The structure of the universe The structure of the universe Milky Way light years The Milky Way The galaxy contains, according to the lowest estimate, about 200 billion stars. The bulk of the stars are located in the form of a flat disk. As of January 2009, the mass of the Galaxy is estimated at 3·10^12 solar masses, or 6·10^42 kg.
Nucleus In the middle part of the Galaxy there is a thickening, which is called a bulge (English bulge thickening), which is about 8 thousand parsecs in diameter. At the center of the Galaxy, apparently, there is a supermassive black hole(Sagittarius A*) around which, presumably, a medium-mass black hole rotates. Their combined gravitational action on neighboring stars causes the latter to move along unusual trajectories. bulgemangle supermassive black hole Sagittarius A* The center of the nucleus of the Galaxy is in the constellation Sagittarius (α = 265°, δ = 29°). The distance from the Sun to the center of the Galaxy is 8.5 kiloparsecs (2.62 10 ^ 17 km, or light years). Sagittarius constellation
Arms The Galaxy belongs to the class of spiral galaxies, which means that the Galaxy has spiral arms located in the plane of the disk. The disk is immersed in a spherical halo, and around it is a spherical corona. solar system is located at a distance of 8.5 thousand parsecs from the galactic center, near the plane of the Galaxy (shift to North Pole The galaxy is only 10 parsecs), inner edge arm, which is called the arm of Orion. This arrangement makes it impossible to observe the shape of the sleeves visually. New data from observations of molecular gas (CO) suggest that our Galaxy has two arms starting at a bar in the inner part of the Galaxy. In addition, there are a couple of sleeves in the inner part. Then these arms pass into the four-arm structure observed in the line of neutral hydrogen in the outer parts of the Galaxy. The Galaxy belongs to the class of spiral galaxies, which means that the Galaxy has spiral arms located in the plane of the disk. The disk is immersed in a spherical halo, and around it is a spherical corona. The solar system is located at a distance of 8.5 thousand parsecs from the galactic center, near the plane of the Galaxy (the shift to the North Pole of the Galaxy is only 10 parsecs), on the inner edge of the arm called the Orion arm. This arrangement makes it impossible to observe the shape of the sleeves visually. New data from observations of molecular gas (CO) suggest that our Galaxy has two arms starting at a bar in the inner part of the Galaxy. In addition, there are a couple of sleeves in the inner part. These arms then transition into a four-arm structure observed in the line of neutral hydrogen in the outer parts of the Galaxy.
Halo The halo of a galaxy is the invisible component of a spherical galaxy that extends beyond the visible part of the galaxy. It mainly consists of rarefied hot gas, stars and dark matter. The latter makes up the main mass of the galaxy. Galaxy of spherical dark matter Galactic halo The galactic halo has a spherical shape, extending beyond the galaxy by 510 thousand light years, and a temperature of about 5 10^5 K.
History of the discovery of the Galaxy Most celestial bodies combined into various rotating systems. So, the Moon revolves around the Earth, the satellites of the giant planets form their own, rich in bodies, systems. For more high level The Earth and other planets revolve around the Sun. A natural question arose: isn't the Sun included in an even larger system? Most celestial bodies are combined into various rotating systems. So, the Moon revolves around the Earth, the satellites of the giant planets form their own, rich in bodies, systems. At a higher level, the Earth and the rest of the planets revolve around the Sun. A natural question arose: isn't the Sun included in an even larger system? Moon Earth satellites of giant planets planets Moon Earth satellites of giant planets planets The first systematic study of this issue was carried out in the 18th century by the English astronomer William Herschel. He counted the number of stars in different areas of the sky and found that there is a large circle in the sky (later it was called the galactic equator), which divides the sky into two equal parts and in which the number of stars is the largest. In addition, there are more stars, the closer the area of the sky is located to this circle. Finally, it was found that the Milky Way is located on this circle. Thanks to this, Herschel guessed that all the stars we observed form a giant star system that is flattened towards the galactic equator. The first systematic study of this issue was carried out in the 18th century by the English astronomer William Herschel. He counted the number of stars in different areas of the sky and found that there is a large circle in the sky (later it was called the galactic equator), which divides the sky into two equal parts and in which the number of stars is the largest. In addition, there are more stars, the closer the area of the sky is located to this circle. Finally, it was found that the Milky Way is located on this circle. Thanks to this, Herschel guessed that all the stars we observe form a giant star system that is flattened towards the galactic equator.XVIII centuryWilliam HerschelGalactic equatorMilky WayXVIII centuryWilliam HerschelGalactic equatorMilky Way At first it was assumed that all objects of the Universe are parts of our Galaxy, although even Kant suggested that some nebulae may be galaxies like the Milky Way. As early as 1920, the question of the existence of extragalactic objects caused debate (for example, the famous Great Debate between Harlow Shapley and Geber Curtis; the former defended the uniqueness of our Galaxy). Kant's hypothesis was finally proved only in the 1920s, when Edwin Hubble managed to measure the distance to some spiral nebulae and show that, by their distance, they cannot be part of the Galaxy. Initially, it was assumed that all objects in the Universe are parts of our Galaxy, although even Kant suggested that some nebulae could be galaxies similar to the Milky Way. As early as 1920, the question of the existence of extragalactic objects caused debate (for example, the famous Great Debate between Harlow Shapley and Geber Curtis; the former defended the uniqueness of our Galaxy). Kant's hypothesis was finally proved only in the 1920s, when Edwin Hubble managed to measure the distance to some spiral nebulae and show that, by their distance, they cannot be part of the Galaxy.
Early classification attempts Attempts to classify galaxies began at the same time as the discovery of the first spiral nebulae by Lord Ross in BC. However, at that time the theory dominated, according to which all nebulae belong to our Galaxy. The fact that a number of nebulae have a non-galactic nature was proved only by E. Hubble in 1924. Thus, galaxies were classified in the same way as galactic nebulae. Galaxies of nebulae with a spiral pattern by Lord Rossom in our Galaxy by E. Hubble in 1924 In early photographic surveys, spiral nebulae dominated, which made it possible to distinguish them into a separate class. In 1888, A. Roberts carried out a deep survey of the sky, as a result of which a large number of elliptical structureless and very elongated spindle-shaped nebulae were discovered. In 1918, G. D. Curtis singled out helices with a bridge and an annular structure into a separate group into a separate Φ-group. In addition, he interpreted spindle nebulae as edge-on spirals. D. Curtis jumper
Harvard classification All galaxies in the Harvard classification were divided into 5 classes: All galaxies in the Harvard classification were divided into 5 classes: Class A galaxies brighter than 12m Class A galaxies brighter than 12mm Class B galaxies from 12m to 14m Class B galaxies from 12m to 14mm Class C galaxies from 14m to 16m Class C galaxies from 14m to 16mm Class D galaxies from 16m to 18m Class D galaxies from 16m to 18mm Class E galaxies from 18m to 20m Class E galaxies from 18m to 20mm
Elliptical galaxies Elliptical galaxies have a smooth elliptical shape (from strongly oblate to almost round) without distinctive features with a uniform decrease in brightness from the center to the periphery. They are denoted by the letter E and a number, which is an index of the oblateness of the galaxy. So, a round galaxy will have the designation E0, and a galaxy in which one of the major semi-axes is two times larger than the other, E5. Elliptical galaxies have a smooth elliptical shape (from strongly oblate to almost round) without distinctive features with a uniform decrease in brightness from the center to the periphery. They are denoted by the letter E and a number, which is an index of the oblateness of the galaxy. So, a round galaxy will have the designation E0, and a galaxy in which one of the major semi-axes is two times larger than the other, E5. Elliptical galaxies Elliptical galaxies M87
Spiral galaxies Spiral galaxies consist of a flattened disk of stars and gas, at the center of which is a spherical compaction called a bulge, and an extensive spherical halo. In the plane of the disk, bright spiral arms are formed, consisting mainly of young stars, gas, and dust. Hubble divided all known spiral galaxies into normal spirals (denoted by the symbol S) and bar spirals (SB), which in domestic literature often referred to as barred or crossed galaxies. In normal spirals, spiral arms radiate tangentially from the bright central core and extend for one revolution. The number of branches can be different: 1, 2, 3, ... but most often there are galaxies with only two branches. In crossed galaxies, the spiral arms extend at right angles from the ends of the bar. Among them, there are also galaxies with a number of branches not equal to two, but, in the bulk, crossed galaxies have two spiral branches. Symbols a, b, or c are added depending on whether the spiral arms are tightly coiled or ragged, or according to the core-to-bulge size ratio. Thus, Sa galaxies are characterized by a large bulge and a tightly twisted regular structure, while Sc galaxies have a small bulge and a ragged spiral structure. The Sb subclass includes galaxies that for some reason cannot be attributed to one of the extreme subclasses: Sa or Sc. Thus, the M81 galaxy has a large bulge and a ragged spiral structure. Spiral galaxies are composed of a flattened disk of stars and gas, at the center of which is a spherical compaction called a bulge, and an extensive spherical halo. In the plane of the disk, bright spiral arms are formed, consisting mainly of young stars, gas, and dust. Hubble divided all known spiral galaxies into normal spirals (denoted by the symbol S) and barred spirals (SB), which are often called barred or crossed galaxies in Russian literature. In normal spirals, spiral arms radiate tangentially from the bright central core and extend for one revolution. The number of branches can be different: 1, 2, 3, ... but most often there are galaxies with only two branches. In crossed galaxies, the spiral arms extend at right angles from the ends of the bar. Among them, there are also galaxies with a number of branches not equal to two, but, in the bulk, crossed galaxies have two spiral branches. Symbols a, b, or c are added depending on whether the spiral arms are tightly coiled or ragged, or according to the core-to-bulge size ratio. Thus, Sa galaxies are characterized by a large bulge and a tightly twisted regular structure, while Sc galaxies have a small bulge and a ragged spiral structure. The Sb subclass includes galaxies that for some reason cannot be attributed to one of the extreme subclasses: Sa or Sc. Thus, the M81 galaxy has a large bulge and a ragged spiral structure. Spiral galaxies bulgem halo bar Spiral galaxies bulgem halo bar
Irregular or irregular galaxies An irregular or irregular galaxy is a galaxy lacking both rotational symmetry and a significant core. Magellanic clouds are a characteristic representative of irregular galaxies. There was even the term "magellanic nebulae". Irregular galaxies are distinguished by a variety of shapes, usually small in size and an abundance of gas, dust and young stars. Designated I. Due to the fact that the shape of irregular galaxies is not firmly defined, peculiar galaxies have often been classified as irregular galaxies. An irregular or irregular galaxy is a galaxy lacking both rotational symmetry and a significant core. Magellanic clouds are a characteristic representative of irregular galaxies. There was even the term "magellanic nebulae". Irregular galaxies are distinguished by a variety of shapes, usually small in size and an abundance of gas, dust and young stars. Designated I. Due to the fact that the shape of irregular galaxies is not firmly defined, peculiar galaxies have often been classified as irregular galaxies. Irregular or irregular galaxies Magellanic clouds Peculiar galaxies Irregular or irregular galaxies Magellanic clouds Peculiar galaxies M82
Lenticular Galaxies Lenticular galaxies are disk galaxies (like spiral galaxies, for example) that have spent or lost their interstellar matter (like ellipticals). In cases where the galaxy is facing the observer, it is often difficult to clearly distinguish between lenticular and elliptical galaxies due to the lack of expressiveness of the spiral arms of a lenticular galaxy. Lenticular galaxies are disk galaxies (like spiral galaxies, for example) that have spent or lost their interstellar matter (like ellipticals). In cases where the galaxy is facing the observer, it is often difficult to clearly distinguish between lenticular and elliptical galaxies due to the lack of expressiveness of the spiral arms of a lenticular galaxy. disk galaxies interstellar matter disk galaxies interstellar matter NGC 5866
A black hole is a region in space-time, the gravitational attraction of which is so great that even objects moving at the speed of light (including quanta of light itself) cannot leave it. A black hole is a region in space-time, the gravitational attraction of which is so strong that even objects moving at the speed of light (including quanta of light itself) cannot leave it. is called the event horizon, and its characteristic size is called the gravitational radius. In the simplest case of a spherically symmetric black hole, it is equal to the Schwarzschild radius. The question of the real existence of black holes is closely related to how correct the theory of gravity, from which their existence follows. In modern physics, the standard theory of gravity, best confirmed experimentally, is the general theory of relativity (GR), which confidently predicts the possibility of the formation of black holes (but their existence is also possible in the framework of other (not all) models, see: Alternative theories of gravity). Therefore, observational data are analyzed and interpreted primarily in the context of general relativity, although, strictly speaking, this theory is not experimentally confirmed for conditions corresponding to the space-time region in the immediate vicinity of stellar-mass black holes (however, it is well confirmed under conditions corresponding to supermassive black holes). Therefore, statements about direct evidence of the existence of black holes, including those in this article below, strictly speaking, should be understood in the sense of confirming the existence of astronomical objects that are so dense and massive, and also have some other observable properties, that they can be interpreted as black holes. general theory relativity. The boundary of this region is called the event horizon, and its characteristic size is called the gravitational radius. In the simplest case of a spherically symmetric black hole, it is equal to the Schwarzschild radius. The question of the real existence of black holes is closely related to how correct the theory of gravity, from which their existence follows. In modern physics, the standard theory of gravity, best confirmed experimentally, is the general theory of relativity (GR), which confidently predicts the possibility of the formation of black holes (but their existence is also possible in the framework of other (not all) models, see: Alternative theories of gravity). Therefore, observational data are analyzed and interpreted primarily in the context of general relativity, although, strictly speaking, this theory is not experimentally confirmed for conditions corresponding to the space-time region in the immediate vicinity of stellar-mass black holes (however, it is well confirmed under conditions corresponding to supermassive black holes). Therefore, statements about direct evidence of the existence of black holes, including those in this article below, strictly speaking, should be understood in the sense of confirming the existence of astronomical objects that are so dense and massive, and also have some other observable properties, that they can be interpreted as black holes. general relativity.event horizongravitational radiusschwarzschild radius theory of gravitygeneral relativity alternative theories of gravity
Magnetar or magnetar is a neutron star with exceptionally strong magnetic field(up to 1011 T). Theoretically, the existence of magnetars was predicted in 1992, and the first evidence of their real existence was obtained in 1998 when observing powerful flash gamma and x-ray radiation from the SGR source in the constellation Aquila. The lifetime of magnetars is short, it is about years. Magnetars are a poorly understood type of neutron star due to the fact that few are close enough to Earth. Magnetars have a diameter of about 20 km, but the masses of most exceed the mass of the Sun. The magnetar is so compressed that a pea of its matter would weigh more than 100 million tons. Most of the known magnetars rotate very quickly, at least a few rotations around the axis per second. The life cycle of a magnetar is quite short. Their strong magnetic fields disappear after about a year, after which their activity and radiation x-rays stops. According to one of the assumptions, up to 30 million magnetars could have formed in our galaxy during its entire existence. Magnetars are formed from massive stars with an initial mass of about 40 M. A magnetar or magnetar is a neutron star with an exceptionally strong magnetic field (up to 1011 T). Theoretically, the existence of magnetars was predicted in 1992, and the first evidence of their real existence was obtained in 1998 when observing a powerful burst of gamma and X-ray radiation from an SGR source in the constellation Aquila. The lifetime of magnetars is short, it is about years. Magnetars are a poorly understood type of neutron star due to the fact that few are close enough to Earth. Magnetars have a diameter of about 20 km, but the masses of most exceed the mass of the Sun. The magnetar is so compressed that a pea of its matter would weigh more than 100 million tons. Most of the known magnetars rotate very quickly, at least a few rotations around the axis per second. The life cycle of a magnetar is quite short. Their strong magnetic fields disappear after about a year, after which their activity and X-ray emission cease. According to one of the assumptions, up to 30 million magnetars could have formed in our galaxy during its entire existence. Magnetars are formed from massive stars with an initial mass of about 40 M. a neutron star by a magnetic field of Tl in 1992 in 1998 gamma-ray radiation SGR Eagle neutron stars of the Earth the Sun of our galaxy huge fluctuations in the star, and also, the magnetic field fluctuations that accompany them often lead to huge gamma-ray emissions that were recorded on Earth in 1979, 1998 and 2004. A neutron star's magnetic field is a million million times greater than Earth's magnetic field. The tremors formed on the surface of a magnetar cause huge oscillations in the star, and the magnetic field oscillations that accompany them often lead to huge bursts of gamma radiation, which have been recorded on Earth in 1979, 1998 and 2004. The magnetic field of a neutron star is one million million times greater than the Earth's magnetic field in years.
A pulsar is a cosmic source of radio (radio pulsar), optical (optical pulsar), X-ray (X-ray pulsar) and/or gamma (gamma pulsar) radiation coming to Earth in the form of periodic bursts (pulses). According to the dominant astrophysical model, pulsars are rotating neutron stars with a magnetic field that is tilted to the axis of rotation, which causes the radiation coming to Earth to be modulated. The first pulsar was discovered in June 1967 by Jocelyn Bell, E. Hewish's graduate student, on the meridian radio telescope of the Mullard Radio Astronomy Observatory, Cambridge University at a wavelength of 3.5 m (85.7 MHz). For this outstanding result, Hewish received in 1974 Nobel Prize. Modern titles of this pulsar PSR B or PSR J Pulsar is a cosmic source of radio (radio pulsar), optical (optical pulsar), X-ray (X-ray pulsar) and / or gamma (gamma-pulsar) radiation coming to Earth in the form of periodic bursts (pulses). According to the dominant astrophysical model, pulsars are rotating neutron stars with a magnetic field that is tilted to the axis of rotation, which causes the radiation coming to Earth to be modulated. The first pulsar was discovered in June 1967 by Jocelyn Bell, E. Hewish's graduate student, on the meridian radio telescope of the Mullard Radio Astronomy Observatory, Cambridge University at a wavelength of 3.5 m (85.7 MHz). For this outstanding result, Hewish received the Nobel Prize in 1974. The modern names of this pulsar PSR B or PSR J space radio-radio pulsar optical optical pulsar X-ray X-ray pulsar gamma-gamma-ray pulsar Earth periodic pulse astrophysical neutron stars magnetic field rotation axis modulation 1967 Jocelyn Bellaspirant E. Hewish radio telescopeMallard Radio Astronomy Observatory, Cambridge University wavelength1974 Nobel Prize PSR B cosmicradio-radio pulsaroptical pulsar X-ray pulsargamma-gamma-ray pulsar Earthperiodic pulsesastrophysicalneutron starsmagnetic fieldrotation axismodulation1967Jocelyn BellaspirantekE. Hewish radio telescope of the Mallard Radio Astronomy Observatory, University of Cambridge, wavelength 1974 Nobel Prize PSR B Observations were kept secret for several months, and the first discovered pulsar was given the name LGM-1 (short for Little Green Men small little green men ). This name was associated with the assumption that these strictly periodic radio emission pulses are of artificial origin. However, the Doppler frequency shift (characteristic of a source orbiting a star) was not detected. In addition, Hewish's group found 3 more sources of similar signals. After that, the hypothesis about the signals of an extraterrestrial civilization disappeared, and in February 1968, a report appeared in the journal Nature about the discovery of rapidly variable extraterrestrial radio sources of an unknown nature with a highly stable frequency. The results of the observations were kept secret for several months, and the first discovered pulsar was given the name LGM-1 (short for Little Green Men, little green men). This name was associated with the assumption that these strictly periodic radio emission pulses are of artificial origin. However, the Doppler frequency shift (characteristic of a source orbiting a star) was not detected. In addition, Hewish's group found 3 more sources of similar signals. After that, the hypothesis of extraterrestrial civilization signals disappeared, and in February 1968, the journal Nature published a report on the discovery of rapidly variable extraterrestrial radio sources of an unknown nature with a highly stable frequency. Until the end of 1968, various observatories around the world discovered another 58 objects, called pulsars, the number of publications devoted to them in the very first years after the discovery amounted to several hundred. Astrophysicists soon came to the consensus that a pulsar, or rather a radio pulsar, was a neutron star. It emits narrowly directed streams of radio emission, and as a result of the rotation of a neutron star, the stream falls into the field of view of an external observer at regular intervals, so pulsar pulses are formed. The message caused a scientific sensation. Until the end of 1968, various observatories around the world discovered another 58 objects, called pulsars, the number of publications devoted to them in the very first years after the discovery amounted to several hundred. Astrophysicists soon came to the consensus that a pulsar, or rather a radio pulsar, was a neutron star. It emits narrowly directed streams of radio emission, and as a result of the rotation of a neutron star, the stream enters the field of view of an external observer at regular intervals, so pulsar pulses are formed. The nearest of them are located at a distance of about 0.12 kpc (about 390 light years) from the Sun. For 2008, about 1790 radio pulsars are already known (according to the ATNF catalog). The nearest of them are located at a distance of about 0.12 kpc (about 390 light years) from the Sun. Like radio and X-ray pulsars, they are highly magnetized neutron stars. Unlike radio pulsars, which expend their own rotational energy on radiation, X-ray pulsars radiate due to the accretion of matter from a neighboring star that has filled its Roche lobe and gradually turns into a white dwarf under the action of the pulsar. As a result, the mass of the pulsar slowly grows, its moment of inertia and frequency of rotation increase, while radio pulsars, on the contrary, slow down with time. An ordinary pulsar rotates in times ranging from a few seconds to a few tenths of a second, while an X-ray pulsar rotates hundreds of times per second. Somewhat later, sources of periodic X-ray radiation, called X-ray pulsars, were discovered. Like radio and X-ray pulsars, they are highly magnetized neutron stars. Unlike radio pulsars, which expend their own rotational energy on radiation, X-ray pulsars radiate due to the accretion of matter from a neighboring star that has filled its Roche lobe and gradually turns into a white dwarf under the action of the pulsar. As a result, the mass of the pulsar slowly grows, its moment of inertia and frequency of rotation increase, while radio pulsars, on the contrary, slow down with time. An ordinary pulsar rotates in times ranging from a few seconds to a few tenths of a second, while an X-ray pulsar rotates hundreds of times per second. Accretion X-ray pulsars Rocham lobe Moment of inertia rotation frequency X-ray accretion pulsars Rocham lobe Moment of inertia rotation frequency
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The Milky Way is a galaxy that contains the Earth, the solar system and all the individual stars visible naked eye. Refers to barred spiral galaxies. The Milky Way, together with the Andromeda Galaxy (M31), the Triangulum Galaxy (M33), and more than 40 small satellite galaxies of it and Andromeda form the Local Group of galaxies, which is part of the Local Supercluster (Virgo Supercluster).
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Etymology The name Milky Way is a tracing paper from lat. vialactea "milk road", which, in turn, is a tracing paper from other Greek. ϰύϰλος γαλαξίας "milky circle". According to ancient Greek legend, Zeus decided to make his son Hercules, born of a mortal woman, immortal, and for this he placed him on his sleeping wife Hera so that Hercules would drink divine milk. Hera, waking up, saw that she was not feeding her own child, and pushed him away from her. A jet of milk splashed from the breast of the goddess turned into the Milky Way. In the Soviet astronomical school, the Milky Way was simply called "our Galaxy" or "the Milky Way system"; the phrase "Milky Way" was used to refer to visible stars, which optically constitute the Milky Way for the observer.
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Structure of the Galaxy The diameter of the Galaxy is about 30 thousand parsecs (about 100,000 light years, 1 quintillion kilometers) with an estimated average thickness of about 1000 light years. The galaxy contains, according to the lowest estimate, about 200 billion stars (modern estimates range from 200 to 400 billion). Most of the stars are in the form of a flat disk. As of January 2009, the mass of the Galaxy is estimated at 3 x 1012 solar masses, or 6 x 1042 kg. The new minimum estimate determines the mass of the galaxy as only 5 1011 solar masses. Most of the mass of the Galaxy is contained not in stars and interstellar gas, but in a nonluminous halo of dark matter.
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Disk According to scientists, the galactic disk, which protrudes in different directions in the region of the galactic center, has a diameter of about 100,000 light years. Compared to the halo, the disk rotates noticeably faster. The speed of its rotation is not the same at different distances from the center.
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Nucleus In the middle part of the Galaxy there is a thickening, which is called a bulge (English bulge - thickening), which is about 8 thousand parsecs in diameter. The center of the nucleus of the Galaxy is located in the constellation Sagittarius (α = 265°, δ = −29°). The distance from the Sun to the center of the Galaxy is 8.5 kiloparsecs (2.62 1017 km, or 27,700 light years). In the center of the Galaxy, apparently, there is a supermassive black hole (Sagittarius A *) around which, presumably. The central regions of the Galaxy are characterized by a strong concentration of stars: each cubic parsec near the center contains many thousands of them. Distances between stars are tens and hundreds of times less than in the vicinity of the Sun. As in most other galaxies, the distribution of mass in the Milky Way is such that the orbital velocity of most of the stars in this Galaxy does not depend to a large extent on their distance from the center. Further from the central bridge to the outer circle, the usual speed of rotation of stars is 210-240 km / s. Thus, such a velocity distribution, which is not observed in the solar system, where different orbits have significantly different revolution velocities, is one of the prerequisites for the existence of dark matter.
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Arms The Galaxy belongs to the class of spiral galaxies, which means that the Galaxy has spiral arms located in the plane of the disk. The disk is immersed in a spherical halo, and around it is a spherical corona. The solar system is located at a distance of 8.5 thousand parsecs from the galactic center, near the plane of the Galaxy, on the inner edge of the arm, called the arm of Orion. This arrangement makes it impossible to observe the shape of the sleeves visually. New data from observations of molecular gas (CO) suggest that our Galaxy has two arms starting at a bar in the inner part of the Galaxy. In addition, there are a couple of sleeves in the inner part. Then these arms pass into the four-arm structure observed in the line of neutral hydrogen in the outer parts of the Galaxy.
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Halo The Galactic halo has a spherical shape, extending beyond the galaxy by 5-10 thousand light years, and a temperature of about 5·105 K. The center of symmetry of the Milky Way halo coincides with the center of the galactic disk. The halo consists mainly of very old, dim, low-mass stars. They occur both singly and in the form of globular clusters, which can contain up to a million stars. The age of the population of the spherical component of the Galaxy exceeds 12 billion years, it is usually considered the age of the Galaxy itself.
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Evolution and the future of the Galaxy Collisions of our Galaxy with other galaxies are possible, including such a large one as the Andromeda galaxy, but specific predictions are still impossible due to ignorance of the transverse velocity of extragalactic objects.
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The work was done by a student of 7 (11) -B class of the Pervomaisky gymnasium Klimenko Daria
Our Galaxy - the star system in which the solar system is immersed, is called the Milky Way. The Milky Way is a grandiose cluster of stars visible in the sky as a bright hazy band.
In our Galaxy - the Milky Way - there are more than 200 billion stars of various luminosities and colors.
OUR GALAXY IS THE MILKY WAY
THE MILKY WAY, the hazy glow in the night sky from the billions of stars in our Galaxy. The band of the Milky Way surrounds the sky with a wide ring. The Milky Way is especially visible far from city lights. In the Northern Hemisphere, it is convenient to observe it around midnight in July, at 10 pm in August, or at 8 pm in September, when the Northern Cross of the constellation Cygnus is near the zenith. As we follow the Milky Way's twinkling band to the north or northeast, we pass the constellation Cassiopeia (in the shape of a W) and move towards the bright star Capella. Behind Capella, you can see how the less wide and bright part of the Milky Way passes just east of Orion's Belt and leans towards the horizon not far from Sirius - the brightest star in the sky. The brightest part of the Milky Way is visible to the south or southwest when the Northern Cross is overhead. In this case, two branches of the Milky Way are visible, separated by a dark gap. The cloud in the Shield, which E. Barnard called the "pearl of the Milky Way", is located halfway to the zenith, and below the magnificent constellations Sagittarius and Scorpio are visible.
What is the galaxy made of?
In 1609, when the great Italian Galileo Galilei was the first to point a telescope into the sky, he immediately made a great discovery: he figured out what the Milky Way was. Using a primitive telescope, Galileo managed to separate the brightest clouds of the Milky Way into individual stars. But behind them, he discovered new, dimmer clouds, the riddle of which he could no longer solve with his primitive telescope. But Galileo correctly concluded that these faintly luminous clouds, visible in his telescope, must also consist of stars.
The Milky Way, which we call our Galaxy, is actually made up of about 200 billion stars. And the Sun with its planets is only one of them. At the same time, our solar system is not located in the center of the Milky Way, but is removed from it by about two-thirds of its radius. We live on the outskirts of our galaxy.
The Horsehead Nebula is a cold cloud of gas and dust that obscures the stars and galaxies behind it.
The Milky Way encircles the celestial sphere in a large circle. The inhabitants of the Northern Hemisphere of the Earth, in the autumn evenings, manage to see that part of the Milky Way, which passes through Cassiopeia, Cepheus, Cygnus, Eagle and Sagittarius, and in the morning other constellations appear. In the southern hemisphere of the Earth, the Milky Way extends from the constellation Sagittarius to the constellations Scorpio, Circulus, Centaurus, Southern Cross, Carina, Arrow.
There are many legends about the origin of the Milky Way. Two similar ancient Greek myths deserve special attention, which reveal the etymology of the word Galaxias and its connection with milk. One of the legends tells about the mother's milk spilled across the sky of the goddess Hera, who was breastfeeding Hercules. When Hera learned that the baby she was breastfeeding was not her own child, but the illegitimate son of Zeus and an earthly woman, she pushed him away and the spilled milk became the Milky Way. Another legend says that the spilled milk is the milk of Rhea, the wife of Kronos, and Zeus himself was the baby. Kronos devoured his children, as it was predicted to him that he would be overthrown from the top of the Pantheon by his own son. Rhea hatches a plan to save her sixth son, the newborn Zeus. She wrapped a stone in baby clothes and slipped it to Kronos. Kronos asked her to feed her son one more time before he swallowed him. The milk spilled from Rhea's chest on a bare rock was subsequently called the Milky Way.
Legend…
Milky Way system
The Milky Way system is a vast star system (galaxy) to which the Sun belongs. The Milky Way system consists of many stars of various types, as well as star clusters and associations, gas and dust nebulae, and individual atoms and particles scattered in interstellar space. Most of them occupy a lenticular volume about 100,000 across and about 12,000 light-years thick. A smaller part fills an almost spherical volume with a radius of about 50,000 light years. All components of the Galaxy are connected into a single dynamic system, rotating around a minor axis of symmetry. The center of the System is in the direction of the constellation Sagittarius.
Heart of the Milky Way
Scientists have managed to look at the heart of our galaxy. Using the Chandra Space Telescope, a mosaic image was compiled that covers a distance of 400 by 900 light years. On it, scientists saw a place where stars die and are reborn with amazing frequency. In addition, more than a thousand new X-ray sources have been discovered in this sector. Most X-rays do not penetrate beyond earth's atmosphere Therefore, such observations can only be made using space telescopes. As stars die, they leave clouds of gas and dust that are squeezed out of the center and, cooling, move to the outer regions of the galaxy. This cosmic dust contains the whole range of elements, including those that are the builders of our body. So we are literally made of stellar ash.
There are many space objects that we can see - these are stars, nebulae, planets. But most of the universe is invisible. For example, black holes. A black hole is the core of a massive star, the density and attraction of which after a supernova explosion have increased so much that even light does not escape from its surface. Therefore, no one has yet been able to see black holes. These objects are still being studied by theoretical astronomy. However, many scientists are convinced that black holes exist. They believe that there are more than 100 million of them in our Galaxy alone, and each of them is the remnant of a giant star that exploded in the distant past. The mass of a black hole must be colossal, many times greater than the mass of the Sun, since it absorbs everything that is nearby: both interstellar gas and any other cosmic matter. According to astronomers, most of the mass of the universe is hidden in black holes. Their existence is still evidenced only by x-rays, observed in some places in space, where nothing can be seen either in an optical or in a radio telescope.
What is a black hole?
On Earth, a year is the time it takes the Earth to complete one revolution around the Sun. Every 365 days we return to the same point. Our solar system revolves around the black hole at the center of the galaxy in the same way. However, it makes a complete revolution in 250 million years. That is, since the dinosaurs disappeared, we have made only a quarter of a complete revolution. In descriptions of the solar system, it is rarely mentioned that it moves in outer space, like everything else in our world. Relative to the center of the Milky Way, the solar system moves at a speed of 792 thousand kilometers per hour. For comparison: if you were moving at the same speed, you could make trip around the world in 3 minutes. The period of time during which the Sun has time to make a complete revolution around the center of the Milky Way is called the galactic year. It is estimated that the Sun has lived only 18 galactic years so far.
When the evenings turn dark in autumn, a wide shimmering band can be clearly seen in the starry sky. This is the Milky Way - a giant arch thrown across the entire sky. "Heavenly River" is called the Milky Way in Chinese legends. The ancient Greeks and Romans called it the "Heavenly Road". The telescope made it possible to find out the nature of the Milky Way. This is the radiance of a myriad of stars, so far from us that they cannot be distinguished individually with the naked eye.
The diameter of the Galaxy is about 30 thousand parsecs (of the order of light years) The Galaxy contains, according to the lowest estimate, about 200 billion stars (the current estimate ranges from 200 to 400 billion assumptions) As of January 2009, the mass of the Galaxy is estimated at 3 × 1012 masses of the Sun, or 6 × 1042 kg. Most of the mass of the Galaxy is contained not in stars and interstellar gas, but in a nonluminous halo of dark matter.
In the middle part of the Galaxy there is a thickening, which is called the bulge (English bulge thickening), which is about 8 thousand parsecs in diameter. In the center of the Galaxy, apparently, there is a supermassive black hole (Sagittarius A *) around which, presumably, a medium-mass black hole rotates
The Galaxy belongs to the class of spiral galaxies, which means that the Galaxy has spiral arms located in the plane of the disk. In addition, there are a couple of sleeves in the inner part. These arms then transition into a four-arm structure observed in the line of neutral hydrogen in the outer parts of the Galaxy.
The Milky Way is observed in the sky as a dimly luminous diffuse whitish band, passing approximately along a large circle of the celestial sphere. In the northern hemisphere, the Milky Way crosses the constellations Aquila, Arrow, Chanterelle, Cygnus, Cepheus, Cassiopeia, Perseus, Auriga, Taurus and Gemini; in the southern Unicorn, Stern, Sails, Southern Cross, Compasses, Southern Triangle, Scorpio and Sagittarius. The galactic center is in Sagittarius.
Most celestial bodies are combined into various rotating systems. So, the Moon revolves around the Earth, the satellites of the giant planets form their own, rich in bodies, systems. At a higher level, the Earth and the rest of the planets revolve around the Sun. A natural question arose whether the Sun is also part of an even larger system? The first systematic study of this issue was carried out in the 18th century by the English astronomer William Herschel.
He counted the number of stars in different areas of the sky and found that there is a large circle in the sky (later it was called the galactic equator), which divides the sky into two equal parts and in which the number of stars is the largest. In addition, there are more stars, the closer the area of the sky is located to this circle. Finally, it was found that the Milky Way is located on this circle. Thanks to this, Herschel guessed that all the stars we observed form a giant star system that is flattened towards the galactic equator.
The history of the origin of galaxies is still not entirely clear. Initially, the Milky Way had much more interstellar matter (mostly in the form of hydrogen and helium) than it does now, which was used up and continues to be used up in star formation. There is no reason to believe that this trend will change, so that as billions of years pass, further fading of natural star formation should be expected. At present, stars form mainly in the arms of the galaxy.
