole soul, will I be alive? What do you think?
- I'm sure, I'm sure! – Natasha almost screamed, taking both his hands with a passionate movement.
He paused.
- How good it would be! - And, taking her hand, he kissed it.
Natasha was happy and excited; and immediately she remembered that this was impossible, that he needed calm.
“But you didn’t sleep,” she said, suppressing her joy. – Try to sleep... please.
He released her hand, shaking it; she moved to the candle and sat down again in her previous position. She looked back at him twice, his eyes shining towards her. She gave herself a lesson on the stocking and told herself that she wouldn't look back until she finished it.
Indeed, soon after that he closed his eyes and fell asleep. He did not sleep for long and suddenly woke up in a cold sweat.
As he fell asleep, he kept thinking about the same thing he had been thinking about all the time - about life and death. And more about death. He felt closer to her.
"Love? What is love? - he thought. – Love interferes with death. Love is life. Everything, everything that I understand, I understand only because I love. Everything is, everything exists only because I love. Everything is connected by one thing. Love is God, and to die means for me, a particle of love, to return to the common and eternal source" These thoughts seemed comforting to him. But these were just thoughts. Something was missing in them, something was one-sided, personal, mental - it was not obvious. And there was the same anxiety and uncertainty. He fell asleep.
He saw in a dream that he was lying in the same room in which he was actually lying, but that he was not wounded, but healthy. A lot of different persons, insignificant, indifferent, appear before Prince Andrei. He talks to them, argues about something unnecessary. They are getting ready to go somewhere. Prince Andrey vaguely remembers that all this is insignificant and that he has other, more important concerns, but continues to speak, surprising them, somehow empty, witty words. Little by little, imperceptibly, all these faces begin to disappear, and everything is replaced by one question about the closed door. He gets up and goes to the door to slide the bolt and lock it. Everything depends on whether he has time or not time to lock her. He walks, he hurries, his legs don’t move, and he knows that he won’t have time to lock the door, but still he painfully strains all his strength. And a painful fear seizes him. And this fear is the fear of death: it stands behind the door. But at the same time, as he powerlessly and awkwardly crawls towards the door, something terrible, on the other hand, is already, pressing, breaking into it. Something inhuman - death - is breaking at the door, and we must hold it back. He grabs the door, strains last efforts- it is no longer possible to lock her up - at least to hold her; but his strength is weak, clumsy, and, pressed by the terrible, the door opens and closes again.