Our Milky Way galaxy is what it is. The location of the sun in the milky way galaxy
Divided into social groups, our Milky Way galaxy will belong to the robust "middle class". So, it belongs to the most common type of galaxies, but at the same time it is not average in size or mass. There are more galaxies smaller than the Milky Way than larger ones. Our "star island" also has at least 14 satellites - other dwarf galaxies. They are doomed to circle around the Milky Way until they are absorbed by it, or fly away from the intergalactic collision. Well, so far this is the only place where life probably exists - that is, you and me.
But the Milky Way remains the most mysterious galaxy in the Universe: being on the very edge of the "star island", we see only a part of its billions of stars. And the galaxies are completely invisible - it is covered with dense arms of stars, gas and dust. The facts and secrets of the Milky Way will be discussed today.
We are used to the fact that the Milky Way is a cluster of stars in the sky, along which our ancestors were guided. But in fact, this is more than ordinary night lights - this is a huge and unexplored world.
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The structure of the Milky Way galaxy
It sometimes seems incredible how dynamically space science is developing. It is difficult to imagine, but 4 centuries ago, even the statement that the Earth revolves around the Sun caused condemnation and rejection in society. Judgments about these and other cosmic phenomena could lead not only to imprisonment, but also to death. Fortunately, times have changed, and the study of the Universe has long been a priority in science. Especially important in this regard are the studies of the Milky Way - a galaxy of thousands of stars, one of which is our Sun.
Studying the structure of the galaxy and its development helps to answer the main questions that have been of interest to humanity since the beginning of time. These are such sacramental mysteries about how the solar system originated, what factors contributed to the emergence of life on Earth, and whether life exists on other planets.
The fact that the Milky Way galaxy is a huge arm of an infinite star system became known relatively recently - just over half a century ago. The structure of our galaxy is similar to a colossal spiral in which our solar system is located somewhere on the periphery. From the side, it looks like a giant magnifying glass with a bilaterally convex center with a crown.
What is the Milky Way Galaxy? These are billions of stars and planets, which are interconnected by some kind of algorithm for the structure of the Universe. In addition to stars, the Milky Way contains interstellar gas, galactic dust, and globular clusters.
The disk of our galaxy constantly revolves around the central part, which is located in the constellation Sagittarius. In order for the Milky Way to make one complete revolution around its axis, it takes 220 million years (and this despite the fact that the rotation occurs at a speed of 250 kilometers per second). Thus, all the stars of our galaxy have been moving in a single rush for many years and our solar system with them. What makes them revolve around the core at a truly breakneck speed? Scientists suggest that both the colossal weight of the center and an almost incomprehensible amount of energy (it can exceed the size of 150 million suns).
Why don't we see either spirals or a giant core, why don't we feel this universal rotation? The fact is that we are in the sleeve of this spiral Universe, and the frantic rhythm of its life is perceived by us on a daily basis.
Of course, there will be skeptics who will deny such a structure of our galaxy, citing the fact that there is no exact picture of the galactic disk (and indeed it cannot be). The fact is that the Universe is by no means limited to the Milky Way galaxy and in space there are a bunch of the same formations. They are very similar to our galaxy in structure - these are the same disks with a center around which the stars revolve. That is, beyond our Milky Way, there are billions of systems similar to the Sun.
The nearest galaxy is the Large and Small Magellanic Clouds. They can be seen almost with the naked eye in the Southern Hemisphere. These two small luminous points, similar to clouds, were first described by the great traveler, from whose name the names of space objects originated. The diameter of the Magellanic Clouds is relatively small - less than half the Milky Way. And there are much fewer stellar systems in the Clouds.
The Andromeda Nebula is different. This is another spiral-shaped galaxy that is very similar in appearance and composition to the Milky Way. Its dimensions are striking - by the most conservative estimates, it is three times larger than our Path. And the number of such gigantic galaxies in the Universe has long exceeded one billion - this is only what we can see at this stage in the development of astronomy. It is quite possible that a few years later we will become aware of another, previously unnoticed galaxy.
Milky Way characteristics
As stated earlier, the Milky Way is a cluster of millions of stars with their own solar-like systems. How many planets exist in our galaxy is a real mystery, the solution of which has been struggling for more than one generation of astronomers. Although, to be honest, they are more worried about another question - what is the probability that there is a star system within our galaxy, the characteristics of which are similar to ours? Scientists are especially interested in stars that have similar rotational speed and technical characteristics to the Sun, and also occupy our place on the scale of the galaxy. This is because on planets with the approximate age and conditions of our Earth, there is a high probability of the presence of intelligent life.
Unfortunately, attempts by scientists to find anything similar to the solar system in the arms of the galaxy have not been crowned with success. And this is perhaps for the best. It remains to be seen who or what may be waiting for us in an unfamiliar constellation.
Black Hole - Planet Killer or Galaxy Creator?
At the end of its life, the star sheds its gaseous envelope, and its core begins to shrink very quickly. Provided that the mass of the star is large enough (1.4 times the Sun), a Black Hole is formed in its place. It is an object with a critical speed that no object can overcome. As a result, what falls into the Black Hole disappears into it forever. That is, in fact, this space element is a one-way ticket. Any object that comes close enough to the Hole will disappear forever.
Sad, isn't it? But there is also a positive moment in the Black Hole - thanks to it, various space objects are gradually pulled up and new galaxies are formed. It turns out that the core of each of the known star systems is the Black Hole.
Why is our galaxy called the Milky Way?
Each nation has its own legends about how the visible part of the Milky Way was formed. For example, the ancient Greeks believed that it was formed from the spilled milk of the goddess Hera. But in Mesopotamia there was a legend about a river made from the same drink. Thus, many peoples associated a large cluster of stars with milk, thanks to which our galaxy got its name.
How many stars are there in the Milky Way?
It is rather difficult to accurately calculate the number of stars in our galaxy, because they say that there are more than 200 billion of them. As you understand, it is very problematic to study them all with the modern development of science, therefore scientists turn their attention only to the most interesting representatives of these space objects. Take at least the alpha star from the constellation Karina (Carina). This is a supergiant star that has long held the title of the biggest and brightest.
The Sun is also one of the stars of the Milky Way, which, however, does not have any outstanding characteristics. This is a small yellow dwarf, which became famous only for the fact that for millions of years it has been the source of life on our planet.
Astronomers from all over the world have long compiled lists of stars that are distinguished by their outstanding mass or brightness. But this does not mean at all that each of them received its own name. Usually, the names of the stars consist of letters, numbers and the names of the constellations to which they refer. So, the brightest star in the Milky Way is designated on astronomical maps as R136a1, and R136 is nothing more than the name of the nebula from which it comes. This star has indescribable power that cannot be compared with anything. R136a1 shines 8.7 million times brighter than our Sun, and therefore it is very difficult to imagine at least some kind of life near it.
But the colossal power does not at all mean that the R136a1 has impressive dimensions. The list of the largest stars is headed by UY Shield, which is 1.7 thousand times the size of our star. That is, if instead of the Sun there was this star, then it would take all the place from the center of our system to Saturn.
Although these stars would not be as large and powerful, the total number of their masses does not match the mass of the Black Hole, which is located in the center of the galaxy. It is her colossal energy that holds the Milky Way, forcing it to move in a specific order.
Our galaxy is not just a scattering of stars in the night sky. This is a huge system that consists of hundreds of billions of stars, including our Sun.
Our solar system, all the stars that are visible in the night sky, and many others make up the system - The galaxy... There are millions of such systems (galaxies) in outer space. Our Galaxy, or the Milky Way Galaxy, is a spiral galaxy with a bar of bright stars.
What does it mean? A bar of bright stars emerges from the center of the Galaxy and crosses the Galaxy in the middle. In such galaxies, the spiral arms start at the ends of the barriers, whereas in ordinary spiral galaxies they exit directly from the core. Look at the picture "Computer model of the Milky Way Galaxy".
If you are interested in why our Galaxy was named "Milky Way", then listen to the ancient Greek legend.
Zeus, the god of the sky, thunder and lightning, who knows the whole world, decided to make his son Hercules, born of a mortal woman, immortal. To do this, he planted the baby in his sleeping wife Hera so that Hercules would drink divine milk. Hera, waking up, saw that she was not feeding her child, and pushed him away from her. A stream of milk spraying from the goddess's chest turned into the Milky Way.
Of course, this is just a legend, but the Milky Way is visible in the sky as a hazy streak of light that stretches across the entire sky - an artistic image created by ancient people is fully justified.
When we talk about our Galaxy, we capitalize this word. When it comes to other galaxies, we write with a capital letter.
The structure of our Galaxy
The diameter of the Galaxy is about 100,000 light years (a unit of length equal to the distance traveled by light in one year, a light year is equal to 9,460,730,472,580,800 meters).
The galaxy contains between 200 and 400 billion stars. Scientists believe that most of the mass of the Galaxy is contained not in stars and interstellar gas, but in non-luminous halo from dark matter. Halo Is an invisible component of the galaxy, spherical in shape and extending beyond its visible part. Mainly composed of rarefied hot gas, stars and dark matter, it makes up the bulk of the Galaxy. Dark matter Is a form of matter that does not emit or interact with electromagnetic radiation. This property of this form of matter makes its direct observation impossible.
In the middle of the Galaxy there is a thickening called bulge... If we could look at our Galaxy from the side, we would see this thickening in its center, similar to two yolks in a frying pan, if they are folded with their lower bases - look at the picture.
There is a strong concentration of stars in the central part of the Galaxy. The galactic bar is believed to be about 27,000 light years long. This bar passes through the center of the Galaxy at an angle of ~ 44º to the line between our Sun and the center of the Galaxy. It consists mainly of red stars, which are considered to be very old. The bridge is surrounded by a ring. This ring contains most of the galactic molecular hydrogen and is an active star-forming region in our galaxy. If observing from the Andromeda galaxy, then the galactic bar of the Milky Way would be a bright part of it.
All spiral galaxies, including ours, have spiral arms in the plane of the disk: two arms starting at the bar in the inner part of the Galaxy, and in the inner part there are a couple more arms. Then these arms transform into a four-arm structure observed in the neutral hydrogen line in the outer parts of the Galaxy.
Discovery of the Galaxy
At first it was discovered theoretically: astronomers have already learned that the Moon revolves around the Earth, the satellites of the giant planets form systems. The earth and the rest of the planets revolve around the sun. Then a natural question arose: is not the Sun also included in an even larger system? The first systematic study of this issue was carried out in the 18th century. english astronomer William Herschel... In accordance with his observations, he guessed that all the stars we observe form a giant star system, which is flattened towards the galactic equator. For a long time it was believed that all objects in the Universe are parts of our Galaxy, although even Kant suggested that some nebulae may be other galaxies like the Milky Way. This hypothesis of Kant was finally proved only in the 1920s, when Edwin Hubble measured the distance to some spiral nebulae and showed that, due to their distance, they could not be part of the Galaxy.
Where are we in the Galaxy?
Our solar system is located closer to the edge of the galactic disk. Together with other stars, the Sun revolves around the center of the Galaxy at a speed of 220-240 km / s, making one revolution every 200 million years. Thus, for the entire time of its existence, the Earth has flown around the center of the Galaxy no more than 30 times.
The spiral arms of the Galaxy rotate at a constant angular velocity, like spokes in wheels, and the movement of stars occurs with a different pattern, therefore, almost all the stars of the disk sometimes fall inside the spiral arms, sometimes fall out of them. The only place where the speeds of stars and spiral arms coincide is the so-called corotation circle, and it is on this circle that the Sun is located.
For us, earthlings, this is very important, since violent processes occur in the spiral arms, forming powerful radiation, destructive for all living things. No atmosphere could protect against him. But our planet exists in a relatively quiet place in the Galaxy and has not been affected by these cosmic cataclysms. That is why life on Earth was able to be born and survive - the Creator chose a calm place for our cradle of the Earth.
Our Galaxy is included in Local group galactic- a gravitationally bound group of galaxies, including the Milky Way galaxy, the Andromeda galaxy (M31) and the Triangle galaxy (M33), you can see this group in the picture.
Planet Earth, the Solar System, billions of other stars and celestial bodies - all this is our Milky Way galaxy - a huge intergalactic formation, where everything obeys the laws of gravity. The data on what the true dimensions of the galaxy are are only approximate. And the most interesting thing is that there are hundreds of such formations, larger or smaller, in the Universe, maybe even thousands.
The Milky Way Galaxy and its Surroundings
All celestial bodies, including the planets of the Milky Way, satellites, asteroids, comets and stars, are constantly in motion. Born in the cosmic vortex of the Big Bang, all these objects are on the way of their development. Some are older, others are clearly younger.
The gravitational formation rotates around the center, while individual parts of the galaxy rotate at different speeds. If in the center the rotation speed of the galactic disk is rather moderate, then at the periphery this parameter reaches values of 200-250 km / s. In one of these areas, closer to the center of the galactic disk, the Sun is located. The distance from it to the center of the galaxy is 25-28 thousand light years. The sun and the solar system complete a revolution around the central axis of the gravitational formation in 225-250 million years. Accordingly, in the entire history of its existence, the solar system has flown around the center only 30 times.
The place of the galaxy in the universe
One notable feature should be noted. The position of the Sun and, accordingly, the planet Earth is very convenient. The process of compaction is constantly taking place in the galactic disk. This mechanism is caused by the discrepancy between the speed of rotation of the spiral branches and the movement of stars, which move within the galactic disk according to their own laws. During compaction, violent processes occur, accompanied by powerful ultraviolet radiation. The Sun and the Earth are comfortably located in a corotation circle, where such violent activity is absent: between two spiral branches at the border of the arms of the Milky Way - Sagittarius and Perseus. This explains the calmness in which we have been for such a long time. For more than 4.5 billion years we have not been affected by cosmic cataclysms.
The structure of the Milky Way galaxy
The galactic disk is not uniform in composition. Like other spiral gravitational systems, the Milky Way has three distinct regions:
- a core formed by a dense star cluster containing a billion stars of different ages;
- the galactic disk itself, formed from clusters of stars, stellar gas and dust;
- corona, spherical halo - an area in which globular clusters, dwarf galaxies, individual groups of stars, cosmic dust and gas are located.
Young stars gathered in clusters are located near the plane of the galactic disk. The density of star clusters in the center of the disk is higher. Near the center, the density is 10,000 stars per cubic parsec. In the area where the solar system is located, the density of stars is already 1-2 luminaries per 16 cubic parsecs. As a rule, the age of these celestial bodies is no more than a few billion years.
Interstellar gas also concentrates around the plane of the disk, subject to centrifugal forces. Despite the constant rotation speed of the spiral branches, the interstellar gas is unevenly distributed, forming large and small zones of clouds, nebulae. However, the main galactic building material is dark matter. Its mass prevails over the total mass of all celestial bodies that make up the Milky Way galaxy.
If the structure of the galaxy is clear enough and transparent on the diagram, then in reality it is almost impossible to consider the central regions of the galactic disk. Gas and dust clouds and clusters of stellar gas hide from our view the light from the center of the Milky Way, in which lives a real cosmic monster - a supermassive black hole. The mass of this supergiant is approximately 4.3 million M☉. A smaller black hole is located next to the supergiant. This gloomy company is complemented by hundreds of dwarf black holes. Black holes in the Milky Way are not only eaters of stellar matter, but also perform the function of a maternity hospital, throwing huge bunches of protons, neutrons and electrons into space. It is from them that atomic hydrogen is formed - the main fuel of the star tribe.
Jumper - the bar is located in the area of the galactic nucleus. Its length is 27 thousand light years. Old stars, red giants, whose stellar matter feed on black holes, reign here. In this area, the main part of molecular hydrogen is concentrated, which is the main building material of the star formation process.
Geometrically, the structure of the galaxy looks simple enough. Each spiral arm, and there are four of them in the Milky Way, originates from a gas ring. The sleeves diverge at an angle of 20⁰. At the outer edges of the galactic disk, the main element is atomic hydrogen, which spreads from the center of the galaxy to the periphery. The thickness of the hydrogen layer on the outskirts of the Milky Way is much wider than in the center, while its density is extremely low. The discharging of the hydrogen layer is facilitated by the impact of dwarf galaxies that have been closely following with our galaxy for tens of billions of years.
Theoretical models of our galaxy
Even ancient astronomers tried to prove that the visible stripe in the sky is part of a huge stellar disk revolving around its center. This statement was facilitated by the ongoing mathematical calculations. It was possible to get an idea of our galaxy only thousands of years later, when instrumental methods of space exploration came to the aid of science. A breakthrough in the study of the nature of the Milky Way was the work of the Englishman William Herschel. In 1700, he was able to experimentally prove that our galaxy has the shape of a disk.
Already in our time, research has taken a different turn. Scientists relied on comparing the movement of stars, between which there were different distances. Using the parallax method, Jacob Kaptein was able to roughly determine the diameter of the galaxy, which, according to his calculations, is 60-70 thousand light years. Accordingly, the place of the Sun was determined. It turned out that it is located relatively far from the stormy center of the galaxy and at a decent distance from the periphery of the Milky Way.
The fundamental theory of the existence of galaxies is the theory of the American astrophysicist Edwin Hubble. He came up with the idea to classify all gravitational formations, dividing them into elliptical galaxies and spiral formations. The latter, spiral galaxies represent the most extensive group, which includes formations of various sizes. The largest recently discovered spiral galaxy is NGC 6872, with a diameter of more than 552,000 light years.
Expected future and projections
The Milky Way Galaxy appears to be a compact and ordered gravitational formation. Unlike its neighbors, our intergalactic home is pretty quiet. Black holes systematically affect the galactic disk, reducing it in size. This process has already been going on for tens of billions of years and how long it will continue is unknown. The only threat hanging over our galaxy comes from its nearest neighbor. The Andromeda Galaxy is rapidly approaching us. Scientists suggest that the collision of two gravitational systems could occur in 4.5 billion years.
Such a meeting-merger will mean the end of the world in which we are used to living. A smaller Milky Way will be swallowed up by a larger entity. Instead of two large spiral formations, a new elliptical galaxy will appear in the Universe. Until that time, our galaxy will be able to deal with its satellites. Two dwarf galaxies - the Large and Small Magellanic Clouds - will be swallowed up by the Milky Way in 4 billion years.
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Milky Way(or the Milky Way Galaxy) is a galaxy that contains the Earth, the Solar System and all the individual stars visible to the naked eye. Refers to barred spiral galaxies.
The Milky Way together with the Andromeda Galaxy, the Triangle Galaxy and more than 40 dwarf satellite galaxies - their own and Andromeda - form the Local Group of Galaxies, which is part of the Local Supercluster (Virgo Supercluster).
According to the latest scientific estimates, the distance from the Sun to the galactic center is 26,000 ± 1,400 light years, while, according to preliminary estimates, our star should be about 35,000 light years from the bar. It means that The sun is closer to the edge of the disk than to its center... Together with other stars, the Sun revolves around the center of the Galaxy at a speed of 220-240 km / s, making one revolution in about 200 million years. Thus, for the entire time of its existence, the Earth has flown around the center of the Galaxy no more than 30 times.
In the vicinity of the Sun, it is possible to track sections of two spiral arms, which are approximately 3 thousand light years distant from us. According to the constellations where these areas are observed, they were named the Sagittarius arm and the Perseus arm. The sun is located almost midway between these spiral branches. But relatively close to us (by galactic standards), in the constellation of Orion, there is another, not very clearly expressed arm - the Orion arm, which is considered an offshoot of one of the main spiral arms of the Galaxy.
The speed of rotation of the Sun around the center of the Galaxy almost coincides with the speed of the compaction wave that forms the spiral arm. Such a situation is atypical for the Galaxy as a whole: the spiral arms rotate at a constant angular velocity, like spokes in wheels, and the movement of stars occurs with a different pattern, therefore, almost the entire stellar population of the disk either falls into the spiral arms or falls out of them. The only place where the speeds of the stars and spiral arms coincide is the so-called corotation circle, and it is on this circle that the Sun is located.
For the Earth, this circumstance is extremely important, since violent processes occur in the spiral arms, forming powerful radiation, destructive for all living things. And no atmosphere could protect against him. But our planet exists in a relatively quiet place in the Galaxy and has not been affected by these cosmic cataclysms for hundreds of millions (or even billions) years. Perhaps that is why life on Earth was able to be born and survive.
Disk
It wasn't until the 1980s that astronomers suggested that the Milky Way was a barred spiral galaxy, not a normal spiral galaxy. This assumption was confirmed in 2005 by the Lyman Spitzer Space Telescope, which showed that the central bar of our galaxy is larger than previously thought.
Scientists estimate that the galactic disk, protruding in different directions in the region of the galactic center, has a diameter of about 100,000 light years. Compared to the halo, the disk rotates noticeably faster. Its rotation speed is not the same at different distances from the center. It rapidly increases from zero in the center to 200-240 km / s at a distance of 2 thousand light years from it, then decreases slightly, increases again to approximately the same value, and then remains almost constant. The study of the peculiarities of the disk rotation allowed us to estimate its mass; it turned out that it is 150 billion times greater than M☉.
Young stars and star clusters, whose age does not exceed several billion years, are concentrated near the plane of the disk. They form the so-called flat component. There are a lot of bright and hot stars among them. Gas in the disk of the Galaxy is also concentrated mainly near its plane. It is unevenly distributed, forming numerous gas clouds - from giant clouds of heterogeneous structure, over several thousand light years in length, to small clouds no more than a parsec in size.
Core
Galactic center of the Milky Way in the infrared range.
In the middle of the galaxy is a bulge called the bulge, which is about 8,000 parsecs across. The center of the galactic nucleus is located in the constellation Sagittarius (α = 265 °, δ = −29 °). The distance from the Sun to the center of the Galaxy is 8.5 kiloparsecs (2.62 · 1017 km, or 27,700 light years). In the center of the Galaxy, apparently, there is a supermassive black hole (Sagittarius A *) (about 4.3 million M☉) around which, presumably, a black hole with an average mass from 1000 to 10 000 M☉ and an orbital period of about 100 years and several thousand relatively small. Their combined gravitational action on neighboring stars makes the latter move along unusual trajectories. There is speculation that most galaxies have supermassive black holes in their cores.
The central regions of the Galaxy are characterized by a strong concentration of stars: in each cubic parsec near the center there are many thousands of them. The distances between the stars are tens and hundreds of times less than in the vicinity of the Sun. As in most other galaxies, the distribution of mass in the Milky Way is such that the orbital speed of most stars in the Galaxy does not depend to a large extent on their distance from the center. Further from the central bar to the outer circle, the usual speed of rotation of the stars is 210-240 km / s. Thus, such a velocity distribution, which is not observed in the solar system, where different orbits have significantly different orbital velocities, is one of the prerequisites for the existence of dark matter.
The galactic bar is believed to be about 27,000 light years long. This bar passes through the center of the galaxy at an angle of 44 ± 10 degrees to the line between our Sun and the center of the galaxy. It consists mainly of red stars, which are considered to be very old. The bulkhead is surrounded by a ring called the Five Kiloparsec Ring. This ring contains most of the galactic molecular hydrogen and is an active star-forming region in our galaxy. If observing from the Andromeda galaxy, then the galactic bar of the Milky Way would be a bright part of it.
In 2016, Japanese astrophysicists reported the discovery of a second giant black hole in the Galactic Center. This black hole is located 200 light years from the center of the Milky Way. The observed astronomical object with a cloud occupies an area of space with a diameter of 0.3 light years, and its mass is 100 thousand solar masses. The nature of this object has not yet been precisely established - is it a black hole or another object.
Galaxy Sleeves
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 a spherical crown is located around it. 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, which is 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 transform into a four-arm structure observed in the neutral hydrogen line in the outer parts of the Galaxy.
Halo
The vicinity of the Milky Way and its halo.
The galactic halo has a spherical shape, extending beyond the galaxy by 5-10 thousand light years, and a temperature of about 5 105 K. The galactic disk is surrounded by a spheroidal halo consisting of old stars and globular clusters, 90% of which are located at a distance of less than 100,000 light years from the center of the galaxy. Recently, however, several globular clusters have been found, such as Pal 4 and AM 1, located more than 200,000 light-years from the center of the galaxy. The center of symmetry of the Milky Way's halo coincides with the center of the galactic disk. The halo consists mainly of very old, dim, low-mass stars. They are found both singly and in the form of globular clusters, which can contain up to a million stars. The age of the population of the spherical component of the Galaxy exceeds 12 billion years, it is usually considered the age of the Galaxy itself.
While the galactic disk contains gas and dust, making it difficult for visible light to pass, the spheroid component does not. Active star formation occurs in the disk (especially in the spiral arms, which are zones of increased density). In the halo, star formation has ended. Open clusters are also found predominantly in the disk. It is believed that the bulk of our galaxy is dark matter, which forms a dark matter halo with a mass of about 600 - 3000 billion M☉. The dark matter halo is concentrated towards the center of the galaxy.
Stars and star clusters in the halo move around the center of the Galaxy in very elongated orbits. Since the rotation of individual stars is somewhat random (that is, the speeds of neighboring stars can have any directions), the halo as a whole rotates very slowly.
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