What is the name and what does our Galaxy look like? The names of the stars in our Galaxy
Our Galaxy. Mysteries of the Milky Way
To some extent, we know more about distant star systems than about our home Galaxy - the Milky Way. It is more difficult to study its structure than the structure of any other galaxies, because it has to be studied from the inside, and many things are not so easy to see. Interstellar dust clouds absorb the light emitted by myriads of distant stars.
Only with the development of radio astronomy and the advent of infrared telescopes were scientists able to understand how our Galaxy works. But many details remain unclear to this day. Even the number of stars in the Milky Way is estimated rather roughly. The latest electronic reference books give figures from 100 to 300 billion stars.
Not so long ago, it was believed that our Galaxy has 4 large arms. But in 2008, astronomers from the University of Wisconsin published the results of processing about 800,000 infrared images taken by the Spitzer Space Telescope. Their analysis showed that the Milky Way has only two arms. As for the other branches, they are only narrow side branches. So, the Milky Way is a spiral galaxy with two arms. It should be noted that most spiral galaxies known to us also have only two arms.
“Thanks to the Spitzer telescope, we have the opportunity to rethink the structure of the Milky Way,” said astronomer Robert Benjamin of the University of Wisconsin, speaking at a conference of the American Astronomical Society. “We are refining our understanding of the Galaxy in the same way that centuries ago, pioneers, traveling around the globe, refined and rethought previous ideas about what the Earth looks like.”
Since the early 90s of the 20th century, observations carried out in the infrared range have increasingly changed our knowledge of the structure of the Milky Way, because infrared telescopes make it possible to look through gas and dust clouds and see what is inaccessible to conventional telescopes.
2004 - The age of our Galaxy was estimated at 13.6 billion years. It arose shortly after. At first it was a diffuse gas bubble containing mainly hydrogen and helium. Over time, it turned into the huge spiral galaxy in which we now live.
general characteristics
But how did the evolution of our Galaxy proceed? How was it formed - slowly or, on the contrary, very quickly? How did it become saturated with heavy elements? How has the shape of the Milky Way and its chemical composition changed over billions of years? Scientists have yet to provide detailed answers to these questions.
The extent of our Galaxy is about 100,000 light years, and the average thickness of the galactic disk is about 3,000 light years (the thickness of its convex part, the bulge, reaches 16,000 light years). However, in 2008, Australian astronomer Brian Gensler, after analyzing the results of observations of pulsars, suggested that the galactic disk is probably twice as thick as is commonly believed.
Is our Galaxy large or small by cosmic standards? By comparison, the Andromeda nebula, our closest large galaxy, is approximately 150,000 light years across.
At the end of 2008, researchers established using radio astronomy methods that the Milky Way is rotating faster than previously thought. Judging by this indicator, its mass is approximately one and a half times higher than was commonly believed. According to various estimates, it varies from 1.0 to 1.9 trillion solar masses. Again, for comparison: the mass of the Andromeda nebula is estimated at at least 1.2 trillion solar masses.
Structure of galaxies
Black hole
So, the Milky Way is not inferior in size to the Andromeda nebula. “We should no longer think of our galaxy as the little sister of the Andromeda nebula,” said astronomer Mark Reid of the Smithsonian Center for Astrophysics at Harvard University. At the same time, since the mass of our Galaxy is greater than expected, its gravitational force is also greater, which means that the likelihood of it colliding with other galaxies in our vicinity increases.
Our Galaxy is surrounded by a spherical halo, reaching a diameter of 165,000 light years. Astronomers sometimes call the halo a “galactic atmosphere.” It contains approximately 150 globular clusters, as well as a small number of ancient stars. The rest of the halo space is filled with rarefied gas, as well as dark matter. The mass of the latter is estimated at approximately a trillion solar masses.
The spiral arms of the Milky Way contain enormous amounts of hydrogen. This is where stars continue to be born. Over time, young stars leave the arms of galaxies and “move” into the galactic disk. However, the most massive and bright stars do not live long enough, so they do not have time to move away from their place of birth. It is no coincidence that the arms of our Galaxy glow so brightly. Most of the Milky Way consists of small, not very massive stars.
The central part of the Milky Way is located in the constellation Sagittarius. This area is surrounded by dark gas and dust clouds, behind which nothing can be seen. Only since the 1950s, using radio astronomy, have scientists been able to gradually discern what lies there. In this part of the Galaxy, a powerful radio source was discovered, called Sagittarius A. As observations have shown, a mass is concentrated here that exceeds the mass of the Sun by several million times. The most acceptable explanation for this fact is only one: in the center of our Galaxy is located.
Now, for some reason, she has taken a break for herself and is not particularly active. The flow of matter here is very poor. Maybe over time the black hole will develop an appetite. Then it will again begin to absorb the veil of gas and dust that surrounds it, and the Milky Way will join the list of active galaxies. It is possible that before this, stars will begin to rapidly form in the center of the Galaxy. Similar processes are likely to be repeated regularly.
2010 - American astronomers, using the Fermi Space Telescope, designed to observe sources of gamma radiation, discovered two mysterious structures in our Galaxy - two huge bubbles emitting gamma radiation. The diameter of each of them is on average 25,000 light years. They fly away from the center of the Galaxy in northern and southern directions. Perhaps we are talking about streams of particles that were once emitted by a black hole located in the middle of the Galaxy. Other researchers believe that we are talking about gas clouds that exploded during the birth of stars.
There are several dwarf galaxies around the Milky Way. The most famous of them are the Large and Small Magellanic Clouds, which are connected to the Milky Way by a kind of hydrogen bridge, a huge plume of gas that stretches behind these galaxies. It was called the Magellanic Stream. Its extent is about 300,000 light years. Our Galaxy constantly absorbs the dwarf galaxies closest to it, in particular the Sagitarius Galaxy, which is located at a distance of 50,000 light years from the galactic center.
It remains to add that the Milky Way and the Andromeda nebula are moving towards each other. Presumably, after 3 billion years, both galaxies will merge together, forming a larger elliptical galaxy, which has already been called Milkyhoney.
Origin of the Milky Way
Andromeda's nebula
For a long time it was believed that the Milky Way formed gradually. 1962 - Olin Eggen, Donald Linden-Bell and Allan Sandage proposed a hypothesis that became known as the ELS model (named after the initial letters of their last names). According to it, a homogeneous cloud of gas once slowly rotated in place of the Milky Way. It resembled a ball and reached approximately 300,000 light years in diameter, and consisted mainly of hydrogen and helium. Under the influence of gravity, the protogalaxy shrank and became flat; at the same time, its rotation noticeably accelerated.
For almost two decades, this model suited scientists. But new observational results show that the Milky Way could not have arisen in the way theorists predicted.
According to this model, a halo forms first, and then a galactic disk. But the disk also contains very ancient stars, for example, the red giant Arcturus, whose age is more than 10 billion years, or numerous white dwarfs of the same age.
Globular clusters have been discovered in both the galactic disk and halo that are younger than the ELS model allows. Obviously, they are absorbed by our late Galaxy.
Many stars in the halo rotate in a different direction than the Milky Way. Maybe they, too, were once outside the Galaxy, but then they were drawn into this “stellar vortex” - like a random swimmer in a whirlpool.
1978 - Leonard Searle and Robert Zinn proposed their model of the formation of the Milky Way. It was designated as "Model SZ". Now the history of the Galaxy has become noticeably more complicated. Not so long ago, its youth, in the opinion of astronomers, was described as simply as in the opinion of physicists - rectilinear translational motion. The mechanics of what was happening were clearly visible: there was a homogeneous cloud; it consisted only of evenly spread gas. Nothing by its presence complicated the theorists' calculations.
Now, instead of one huge cloud in the visions of scientists, several small, intricately scattered clouds appeared at once. Stars were visible among them; however, they were located only in the halo. Inside the halo everything was seething: clouds collided; gas masses were mixed and compacted. Over time, a galactic disk was formed from this mixture. New stars began to appear in it. But this model was subsequently criticized.
It was impossible to understand what connected the halo and the galactic disk. This condensed disk and the sparse stellar shell around it had little in common. After Searle and Zinn compiled their model, it turned out that the halo rotates too slowly to form a galactic disk. Judging by the distribution of chemical elements, the latter arose from protogalactic gas. Finally, the angular momentum of the disk turned out to be 10 times higher than the halo.
The whole secret is that both models contain a grain of truth. The trouble is that they are too simple and one-sided. Both now seem to be fragments of the same recipe that created the Milky Way. Eggen and his colleagues read a few lines from this recipe, Searle and Zinn read a few others. Therefore, trying to re-imagine the history of our Galaxy, we now and then notice familiar lines that we have already read once.
Milky Way. Computer model
So it all started shortly after the Big Bang. “Today it is generally accepted that fluctuations in the density of dark matter gave rise to the first structures - the so-called dark halos. Thanks to the force of gravity, these structures did not disintegrate,” notes German astronomer Andreas Burkert, author of a new model of the birth of the Galaxy.
Dark halos became embryos - nuclei - of future galaxies. Gas accumulated around them under the influence of gravity. A homogeneous collapse occurred, as described by the ELS model. Already 500-1000 million years after the Big Bang, gas accumulations surrounding dark halos became “incubators” of stars. Small protogalaxies appeared here. The first globular clusters arose in dense clouds of gas, because stars were born here hundreds of times more often than anywhere else. Protogalaxies collided and merged with each other - this is how large galaxies were formed, including our Milky Way. Today it is surrounded by dark matter and a halo of single stars and their globular clusters, ruins of a universe more than 12 billion years old.
There were many very massive stars in the protogalaxies. Less than a few tens of millions of years passed before most of them exploded. These explosions enriched the gas clouds with heavy chemical elements. Therefore, the stars that were born in the galactic disk were not the same as in the halo - they contained hundreds of times more metals. In addition, these explosions generated powerful galactic vortices that heated the gas and swept it beyond the protogalaxies. A separation of gas masses and dark matter occurred. This was the most important stage in the formation of galaxies, not previously taken into account in any model.
At the same time, dark halos increasingly collided with each other. Moreover, the protogalaxies stretched out or disintegrated. These catastrophes are reminiscent of the chains of stars preserved in the halo of the Milky Way since the days of “youth”. By studying their location, it is possible to assess the events that took place in that era. Gradually, these stars formed a vast sphere - the halo we see. As it cooled, gas clouds penetrated inside it. Their angular momentum was conserved, so they did not collapse into one single point, but formed a rotating disk. All this happened more than 12 billion years ago. The gas was now compressed as described in the ELS model.
At this time, the “bulge” of the Milky Way is formed - its middle part, reminiscent of an ellipsoid. The bulge is made up of very old stars. It probably arose during the merger of the largest protogalaxies that held gas clouds for the longest time. In the middle of it were neutron stars and tiny black holes - relics of exploding supernovae. They merged with each other, simultaneously absorbing gas streams. Perhaps this is how the huge black hole that now resides in the center of our Galaxy was born.
The history of the Milky Way is much more chaotic than previously thought. Our native Galaxy, impressive even by cosmic standards, was formed after a series of impacts and mergers - after a series of cosmic disasters. Traces of those ancient events can still be found today.
For example, not all stars in the Milky Way revolve around the galactic center. Probably, over the billions of years of its existence, our Galaxy has “absorbed” many fellow travelers. Every tenth star in the galactic halo is less than 10 billion years old. By that time, the Milky Way had already formed. Perhaps these are the remnants of once captured dwarf galaxies. A group of English scientists from the Astronomical Institute (Cambridge), led by Gerard Gilmour, calculated that the Milky Way could apparently absorb from 40 to 60 Carina-type dwarf galaxies.
In addition, the Milky Way attracts huge masses of gas. Thus, in 1958, Dutch astronomers noticed many small spots in the halo. In fact, they turned out to be gas clouds, which consisted mainly of hydrogen atoms and were rushing towards the galactic disk.
Our Galaxy will not restrain its appetite in the future. Perhaps it will absorb the dwarf galaxies closest to us - Fornax, Carina and, probably, Sextans, and then merge with the Andromeda nebula. Around the Milky Way – this insatiable “stellar cannibal” – it will become even more deserted.
We live in a galaxy called the Milky Way. Our planet Earth is just a grain of sand in the Milky Way galaxy. In the course of filling the site, every now and then moments arise that it would seem that I should have written about a long time ago, but were either forgotten, or did not have time, or switched to something else. Today we will try to fill one of these niches. Today our topic is the Milky Way galaxy.
Once upon a time, people thought that the center of the World was the Earth. Over time, this opinion was recognized as erroneous and the Sun began to be considered the center of everything. But then it turned out that the star that gives life to all life on the blue planet is by no means the center of outer space, but only a tiny grain of sand in a boundless ocean of stars.
Space, galaxy, Milky way
The cosmos visible to the human eye includes myriads of stars. They all unite into a huge star system, which has a very beautiful and intriguing name - the Milky Way galaxy. From Earth, this celestial splendor is observed in the form of a wide whitish stripe, glowing dimly on the celestial sphere.
It stretches across the entire northern hemisphere and crosses the constellations Gemini, Auriga, Cassiopeia, Chanterelle, Cygnus, Taurus, Eagle, Sagittarius, Cepheus. It encircles the southern hemisphere and passes through the constellations Monoceros, Southern Cross, Southern Triangle, Scorpio, Sagittarius, Vela, Compass.
If you arm yourself with a telescope and look through it at the night sky, the picture will be different. The wide whitish stripe will turn into countless luminous stars. Their faint, distant, alluring light will tell without words about the greatness and endless expanses of the Cosmos, will make you hold your breath and realize the insignificance and worthlessness of momentary human problems.
The Milky Way is called Galaxy or a giant star system. According to estimates, there is currently an increasing tendency towards a figure of 400 billion stars in the Milky Way. All these stars move in closed orbits. They are connected to each other by gravitational forces, and most of them have planets. Stars together with planets form star systems. Such systems can be with one star (Solar system), double (Sirius - two stars), triple (Alpha Centauri). There are four, five stars, and even seven.
Milky Way in disk shape
Structure of the Milky Way
All this countless variety of star systems that make up the Milky Way are not scattered haphazardly throughout outer space, but are united into a colossal formation, shaped like a disk with a thickening in the middle. The diameter of the disk is 100,000 light years (one light year corresponds to the distance that light travels in a year, which is approximately 10¹³ km) or 30,659 parsecs (one parsec is 3.2616 light years). The thickness of the disk is several thousand light years, and its mass exceeds the mass of the Sun by 3 × 10¹² times.
The mass of the Milky Way consists of the mass of stars, interstellar gas, dust clouds and a halo, which has the shape of a huge sphere consisting of rarefied hot gas, stars and dark matter. Dark matter appears to be a collection of hypothetical cosmic objects, the masses of which make up 95% of the entire Universe. These mysterious objects are invisible and do not react in any way to modern technical means of detection.
The presence of dark matter can be guessed only by its gravitational effect on visible clusters of suns. There are not so many of them available for observation. The human eye, even enhanced by the most powerful telescope, can only contemplate two billion stars. The rest of outer space is hidden by huge impenetrable clouds consisting of interstellar dust and gas.
Thickening ( bulge) in the central part of the Milky Way's disk is called the Galactic center or core. Billions of old stars move in it in very elongated orbits. Their mass is very large and is estimated at 10 billion solar masses. The core dimensions are not that impressive. It is 8000 parsecs across.
Galaxy Core- This is a brightly shining ball. If earthlings could observe it in the sky, then their eyes would see a gigantic luminous ellipsoid, which in size would be a hundred times larger than the Moon. Unfortunately, this most beautiful and magnificent spectacle is inaccessible to people due to powerful gas and dust clouds that obscure the galactic center from planet Earth.
At a distance of 3000 parsecs from the center of the Galaxy there is a gas ring with a width of 1500 parsecs and a mass of 100 million solar masses. It is here that the central region of new star formation is believed to be located. Gas sleeves about 4 thousand parsecs long spread out from it. At the very center of the core there is black hole, with a mass of more than three million Suns.
Galactic disk its structure is heterogeneous. It has separate high-density zones, which are spiral arms. The continuous process of formation of new stars continues in them, and the arms themselves stretch along the core and seem to bend around it in a semicircle. Currently there are five of them. These are the Cygnus arm, the Perseus arm, the Centauri arm and the Sagittarius arm. In the fifth sleeve - Orion's sleeve- The solar system is located.
Please note - this is a spiral structure. Increasingly, people notice this structure literally everywhere. Many will be surprised, but flight path of our Earth Also there is a spiral!
It is separated from the galactic core by 28,000 light years. Around the center of the Galaxy, the Sun and its planets rush at a speed of 220 km/s, and complete a revolution in 220 million years. True, there is another figure - 250 million years.
The solar system is located just below the galactic equator, and in its orbit it does not move smoothly and calmly, but as if bouncing. Once every 33 million years, it crosses the galactic equator and rises above it to a distance of 230 light years. Then it descends back to repeat its takeoff after another interval of 33 million years.
The galactic disk rotates, but it does not rotate as a single body. The core rotates faster, the spiral arms in the plane of the disk rotate slower. Naturally, a logical question arises: why do the spiral arms not twist around the center of the Galaxy, but always remain the same shape and configuration for 12 billion years (the age of the Milky Way is estimated at this figure).
There is a certain theory that quite plausibly explains this phenomenon. She views spiral arms not as material objects, but as waves of matter density arising against the galactic background. This is caused by star formation and the birth of high luminosity stars. In other words, the rotation of the spiral arms has nothing to do with the movement of stars in their galactic orbits.
The latter, only, pass through the arms either ahead of them in speed if they are closer to the Galactic center, or behind them if they are located in the peripheral regions of the Milky Way. The outlines of these spiral waves are given by the brightest stars, which have a very short life and manage to live it without leaving the sleeve.
As can be seen from all of the above, the Milky Way is a very complex cosmic formation, but it is not limited to the surface of the disk. There is a huge spherical cloud around ( halo). It consists of rarefied hot gases, individual stars, globular star clusters, dwarf galaxies and dark matter. On the outskirts of the Milky Way there are dense clouds of gas. Their extent is several thousand light years, their temperature reaches 10,000 degrees, and their mass is equal to at least ten million Suns.
Neighbors of the Milky Way Galaxy
In the vast Cosmos, the Milky Way is far from alone. At a distance of 772 thousand parsecs from it there is an even more huge star system. It's called Andromeda Galaxy(possibly more romantic - Andromeda Nebula). It has been known since ancient times as “a small heavenly cloud, easily visible in the dark night.” Even at the beginning of the 17th century, religiously minded astronomers believed that “in this place the crystal firmament is thinner than usual, and through it the light of the kingdom of heaven pours out.” 
The Andromeda nebula is the only galaxy that can be seen in the sky with the naked eye. It appears as a small oval luminous spot. The light in it is distributed unevenly: the central part is brighter. If you strengthen your eye with a telescope, the speck will turn into a giant star system, the diameter of which is 150 thousand light years. This is one and a half times the diameter of the Milky Way.
Dangerous neighbor
But Andromeda is not unique in size from the galaxy in which the Solar System exists. Back in 1991, the planetary camera of the space telescope. Hubble recorded the presence of two nuclei. Moreover, one of them is smaller in size and revolves around another, larger and brighter one, gradually collapsing under the influence of the tidal forces of the latter. This slow death throes of one of the cores suggests that it is the remnant of some other galaxy that Andromeda absorbed.
For many, it will be an unpleasant surprise to learn that the Andromeda Nebula is moving towards the Milky Way, and, therefore, towards the Solar System. The approach speed is about 140 km/s. Accordingly, the meeting of two stellar giants will take place somewhere in 2.5-3 billion years. This will not be a meeting on the Elbe, but it will not be a global catastrophe on a cosmic scale either..
Two Galaxies will simply merge into one. But which one will dominate - here the scales tip in favor of Andromeda. It has more mass, and it already has experience in absorbing other galactic systems.
As for the solar system, forecasts vary. The most pessimistic indicates that the Sun with all the planets will simply be thrown into intergalactic space, that is, there will be no place for it in the new formation.
But maybe this is for the better. After all, it is clear from everything that the Andromeda Galaxy is a kind of bloodthirsty monster, devouring its own kind. Having absorbed the Milky Way and destroyed its core, the Nebula will turn into a huge Nebula and continue its path across the expanses of the Universe, eating more and more new galaxies. The end result of this journey will be the collapse of an incredibly swollen, overly gigantic star system.
The Andromeda nebula will disintegrate into countless small stellar formations, exactly repeating the fate of the huge empires of human civilization, which first grew to unprecedented sizes, and then collapsed with a roar, unable to bear the burden of their own greed, self-interest and lust for power.
But you shouldn’t worry about the events of future tragedies. It is better to consider another galaxy, which is called Triangulum Galaxy. It is located in the vastness of the Universe at a distance of 730 thousand parsecs from the Milky Way and is two times smaller in size, and no less than seven times smaller in mass. That is, this is an ordinary mediocre galaxy, of which there are a great many in Space.
All these three star systems, along with several dozen more dwarf galaxies, are part of the so-called Local Group, which is part of Virgo Supercluster– a huge star formation, the size of which is 200 million light years.
The Milky Way, the Andromeda Galaxy and the Triangulum Galaxy have many similarities. All of them belong to the so-called spiral galaxies. Their disks are flat and consist of young stars, open star clusters and interstellar matter. In the center of each disc there is a thickening (bulge). The main feature, of course, is the presence of bright spiral arms containing many young and hot stars.
The cores of these galaxies are also similar in that they contain clusters of old stars and gas rings in which new stars are born. An invariable attribute of the central part of each nucleus is the presence of a black hole with a very large mass. It has already been mentioned that the mass of the Milky Way black hole corresponds to more than three million masses of the Suns.
Black holes– one of the most impenetrable mysteries of the Universe. Of course, they are observed and studied, but these mysterious formations are in no hurry to reveal their secrets. It is known that black holes have a very high density, and their gravitational field is so powerful that even light cannot escape from them.
But any cosmic body that finds itself in the zone of influence of one of them ( event threshold), will be immediately “swallowed” by this terrible universal monster. What will be the future fate of the “unfortunate” is unknown. In short, it’s easy to get into a black hole, but impossible to get out of.
There are many black holes scattered across the expanses of space, some of them have a mass many times greater than the mass of the black hole at the center of the Milky Way. But this does not mean that the monster “native” to the Solar System is more harmless than its larger colleagues. It is also insatiable and bloodthirsty and is a compact (diameter equal to 12.5 light hours) and powerful source of X-ray radiation.
The name of this mysterious object Sagittarius A. Its mass has already been mentioned - more than 3 million solar masses, and the gravitational trap (event threshold) of the baby is measured at 68 astronomical units (1 AU is equal to the average distance of the Earth from the Sun). It is within these limits that the border of his bloodthirstiness and treachery lies in relation to various cosmic bodies, which, for a number of reasons, frivolously cross it.
Someone probably naively thinks that the baby is content with random victims - nothing like that: he has a constant source of food. This is the star S2. It revolves around a black hole in a very compact orbit - a full revolution is only 15.6 years. The maximum distance of S2 from the terrible monster is within 5 light days, and the minimum is only 17 light hours.
Under the influence of the tidal forces of a black hole, part of its substance is torn off from the star doomed to be slaughtered and flies at great speed towards this terrible cosmic monster. As it approaches, the substance turns into a state of hot plasma and, emitting a farewell bright glow, disappears forever into the insatiable invisible abyss.
But that’s not all: the insidiousness of a black hole has no limits. Next to it there is another, less massive and dense black hole. Its task is to adjust stars, planets, interstellar dust and gas clouds to its more powerful brother. All this also turns into plasma, emits bright light and disappears into nothingness.
However, not all scientists, despite such a demonstrative bloody interpretation of events, are of the opinion that black holes exist. Some argue that this is an unknown mass, driven under a cold, dense shell. It has enormous density and is bursting from the inside, squeezing it with incredible force. This kind of education is called gravastar– gravitational star.
They are trying to fit the entire Universe under this model, thus explaining its expansion. Proponents of this concept argue that outer space is a giant bubble, inflated by an unknown force. That is, the entire Cosmos is a huge gravastor, in which smaller models of gravastors coexist, periodically absorbing individual stars and other formations.
The absorbed bodies are, as it were, thrown into other outer spaces, which are essentially invisible, since they do not let out light from under the absolutely black shell. Maybe gravastors are other dimensions or parallel worlds? A specific answer to this question will not be found for a very, very long time.
But it’s not just the presence or absence of black holes that occupies the minds of space researchers. Much more interesting and exciting are thoughts about the existence of intelligent life in other star systems of the Universe.
The Sun, which gives life to earthlings, rotates among many other suns of the Milky Way. Its disk is visible from Earth as a pale shining strip encircling the celestial sphere. These are distant billions and billions of stars, many of which have their own planetary systems. Is there really not one among the countless number of these planets where intelligent beings live - brothers in mind?
The most reasonable assumption is that life similar to Earth could arise on a planet that orbits a star of the same class as the Sun. There is such a star in the sky, and besides, it is located in the star system closest to the earth’s body. This is Alpha Centauri A, located in the constellation Centaurus. From the earth it is visible to the naked eye, and its distance from the Sun is 4.36 light years.
It would be nice, of course, to have reasonable neighbors right next door. But what is desired does not always coincide with reality. Finding signs of an extraterrestrial civilization, even at a distance of some 4-6 light years, is a rather difficult task with current technological advances. Therefore, it is premature to talk about the existence of any intelligence in the constellation Centaurus.
Nowadays, it is only possible to send radio signals into space, hoping that someone unknown will answer the call of human intelligence. The most powerful radio stations in the world have been persistently and non-stop engaged in such activities since the first half of the 20th century. As a result, the level of radio emission from the Earth has increased significantly. The blue planet began to differ sharply in its radiation background from all other planets in the solar system.
Signals from Earth cover outer space with a radius of at least 90 light years. On the scale of the Universe, this is a drop in the ocean, but as you know, this little thing wears away the stone. If somewhere far, far away in Space there is highly developed intelligent life, then, in any case, it must someday turn its attention to both the increased background radiation in the depths of the Milky Way galaxy and the radio signals coming from there. Such an interesting phenomenon will not leave the inquisitive minds of aliens indifferent.
Accordingly, an active search for signals from space has been established. But the dark abyss is silent, which indicates that within the Milky Way there are most likely no intelligent creatures ready to come into contact with the inhabitants of planet Earth, or their technical development is at a very primitive level. The truth suggests another thought, which suggests that a highly developed civilization, or civilizations, exists, but sends some other signals into the expanses of the Galaxy that cannot be picked up by earthly technical means.
Progress on the blue planet is steadily developing and improving. Scientists are developing new, completely different ways to transmit information over long distances. All this can have a positive effect. But we must not forget that the vastness of the Universe is limitless. There are stars, the light from which reaches the Earth after billions of years. In fact, a person sees a picture of the distant past when he observes such a cosmic object through a telescope.
It may happen that the signal received by earthlings from Space will turn out to be the voice of a long-vanished extraterrestrial civilization that lived at a time when neither the Solar System nor the Milky Way existed. The response message from Earth will reach the aliens, who were not even in the project at the time when it was sent.
Well, we must take into account the laws of harsh reality. In any case, the search for intelligence in distant galactic worlds cannot be stopped. If current generations are unlucky, future generations will be lucky. Hope in this case will never die, and perseverance and perseverance will undoubtedly pay off handsomely.
But the exploration of galactic space seems quite realistic and close. Already in the next century, fast and graceful spaceships will fly to the nearest constellations. The astronauts on board will observe through their windows not the planet Earth, but the entire solar system. They will see her in the form of a distant, bright star. But this will not be the cold, soulless shine of one of the countless suns of the Galaxy, but the native radiance of the Sun, around which Mother Earth will revolve as an invisible, soul-warming speck of dust.
Very soon, the dreams of science fiction writers, reflected in their works, will become an ordinary everyday reality, and a walk along the Milky Way will become a rather boring and tedious activity, like, for example, a trip in a subway car from one end of Moscow to the other.
The cosmos that we are trying to study is a huge and endless 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 formation.
Our Earth, like the other planets of the Milky Way, our star called the Sun, like other stars of the Milky Way, move in the Universe in a certain order and occupy designated 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 Big Bang theory is a nuclear chain reaction at the microscopic level. Initially, there was some kind of substance that, for certain reasons, instantly began to move and exploded. There is no need to talk about the conditions that led to the onset of the explosive reaction. This is far from our understanding. Now the Universe, formed 15 billion years ago as a result of a cataclysm, is a huge, endless polygon.
The primary products of the explosion initially consisted of accumulations and clouds of gas. Subsequently, under the influence of gravitational forces and other physical processes, the formation of larger objects on a universal scale occurred. Everything happened very quickly by cosmic standards, over billions of years. First there was the formation of stars, which formed clusters and later merged into galaxies, the exact number of which is unknown. In its composition, galactic matter is atoms of hydrogen and helium 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 exact center of the universe is unknown.
Due to the similarity of the processes that formed the Universe, our galaxy is very similar in structure to many others. By its type, it is a typical spiral galaxy, a type of object that is widespread in the Universe. In terms of its size, the galaxy is in the golden mean - neither small nor huge. Our galaxy has many more smaller stellar neighbors than those of colossal size.
The age of all galaxies that exist in outer space is also the same. Our galaxy is almost the same age as the Universe and is 14.5 billion years old. Over this enormous period of time, the structure of the Milky Way has changed several times, and this is still happening today, only imperceptibly, in comparison with the pace of earthly life.
There is a curious story about the name of our galaxy. 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 a nurse to be fattened. During feeding, splashes of milk fell on the sky, thereby creating a milk trail. Subsequently, scientists and astronomers of all times and peoples agreed that our galaxy is indeed very similar to a milk road.
The Milky Way is currently in the middle of its development cycle. In other words, the cosmic gas and material to form new stars is running out. 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 cease to exist as a result of another universal cataclysm. Research topics in recent years are focused on the upcoming meeting of the Milky Way with our closest neighbor, the Andromeda galaxy, in the distant future. It is likely that the Milky Way will break up into several small galaxies after meeting the Andromeda Galaxy. In any case, this will be the reason for the emergence of new stars and the reorganization of the space closest to us. We can only guess what the fate of the Universe and our galaxy will be in the distant future.
Astrophysical parameters of the Milky Way
In order to imagine what the Milky Way looks like on a cosmic scale, 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 formation. Here our cosmic metropolis neighbors the Andromeda and Triangulum galaxies. The trio is surrounded by 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 located. The scale of the formations is so enormous that it is almost impossible to imagine it all. Today we know the distance to the nearest neighboring galaxies. Other deep space objects are out of sight. Their existence is only theoretically and mathematically allowed.
The location of the galaxy became known only thanks to approximate calculations that determined the distance to its nearest neighbors. The Milky Way's satellites are dwarf galaxies - the Small and Large Magellanic Clouds. In total, according to scientists, there are up to 14 satellite galaxies that form 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, is compiled on the basis of mathematical calculations, data obtained as a result of astrophysical observations. Each cosmic body or fragment of the galaxy takes its place. It’s like in the Universe, only on a smaller scale. The astrophysical parameters of our cosmic metropolis are interesting, and they are impressive.
Our galaxy is a barred spiral galaxy, which is designated on star maps 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 our neighbor is than the Milky Way. The sizes of the dwarf galaxies closest to the Milky Way are tens of times smaller than those of our galaxy. Magellanic clouds have a diameter of only 7-10 thousand light years. There are about 200-400 billion stars in this huge stellar cycle. 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 there are, the more crowded outer 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 more than the mass of our Sun. Almost all the stars inhabiting 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, which 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 rapidly moves around the center of the galaxy, completing a full revolution every 240 million years.
The center of the galaxy has a diameter of 1000 parsecs 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 total is greater than that emitted by the billions of stars that make up the galaxy. This part of the core is the most active and brightest part of the galaxy. At the edges of the core there is a bridge, which is the beginning of the arms of our galaxy. Such a bridge arises as a result of the colossal gravitational force caused by the rapid speed of rotation of the galaxy itself.
Considering the central part of the galaxy, the following fact appears paradoxical. Scientists for a long time could not understand what is in the center of the Milky Way. It turns out that in the very center of a star country called the Milky Way there is a supermassive black hole, the diameter of which is about 140 km. It is there that most of the energy released by the galactic core goes; it is in this bottomless abyss that 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 end someday. Matter will turn into antimatter and everything will happen 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 strength.
The two main arms of the galaxy extend from the center - the Shield of the Centaur and the Shield of Perseus. These structural formations received their names from the constellations located in the sky. In addition to the main arms, the galaxy is surrounded by 5 more minor arms.
Near and distant future
The arms, born from the core of the Milky Way, unwind in a spiral, 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 natures, spins on a giant carousel. All of them create a wonderful picture of the starry sky, which people have been looking at for thousands of years. When studying our galaxy, you should know that the stars in the galaxy live according to their own laws, being today in one of the arms of the galaxy, tomorrow they will begin their journey in the other direction, leaving one arm and flying to 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 is lost in the vast star world of our galaxy. There can be a huge number of such Earth-like planets in the galaxy. It is enough to imagine the number of stars that in one way or another 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, present in neighboring areas that are hidden from us by the arms of the Milky Way.
Hello, dear guys! And greetings to you, dear parents! I invite you to go on a small journey into the cosmic world, full of the unknown and enchanting.
How often do we look into a dark sky full of bright stars, trying to find the constellations discovered by astronomers. Have you ever seen the Milky Way in the sky? Let's take a closer look at this unique cosmic phenomenon. And at the same time we will get information for an educational and interesting “space” project.
Lesson plan:
Why is it called that?
This star trail in the sky looks like a white stripe. Ancient people explained this phenomenon seen in the starry night sky with the help of mythological stories. Different peoples had their own versions of the appearance of an unusual sky strip.
The most widespread hypothesis is that of the ancient Greeks, according to which the Milky Way is nothing more than the spilled mother’s milk of the Greek goddess Hera. Likewise, explanatory dictionaries interpret the adjective “milky” as “reminiscent of milk.”
There’s even a song about it, you’ve probably heard it at least once. And if not, then listen right now.
Because of the way the Milky Way looks, it has several names:
- the Chinese call it the “yellow road”, believing that it looks more like straw;
- The Buryats call the star stripe the “seam of the sky” from which the stars scattered;
- among the Hungarians it is associated with the road of warriors;
- ancient Indians considered it the milk of the evening red cow.
How to see the “milk track”?
Of course, this is not milk that someone spills across the night sky every day. The Milky Way is a giant star system called a “Galaxy”. In appearance, it looks like a spiral, in the center of which there is a core, and arms extend from it like rays, of which the Galaxy has four.
How to find this white path of stars? You can even see a star cluster with the naked eye in the night sky when there are no clouds. All inhabitants of the Milky Way are located on the same line.
If you are a resident of the northern hemisphere, then you can find a place where there is a scattering of stars at midnight in July. In August, when it gets dark earlier, it will be possible to search for the spiral of the Galaxy starting at ten in the evening, and in September - after 20.00. You can see all the beauty by first finding the constellation Cygnus and moving from it with your gaze to the north - northeast.
To see the brightest stellar segments, you need to go to the equator, or even better, closer to 20-40 degrees south latitude. It is there that at the end of April - beginning of May the Southern Cross and Sirius flaunt in the night sky, between which the treasured galactic star path passes.
When the constellations Sagittarius and Scorpio rise in the eastern part by June-July, the Milky Way gains particular brightness, and clouds of cosmic dust can even be seen between distant stars.
Seeing various photographs, many wonder: why do we see not a spiral, but only a stripe? The answer to this question is very simple: we are inside the Galaxy! If we stand in the center of a sports hoop and raise it at eye level, what will we see? That's right: a stripe in front of your eyes!
The galactic core can be found in the constellation Sagittarius using radio telescopes. But you shouldn’t expect much brightness from it. The central part is the darkest due to the large amount of cosmic dust in it.
What is the Milky Way made of?
Our Galaxy is just one of millions of star systems that have been found by astronomers, but it is quite a large one. The Milky Way has approximately 300 billion stars. The Sun, which rises every day in the sky, is also part of them, revolving around the core. The Galaxy has stars much larger and brighter than the Sun, and there are smaller ones that emit faint light.
They differ not only in size, but also in color - they can be white-blue (they are the hottest) and red (the coldest). They all move together in a circle along with the planets. Just imagine that we go through a full revolution around the galactic circle in almost 250 million years - that’s how long one galactic year lasts.
Stars live in the strip of the Milky Way, forming groups that scientists call clusters, differing in age and stellar composition.
- Small open clusters are the youngest, they are only about 10 million years old, but this is where the massive and bright celestial representatives live. Such groups of stars are located along the edge of the plane.
- Globular clusters are very old, they were formed over 10 - 15 billion years, they are located in the center.
10 interesting facts
As always, I advise you to decorate your research work with the most interesting “galactic” facts. Watch the video carefully and be surprised!
This is our Galaxy, in which we live among wonderful, bright neighbors. If you are not yet personally familiar with the “milk path,” then quickly go outside to see all the starry beauty in the night sky.
By the way, have you already read the article about our cosmic neighbor the Moon? Not yet? Then take a look soon)
Good luck in your studies!
Evgenia Klimkovich.
The solar system is immersed in a huge star system - the Galaxy, numbering hundreds of billions of stars of very different luminosity and color (Stars in the section: "Life of stars"). The properties of different types of stars in the Galaxy are quite well known to astronomers. Our neighbors are not just typical stars and other celestial objects, but rather representatives of the most numerous “tribes” of the Galaxy. At present, all or almost all stars in the vicinity of the Sun have been studied, with the exception of very dwarf ones, which emit very little light. Most of them are very faint red dwarfs - their masses are 3-10 times less than that of the Sun. Stars similar to the Sun are very rare, only 6% of them. Many of our neighbors (72%) are grouped into multiple systems, where the components are connected to each other by gravitational forces. Which of the hundreds of nearby stars can claim the title of the closest neighbor of the Sun? Now it is considered a component of the famous triple system Alpha Centauri - the faint red dwarf Proxima. The distance to the proxima is 1.31 pc, the light from it travels to us in 4.2 years. Statistics of the circumsolar population provide insight into the evolution of the galactic disk and the galaxy as a whole. For example, the luminosity distribution of solar-type stars shows that the age of the disk is 10-13 billion years.
In the 17th century, after the invention of the telescope, scientists first realized how large the number of stars is in outer space. In 1755, German philosopher and naturalist Immanuel Kant proposed that stars form groups in the cosmos, just as the planets form the solar system. He called these groups “star islands.” According to Kant, one of these countless islands is the Milky Way - a grandiose cluster of stars, visible in the sky as a light, foggy stripe. In ancient Greek, the word "galaktikos" means "milky", which is why the Milky Way and similar star systems are called galaxies.
Dimensions and structure of our Galaxy
Based on the results of his calculations, Herschel attempted to determine the size and forms a kind of thick disk: in the plane of the Milky Way it extends to a distance of no more than 850 units, and in the perpendicular direction - to 200 units, if we take the distance to Sirius as one. According to the modern distance scale, this corresponds to 7300X1700 light years. This estimate generally correctly reflects the structure of the Milky Way, although it is highly imprecise. The fact is that in addition to stars, the Galaxy’s disk also includes numerous gas and dust clouds that weaken the light of distant stars. The first explorers of the Galaxy did not know about this absorbing substance and believed that they saw all its stars.
The true size of the Galaxy was established only in the 20th century. It turned out that it is a much flatter formation than previously thought. The diameter of the galactic disk exceeds 100 thousand light years, and the thickness is about 1000 light years. Due to the fact that the Solar System is located practically in the plane of the Galaxy, filled with absorbing matter, many details of the structure of the Milky Way are hidden from the view of an earthly observer. However, they can be studied using the example of other galaxies similar to Shasha. So, in the 40s. XX century, observing the galaxy M 31, better known as the Andromeda nebula, German astronomer Walter Baade noticed that the flat lens-shaped disk of this huge galaxy is immersed in a more rarefied spherical star cloud - a halo. Since the nebula is very similar to our Galaxy, he suggested that the Milky Way also has a similar structure. Galactic disk stars were called population type I, and halo stars were called population type II.
As modern research shows, the two types of stellar populations differ not only in their spatial position, but also in the nature of their motion, as well as their chemical composition. These features are associated primarily with the different origin of the disk and the spherical component.
Galaxy Structure: Halo
The boundaries of our Galaxy are determined by the size of the halo. The radius of the halo is significantly larger than the size of the disk and, according to some data, reaches several hundred thousand light years. The center of symmetry of the Milky Way halo coincides with the center of the galactic disk. The halo consists mainly of very old, dim, low-mass stars. They occur individually and in globular clusters that can contain more than a million stars. The age of the population of the spherical component of the Galaxy exceeds 12 billion years. It is usually taken to be the age of the Galaxy itself. A characteristic feature of halo stars is the extremely small proportion of heavy chemical elements in them. The stars that form globular clusters contain hundreds of times less metal than the Sun.
Stars of the spherical component are concentrated towards the center of the Galaxy. The central, densest part of the halo within several thousand light years from the center of the Galaxy is called the “bulge”. Stars and halo star clusters move around the center of the Galaxy in very elongated orbits. Because individual stars rotate almost randomly, the halo as a whole rotates very slowly.
Structure of the Galaxy: Disk
Compared to a halo, the disk rotates noticeably faster. The speed of its rotation is not the same at different distances from the center. It quickly increases from zero at the center to 200-240 km/s at a distance of 2 thousand light years from it, then decreases somewhat, increases again to approximately the same value and then remains almost constant. Studying the characteristics of the disk's rotation made it possible to estimate its mass. It turned out that it is 150 billion times the mass of the Sun. The population of the disk is very different from the population of the halo. 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.
The gas in the Galaxy's disk is also concentrated mainly near its plane. It is located unevenly, forming numerous gas clouds - giant superclouds, heterogeneous in structure, extending several thousand light years to small clouds no larger than a parsec in size. The main chemical element in our Galaxy is hydrogen. Approximately 1/4 of it consists of helium. Compared to these two elements, the others are present in very small quantities. On average, the chemical composition of the stars and gas in the disk is almost the same as that of the Sun.
Structure of the Galaxy: Core
One of the most interesting regions of the Galaxy is considered to be its center, or core, located in the direction of the constellation Sagittarius. The visible radiation from the central regions of the Galaxy is completely hidden from us by thick layers of absorbing matter. Therefore, it began to be studied only after the creation of receivers for infrared and radio radiation, which are absorbed to a lesser extent. The central regions of the Galaxy are characterized by a strong concentration of stars: each cubic parsec near the center contains many thousands of them. The distances between stars are tens and hundreds of times smaller than in the vicinity of the Sun. If we lived on a planet near a star located near the core of the Galaxy, then dozens of stars would be visible in the sky, comparable in brightness to the Moon, and many thousands brighter than the brightest stars in our sky.
In addition to a large number of stars, a circumnuclear gas disk consisting predominantly of molecular hydrogen is observed in the central region of the Galaxy. Its radius exceeds 1000 light years. Closer to the center, areas of ionized hydrogen and numerous sources of infrared radiation are noted, indicating star formation occurring there. In the very center of the Galaxy, the existence of a massive compact object is assumed - a black hole with a mass of about a million solar masses. In the center there is also a bright radio source, Sagittarius A, the origin of which is associated with the activity of the nucleus.
