Structure of the Universe Structure of the Universe The Milky Way Light years The Milky Way The galaxy contains, according to the lowest estimate, about 200 billion stars The bulk of the stars is 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. In the center of the Galaxy, apparently, there is a supermassive black hole (Sagittarius A *) around which, presumably, a black hole of average mass rotates. Their joint 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. 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. 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. 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.

The history of the discovery of the Galaxy Most of the 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? 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 the giant planets planets Moon Earth satellites of the 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 of 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 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 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 within 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 of 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 possible in the framework of other (not all) models, see below). : 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 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 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 40M. 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 one million million times greater than Earth's magnetic field. The shocks 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 gamma-ray bursts that 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, at 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 for this pulsar are 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, at 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 pulses astrophysical neutron stars magnetic field rotational modulation 1967 Jocelyn Bellaspirant E. Hewish radio telescopeMallard Radio Astronomy Observatory, Cambridge University wavelength1974 Nobel Prize PSR B spaceradio radio pulsaroptical pulsar X-ray pulsargamma-gamma-ray pulsar Earthperiodic pulsesastrophysicalneutron starsmagnetic fieldrotation axismodulation1967Jocelyn BellaspirantE. Hewish radio telescope of the Mallard Radio Astronomy Observatory of the University of Cambridge at a wavelength of 1974 Nobel Prize PSR B The results of 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 about the signals of 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 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 of 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 of 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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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 is. With his primitive telescope, he was able to separate the brightest clouds of the Milky Way into individual stars! But behind them he distinguished dimmer clouds, but he could not solve their riddle, although he correctly concluded that they should also consist of stars. Today we know that he was right.

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The Milky Way is actually made up of 200 billion stars. And the Sun with its planets is only one of them. At the same time, our solar system is removed from the center of the Milky Way by about two-thirds of its radius. We live on the outskirts of our galaxy. The Milky Way is in the shape of a circle. In the center of it, the stars are denser and form a huge dense cluster. The outer borders of the circle are visibly smoothed and become thinner at the edges. When viewed from the side, the Milky Way probably resembles the planet Saturn with its rings.

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Gaseous nebulae It was later discovered that the Milky Way is composed not only of stars, but of gas and dust clouds, which swirl rather slowly and erratically. However, in this case, gas clouds are located only inside the disk. Some gaseous nebulae glow with multicolored light. One of the most famous is the nebula in the constellation Orion, which is visible even to the naked eye. Today we know that such gaseous or diffuse nebulae serve as a cradle for young stars.

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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.

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The Milky Way, passing through the starry scattering of the southern hemisphere, is surprisingly beautiful and bright. In the constellations of Sagittarius, Scorpio, Scutum, there are many brightly glowing star clouds. It is in this direction that the center of our galaxy is located. In the same part of the Milky Way, dark clouds of cosmic dust - dark nebulae - are especially clearly distinguished. If it were not for these dark, opaque nebulae, then the Milky Way towards the center of the Galaxy would be a thousand times brighter. Looking at the Milky Way, it is not easy to imagine that it consists of many stars that are indistinguishable to the naked eye. But people have known this for a long time. One of these guesses is attributed to the scientist and philosopher of Ancient Greece, Democritus. He lived almost two thousand years earlier than Galileo, who first proved the stellar nature of the Milky Way based on telescope observations. In his famous "Starry Herald" in 1609, Galileo wrote: "I turned to the observation of the essence or substance of the Milky Way, and with the help of a telescope it was possible to make it so accessible to our vision that all disputes were silent by themselves due to the visibility and evidence, which and I am relieved of a verbose dispute. In fact, the Milky Way is nothing but an innumerable multitude of stars, as if arranged in heaps, no matter where the telescope is directed, a huge number of stars immediately become visible, of which very many are quite bright and quite distinguishable, the number of weaker stars does not allow any calculation at all. What relation do the stars of the Milky Way have to the only star in the solar system, to our Sun? The answer is now public knowledge. The Sun is one of the stars in our Galaxy, the Galaxy is the Milky Way. What is the position of the Sun in the Milky Way? Already from the fact that the Milky Way encircles our sky in a large circle, scientists have concluded that the Sun is located near the main plane of the Milky Way. In order to get a more accurate idea of ​​the position of the Sun in the Milky Way, and then to imagine what the shape of our Galaxy is in space, astronomers (V. Herschel, V. Ya. Struve, etc.) used the method of stellar counts. The bottom line is that in different parts of the sky, the number of stars is counted in a sequential interval of stellar magnitudes. If we assume that the luminosities of the stars are the same, then the observed brightness can be used to judge the distances to the stars, then, assuming that the stars are evenly spaced in space, they consider the number of stars that are in spherical volumes centered on the Sun.

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Hot Stars in the Southern Milky Way Hot blue stars, brightly glowing red hydrogen, and dark, eclipsing dust clouds are scattered across this spectacular region of the Milky Way in the southern constellation of Ara. The stars on the left, 4,000 light-years from Earth, are young, massive, emitting energetic ultraviolet radiation that ionizes the surrounding hydrogen clouds where star formation is taking place, causing the line's characteristic red glow. A small cluster of nascent stars can be seen to the right, against a dark dusty nebula.

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The central region of the Milky Way. In the 1990s, the COsmic Background Explorer (COBE) satellite scanned the entire sky in infrared light. The picture you see is the result of a study of the central region of the Milky Way. The Milky Way is an ordinary spiral galaxy that has a central bulge and an extended stellar disk. Gas and dust in the disk absorb radiation in the visible range, which interferes with observations of the center of the galaxy. Since infrared light is less absorbed by gas and dust, the Diffuse InfraRed Background Experiment (DIRBE) aboard the COBE Cosmic Background Survey satellite detects this radiation from stars surrounding the galactic center. The above image is a view of the galactic center from a distance of 30,000 light years (this is the distance from the Sun to the center of our galaxy). The DIBRE experiment uses liquid helium-cooled equipment specifically to detect infrared radiation, to which the human eye is insensitive.

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At the Center of the Milky Way At the center of our Milky Way Galaxy lies a black hole with a mass more than two million times that of the Sun. This was previously a controversial statement, but now this startling conclusion is almost beyond doubt. It is based on the results of observations of stars orbiting the center of the Galaxy very close to it. Using one of the Paranal Observatory's Very Large Telescopes and NACO's advanced infrared camera, astronomers patiently traced the orbit of one of the stars, designated S2, as it approached the center of the Milky Way at a distance of about 17 light hours (17 light hours is only three times the radius of the orbit). Pluto). Their results conclusively show that S2 is moving under the colossal gravitational pull of an invisible object that should be exceptionally compact - a supermassive black hole. This deep near-infrared image from NACO shows a 2-light-year star-filled region at the center of the Milky Way, the exact position of the center marked with arrows. Thanks to the NACO camera's ability to track stars so close to the center of the galaxy, astronomers can observe the star's orbit around the supermassive black hole. This allows us to accurately determine the mass of a black hole and, probably, to carry out a previously impossible test of Einstein's theory of gravity.

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What does the Milky Way look like? What does our Milky Way Galaxy look like from a distance? No one knows for sure, since we are inside our Galaxy, in addition, opaque dust limits our view in visible light. However, this figure shows a fairly plausible assumption based on numerous observations. At the center of the Milky Way is a very bright nucleus surrounding a giant black hole. The Milky Way's bright central bulge is currently thought to be an asymmetric bar of relatively old red stars. In the outer regions are spiral arms, their appearance due to open clusters of young, bright blue stars, red emission nebulae and dark dust. Spiral arms are located in a disk, the bulk of the mass of which is made up of relatively faint stars and rarefied gas - mostly hydrogen. The figure does not show a huge spherical halo of invisible dark matter, which makes up most of the mass of the Milky Way and determines the movement of stars away from its center.

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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. Beyond 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.

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THE MILKY WAY WERE COLLISION WITH ANOTHER GALAXY Recent studies by astronomers suggest that billions of years ago our Milky Way galaxy collided with another, smaller galaxy, and the results of this interaction in the form of remnants of this galaxy are still present in the Universe. Observing about 1,500 sun-like stars, an international team of researchers concluded that their trajectory, as well as their relative positions, may be evidence of such a collision. "The Milky Way is a large galaxy and we believe it was formed from the merger of several smaller ones," said Rosemary Wyse of Johns Hopkins University. Whis and her colleagues in the UK and Australia have been observing the outer regions of the Milky Way, believing that this is where collision traces may be present. Preliminary analysis of the research results confirmed their assumption, and an advanced search (scientists expect to study about 10 thousand stars) will make it possible to establish this with accuracy. Collisions that have taken place in the past may be repeated in the future. So, according to calculations, in billions of years the Milky Way and the Andromeda Nebula, the nearest spiral galaxy to us, should collide.

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Legend... 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.

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Supercomputer (part 1) One of the fastest computers in the world was designed specifically to simulate the gravitational interaction of astronomical objects. With its commissioning, scientists received a powerful tool for studying the evolution of clusters of stars and galaxies. The new supercomputer, dubbed GravitySimulator (simulator of gravitational interaction), designed by David Merit (David Merritt) of the Rochester Institute of Technology (RIT), New York. It implements a new technology - performance gains were achieved through the use of special Gravity Pipelines acceleration boards. With the achievement of productivity 4 trillion. operations per second GravitySimulator entered the top 100 most powerful supercomputers in the world and became the second most powerful machine of this architecture. Its cost is $500,000. According to Universe Today, GravitySimulator is designed to solve the classical problem of N-body gravitational interaction. Productivity in 4 trillion. operations per second makes it possible to build a model of the simultaneous interaction of 4 million stars, which is an absolute record in the practice of astronomical calculations. Until now, with the help of standard computers, it was possible to simulate the gravitational interaction of no more than a few thousand stars at the same time. With the installation of a supercomputer at RIT this spring, Merit and his collaborators have for the first time been able to model the close pair of black holes that form when two galaxies merge.

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Supercomputer (part 2) “It is known that in the center of most galaxies there is a black hole,” Dr. Merit explains the essence of the problem. - When galaxies merge, one larger black hole is formed. The merging process itself is accompanied by the absorption and simultaneous ejection of stars located in the immediate vicinity of the center of galaxies. Observations of nearby interacting galaxies seem to confirm the theoretical models. However, until now, the available power of computers has not made it possible to build a numerical model to test the theory. We succeeded for the first time." The next task that RIT astrophysicists will work on is studying the dynamics of stars in the central regions of the Milky Way to understand the nature of the formation of a black hole at the center of our own galaxy. Dr. Merit believes that, in addition to solving particular large-scale problems in the field of astronomy, the installation of one of the most powerful computers in the world will make the Rochester Institute of Technology a leader in other areas of science. The most powerful supercomputer for the second year has been BlueGene / L, created by IBM and installed in the Lawrence laboratory in Livermore, USA. Currently, it reaches 136.8 teraflops, but in its final configuration, which includes 65536 processors, this figure will be at least doubled.

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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.

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The age of the Milky Way was estimated using radioisotopes The age of the Galaxy (and, generally speaking, the Universe) was tried to be determined in a way similar to that used by archaeologists. Nicholas Daufas from the University of Chicago suggested comparing the content of various radioisotopes on the periphery of the Milky Way and in the bodies of the solar system for this. An article about this was published in the journal Nature. Thorium-232 and uranium-238 were chosen for evaluation: their half-lives are comparable to the time that has passed since the Big Bang. If you know the exact ratio of their quantities at the beginning, then it is easy to estimate how much time has passed by the current concentrations. From the spectrum of one old star, which is located on the border of the Milky Way, astronomers were able to find out how much thorium and uranium is contained in it. The problem was that the star's original composition is unknown. Daufas had to turn to information about meteorites. Their age (about 4.5 billion years) is known with sufficient accuracy and is comparable with the age of the solar system, and the content of heavy elements at the time of formation was the same as that of the solar matter. Considering the Sun an "averaged" star, Daufas transferred these characteristics to the original subject of analysis. Calculations have shown that the age of the Galaxy is 14 billion years, and the error is approximately one-seventh of the value itself. The previous figure - 12 billion - is quite close to this result. Astronomers got it by comparing the properties of globular clusters and individual white dwarfs. However, as Daufas notes, this approach requires additional assumptions about the evolution of stars, while his method is based on fundamental physical principles.

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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 the earth's atmosphere, so 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.

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The Milky Way found four more satellites Five centuries ago, in August 1519, the Portuguese admiral Fernando Magellan set off on a journey around the world. During the voyage, the exact dimensions of the Earth were determined, the date line was discovered, as well as two small foggy clouds in the sky of southern latitudes, which accompanied the sailors on clear starry nights. And although the great naval commander had no idea about the true origin of these ghostly concentrations, later called the Large and Small Magellanic Clouds, it was then that the first satellites (dwarf galaxies) of the Milky Way were discovered. The nature of these large clusters of stars finally became clear only at the beginning of the 20th century, when astronomers learned to determine the distances to such celestial objects. It turned out that the light from the Large Magellanic Cloud comes to us for 170 thousand years, and from the Small one - 200 thousand years, and they themselves are a vast cluster of stars. For more than half a century, these dwarf galaxies were considered the only ones in the vicinity of our Galaxy, but in the current century their number has grown to 20, with the last 10 satellites discovered within two years! The next step in the search for new members of the Milky Way family was made possible by observations from the Sloan Digital Sky Survey (SDSS). More recently, scientists have found four new satellites on SDSS images, distant from Earth at distances from 100 to 500 thousand light years. They are located in the sky in the direction of the constellations Coma Berenices, Hounds of the Dogs, Hercules and Leo. Among astronomers, dwarf galaxies revolving around the center of our star system (having a diameter of about 100,000 light years) are usually named after the constellations where they are located. As a result, the new celestial objects were named Veronica's Hair, Hounds II, Hercules, and Leo IV. This means that the second such galaxy has already been discovered in the constellation Canis Hounds, and the fourth in the constellation Leo. The largest representative of this group is Hercules, which is 1000 light years across, and the smallest is Veronica's Coma (200 light years). It is gratifying to note that all four mini-galaxies were discovered by a group of the University of Cambridge (Great Britain), headed by a Russian scientist Vasily Belokurov.

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Such relatively small star systems can be attributed more to large star globular clusters than to galaxies, so scientists are thinking of applying a new term to such objects - "hobbits" (hobbits, or little gnomes). The name of a new class of objects is only a matter of time. Most importantly, now astronomers have a unique opportunity to estimate the total number of dwarf star systems in the vicinity of the Milky Way. Preliminary calculations allow us to think that this figure reaches fifty. Finding the rest of the hidden "gnomes" will be more difficult, since their brilliance is extremely weak. Other clusters of stars help them hide, creating an extra background for radiation receivers. Only the peculiarity of dwarf galaxies to contain in their composition stars that are characteristic only for this type of objects helps out. Therefore, after finding the necessary stellar associations in the images, it remains only to make sure of their true location in the sky. Still, a sufficiently large number of such objects raises new questions for supporters of the so-called "warm" dark matter, the movement of which is faster than in the framework of the theory of "cold" invisible substance. The formation of dwarf galaxies, rather, is possible with a slow motion of matter, which better ensures the merging of gravitational "lumps" and, as a result, the emergence of galactic clusters. Nevertheless, in any case, the presence of dark matter during the formation of mini-galaxies is mandatory, which is why these objects receive such close attention. In addition, according to modern cosmological views, prototypes of future giant star systems “grow” from dwarf galaxies in the process of merging. Thanks to recent discoveries, we are learning more and more about the periphery in the general sense of the word. The periphery of the solar system makes itself felt with new objects of the Kuiper belt, the neighborhood of our Galaxy, as we see, is also not empty. Finally, the outskirts of the observable universe have become even more famous: at a distance of 11 billion light years, the most distant cluster of galaxies has been discovered. But more on that in the next post.

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 travel 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.

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Galaxies are giant stellar islands located outside of our star system (our Galaxy). They differ in their size, appearance and composition, conditions of formation and evolutionary changes.

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Democritus, an ancient Greek philosopher, believed that the Milky Way is a collection of faintly luminous stars. V. Herschel discovered many double, triple multiple stars. He presented a diagram of the structure of the Galaxy and its structure.

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I. Kant believed that our Galaxy does not include the entire stellar world and there are other stellar systems similar to it. E. Hubble discovered Cepheids in the Andromeda and Triangulum nebulae. His discoveries gave rise to a science called extragalactic astronomy.

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The distance from the center of the Galaxy to the Sun is 32,000 sv. years The diameter of the Galaxy is 100,000 sv. years The thickness of the galactic disk is 10,000 sv. years Mass - 165 billion solar masses Age of the Galaxy - 12 billion years

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The largest and smallest diameters of the bulge are respectively close to 20,000 and 30,000 sv. years The mass of the disk is 150 million times the mass of the Sun. The speed of rotation of the disk from the center is 200 - 240 m / s (at a distance of 2,000 light years. The rotation of the Sun around the center of the Galaxy is 200 - 220 km / s (one revolution in 200 million years). Satellites of the Galaxy: Large and Small Magellanic Clouds Large Magellanic Cloud Small Magellanic Cloud

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The location of the Sun in our Galaxy is rather unfortunate for studying this system as a whole: we are located near the plane of the stellar disk and it is difficult to determine the structure of the Galaxy from the Earth. In the area where the Sun is located, there is quite a lot of interstellar matter that absorbs light and the stellar disk is opaque.

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There are three main parts in the Galaxy - the disk, the halo and the crown. The central thickening of the disk is called the bulge.

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The halo consists mainly of very old, dim, low-mass stars. They occur both singly and in the form of globular clusters, which can include more than a million stars. The age of the population of the spherical component of the Galaxy exceeds 12 billion years. It is usually taken as the age of the Galaxy itself.

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Disk. The disk population is very different from the halo population. Near the plane of the disk, young stars and star clusters are concentrated, the age of which does not exceed several billion years. They form the so-called flat component. There are many bright and hot stars among them.

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The core of the central regions of the Galaxy is characterized by a strong concentration of stars: each cubic parsec near the center contains many thousands of them. The distance between stars is tens and hundreds of times less than in the vicinity of the Sun.

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I - Spherical II - Intermediate spherical III - Intermediate disc IV - Flat old V - Flat young

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Their diameter is 20-100 pc. Age 10 - 15 billion years Formed in the era of the formation of the Galaxy itself.

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Found near the galactic plane. Consist of hundreds or thousands of stars. There are also young (blue) stars in them.

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 (modern estimates range from 200 to 400 billion) 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 has been 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.