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Milky Way. Astronomy: Milky Way. Our Galaxy Student of the Baku Computer College Aslanov Murad. Milky way physics presentation

Milky Way. Astronomy: Milky Way. Our Galaxy Student of the Baku Computer College Aslanov Murad. Milky way physics presentation

amazingly beautiful and bright. There are many brightly glowing star clouds in the constellations Sagittarius, Scorpio, and Scutum. It is in this direction that the center of our Galaxy is located. In this same part of the Milky Way, dark clouds of cosmic dust - dark nebulae - stand out especially clearly. If these dark, opaque nebulae were not present, 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 indistinguishable to the naked eye. But people figured this out a long time ago. 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 Messenger” 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 turned out to be possible to make it so accessible to our vision that all disputes fell silent by themselves thanks to the clarity and evidence that I am freed from a long-winded debate. In fact, the Milky Way is nothing more than a countless number of stars, as if located in heaps, no matter what area the telescope is pointed at, a huge number of stars now become visible, many of which are quite bright and quite visible, but the number weaker stars cannot be counted at all.” What relation do the stars of the Milky Way have to the only star in the solar system, our Sun? The answer is now generally known. The Sun is one of the stars of our Galaxy, the Milky Way Galaxy. What place does the Sun occupy 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 star counts. The point is that in different parts of the sky the number of stars in a successive interval of stellar magnitudes is counted. If we assume that the luminosities of the stars are the same, then from the observed brightness we can judge the distances to the stars, then, assuming that the stars are evenly distributed in space, we consider the number of stars that are in spherical volumes centered on the Sun.

Our Galaxy Milky Way

Vera Viktorovna Ryzhakova, physics teacher, MOAU Secondary School No. 1, Shimanovsk, Amur Region


Problematic question

  • What happens when two galaxies collide?
  • What happens when two galaxies collide?
  • What happens when two galaxies collide?
  • What happens when two galaxies collide?
  • What happens when two galaxies collide?
  • What happens when two galaxies collide?

Hypotheses

  • They will disperse without noticing each other
  • Will merge into one new one
  • They will explode and fly in different directions

Object of study

  • Galaxy

Tasks

  • Find out the structure of our Galaxy
  • Find out the size of the Milky Way galaxy
  • Consider the movement of stars and the Galaxy as a whole
  • Answer a problematic question

Information sources

  • Textbook B.A. Vorontsov-Velyamov, E.K. Strout “Astronomy 11th grade basic level”, Bustard, 2014, Paragraph 25, pp. 171-187
  • Internet astrogalaxy.ru/151.html Our Galaxy. Our Galaxy is the stellar house in which we live.
  • Video https://www.youtube.com/watch?v=ZdF2wX5GfdU (4.08 min)
  • https://www.youtube.com/watch?v=DGvvEPBtPCI (1.17 min)
  • Lesson route sheet

  • Milky galaxy,
  • in which we live
  • Scattered into space
  • Sparkling rain.
  • We can fly around
  • her someday
  • Calling our Galaxy
  • We're just...

Working in a notebook

Characteristic

Graphic image

Projection of the Galaxy onto the celestial sphere (view of the galaxy from Earth)

Model of the structure of the Galaxy (side view) indicating the sizes and dominant celestial bodies in each of the structural components

Model of the structure of the Galaxy (view of the galactic disk from above) with an image of spatial structural components and an indication of the position of the Sun


star cluster

Cluster name

Example, location in the galaxy

Globular clusters

Stellar "population"

Open clusters

Cluster age

Star associations

Number of stars in the cluster

Special

ness


Main conclusions

  • - stars do not form alone, but in groups;
  • - the star formation process continues to this day;
  • - the evolution of the Galaxy - the history of the star formation process in it;
  • the stars are moving

Methods for detecting features of the motion of stars

  • - comparison of the appearance of the constellation in different periods of time, distant from each other;
  • - photographic comparison of areas of the starry sky using the same telescope at intervals of time;
  • - study of radial velocity, which is determined by the displacement of lines in the star’s spectrum (by the Doppler effect).

S/R Clause 25, paragraph 4

1 . Where is the Sun located in the Galaxy and what are the features of the radial velocities of stars relative to the Sun?

2. Define the concept of “star apex”. In what direction is the apex of the Sun located?

3. What is the period of revolution of the Sun around the center of the Galaxy?

4. Formulate a definition of the concept “corotation circle”. What is the advantage of the position of the Solar System in the Galaxy?


conclusions- the galactic disk rotates; - the rotation period is different for different distances from the center, the Galaxy does not rotate like a rigid body; - the linear speed with distance from the center first increases quickly, then at a very large distance it remains constant and even increases


Work with computer

1. Watch the video

“Collision of the Milky Way and Andromeda Galaxies” https://www.youtube.com/watch?v=DGvvEPBtPCI (1.17 min)

2. Answer the problem question


Homework

§ 25.1, 25.2, 25.4; practical tasks.

  • With what angular diameter will our Galaxy, whose diameter is 0.03 Mpc, be visible to an observer located in the M31 galaxy (Andromeda nebula) at a distance of 600 kpc?
  • 2. Using a moving star chart, determine which constellations the Milky Way passes through.

Project topics (by groups) 1. History of exploration of the Galaxy. 2. Legends of the peoples of the world, characterizing the Milky Way visible in the sky. 3. Discovery of the “island” structure of the Universe by V. Ya. Struve. 4. Model of the Galaxy by V. Herschel. 5. The mystery of the hidden mass. 6 Experiments to detect Weakly Interactive Massive Particles - weakly interacting massive particles. 7. Study by B. A. Vorontsov-Velyaminov and R. Trumpler of interstellar absorption of light. Internet resources http://www.youtube.com/watch?v=_sQD0Fbr FCw - Our Galaxy. Milky Way. http://www.youtube.com/watch?v=99PR9HSDp BI - Our Galaxy. View from the outside.




When the evenings become dark in autumn, a wide flickering stripe can be clearly visible in the starry sky. This is the Milky Way - a giant arch spanning the entire sky. The Milky Way is called the "Heavenly River" 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 glow of a myriad of stars, so far from us that they individually cannot be distinguished with the naked eye.


The diameter of the Galaxy is about 30 thousand parsecs (on 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 mass of the Sun, or 6×1042 kg. Most of the Galaxy's mass is contained not in stars and interstellar gas, but in a non-luminous halo of dark matter.


In the middle part of the Galaxy there is a thickening called a bulge, which is about 8 thousand parsecs in diameter. In the center of the Galaxy, there appears to be a supermassive black hole (Sagittarius A*), around which a medium-mass black hole is presumably rotating


The Galaxy belongs to the class of spiral galaxies, which means that the Galaxy has spiral arms located in the plane of the disk. 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 more sleeves in the inner part. These arms then transform into a four-arm structure observed in the neutral hydrogen line in the outer parts of the Galaxy.




The Milky Way is observed in the sky as a dimly luminous diffuse whitish stripe passing approximately along the great circle of the celestial sphere. In the northern hemisphere, the Milky Way crosses the constellations Aquila, Sagittarius, Chanterelle, Cygnus, Cepheus, Cassiopeia, Perseus, Auriga, Taurus and Gemini; in the southern Unicorn, Poop, Sails, Southern Cross, Compass, Southern Triangle, Scorpio and Sagittarius. The galactic center is located in Sagittarius.


Most celestial bodies are combined into various rotating systems. Thus, the Moon revolves around the Earth, the satellites of the giant planets form their own systems, rich in bodies. At a higher level, the Earth and the rest of the planets revolve around the Sun. A natural question arose: is the Sun 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 discovered that there was a large circle in the sky (later it was called the galactic equator), which divides the sky into two equal parts and on which the number of stars is greatest. In addition, the closer the part of the sky is to this circle, the more stars there are. Finally it was discovered that it was on this circle that the Milky Way was located. Thanks to this, Herschel guessed that all the stars we observed form a giant star system, which is flattened towards the galactic equator.


The history of the formation of galaxies is not yet entirely clear. Originally, the Milky Way had much more interstellar matter (mostly in the form of hydrogen and helium) than it does now, which was, and continues to be, used up to form stars. There is no reason to believe that this trend will change, so over billions of years we should expect a further decline in natural star formation. Currently, stars are formed mainly in the arms of the Galaxy.



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What does the Galaxy consist 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 his primitive telescope, he was able to separate the brightest clouds of the Milky Way into individual stars! But behind them he discerned dimmer clouds, but could not solve their mystery, although he correctly concluded that they, too, must 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 approximately two-thirds of its radius. We live on the outskirts of our Galaxy. The Milky Way is shaped like a circle. In its center, the stars are denser and form a huge dense cluster. The outer boundaries of the circle are noticeably smoothed and become thinner at the edges. When viewed from the outside, the Milky Way probably resembles the planet Saturn with its rings.

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

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The Milky Way encircles the celestial sphere in a great circle. Residents of the Northern Hemisphere of the Earth, on autumn evenings, manage to see that part of the Milky Way that 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, Compass, Centaurus, Southern Cross, Carina, Sagittarius.

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The Milky Way, passing through the starry scattering of the southern hemisphere, is amazingly beautiful and bright. There are many brightly glowing star clouds in the constellations Sagittarius, Scorpio, and Scutum. It is in this direction that the center of our Galaxy is located. In this same part of the Milky Way, dark clouds of cosmic dust - dark nebulae - stand out especially clearly. If these dark, opaque nebulae were not present, 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 indistinguishable to the naked eye. But people figured this out a long time ago. 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 Messenger” 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 turned out to be possible to make it so accessible to our vision that all disputes fell silent by themselves thanks to the clarity and evidence that I am freed from a long-winded debate. In fact, the Milky Way is nothing more than a countless number of stars, as if located in heaps, no matter what area the telescope is pointed at, a huge number of stars now become visible, many of which are quite bright and quite visible, but the number weaker stars cannot be counted at all.” What relation do the stars of the Milky Way have to the only star in the solar system, our Sun? The answer is now generally known. The Sun is one of the stars of our Galaxy, the Milky Way Galaxy. What place does the Sun occupy 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 star counts. The point is that in different parts of the sky the number of stars in a successive interval of stellar magnitudes is counted. If we assume that the luminosities of the stars are the same, then from the observed brightness we can judge the distances to the stars, then, assuming that the stars are evenly distributed in space, we 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, red glowing hydrogen and dark, eclipsing dust clouds are scattered throughout 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 star-forming hydrogen clouds, causing the line's characteristic red glow. A small cluster of newborn stars is visible to the right, against the backdrop of 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 visible radiation, interfering with observations of the galaxy's center. Because infrared light is less absorbed by gas and dust, the Diffuse InfraRed Background Experiment (DIRBE) on the COBE 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.

Slide 9

At the Center of the Milky Way At the center of our Milky Way Galaxy is a black hole with a mass more than two million times the mass of the Sun. This was previously a controversial statement, but this astonishing conclusion is now virtually beyond doubt. It is based on observations of stars orbiting very close to the center of the Galaxy. Using one of Paranal Observatory's Very Large Telescopes and NACO's Advanced Infrared Camera, astronomers patiently tracked the orbit of one star, designated S2, as it came within about 17 light-hours of the Milky Way's center (17 light-hours is just three times the orbital radius Pluto). Their results convincingly show that S2 is driven by the colossal gravitational force of an invisible object that should be extremely compact - a supermassive black hole. This deep near-infrared image from NACO shows a 2-light-year-wide star-filled region at the center of the Milky Way, with the exact location of the center indicated by arrows. Thanks to the NACO camera's ability to track stars so close to the galactic center, astronomers can observe a star's orbit around a supermassive black hole. This makes it possible to accurately determine the mass of the black hole and, perhaps, 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 located inside our Galaxy, and 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 there is a very bright core surrounding a giant black hole. It is currently assumed that the bright central bulge of the Milky Way is an asymmetrical bar of relatively old red stars. The outer regions contain spiral arms, their appearance caused by open clusters of young, bright blue stars, red emission nebulae and dark dust. The spiral arms are located in a disk, the bulk of which consists of relatively faint stars and rarefied gas - mostly hydrogen. Not shown is the huge spherical halo of invisible dark matter that makes up most of the Milky Way's mass and drives the motion of stars far from its center

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MILKY WAY, a hazy glow in the night sky from the billions of stars in our Galaxy. The Milky Way band encircles the sky in a wide ring. The Milky Way is especially visible away 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 Cygnus constellation is near the zenith. As we follow the Milky Way's shimmering streak north or northeast, we pass the W-shaped constellation Cassiopeia and head toward the bright star Capella. Beyond the Chapel, you can see how the less wide and bright part of the Milky Way passes just east of Orion's Belt and leans toward 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 at times when the Northern Cross is overhead. At the same time, two branches of the Milky Way are visible, separated by a dark gap. The Scutum Cloud, which E. Barnard called “the jewel of the Milky Way,” is located halfway to the zenith, and below are the magnificent constellations Sagittarius and Scorpio.

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ONCE ONCE THE MILKY WAY COLLIDED WITH ANOTHER GALAXY Recent research by astronomers suggests that billions of years ago our Milky Way galaxy collided with another, smaller one, and the results of this interaction in the form of remnants of this galaxy are still present in the Universe. After 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 by the merger of several smaller ones," said Rosemary Wyse of Johns Hopkins University. Vis and her colleagues from the UK and Australia observed the peripheral zones of the Milky Way, believing that it was there that traces of collisions might be present. A preliminary analysis of the research results confirmed their assumption, and an extended search (scientists expect to study about 10 thousand stars) will make it possible to establish this with accuracy. Clashes that have occurred in the past may occur again in the future. So, according to calculations, in billions of years the Milky Way and the Andromeda nebula, the closest spiral galaxy to us, should collide.

Slide 13

Legend... There are many legends telling 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 spilling across the sky from the goddess Hera, who was breastfeeding Hercules. When Hera found out 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 the baby was Zeus himself. Kronos devoured his children because it was foretold that he would be dethroned from the top of the Pantheon by his own son. Rhea hatched 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 breast onto a bare rock later became known as the Milky Way.

Slide 14

Supercomputer (1 part) 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, called the GravitySimulator, was designed by 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 productivity reaching 4 trillion. operations per second GravitySimulator entered the top hundred most powerful supercomputers in the world and became the second most powerful among machines of a similar architecture. Its cost is $500 thousand. According to Universe Today, GravitySimulator is designed to solve the classical problem of gravitational interaction of N-bodies. Productivity of 4 trillion. operations per second allows us to build a model of simultaneous interaction of 4 million stars, which is an absolute record in the practice of astronomical calculations. Until now, using standard computers, it was possible to simulate the gravitational interaction of no more than several thousand stars simultaneously. With the installation of a supercomputer at RIT this spring, Merit and his collaborators were able for the first time to build a model of the tight pair of black holes that form when two galaxies merge.

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Supercomputer (part 2) “It is known that at 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 merger process itself is accompanied by the absorption and simultaneous ejection of stars located in close proximity to the center of the galaxies. Observations of nearby interacting galaxies seem to confirm theoretical models. However, until now the available computer power has not made it possible to build a numerical model to test the theory. This is the first time we have succeeded." 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 the black hole at the center of our own galaxy. Dr. Meritt believes that, in addition to solving specific large-scale problems in the field of astronomy, installing one of the most powerful computers in the world will make Rochester Institute of Technology a leader in other scientific fields. For the second year now, the most powerful supercomputer remains BlueGene/L, created at IBM and installed at the Lawrence Livermore Laboratory, USA. It currently has speeds of 136.8 teraflops, but its final configuration of 65,536 processors will at least double that.

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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 lens-shaped volume with a diameter of about 100,000 and a thickness of about 12,000 light years. The 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. They tried to determine the age of the Galaxy (and, generally speaking, the Universe) in a way similar to the one used by archaeologists. Nicholas Daufas from the University of Chicago proposed to compare the content of various radioisotopes on the periphery of the Milky Way and in the bodies of the Solar System. An article about this was published in the journal Nature. Thorium-232 and uranium-238 were chosen for the assessment: 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 from the current concentrations it is easy to estimate how much time has passed. 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 it contains. The problem was that the star's original composition was unknown. Daufas had to turn to information about meteorites. Their age (about 4.5 billion years) is known with sufficient accuracy and is comparable to the age of the Solar System, and the content of heavy elements at the time of formation was the same as that of solar matter. Considering the Sun to be an “average” 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 actual value. The previous figure - 12 billion - is quite close to this result. Astronomers obtained 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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The heart of the Milky Way Scientists 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 the Earth's atmosphere, so such observations can only be made using space telescopes. When dying, stars leave clouds of gas and dust that are squeezed out of the center and, cooling, move to distant zones of the galaxy. This cosmic dust contains the entire spectrum of elements, including those that are the builders of our body. So we are literally made of star 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 international 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 condensations, 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 was finally clarified only at the beginning of the 20th century, when astronomers learned to determine the distances to such celestial objects. It turned out that light from the Large Magellanic Cloud travels to us for 170 thousand years, and from the Small Magellanic Cloud - 200 thousand years, and they themselves represent 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 being discovered within two years! The next step in the search for new members of the Milky Way family was helped by observations as part of the Sloan Digital Sky Survey (SDSS). More recently, scientists found four new satellites in 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, Canes Venatici, Hercules and Leo. Among astronomers, dwarf galaxies orbiting around the center of our star system (which is about 100,000 light years across) are usually called by the name of the constellations where they are located. As a result, the new celestial objects were named Coma Berenices, Canes Venatici II, Hercules and Leo IV. This means that the second such galaxy has already been discovered in the constellation Canes Venatici, and the fourth in the constellation Leo. The largest representative of this group is Hercules, 1000 light years across, and the smallest is Coma Berenices (200 light years). It is gratifying to note that all four mini-galaxies were discovered by a group at the University of Cambridge (UK), led by Russian scientist Vasily Belokurov.

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Such relatively small star systems can be classified as large globular clusters rather than galaxies, so scientists are considering 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. The main thing is that astronomers now have a unique opportunity to estimate the total number of dwarf star systems in the vicinity of the Milky Way. Preliminary calculations suggest that this figure reaches fifty. It will be more difficult to detect the remaining hidden “gnomes”, since their shine is extremely weak. Other clusters of stars help them hide, creating an extra background for radiation receivers. The only thing that helps is the peculiarity of dwarf galaxies to contain stars that are characteristic only of this type of object. Therefore, after discovering the necessary star associations in the photographs, all that remains is to verify their true location in the sky. Still, a fairly large number of such objects raises new questions for supporters of the so-called “warm” dark matter, the movement of which occurs faster than within the framework of the theory of “cold” invisible substance. The formation of dwarf galaxies is, rather, possible with the slow movement of matter, which better ensures the merging of gravitational “lumps” and, as a consequence, the emergence of galaxy clusters. However, 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 merger. Thanks to recent discoveries, we are learning more and more details about the periphery in the general sense of the word. The periphery of the Solar system makes itself felt with new Kuiper Belt objects; the surroundings of our Galaxy, as we see, are 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 this in the next news.

The structure of the Universe The structure of the Universe The Milky Way of ancient times The Milky Way The Galaxy contains, according to the lowest estimate, about 200 billion stars. The bulk of the stars are located in the shape 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.


Core In the middle part of the Galaxy there is a thickening called a bulge, which is about 8 thousand parsecs in diameter. In the center of the Galaxy, there appears to be a supermassive black hole (Sagittarius A*), around which an intermediate-mass black hole is presumably rotating. Their joint gravitational effect on neighboring stars causes the latter to move along unusual trajectories. balgemangl.supermassive black hole Sagittarius A* The center of the galactic core 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 (2.62·10^17 km, or light years). Constellation Sagittarius


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 offset to the North Pole of the Galaxy is only 10 parsecs), on the inner edge of the arm called the Orion arm. This arrangement does not make it possible 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 more sleeves in the inner part. These arms then transform into a four-arm structure observed in the neutral hydrogen line 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 offset to the North Pole of the Galaxy is only 10 parsecs), on the inner edge of the arm called the Orion arm. This arrangement does not make it possible 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 more sleeves in the inner part. These arms then transform into a four-arm structure observed in the neutral hydrogen line in the outer parts of the Galaxy. halocoronaSolar system Orion armhalocoronaSolar system Orion arm


Halo A galaxy halo is the invisible component of a spherical galaxy that extends beyond the visible part of the galaxy. It mainly consists of tenuous hot gas, stars and dark matter. The latter makes up the bulk of the galaxy.galaxy spherical dark matter Galactic haloThe 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 are combined into various rotating systems. Thus, the Moon revolves around the Earth, the satellites of the giant planets form their own systems, rich in bodies. At a higher level, the Earth and the rest of the planets revolve around the Sun. A natural question arose: is the Sun also part of an even larger system? Most celestial bodies are combined into various rotating systems. Thus, the Moon revolves around the Earth, the satellites of the giant planets form their own systems, rich in bodies. At a higher level, the Earth and the rest of the planets revolve around the Sun. A natural question arose: is the Sun also part of an even larger system? MoonEarthsatellites of giant planetsplanets MoonEarthsatellites of giant planetsplanets 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 discovered that there was a large circle in the sky (later it was called the galactic equator), which divides the sky into two equal parts and on which the number of stars is greatest. In addition, the closer the part of the sky is to this circle, the more stars there are. Finally it was discovered that it was on this circle that the Milky Way was located. Thanks to this, Herschel guessed that all the stars we observed form a giant star system, which 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 discovered that there was a large circle in the sky (later it was called the galactic equator), which divides the sky into two equal parts and on which the number of stars is greatest. In addition, the closer the part of the sky is to this circle, the more stars there are. Finally it was discovered that it was on this circle that the Milky Way was located. Thanks to this, Herschel guessed that all the stars we observed form a giant star system, which is flattened towards the galactic equator. XVIII century William Herschel galactic equator Milky Way 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 Heber Curtis; the former defended the uniqueness of our Galaxy). Kant's hypothesis was finally proven only in the 1920s, when Edwin Hubble was able to measure the distance to some spiral nebulae and show that, due to their distance, they cannot be part of the Galaxy. At first it was assumed that all objects in the Universe are parts of our Galaxy, although Kant also 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 Heber Curtis; the former defended the uniqueness of our Galaxy). Kant's hypothesis was finally proven only in the 1920s, when Edwin Hubble managed to measure the distance to some spiral nebulae and show that, due to their distance, they cannot be part of the Galaxy. Kant 1920 Great Controversy Harlow Shapley by Geber Curtis Edwin Hubble Kant 1920 Great Controversy Harlow Shapley Geber Curtis Edwin Hubble




Early Attempts at Classification Attempts to classify galaxies began simultaneously with the discovery of the first spiral-patterned nebulae by Lord Ross in However, at that time the prevailing theory was that all nebulae belonged to our Galaxy. The fact that a number of nebulae are of a non-galactic nature was proven 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 Ross in our Galaxy by E. Hubble in 1924. Early photographic surveys were dominated by spiral nebulae, 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 fusiform nebulae were discovered. In 1918, G. D. Curtis identified barred helices with a ring-shaped structure as a separate group of Φ-groups. In addition, he interpreted fusiform nebulae as spirals visible edge-on. 1888 A. Robertselliptic structureless fusiforms 1918 G. 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 highly flattened to almost circular) without distinctive features with a uniform decrease in brightness from the center to the periphery. They are designated by the letter E and a number, which is an index of the oblateness of the galaxy. So, a round galaxy will be designated E0, and a galaxy in which one of the semi-major axes is twice as large as the other will be designated E5. Elliptical galaxies have a smooth elliptical shape (from highly oblate to almost circular) without distinctive features with a uniform decrease in brightness from the center to the periphery. They are designated by the letter E and a number, which is an index of the oblateness of the galaxy. So, a round galaxy will be designated E0, and a galaxy in which one of the semi-major axes is twice as large as the other will be designated 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 condensation called a bulge, and an extensive spherical halo. Bright spiral arms are formed in the plane of the disk, 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 in the Russian literature are often called barred or crossed galaxies. In normal spirals, the spiral arms extend tangentially from a central bright core and extend throughout 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, spiral arms extend at right angles from the ends of the bar. Among them, there are also galaxies with the number of branches not equal to two, but, for the most part, crossed galaxies have two spiral branches. The symbols a, b, or c are added depending on whether the spiral arms are tightly coiled or ragged, or on the ratio of core to bulge sizes. Thus, Sa galaxies are characterized by a large bulge and a tightly twisted regular structure, while Sc galaxies are characterized by a small bulge and a ragged spiral structure. The Sb subclass includes galaxies that, for some reason, cannot be classified into one of the extreme subclasses: Sa or Sc. Thus, the M81 galaxy has a large bulge and a ragged spiral structure. Spiral galaxies consist of a flattened disk of stars and gas, at the center of which is a spherical condensation called a bulge, and an extensive spherical halo. Bright spiral arms are formed in the plane of the disk, 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 in the Russian literature are often called barred or crossed galaxies. In normal spirals, the spiral arms extend tangentially from a central bright core and extend throughout one turn. The number of branches can be different: 1, 2, 3,... but most often there are galaxies with only two branches. In crossed galaxies, spiral arms extend at right angles from the ends of the bar. Among them, there are also galaxies with the number of branches not equal to two, but, for the most part, crossed galaxies have two spiral branches. The symbols a, b, or c are added depending on whether the spiral arms are tightly coiled or ragged, or on the ratio of core to bulge sizes. Thus, Sa galaxies are characterized by a large bulge and a tightly twisted regular structure, while Sc galaxies are characterized by a small bulge and a ragged spiral structure. The Sb subclass includes galaxies that, for some reason, cannot be classified into one of the extreme subclasses: Sa or Sc. Thus, the M81 galaxy has a large bulge and a ragged spiral structure. Spiral galaxiesbaljamhalo bar Spiral galaxiesbaljamhalo bar




Irregular or irregular galaxies Irregular or irregular galaxies are galaxies lacking both rotational symmetry and a significant core. A typical representative of irregular galaxies are the Magellanic Clouds. There was even the term “Magellan nebulae.” Irregular galaxies come in a variety of shapes, are typically small in size, and contain an abundance of gas, dust, and young stars. They are designated I. Due to the fact that the shape of irregular galaxies is not firmly defined, how irregular galaxies are often classified as peculiar galaxies. Irregular or irregular galaxies are galaxies lacking both rotational symmetry and a significant core. A typical representative of irregular galaxies are the Magellanic Clouds. There was even the term “Magellan nebulae.” Irregular galaxies come in a variety of shapes, are typically small in size, and contain an abundance of gas, dust, and young stars. They are designated I. Due to the fact that the shape of irregular galaxies is not firmly defined, how irregular galaxies are often classified as peculiar 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) that have spent or lost their interstellar matter (like ellipticals). In cases where the galaxy faces the observer, it is often difficult to clearly distinguish between lenticular and elliptical galaxies due to the featurelessness of the spiral arms of the lenticular galaxy. Lenticular galaxies are disk galaxies (like spiral galaxies) that have spent or lost their interstellar matter (like ellipticals). In cases where the galaxy faces the observer, it is often difficult to clearly distinguish between lenticular and elliptical galaxies due to the featurelessness of the spiral arms of the lenticular galaxy. disk galaxies and interstellar matter disk galaxies and interstellar matter NGC 5866




A black hole is a region in space-time whose gravitational attraction is so strong 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. space-time gravitational attraction at the speed of light quanta of light space-time gravitational attraction at the speed of light quanta of light The boundary of this region is called the event horizon, and its characteristic size is 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 is, from which their existence follows. In modern physics, the standard theory of gravity, best confirmed experimentally, is the general theory of relativity (GTR), 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, first of all, in the context of general relativity, although, strictly speaking, this theory is not experimentally confirmed for conditions corresponding to the region of space-time in the immediate vicinity of black holes of stellar masses (however, it is well confirmed in conditions corresponding to supermassive black holes). Therefore, statements about direct evidence of the existence of black holes, including in this article below, strictly speaking, should be understood in the sense of confirmation of the existence of astronomical objects that are so dense and massive, as well as having 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 is, from which their existence follows. In modern physics, the standard theory of gravity, best confirmed experimentally, is the general theory of relativity (GTR), 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 below). : Alternative theories of gravity). Therefore, observational data are analyzed and interpreted, first of all, in the context of general relativity, although, strictly speaking, this theory is not experimentally confirmed for conditions corresponding to the region of space-time in the immediate vicinity of black holes of stellar masses (however, it is well confirmed in conditions corresponding to supermassive black holes). Therefore, statements about direct evidence of the existence of black holes, including in this article below, strictly speaking, should be understood in the sense of confirmation of the existence of astronomical objects that are so dense and massive, as well as having some other observable properties, that they can be interpreted as black holes general theory of relativity.event horizongravitational radiusSchwarzschild radius theory of gravitygeneral theory of relativity Alternative theories of gravityevent horizongravitational radiusSchwarzschild radius theory of gravitygeneral theory of relativity Alternative theories of gravity




A magnetar or magnetar is a neutron star that has an exceptionally strong magnetic field (up to 1011 Tesla). The theoretical existence of magnetars was predicted in 1992, and the first evidence of their real existence was obtained in 1998 when a powerful burst of gamma-ray and X-ray radiation was observed from the SGR source in the constellation Aquila. The lifetime of magnetars is short, it is about years. Magnetars are a little-studied type of neutron star due to the fact that few are close enough to Earth. Magnetars are about 20 km in diameter, but most have masses greater than 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 several rotations around their axis per second. The life cycle of a magnetar is quite short. Their strong magnetic fields disappear after about years, after which their activity and emission of X-rays cease. According to one assumption, 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 that has an exceptionally strong magnetic field (up to 1011 Tesla). The theoretical existence of magnetars was predicted in 1992, and the first evidence of their real existence was obtained in 1998 when a powerful burst of gamma-ray and X-ray radiation was observed from the SGR source in the constellation Aquila. The lifetime of magnetars is short, it is about years. Magnetars are a little-studied type of neutron star due to the fact that few are close enough to Earth. Magnetars are about 20 km in diameter, but most have masses greater than 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 several rotations around their axis per second. The life cycle of a magnetar is quite short. Their strong magnetic fields disappear after about years, after which their activity and emission of X-rays cease. According to one assumption, 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. neutron star magnetic field T19921998 gamma-ray radiation SGR Eagle neutron stars EarthSunour galaxyneutron star magnetic field T19921998 gamma-ray radiationSGR Eagle neutron stars EarthSunour galaxy Shocks formed on the surface of the magnetar cause huge fluctuations in the stars e, a Also, the magnetic field fluctuations that accompany them often lead to huge bursts of gamma radiation, which were recorded on Earth in 1979, 1998 and 2004. The magnetic field of a neutron star is a million million times greater than the magnetic field of the Earth. The tremors formed on the surface of the magnetar cause huge fluctuations in the star, and the magnetic field fluctuations that accompany them often lead to huge bursts of gamma radiation that have been recorded on Earth in 1979, 1998 and 2004. The magnetic field of a neutron star is a million million times greater than the Earth's magnetic field.
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 inclined to the rotation axis, which causes modulation of the radiation arriving at Earth. The first pulsar was discovered in June 1967 by Jocelyn Bell, a graduate student of E. Hewish, at the Meridian Radio Telescope of the Mallard Radio Astronomy Observatory, University of Cambridge, 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 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 inclined to the rotation axis, which causes modulation of the radiation arriving at Earth. The first pulsar was discovered in June 1967 by Jocelyn Bell, a graduate student of E. Hewish, using the Meridian Radio Telescope of the Mallard Radio Astronomy Observatory, University of Cambridge, 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 are PSR B or PSR J cosmic radio-radio pulsar optical optical pulsar x-ray x-ray pulsar gamma-gamma pulsar Earth periodic pulses astrophysical neutron stars magnetic fields rotational modulation 1967 Jocelyn Bella graduate student E. Huish radio telescope Mallard Radio Astronomy Observatory Cambridge University wavelength 1974 Nobel Prize PSR B space radio-radio pulsar optical optical pulsar x-ray x-ray pulsar gamma-gamma pulsar Earth periodic pulses astrophysical neutron stars magnetic fields rotation modulation 1967 Jocelyn Bella graduate student E. Hewish radio telescope Mallard Radio Astronomy Observatory, University of Cambridge wavelength 1974 Nobel Prize PSR B The observation results were kept secret for several months, and the first discovered pulsar was given the name LGM-1 (short for Little Green Men). This name was associated with the assumption that these strictly periodic pulses of radio emission are of artificial origin. However, a Doppler frequency shift (typical of a source orbiting a star) was not detected. In addition, Huish's group found 3 more sources of similar signals. After this, the hypothesis about signals from an extraterrestrial civilization disappeared, and in February 1968, a report appeared in the journal Nature about the discovery of rapidly changing extraterrestrial radio sources of an unknown nature with a highly stable frequency. The observation results were kept secret for several months, and the first discovered pulsar was given the name LGM-1 (short for Little Green Men). This name was associated with the assumption that these strictly periodic pulses of radio emission are of artificial origin. However, a Doppler frequency shift (typical of a source orbiting a star) was not detected. In addition, Huish's group found 3 more sources of similar signals. After this, the hypothesis about signals from an extraterrestrial civilization disappeared, and in February 1968, a message appeared in the journal Nature about the discovery of rapidly changing extraterrestrial radio sources of an unknown nature with a highly stable frequency. little green men Doppler shift 1968 Nature little green men Doppler shift 1968 Nature The message caused a scientific sensation. By the end of 1968, various observatories around the world had discovered another 58 objects called pulsars; the number of publications devoted to them in the first years after the discovery amounted to several hundred. Astrophysicists soon came to a general consensus that a pulsar, or more precisely a radio pulsar, was a neutron star. It emits narrowly directed streams of radio emission, and as a result of the rotation of the neutron star, the stream enters the field of view of an external observer at regular intervals, thus forming pulsar pulses. The message caused a scientific sensation. By the end of 1968, various observatories around the world had discovered another 58 objects called pulsars; the number of publications devoted to them in the first years after the discovery amounted to several hundred. Astrophysicists soon came to a general consensus that a pulsar, or more precisely a radio pulsar, was a neutron star. It emits narrowly directed streams of radio emission, and as a result of the rotation of the neutron star, the stream enters the field of view of an external observer at regular intervals, thus forming pulsar pulses. The closest of them are located at a distance of about 0.12 kpc (about 390 light years) from the Sun. As of 2008, about 1,790 radio pulsars are already known (according to the ATNF catalogue). The closest 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 emit due to the accretion of matter from a neighboring star, which fills its Roche lobe and, under the influence of the pulsar, gradually turns into a white dwarf. As a result, the mass of the pulsar slowly grows, its moment of inertia and rotation frequency increase, while radio pulsars, on the contrary, slow down over time. An ordinary pulsar rotates in a time 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 were discovered, called X-ray pulsars. 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 emit due to the accretion of matter from a neighboring star, which fills its Roche lobe and, under the influence of the pulsar, gradually turns into a white dwarf. As a result, the mass of the pulsar slowly grows, its moment of inertia and rotation frequency increase, while radio pulsars, on the contrary, slow down over time. An ordinary pulsar rotates in a time ranging from a few seconds to a few tenths of a second, while an X-ray pulsar rotates hundreds of times per second. X-ray pulsars accretion Rocham cavity Moment of inertia rotation frequency X-ray pulsars accretion Rocham cavity Moment of inertia rotation frequency

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