The cosmos that we are trying to study is a vast and boundless space in which there are tens, hundreds, thousands of trillions of stars united in certain groups. Our Earth does not live on its own. We are part of the solar system, which is a small particle and part of the Milky Way - a larger cosmic entity.
Our Earth, like other planets of the Milky Way, our star named the Sun, like other stars of the Milky Way, move in the Universe in a certain order and occupy the allotted places. Let's try to understand in more detail what is the structure of the Milky Way, and what are the main features of our galaxy?
Origin of the Milky Way
Our galaxy has its own history, like other areas of outer space, and is the product of a catastrophe on a universal scale. The main theory of the origin of the Universe that dominates the scientific community today is the Big Bang. A model that perfectly characterizes the theory big bang- nuclear chain reaction at the microscopic level. Initially, there was some kind of substance, which, due to certain reasons, in an instant set in motion and exploded. It is not worth talking about the conditions that led to the onset of the explosive reaction. This is far from our understanding. Now formed 15 billion years ago as a result of a cataclysm, the Universe is a huge, endless polygon.
The primary products of the explosion were at first accumulations and clouds of gas. Later, under the influence of gravitational forces and other physical processes, the formation of larger objects of a universal scale took place. Everything happened very quickly by cosmic standards, over billions of years. First there was the formation of stars, which formed clusters and later coalesced into galaxies, the exact number of which is unknown. In its composition, galactic matter is hydrogen and helium atoms in the company of other elements, which are the building material for the formation of stars and other space objects.
It is not possible to say exactly where in the Universe the Milky Way is located, since the center of the universe is not exactly known.
Due to the similarity of the processes that formed the Universe, our galaxy is very similar in its structure to many others. By its type, this is a typical spiral galaxy, a type of objects that is common in the Universe in a huge variety. In terms of size, the galaxy is in the golden mean - not small and not huge. Our galaxy has many more smaller neighbors in a stellar home than those who are colossal in size.
The age of all galaxies that exist in outer space is the same. Our galaxy is almost the same age as the Universe and has an age of 14.5 billion years. During this vast period of time, the structure of the Milky Way has repeatedly changed, and this is happening today, only imperceptibly, in comparison with the pace of earthly life.
The history with the name of our galaxy is curious. Scientists believe that the name Milky Way is legendary. This is an attempt to connect the location of the stars in our sky with the ancient Greek myth about the father of the gods Kronos, who devoured his own children. The last child, who faced the same sad fate, turned out to be thin and was given to the nurse for fattening. During feeding, splashes of milk fell into the sky, thereby creating a milk path. Subsequently, scientists and astronomers of all times and peoples agreed that our galaxy is really very similar to a milky road.
The Milky Way is currently in the middle of its development cycle. In other words, cosmic gas and matter for the formation of new stars are coming to an end. The existing stars are still quite young. As in the story with the Sun, which may turn into a Red Giant in 6-7 billion years, our descendants will observe the transformation of other stars and the entire galaxy as a whole into the red sequence.
Our galaxy may also cease to exist as a result of another universal cataclysm. Research topics recent years they are guided by the forthcoming meeting of the Milky Way with our closest neighbor, the Andromeda galaxy, in the distant future. It is likely that the Milky Way, after meeting with the Andromeda galaxy, will break up into several small galaxies. In any case, this will be the reason for the emergence of new stars and the reconstruction of the space closest to us. It remains only to guess what is the fate of the Universe and our galaxy in the distant future.
Astrophysical parameters of the Milky Way
In order to imagine what the Milky Way looks like on the scale of space, it is enough to look at the Universe itself and compare its individual parts. Our galaxy is part of a subgroup, which in turn is part of the Local Group, a larger entity. Here our space metropolis is adjacent to the Andromeda and Triangulum galaxies. Surrounding the trinity are more than 40 small galaxies. The local group is already part of an even larger formation and is part of the Virgo supercluster. Some argue that these are only rough guesses about where our galaxy is. The scale of formations is so huge that it is almost impossible to imagine all this. Today we know the distance to the nearest neighboring galaxies. Other deep sky objects are out of sight. Only theoretically and mathematically their existence is allowed.
The location of the galaxy became known only thanks to approximate calculations that determined the distance to the nearest neighbors. The satellites of the Milky Way are dwarf galaxies - the Small and Large Magellanic Clouds. In total, according to scientists, there are up to 14 satellite galaxies that make up the escort of the universal chariot called the Milky Way.
As for the visible world, today there is enough information about what our galaxy looks like. The existing model, and with it the map of the Milky Way, was compiled on the basis of mathematical calculations obtained from astrophysical observations. Each cosmic body or fragment of the galaxy takes its place. It's like the universe, only on a smaller scale. The astrophysical parameters of our space metropolis are interesting, and they are impressive.
Our galaxy is a spiral-type galaxy with a bar, which on star maps is denoted by the index SBbc. The diameter of the galactic disk of the Milky Way is about 50-90 thousand light years or 30 thousand parsecs. For comparison, the radius of the Andromeda galaxy is 110 thousand light years on the scale of the universe. One can only imagine how much larger the Milky Way is our neighbor. The dimensions of the dwarf galaxies closest to the Milky Way are ten times smaller than the parameters of our galaxy. Magellanic clouds have a diameter of only 7-10 thousand light years. In this huge stellar cycle, there are about 200-400 billion stars. These stars are collected in clusters and nebulae. A significant part of it is the arms of the Milky Way, in one of which our solar system is located.
Everything else is dark matter, clouds of cosmic gas and bubbles that fill interstellar space. The closer to the center of the galaxy, the more stars, the tighter space becomes. Our Sun is located in a region of space, consisting of smaller space objects located at a considerable distance from each other.
The mass of the Milky Way is 6x1042 kg, which is trillions of times the mass of our Sun. Almost all the stars that inhabit our stellar country are located in the plane of one disk, the thickness of which, according to various estimates, is 1000 light years. It is not possible to know the exact mass of our galaxy, since most of the visible spectrum of stars is hidden from us by the arms of the Milky Way. In addition, the mass of dark matter that occupies vast interstellar spaces is unknown.
The distance from the Sun to the center of our galaxy is 27 thousand light years. Being on the relative periphery, the Sun is rapidly moving around the center of the galaxy, making a complete revolution in 240 million years.
The center of the galaxy is 1000 parsecs in diameter and consists of a core with an interesting sequence. The center of the core has the shape of a bulge, in which the largest stars and a cluster of hot gases are concentrated. It is this region that releases a huge amount of energy, which in aggregate is more than the billions of stars that make up the galaxy radiate. This part of the core is the most active and brightest part of the galaxy. Along the edges of the core there is a jumper, which is the beginning of the arms of our galaxy. Such a bridge arises as a result of the colossal force of gravity caused by the rapid rotation of the galaxy itself.
Considering the central part of the galaxy, the following fact looks paradoxical. Scientists for a long time could not understand what is at the center of the Milky Way. Turns out it's in the middle star country called the Milky Way, a supermassive black hole with a diameter of about 140 km settled down. It is there that most of the energy released by the core of the galaxy goes, it is in this bottomless abyss that the stars dissolve and die. The presence of a black hole at the center of the Milky Way indicates that all processes of formation in the Universe must someday end. Matter will turn into antimatter and everything will repeat again. How this monster will behave in millions and billions of years, the black abyss is silent, which indicates that the processes of absorption of matter are only gaining momentum.
Two main arms of the galaxy extend from the center - the Shield of the Centaur and Perseus. These structural formations were named after the constellations located in the sky. In addition to the main arms, the galaxy is surrounded by 5 more small arms.
Near and distant future
The arms, born from the core of the Milky Way, spiral outward, filling outer space with stars and cosmic material. An analogy with cosmic bodies that revolve around the Sun in our star system is appropriate here. A huge mass of stars, large and small, clusters and nebulae, cosmic objects of various sizes and nature, spins on a giant carousel. All of them create a wonderful picture of the starry sky, which a person has been looking at for more than one thousand years. When studying our galaxy, you should know that the stars in the galaxy live according to their own laws, being in one of the arms of the galaxy today, tomorrow they will start their journey in the other direction, leaving one arm and flying into another.
Earth in the Milky Way galaxy is far from the only planet fit for life. This is just a particle of dust, the size of an atom, which is lost in a huge starry world our galaxy. There can be a huge number of such planets similar to Earth in the galaxy. It is enough to imagine the number of stars that somehow have their own stellar planetary systems. Other life may be far away, at the very edge of the galaxy, tens of thousands of light years away, or, conversely, be present in neighboring regions that are hidden from us by the arms of the Milky Way.
The cosmos that we are trying to study is a vast and boundless space in which there are tens, hundreds, thousands of trillions of stars united in certain groups. Our Earth does not live on its own. We are part of the solar system, which is a small particle and part of the Milky Way - a larger cosmic entity.
Our Earth, like other planets of the Milky Way, our star named the Sun, like other stars of the Milky Way, move in the Universe in a certain order and occupy the allotted places. Let's try to understand in more detail what is the structure of the Milky Way, and what are the main features of our galaxy?
Origin of the Milky Way
Our galaxy has its own history, like other areas of outer space, and is the product of a catastrophe on a universal scale. The main theory of the origin of the Universe that dominates the scientific community today is the Big Bang. The model that perfectly characterizes the Big Bang theory is the nuclear chain reaction at the microscopic level. Initially, there was some kind of substance, which, due to certain reasons, in an instant set in motion and exploded. It is not worth talking about the conditions that led to the onset of the explosive reaction. This is far from our understanding. Now formed 15 billion years ago as a result of a cataclysm, the Universe is a huge, endless polygon.
The primary products of the explosion were at first accumulations and clouds of gas. Later, under the influence of gravitational forces and other physical processes, the formation of larger objects of a universal scale took place. Everything happened very quickly by cosmic standards, over billions of years. First there was the formation of stars, which formed clusters and later coalesced into galaxies, the exact number of which is unknown. In its composition, galactic matter is hydrogen and helium atoms in the company of other elements, which are the building material for the formation of stars and other space objects.
It is not possible to say exactly where in the Universe the Milky Way is located, since the center of the universe is not exactly known.
Due to the similarity of the processes that formed the Universe, our galaxy is very similar in its structure to many others. By its type, this is a typical spiral galaxy, a type of objects that is common in the Universe in a huge variety. In terms of size, the galaxy is in the golden mean - not small and not huge. Our galaxy has many more smaller neighbors in a stellar home than those who are colossal in size.
The age of all galaxies that exist in outer space is the same. Our galaxy is almost the same age as the Universe and has an age of 14.5 billion years. During this vast period of time, the structure of the Milky Way has repeatedly changed, and this is happening today, only imperceptibly, in comparison with the pace of earthly life.
The history with the name of our galaxy is curious. Scientists believe that the name Milky Way is legendary. This is an attempt to connect the location of the stars in our sky with the ancient Greek myth about the father of the gods Kronos, who devoured his own children. The last child, who faced the same sad fate, turned out to be thin and was given to the nurse for fattening. During feeding, splashes of milk fell into the sky, thereby creating a milk path. Subsequently, scientists and astronomers of all times and peoples agreed that our galaxy is really very similar to a milky road.
The Milky Way is currently in the middle of its development cycle. In other words, cosmic gas and matter for the formation of new stars are coming to an end. The existing stars are still quite young. As in the story with the Sun, which may turn into a Red Giant in 6-7 billion years, our descendants will observe the transformation of other stars and the entire galaxy as a whole into the red sequence.
Our galaxy may also cease to exist as a result of another universal cataclysm. Topics of research in recent years are focused on the forthcoming meeting of the Milky Way with our nearest neighbor, the Andromeda galaxy. It is likely that the Milky Way, after meeting with the Andromeda galaxy, will break up into several small galaxies. In any case, this will be the reason for the emergence of new stars and the reconstruction of the space closest to us. It remains only to guess what is the fate of the Universe and our galaxy in the distant future.
Astrophysical parameters of the Milky Way
In order to imagine what the Milky Way looks like on the scale of space, it is enough to look at the Universe itself and compare its individual parts. Our galaxy is part of a subgroup, which in turn is part of the Local Group, a larger entity. Here our space metropolis is adjacent to the Andromeda and Triangulum galaxies. Surrounding the trinity are more than 40 small galaxies. The local group is already part of an even larger formation and is part of the Virgo supercluster. Some argue that these are only rough guesses about where our galaxy is. The scale of formations is so huge that it is almost impossible to imagine all this. Today we know the distance to the nearest neighboring galaxies. Other deep sky objects are out of sight. Only theoretically and mathematically their existence is allowed.
The location of the galaxy became known only thanks to approximate calculations that determined the distance to the nearest neighbors. The satellites of the Milky Way are dwarf galaxies - the Small and Large Magellanic Clouds. In total, according to scientists, there are up to 14 satellite galaxies that make up the escort of the universal chariot called the Milky Way.
As for the visible world, today there is enough information about what our galaxy looks like. The existing model, and with it the map of the Milky Way, was compiled on the basis of mathematical calculations obtained from astrophysical observations. Each cosmic body or fragment of the galaxy takes its place. It's like the universe, only on a smaller scale. The astrophysical parameters of our space metropolis are interesting, and they are impressive.
Our galaxy is a spiral-type galaxy with a bar, which on star maps is denoted by the index SBbc. The diameter of the galactic disk of the Milky Way is about 50-90 thousand light years or 30 thousand parsecs. For comparison, the radius of the Andromeda galaxy is 110 thousand light years on the scale of the universe. One can only imagine how much larger the Milky Way is our neighbor. The dimensions of the dwarf galaxies closest to the Milky Way are ten times smaller than the parameters of our galaxy. Magellanic clouds have a diameter of only 7-10 thousand light years. In this huge stellar cycle, there are about 200-400 billion stars. These stars are collected in clusters and nebulae. A significant part of it is the arms of the Milky Way, in one of which our solar system is located.
Everything else is dark matter, clouds of cosmic gas and bubbles that fill interstellar space. The closer to the center of the galaxy, the more stars, the tighter space becomes. Our Sun is located in a region of space, consisting of smaller space objects located at a considerable distance from each other.
The mass of the Milky Way is 6x1042 kg, which is trillions of times the mass of our Sun. Almost all the stars that inhabit our stellar country are located in the plane of one disk, the thickness of which, according to various estimates, is 1000 light years. It is not possible to know the exact mass of our galaxy, since most of the visible spectrum of stars is hidden from us by the arms of the Milky Way. In addition, the mass of dark matter that occupies vast interstellar spaces is unknown.
The distance from the Sun to the center of our galaxy is 27 thousand light years. Being on the relative periphery, the Sun is rapidly moving around the center of the galaxy, making a complete revolution in 240 million years.
The center of the galaxy is 1000 parsecs in diameter and consists of a core with an interesting sequence. The center of the core has the shape of a bulge, in which the largest stars and a cluster of hot gases are concentrated. It is this region that releases a huge amount of energy, which in aggregate is more than the billions of stars that make up the galaxy radiate. This part of the core is the most active and brightest part of the galaxy. Along the edges of the core there is a jumper, which is the beginning of the arms of our galaxy. Such a bridge arises as a result of the colossal force of gravity caused by the rapid rotation of the galaxy itself.
Considering the central part of the galaxy, the following fact looks paradoxical. Scientists for a long time could not understand what is at the center of the Milky Way. It turns out that in the very center of a starry country called the Milky Way, a supermassive black hole has settled down, the diameter of which is about 140 km. It is there that most of the energy released by the core of the galaxy goes, it is in this bottomless abyss that the stars dissolve and die. The presence of a black hole at the center of the Milky Way indicates that all processes of formation in the Universe must someday end. Matter will turn into antimatter and everything will repeat again. How this monster will behave in millions and billions of years, the black abyss is silent, which indicates that the processes of absorption of matter are only gaining momentum.
Two main arms of the galaxy extend from the center - the Shield of the Centaur and Perseus. These structural formations were named after the constellations located in the sky. In addition to the main arms, the galaxy is surrounded by 5 more small arms.
Near and distant future
The arms, born from the core of the Milky Way, spiral outward, filling outer space with stars and cosmic material. An analogy with cosmic bodies that revolve around the Sun in our star system is appropriate here. A huge mass of stars, large and small, clusters and nebulae, cosmic objects of various sizes and nature, spins on a giant carousel. All of them create a wonderful picture of the starry sky, which a person has been looking at for more than one thousand years. When studying our galaxy, you should know that the stars in the galaxy live according to their own laws, being in one of the arms of the galaxy today, tomorrow they will start their journey in the other direction, leaving one arm and flying into another.
Earth in the Milky Way galaxy is far from the only planet suitable for life. This is just a particle of dust, the size of an atom, which was lost in the vast stellar world of our galaxy. There can be a huge number of such planets similar to Earth in the galaxy. It is enough to imagine the number of stars that somehow have their own stellar planetary systems. Other life may be far away, at the very edge of the galaxy, tens of thousands of light years away, or, conversely, be present in neighboring regions that are hidden from us by the arms of the Milky Way.
How do other stars look from the side and we have already said, but how would an outside observer see our solar system and our star-Sun?
Judging by the analysis of the surrounding outer space, solar system currently moving through the local, consisting mainly of hydrogen and some helium. It is assumed that this local interstellar cloud is spread out at a distance of 30 light years, which, in terms of kilometers, is something like 180 million km.
In turn, "our" cloud is located inside an elongated gas cloud, the so-called local bubble formed by particles of ancient supernovae. The bubble stretches for 300 light years and is located on the inner edge of one of the spiral arms.
However, as I said earlier, we do not know our exact position relative to the arms of the Milky Way - whatever one may say, we simply do not have the opportunity to look at it from the outside and assess the situation.
What to do: if you can determine your location with sufficient accuracy almost anywhere on the planet, then if you are dealing with galactic scales, this is impossible - our galaxy is 100 thousand light years across. Even when studying the outer space around us, much remains unclear.
If we use the intergalactic positioning system, we will probably find ourselves between the upper and bottom Milky Way and halfway between the center and the outer edge of the galaxy. According to one hypothesis, we settled in a rather "prestigious area" of the galaxy.
There is an assumption that stars located at a certain distance from the center of the galaxy are in the so-called habitable zone, that is, where life is theoretically possible. And life is possible only in the right place with the right temperature - on a planet located at such a distance from the star that it has liquid water. Only then can life appear and evolve. In general, the habitable zone extends for 13-35 thousand years from the center of the Milky Way. Considering that our solar system is located 20 to 29 light years from the galactic core, we are right in the middle of the “optimum of life”.
However, at present the solar system is indeed a very calm "region" of space. The planets of the system were formed long ago, the “wandering” planets either crashed into their neighbors or disappeared outside of our stellar home, and the number of asteroids and meteorites has significantly decreased compared to the chaos that reigned around 4 billion years ago.
We believe that early stars formed only from hydrogen and helium. But since stars are a kind, heavier elements formed over time. This is extremely important because when stars die and explode, . Their remnants become the building material for heavier elements and the original seeds of the galaxy. Where else would they come from, if not from "blacksmiths chemical elements» located in the bowels of the stars?
Here, for example, carbon in our cells, oxygen in our lungs, calcium in our bones, iron in our blood - these are all those very heavy elements.
In the uninhabited zone, apparently, there were no those processes that made possible the emergence of life on Earth. Closer to the edge of the galaxy, fewer massive stars exploded, hence fewer heavy elements were ejected. Further in the galaxy, you will not find atoms of such important elements for life as oxygen, carbon, nitrogen. The habitable zone is characterized by the presence of these heavier atoms, and beyond its borders, life is simply impossible.
If the outermost part of the galaxy is a "bad region", then its central part is even worse. And the closer to the galactic core, the more dangerous. In the days of Copernicus, we thought we were at the center of the universe. It seems that after everything we learned about the heavens, we decided that we were in the center of the galaxy. Now that we know even more, we understand how we lucky be out of the center.
At the very center of the Milky Way is an object of enormous mass - Sagittarius A, black hole about 14 million km across, its mass is 3700 times the mass of our Sun. The black hole at the center of the galaxy emits powerful radio emission, enough to incinerate all known life forms. So it's impossible to get close to her. There are other regions of the galaxy that are uninhabitable. For example, due to the strongest radiation.
O-type stars- these are giants much hotter than the Sun, 10 - 15 times larger than it and throwing enormous doses of ultraviolet radiation into space. Under the rays of such a star, everything perishes. Such stars are capable of destroying planets before they have even finished forming. The radiation from them is so great that it simply rips off matter from the forming planets and planetary systems, and literally rips the planets out of their orbits.
O-type stars are the real "death stars". No life is possible within a radius of 10 or more light years from them.
So our corner of the galaxy is like a blooming garden between the desert and the ocean. We have all the elements necessary for life. In our area, the main barrier against cosmic rays is the magnetic field of the Sun, and against radiation from the Sun, the Earth's magnetic field protects us. The Sun's magnetic field is responsible for sunny wind, which is a protection against those troubles that come to us from the edge of the solar system. The magnetic field of the Sun spins the solar wind, which is a charged stream of protons and electrons shooting out of the Sun at a speed of a million kilometers per hour.
The solar wind carries the magnetic field up to three times the orbit of Neptune. But a billion kilometers later in a place called heliopause the solar wind dries up and almost disappears. Slowing down, it ceases to be a barrier to cosmic rays of interstellar space. This place is the border heliosphere.
If there were no heliosphere, cosmic rays would freely penetrate our solar system. The heliosphere works like a cage for diving with sharks, only instead of sharks there is radiation, and instead of a scuba diver - our planet.
Some of the cosmic rays still penetrate the barrier. But at the same time they lose most of their strength. We used to think that the heliosphere is such an elegant barrier, something like a folded curtain of a magnetic field. Until data was received from Voyager 1 and Voyager 2, launched in 1997. At the beginning of the 21st century, data from devices were processed. It turned out that the magnetic field at the edge of the heliosphere is something like a magnetic foam, each bubble of which is about 100 million km wide. We are accustomed to think that the surface of the field is solid, creating a reliable barrier. But, as it turned out, it consists of bubbles and patterns.
When we explore our galactic neighborhood, dust and gas get in the way to see objects in more detail. Over a long history of observations, we found out the following. When we examine the night sky with the naked eye or with a telescope, we see a lot in the visible part of the spectrum. But this is only part of what is actually there. Some telescopes can see through cosmic dust thanks to the infrared vision.
The stars are very hot, but they hide in shells of dust. We can observe them with an infrared telescope. Objects can be transparent or opaque, it all depends on light waves, that is, light that either can or cannot pass through them. If something like gas or cosmic dust gets between the object of observation and the telescope, you can move to a different part of the spectrum, where the light waves will have a different frequency. In this case, this obstacle may become visible.
Armed with infrared and other devices, we found around us a lot of space neighbors, the existence of which we did not suspect. There are a number of instruments for observing space bodies, stars in different parts of the spectrum.
Having discovered many new cosmic bodies around us, we wonder how they behave, how they influenced the Earth at the time of the birth of life on Earth. Some of them are “good neighbors”, that is, they behave in a predictable way, move along a predictable trajectory. "Bad neighbors" are unpredictable. It could be the explosion of a dying star, or a collision that sends debris flying our way.
Some of our neighbors may have brought us a "gift" in ancient times that changed everything. When our Earth finished shaping and cooled, the surface was still very hot. And since the water simply evaporated, again it could be brought to Earth by numerous comets or asteroids. There are many theories about how we could get water.
According to one of them, water could be brought by icy bodies that came into the solar system from outside or remained after the formation of the sun and planets. According to one of the latest theories, about 4 million years ago, the gravity of the heavy gas giant Jupiter sent icy asteroids towards Mars, Earth and Venus. But only on Earth could ice penetrate the mantle. Water softened the Earth and initiated the process of plate tectonics, as a result of which continents and oceans appeared.
How did life originate in the oceans? Maybe the necessary organic compounds got into them from outer space? In some meteorites, which are called carbonic chondrites, scientists have found organic compounds that could contribute to the development of life on Earth. These compounds are similar to those collected from Antarctic meteorites, interstellar dust samples, and comet fragments obtained by NASA from stardust in 2005.
The origin of life is a long chain of reactions of organic compounds. All organic compounds contain carbon and it is possible that different circumstances led to the formation of different organic compounds. Some could form here on the planet, and others in space. It is quite possible that without these intergalactic gifts from our neighbors, life on Earth would not have appeared.
But there are also unpredictable neighbors. For example, a star is an orange dwarf Gliese 710. This star is 60% more massive than the Sun, is currently only 63 light-years from Earth and continues to approach the solar system.
The Oort Cloud is a huge sphere of frozen rocks and blocks of ice that surrounds the solar system (center). The source of comets and wandering meteorites "from outside" our system
Also at a distance of 1 light year from Earth is the so-called Oort cloud. We can observe comets from the Oort cloud if they pass close enough to the Sun, but usually this is not the case and we do not see them.
There are also just “strange neighbors”. One of them (or rather, a whole family) is the stars of the constellation Centaurus.
The star Alpha Centauri, the brightest star in the constellation Centaurus, is the third brightest star in the night sky for us. She is our closest neighbor, located 4 light years from us. Until the 20th century, it was believed that double star, but later it turned out that we are observing nothing more than a star system of three stars revolving around each other at once!
Alpha Centauri A is very similar to our Sun and has the same mass. Alpha Centauri B is slightly smaller and the third star Proxima Centauri is an M-type star with a mass of about 12% of the mass of the Sun. It is so small that we cannot observe it with the naked eye.
It turns out that many of our other star neighbors also have multiple systems. Sirius, located at a distance of about 8.5 light years, is known as one of the most bright stars in the sky, is also a double star. Most stars are smaller than our Sun and are often binary. So our single Sun is rather an exception to the rule.
Most of the stars around are red or brown dwarfs. Red dwarfs make up to 70% of all stars not only in our galaxy, but also in the Universe. We are accustomed to our Sun, it seems to us the standard, but there are much more red dwarfs.
We weren't sure if our neighbors had brown dwarfs until 1990. These space objects are also unique - not quite stars, but not planets, and their color is not brown at all.
Brown dwarfs are one of the most mysterious inhabitants of our solar system, because they are really very cold and very dark. They emit little light, so they are extremely difficult to observe. In 2011, one of NASA's wide-field infrared telescopes, somewhere between 9 and 40 light-years from Earth, discovered many brown dwarfs with surface temperatures once thought impossible. Some of these brown dwarfs are so cool you can even touch them. Their surface temperature is only 26°C. Stars at room temperature - what you just can not see in the universe!
However, outside our "local bubble" there are not only stars, but also planets, or rather exoplanets- that is, not revolving around the Sun. The discovery of such planets is extremely complex events. It's like watching one single light bulb in Las Vegas at night! In fact, we do not even see these planets, but only guess about them when the Kepler Telescope, which tracks the change in the brightness of stars, captures an insignificant change in the brightness of a star when one of the exoplanets passes over its disk.
As far as we know, our nearest exoplanetary neighbor is literally "on the same" street as us, "only" 10 light years away, orbiting the orange star Epsilon Eridani. However, the exoplanet is more likely not like Earth, but like Jupiter, as it is a huge gas giant. However, given that less than two decades have passed since the first discoveries of exoplanets, who knows what awaits us next.
In 2011, in our area, astronomers discovered a new kind of planets - homeless planets. It turns out that there are planets that do not revolve around their parent star. They began their lives like all other planets, but for one reason or another they were displaced from their orbit, left their solar systems and now wander aimlessly around the galaxy without the opportunity to return home. This is surprising, but a new definition for the name of this kind of planets, for planets that exist outside the attraction of their parent stars, will be required.
However, there are a couple of events looming on the horizon that could become a real sensation even on a space scale.
An illustration of the Milky Way galaxy as viewed from the galactic "north pole". Credit: NASA.
When you look into the night sky under just the right conditions, you may notice a faint, white streak across the sky. This band, when observed closely, appears mottled and dusty, filled with millions of tiny points of light and a halo of luminous matter. What you see is Milky Way, something that astronomers and just lovers of looking at the stars have been looking at for a long time.
Opening and naming:
Our galaxy was so named because the haze that stretches across the night sky resembles spilled milk. This name is quite ancient and is a translation from the Latin "Via Lactea", which in turn is a translation from the Greek word "Galaxias", referring to the pale band of light formed by the stars at , seen from .
The Persian astronomer Nasir ad-Din Tusi (1201-1274) even wrote in his book Tadhkira: " Milky Way, i.e. The galaxy is made up of a large number small, closely spaced stars, which, given their concentration and tightness, appear to be cloudy spots. Because of this, it is comparable to milk in color."
Astronomers have long suspected that Milky Way consists of stars, but this was proved only in 1610, when Galileo Galilei turned his simplest telescope to the heavens and saw individual stars in a band in the sky. With the help of telescopes, astronomers realized that there were many, many more stars, and that all of them, visible to us, are part of Milky Way.
In 1755, Immanuel Kant suggested that Milky Way is a large cluster of stars held together by mutual gravity. Just like in , this cluster of stars will rotate and, as it rotates, align itself into a disk with the Solar System embedded in it. , tried to outline the shape Milky Way in 1785, but he did not realize that huge parts of the galaxy are hidden behind gas and dust, which obscure its true appearance.
In the 1920s, Edwin Hubble presented compelling evidence that the spiral nebulae in the sky were in fact other galaxies, that the true shape of our galaxy was known. Since then, astronomers have come to understand that Milky Way is a barred spiral galaxy, and rated, .
Structure and composition:
Milky Way looks bright towards the Galactic Center. The fact that Milky Way divides the night sky into two approximately equal hemispheres, indicates that the solar system is close to. Milky Way has a relatively low brightness due to gases and dust that fill the galactic disk, which prevents us from seeing the bright Galactic center or what is behind it.
A mosaic of images covering the entire sky as observed by the Wide-field Infrared Survey Explorer (WISE) spacecraft as part of the All-Sky Data Release project. Credit: NASA/JPL.
If you could get out of the galaxy and look down on it, you would see that Milky Way is a barred spiral galaxy about 120,000 light-years in diameter and about 1,000 light-years thick. For a long time it was believed that our galaxy has 4 spiral arms, but more recent research has determined that it actually has only two spiral arms, called the Scutum-Centaurus arm and the Carina-Sagittarius arm.
Spiral arms formed from density waves that revolve around the center Milky Way. When these density waves move through a given area, they compress the dust and gas, which results in that region. However, the presence of these sleeves was determined from the observation of parts Milky Way, as well as other galaxies, and not the result of observing our galaxy as a whole.
In truth, all pictures depicting our galaxy are either artistic renderings or images of other spiral galaxies. Until recently, it was difficult for scientists to assess what the Milky Way, mainly due to the fact that we are inside it. If you have never been outside your home, you would not know what it looks like from the outside. But you would understand by looking at the interior and comparing it to other houses in the neighborhood.
As part of current surveys of the night sky by ground-based telescopes and more recent missions involving space telescopes, astronomers estimate that in Milky Way there are from 100 billion to 400 billion stars. They also believe that every star has at least one planet, which means there could be hundreds of billions of planets in our galaxy, and at least 17 billion of them will be.
Illustration of a simulation showing the distribution of dark matter over 350 million light years. Galaxies are shown as high density white dots (left) and as normal baritonic matter (right). Credit: Markus Haider
Milky Way, like all galaxies, which has 90% of the mass. No one knows for sure, but its mass is inferred from observations of how fast galaxies rotate and other general patterns of behavior. More importantly, this mass is believed to help keep the galaxy from tearing it apart as it rotates.
The Milky Way Galaxy and the place of the Solar System in it:
Regions of space between two main arms Milky Way, and at a distance of 27,000 light years from the galactic core. In the heart Milky Way located (Sagittarius A*, pronounced "Sagittarius A-star"). This monster is 4 million times larger than our Sun, which takes about 240 million light years to complete its orbit around the Galactic center, which is called the galactic year, or space year. Just imagine, the last time the sun was in this region of the galaxy,
Milky Way and Andromeda are part of a larger cluster of galaxies known as the Local Group. And they are in an even larger region called the Virgo Supercluster, a mass concentration of galaxies that contain at least 100 galaxy groups and clusters 33 megaparsecs (110 million light years) in diameter.
You may be surprised to know that dung beetles navigate by night. Milky Way. If you have never seen Milky Way with your own eyes, you should see. To do this, you need to find a place without exposure to artificial lighting (), and see and evaluate our galaxy. And be sure to wave to all the neighboring stars that share it with us.
Here are a few interesting facts, figures and photographs that you will find among the links below:
The title of the article you read "Milky Way Galaxy".
The science
Each person has their own idea of what a home is. For some it's a roof over their heads, for others home is planet Earth, a rocky ball that plows outer space along its closed path around the Sun.
No matter how big our planet seems to us, it is just a grain of sand in giant star system whose size is hard to imagine. This star system is the Milky Way galaxy, which can also rightly be called our home.
Arms of the galaxy
Milky Way- a spiral galaxy with a bar that runs along the center of the spiral. Approximately two-thirds of all known galaxies are spiral, and two-thirds of them are barred. That is, the Milky Way is included in the list the most common galaxies.
Spiral galaxies have arms that extend out from the center like wheel spokes that spiral. Our solar system is located in the central part of one of the arms, which is called Orion arm.
The Orion Arm was once thought to be a small "offshoot" of larger arms such as Perseus arm or Shield-Centaurus arm. Not so long ago there was an assumption that the Orion arm is indeed offshoot of the Perseus arm and does not leave the center of the galaxy.
The problem is that we cannot see our galaxy from the outside. We can observe only those things that are around us, and judge what shape the galaxy has, being, as it were, inside it. However, scientists were able to calculate that this sleeve has a length of approximately 11 thousand light years and thickness 3500 light years.
Supermassive black hole
The smallest supermassive black holes that scientists have discovered are approximately in 200 thousand times heavier than the sun. For comparison: ordinary black holes have the mass of everything 10 times greater than the mass of the sun. At the center of the Milky Way is an incredibly massive black hole, the mass of which is hard to imagine. 
For the past 10 years, astronomers have been monitoring the activity of stars in orbit around the star. Sagittarius A, the dense region at the center of our galaxy's spiral. Based on the movement of these stars, it was determined that at the center Sagittarius A*, which is hidden behind a dense cloud of dust and gas, there is a supermassive black hole whose mass is 4.1 million times more than the mass of the sun!
The animation below shows the real movement of stars around a black hole. from 1997 to 2011 around one cubic parsec at the center of our galaxy. As stars approach a black hole, they loop around it at incredible speeds. For example, one of these stars, S 0-2 moving at a speed 18 million kilometers per hour: black hole first attracts it, and then sharply repels it.
More recently, scientists observed how a cloud of gas approached a black hole and was torn to pieces its massive gravitational field. Parts of this cloud were swallowed up by the hole, and the remaining parts began to resemble long thin pasta more than 160 billion kilometers.
Magneticparticles
In addition to having a supermassive all-consuming black hole, the center of our galaxy boasts incredible activity: old stars die, and new ones are born with enviable constancy.
Not so long ago, scientists noticed something else at the galactic center - a stream of high-energy particles that extend into the distance 15 thousand parsecs across the galaxy. This distance is about half the diameter of the Milky Way.
The particles are invisible to the naked eye, however, using magnetic imaging, you can see that the particle geysers take up about two thirds of the visible sky:
What is behind this phenomenon? For one million years, stars have come and gone, feeding never stopping flow, directed towards the outer arms of the galaxy. The total energy of a geyser is a million times greater than that of a supernova.
The particles move at an incredible speed. Based on the structure of the particle stream, astronomers built magnetic field model that dominates our galaxy.
Newstars
How often do new stars form in our galaxy? Researchers have been asking this question for years. It was possible to map the areas of our galaxy where there is aluminum-26, an isotope of aluminum that appears where stars are born or die. Thus, it was possible to find out that every year in the Milky Way galaxy, 7 new stars and about twice in a hundred years a large star explodes, forming a supernova.
The Milky Way galaxy is not the largest producer of stars. When a star dies, it releases into space such raw materials, like hydrogen and helium. After hundreds of thousands of years, these particles coalesce into molecular clouds, which eventually become so dense that their center collapses under their own gravity, thus forming a new star.
It looks like a kind of eco-system: death nourishes new life
. Particles of a particular star in the future will be part of a billion new stars. This is how things are in our galaxy, so it evolves. This leads to the formation of new conditions under which the probability of the emergence of planets similar to the Earth increases.
Planets of the Milky Way Galaxy
Despite the constant death and birth of new stars in our galaxy, their number has been calculated: The Milky Way is home to about 100 billion stars. Based on new research, scientists suggest that every star has at least one or more planets orbiting it. That is, everything in our corner of the universe has 100 to 200 billion planets.
The scientists who came to this conclusion studied stars like red dwarfs of spectral class M. These stars are smaller than our Sun. They make up 75 percent from all the stars in the Milky Way. In particular, the researchers drew attention to the star Kepler-32, who sheltered five planets.
How do astronomers discover new planets?Planets, unlike stars, are difficult to detect because they do not emit their own light. We can say with certainty that there is a planet around a star only when it stands in front of his star and obscures its light.
The planets of the star Kepler -32 behave exactly like exoplanets orbiting other M dwarf stars. They are located approximately at the same distance and have similar sizes. That is, the Kepler-32 system is typical system for our galaxy.
If there are over 100 billion planets in our galaxy, how many planets are Earth-like? It turns out, not so much. There are dozens various types planets: gas giants, pulsar planets, brown dwarfs, and planets that rain molten metal from the sky. Those planets that are composed of rocks can be located too far or too close to the star, so they are hardly similar to the Earth.
The results of recent studies have shown that in our galaxy, it turns out that there are more terrestrial planets than previously thought, namely: 11 to 40 billion. The scientists took as an example 42 thousand stars, similar to our Sun, and began to look for exoplanets that can revolve around them in a zone where it is not too hot and not too cold. Was found 603 exoplanets, among which 10 matched the search criteria.
By analyzing stellar data, scientists have proven the existence of billions of Earth-like planets that they have yet to officially discover. Theoretically, these planets are able to maintain temperatures for existence of liquid water which, in turn, will allow life to emerge.
Collision of galaxies
Even if new stars are constantly formed in the Milky Way galaxy, it will not be able to increase in size, if not receive new material from somewhere else. And the Milky Way is really expanding.
Previously, we were not sure exactly how the galaxy manages to grow, but recent discoveries have suggested that the Milky Way is cannibal galaxy, meaning it has devoured other galaxies in the past and will likely do so again, at least until some larger galaxy engulfs it.
Using a space telescope Hubble and information gained from photographs taken over the course of seven years, scientists have discovered stars near the outer edge of the Milky Way, which moving in a special way. Instead of moving towards or away from the center of the galaxy like other stars, they sort of drift off the edge. It is assumed that this star cluster is all that is left of another galaxy that was swallowed up by the Milky Way galaxy.
This collision appears to have taken place several billion years ago and it probably won't be the last. Given the speed at which we are moving, our galaxy through 4.5 billion years will collide with the Andromeda galaxy.
Influence of satellite galaxies
Although the Milky Way is a spiral galaxy, it is not exactly a perfect spiral. At its center there is peculiar bulge, which appeared as a result of the fact that the molecules of gaseous hydrogen escape from the flat disk of the spiral.
For years, astronomers have puzzled over why the galaxy has such a bulge. It is logical to assume that the gas is drawn into the disk itself, and does not break out. The longer they studied this issue, the more confused they became: the bulge molecules are not only pushed outward, but also vibrate at their own frequency.
What can cause such an effect? Today, scientists believe that dark matter and satellite galaxies are to blame - Magellanic Clouds. These two galaxies are very small: together they make up only 2 percent of the total mass of the Milky Way. It's not enough to have an impact on him.
However, when dark matter moves through the Clouds, it creates waves that apparently affect the gravitational attraction, strengthening it, and hydrogen under the influence of this attraction escaping from the center of the galaxy.
The Magellanic Clouds revolve around the Milky Way. The spiral arms of the Milky Way, under the influence of these galaxies, seem to sway in the place where they float.
twin galaxies
Although the Milky Way galaxy can be called unique in many ways, it is not a rarity. The universe is dominated by spiral galaxies. Considering that only in our field of vision are about 170 billion galaxies, we can assume that somewhere there are galaxies very similar to ours.
But what if somewhere there is a galaxy - an exact copy of the Milky Way? In 2012, astronomers discovered such a galaxy. It even has two small satellites that orbit it and match exactly with our Magellanic Clouds. By the way, only 3 percent spiral galaxies have similar companions whose lifetimes are relatively short. The Magellanic Clouds are likely to dissolve in a couple of billion years.
Finding such a similar galaxy with satellites, a supermassive black hole in the center and the same size is an incredible stroke of luck. This galaxy is called NGC 1073 and it looks so much like the Milky Way that astronomers study it to find out more. about our own galaxy. For example, we can see it from the side and thus better imagine what the Milky Way looks like.
Galactic year
On Earth, a year is the time it takes the Earth to make complete revolution around the sun. Every 365 days we return to the same point. Our solar system revolves around the black hole at the center of the galaxy in the same way. However, it makes a full turn for 250 million years. That is, since the dinosaurs disappeared, we have made only a quarter of a complete revolution.
In descriptions of the solar system, it is rarely mentioned that it moves in outer space, like everything else in our world. Relative to the center of the Milky Way, the solar system moves at a speed 792 thousand kilometers per hour. For comparison: if you were moving at the same speed, you could travel around the world in 3 minutes.
The period of time it takes for the Sun to make a complete revolution around the center of the Milky Way is called galactic year. It is estimated that the Sun has lived only 18 galactic years.