Scale of the Universe

Star systems

You know that our Earth with its planets, other planets and their satellites, comets and small planets revolve around the Sun, that all these bodies make up the Solar System. In turn, the Sun and all other stars visible in the sky are part of a huge star system - our Galaxy. The star closest to the solar system is so far away that light, which travels at a speed of 300,000 km/s, takes more than four years to travel from it to Earth. Stars are the most common type of celestial body; there are more than one in our Galaxy alone several hundred billion. The volume occupied by this star system is so large that light can cross it in only 100 thousand years.

The main structural units of the Universe are “stellar islands” - similar to ours. One of them is located in the constellation Andromeda. This is a giant galaxy, similar in structure to ours and consisting of hundreds of billions of stars. The light from it to the Earth travels more than 2 million years. The Andromeda Galaxy, together with our Galaxy and several other galaxies of smaller mass, form the so-called Local group. Some of the star systems of this group, including the Large and Small Magellanic Clouds, galaxies in the constellations Sculptor, Ursa Minor, Draco, and Orion, are satellites of our Galaxy. Together with her they turn around general center wt. It is the location and movement of galaxies that determines the structure and structure of the Universe as a whole.

The galaxies are so far from each other that only the three closest ones can be seen with the naked eye: two in the Southern Hemisphere - Large Magellanic Cloud, Small Magellanic Cloud, and from the north there is only one - Andromeda's nebula.

Dwarf galaxy in the constellation Sagittarius- closest to . This small galaxy is so close that Milky Way as if absorbing it. The Sagittarius Galaxy lies 80 thousand light years from the Sun and 52 thousand light years from the center of the Milky Way. The next closest galaxy to us is the Large Magellanic Cloud, located 170 thousand light years away. Until 1994, when a dwarf galaxy in the constellation Sagittarius was discovered, it was thought that the closest galaxy was the Large Magellanic Cloud.

The Sagittarius dwarf galaxy was originally a sphere approximately 1,000 light-years across. But now its shape is distorted by the gravity of the Milky Way, and the galaxy has stretched 10 thousand light years in length. Several million stars that belong to the dwarf in Sagittarius are now scattered throughout the constellation Sagittarius. Therefore, if you just look at the sky, the stars of this galaxy cannot be distinguished from the stars of our own Galaxy.

Cosmic distances

From the most distant galaxies, light reaches Earth in 10 billion years. A significant part of the matter of stars and galaxies is in conditions that cannot be created in earthly laboratories. All outer space is filled with electromagnetic radiation, gravitational and magnetic fields; between stars in galaxies and between galaxies there is very rarefied matter in the form of gas, dust, individual molecules, atoms and ions, atomic nuclei and elementary particles. As you know, the distance to the closest celestial body to the Earth, the Moon, is approximately 400,000 km. The most distant objects are located at a distance from us that is more than 10 times greater than the distance to the Moon. Let's try to imagine the sizes of celestial bodies and the distances between them in the Universe, using the well famous model- a school globe of the Earth, which is 50 million times smaller than our planet. In this case, we must depict the Moon as a ball with a diameter of approximately 7 cm, located at a distance of about 7.5 m from the globe. The model of the Sun will have a diameter of 28 m and be at a distance of 3 km, and the model of Pluto will be the most distant planet solar system- will be 120 km away from us. The closest star to us at this scale of the model will be located at a distance of approximately 800,000 km, i.e. 2 times further than the Moon. The size of our Galaxy will shrink to approximately the size of the Solar System, but the most distant stars will still be located outside of it.

Since all galaxies are moving away from us, one involuntarily gets the impression that our Galaxy is in the center of expansion, in a stationary central point expanding universe. In reality, we are dealing with one of the astronomical illusions. The expansion of the Universe occurs in such a way that there is no “predominant” fixed point in it. Whichever two galaxies we choose, the distance between them will increase over time. This means that no matter which galaxy the observer finds himself in, he will also see a picture of the scattering of stellar islands, similar to the one we see.

Local group at a speed of several hundred kilometers per second, it is moving towards another cluster of galaxies in the constellation Virgo. The Virgo cluster is the center of an even more gigantic system of stellar islands - Superclusters of galaxies, which includes the Local Group along with our Galaxy. According to observational data, superclusters include over 90% of all existing galaxies and occupy about 10% of the total volume of space in our Universe. Superclusters have masses of the order of 10 15 solar masses. Modern means A colossal region of space with a radius of about 10-12 billion light years is available for astronomical research. In this area, according to modern estimates, there are 10 10 galaxies. Their totality was called Metagalaxies.

So, we live in a non-stationary, expanding Universe, which changes over time and whose past is not identical to its current state, and the modern is not identical to its future.

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Astronomy is the science of celestial bodies (from the ancient Greek words aston - star and nomos - law). It studies visible and actual movements and the laws that determine these movements, shape, size, mass and surface relief, the nature and physical state of celestial bodies, interaction and their evolution.

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Exploring the Universe The number of stars in the galaxy is in the trillions. The most numerous stars are dwarfs with masses of about 10 times smaller than the sun. In addition to single stars and their satellites (planets), the Galaxy includes double and multiple stars, as well as groups of stars bound by gravity and moving in space as a single whole, called star clusters. Some of them can be found in the sky through a telescope, and sometimes even with the naked eye. Such clusters do not have a regular shape; more than a thousand of them are currently known. Star clusters are divided into open and globular. Unlike open star clusters, which consist primarily of main sequence stars, globular clusters contain red and yellow giants and supergiants. Sky surveys made by X-ray telescopes mounted on special artificial satellites Earth, led to the discovery of X-ray emissions from many globular clusters.

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Structure of the Galaxy The overwhelming majority of stars and diffuse matter in the Galaxy occupies a lens-shaped volume. The Sun is located at a distance of about 10,000 Pc from the center of the Galaxy, hidden from us by clouds of interstellar dust. At the center of the Galaxy there is a nucleus, which has recently been carefully studied in the infrared, radio and X-ray wavelengths. Opaque clouds of dust obscure the core from us, preventing visual and conventional photographic observations of this most interesting object in the Galaxy. If we could look at the galactic disk "from above", we would find huge spiral arms, mainly containing the hottest and most bright stars, as well as massive gas clouds. The disk with spiral branches forms the basis of the flat subsystem of the Galaxy. And objects that concentrate towards the Galactic core and only partially penetrate into the disk belong to the spherical subsystem. This is a simplified form of the structure of the Galaxy.

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Types of galaxies 1 Spiral. This is 30% of galaxies. They come in two types. Normal and crossed. 2 Elliptical. Most galaxies are believed to have the shape of an oblate sphere. Among them there are spherical and almost flat. The largest known elliptical galaxy is M87 in the constellation Virgo. 3 Not correct. Many galaxies have a ragged shape without a clearly defined outline. These include Our Local Group's Magellanic Cloud.

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The Sun The Sun is the center of our planetary system, its main element, without which there would be neither the Earth nor life on it. People have been observing the star since ancient times. Since then, our knowledge of the luminary has expanded significantly, enriched with numerous information about the movement, internal structure and nature of this cosmic object. Moreover, the study of the Sun makes a huge contribution to the understanding of the structure of the Universe as a whole, especially those of its elements that are similar in essence and principles of “work”.

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The Sun The Sun is an object that has existed, by human standards, for a very long time. Its formation began approximately 5 billion years ago. At that time, in place of the solar system there was a vast molecular cloud. Under the influence of gravitational forces, vortices began to appear in it, similar to earthly tornadoes. In the center of one of them, the substance (mostly hydrogen) began to become denser, and 4.5 billion years ago a young star appeared here, which after a long period of time received the name Sun. Planets gradually began to form around it - our corner of the Universe began to acquire the familiar modern man view. -

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The yellow dwarf Sun is not a unique object. It is classified as a yellow dwarf, a relatively small main sequence star. The “service life” allotted to such bodies is approximately 10 billion years. By space standards, this is quite a bit. Now our luminary, one might say, is in the prime of his life: not yet old, no longer young - there is still half his life ahead.

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Light Year A light year is the distance that light travels in one year. The International Astronomical Union has given its explanation of the light year - this is the distance that light travels in a vacuum, without the participation of gravity, in a Julian year. The Julian year is equal to 365 days. It is this decoding that is used in scientific literature. If we take professional literature, then the distance is calculated in parsecs or kilo- and megaparsecs. Until 1984, a light year was the distance that light travels in one tropical year. The new definition differs from the old one by only 0.002%. There is no particular difference between the definitions. There are specific numbers that determine the distance of light hours, minutes, days, etc. A light year is equal to 9,460,800,000,000 km, a month is 788,333 million km, a week is 197,083 million km, a day is 26,277 million km, an hour is 1,094 million km, a minute is about 18 million km., second - about 300 thousand km.

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Galaxy Constellation Virgo Virgo can be best seen in early spring, namely in March - April, when it moves to the southern part of the horizon. Due to the fact that the constellation has an impressive size, the Sun is in it for more than a month - from September 16 to October 30. On ancient star atlases, Virgo was represented as a girl with an ear of wheat in right hand. However, not everyone is able to discern just such an image in a chaotic scattering of stars. However, finding the Virgo constellation in the sky is not that difficult. It contains a star of the first magnitude, thanks to the bright light of which Virgo can be easily found among other constellations.

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Andromeda Nebula The closest large galaxy to the Milky Way. Contains approximately 1 trillion stars, which is 2.5-5 times larger than the Milky Way. It is located in the constellation Andromeda and is distant from Earth at a distance of 2.52 million light years. years. The plane of the galaxy is inclined to the line of sight at an angle of 15°, its apparent size is 3.2 × 1.0°, its apparent magnitude is +3.4m.

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Milky Way The Milky Way is a spiral galaxy. Moreover, it has a bridge in the form of a huge star system, interconnected by gravitational forces. The Milky Way is believed to have existed for over thirteen billion years. This is the period during which about 400 billion constellations and stars, over a thousand huge gas nebulae, clusters and clouds were formed in this Galaxy. The shape of the Milky Way is clearly visible on the map of the Universe. Upon examination, it becomes clear that this cluster of stars is a disk whose diameter is 100 thousand light years (one such light year is ten trillion kilometers). The thickness of the star cluster is 15 thousand, and the depth is about 8 thousand light years. How much does the Milky Way weigh? This (the definition of its mass is very difficult task) it is not possible to calculate. Difficulties arise in determining the mass of dark matter, which does not interact with electromagnetic radiation. This is why astronomers cannot definitively answer this question. But there are rough calculations according to which the weight of the Galaxy ranges from 500 to 3000 billion solar masses

Which are on it. For the most part, we are all chained to the place where we live and work. The size of our world is amazing, but it is absolutely nothing compared to the Universe. As the saying goes - "born too late to explore the world, and too early to explore space". It's even insulting. However, let's get started - just be careful not to get dizzy.

1. This is Earth.

This is the same planet that this moment is the only home for humanity. The place where life magically appeared (or maybe not so magically) and in the course of evolution you and I appeared.

2. Our place in the solar system.

The closest large space objects that surround us, of course, are our neighbors in the solar system. Everyone remembers their names from childhood, and during lessons about the world around them they make models. It so happened that even among them we are not the biggest...

3. The distance between our Earth and the Moon.

It doesn't seem that far, right? And if we also take into account modern speeds, then it’s “nothing at all.”

4. In fact, it’s quite far away.

If you try, then very accurately and comfortably - between the planet and the satellite you can easily place the rest of the planets of the solar system.

5. However, let's continue talking about planets.

Before you is North America, as if it were placed on Jupiter. Yes, this small green speck is North America. Can you imagine how huge our Earth would be if we moved it to the scale of Jupiter? People would probably still be discovering new lands)

6. This is Earth compared to Jupiter.

Well, more precisely six Earths - for clarity.

7. Rings of Saturn, sir.

The rings of Saturn would have such a gorgeous appearance, provided they revolved around the Earth. Look at Polynesia - a bit like the Opera icon, right?

8. Let's compare the Earth with the Sun?

It doesn't look that big in the sky...

9. This is the view of the Earth when looking at it from the Moon.

Beautiful, right? So lonely against the backdrop of empty space. Or not empty? Let's continue...

10. And so from Mars

I bet you wouldn't even be able to tell if it was Earth.

11. This is a shot of Earth just beyond the rings of Saturn

12. But beyond Neptune.

A total of 4.5 billion kilometers. How long would it take to search?

13. So, let's go back to the star called the Sun.

A breathtaking sight, isn't it?

14. Here is the Sun from the surface of Mars.

15. And here is its comparison with the Scale of the star VY Canis Majoris.

How do you like it? More than impressive. Can you imagine the energy concentrated there?

16. But this is all bullshit, if you compare ours native star the size of the Milky Way galaxy.

To make it more clear, imagine that we have compressed our Sun to the size of a white blood cell. In this case, the size of the Milky Way is quite comparable to the size of Russia, for example. This is the Milky Way.

17. In general, stars are huge

Everything that is placed in this yellow circle is everything that you can see at night from Earth. The rest is inaccessible to the naked eye.

18. But there are other galaxies.

Here is the Milky Way compared to the galaxy IC 1011, which is located 350 million light years from Earth.

Let's go over it again?

So, this Earth is our home.

Let's zoom out to the size of the solar system...

Let's zoom out a little more...

And now to the size of the Milky Way...

Let's continue to reduce...

And further…

Almost ready, don't worry...

Ready! Finish!

This is all that humanity can now observe using modern technology. It’s not even an ant... Judge for yourself, just don’t go crazy...

Such scales are hard to even comprehend. But someone confidently declares that we are alone in the Universe, although they themselves are not really sure whether the Americans were on the Moon or not.

Hang in there guys... hang in there.

There were times when the world of people was limited to the surface of the Earth under their feet. With the development of technology, humanity has expanded its horizons. Now people are thinking about whether our world has boundaries and what is the scale of the Universe? In fact, no one can imagine its real size. Because we don't have any suitable reference points. Even professional astronomers imagine (at least in their imagination) models reduced many times over. It is important to accurately correlate the dimensions of objects in the Universe. And when solving mathematical problems, they are generally unimportant, because they turn out to be just numbers that the astronomer operates with.

About the structure of the solar system

To talk about the scale of the Universe, we must first understand what is closest to us. First, there is a star called the Sun. Secondly, the planets orbiting around it. Besides them, there are also satellites moving around some of them. And we must not forget about

The planets on this list have been of interest to people for a long time, since they are the most accessible for observation. From their study, the science of the structure of the Universe began to develop - astronomy. The star is recognized as the center of the solar system. It is also its largest object. Compared to the Earth, the Sun is a million times larger in volume. It only seems relatively small because it is very far from our planet.

All planets of the solar system are divided into three groups:

• Earthly. It includes planets that are similar to Earth in external signs. For example, these are Mercury, Venus and Mars.
• Giant objects. They are much larger in size compared to the first group. In addition, they contain a lot of gases, which is why they are also called gaseous. These include Jupiter, Saturn, Uranus and Neptune.
• Dwarf planets. They are, in fact, large asteroids. One of them, until recently, was included in the composition of the main planets - this is Pluto.

The planets “do not fly away” from the Sun due to the force of gravity. But they cannot fall on a star due to high speeds. The objects are really very “nimble”. For example, the speed of the Earth is approximately 30 kilometers per second.

How to compare the sizes of objects in the Solar System?

Before you try to imagine the scale of the Universe, it is worth understanding the Sun and the planets. After all, they can also be difficult to correlate with each other. Most often, the conventional size of a fiery star is identified with a billiard ball, the diameter of which is 7 cm. It is worth noting that in reality it reaches about 1,400 thousand km. In such a “toy” model, the first planet from the Sun (Mercury) is at a distance of 2 meters 80 centimeters. In this case, the Earth's ball will have a diameter of only half a millimeter. It is located at a distance of 7.6 meters from the star. The distance to Jupiter on this scale will be 40 m, and to Pluto - 300.

If we talk about objects that are outside the Solar System, then the closest star is Proxima Centauri. It will be removed so much that this simplification is too small. And this despite the fact that it is located within the Galaxy. What can we say about the scale of the Universe? As you can see, it is virtually limitless. I always want to know how the Earth and the Universe are related. And after receiving the answer, I can’t believe that our planet and even the Galaxy are an insignificant part of a huge world.

What units are used to measure distances in space?

A centimeter, a meter and even a kilometer - all these quantities turn out to be insignificant already within the solar system. What can we say about the Universe? To indicate the distance within the Galaxy, a value called a light year is used. This is the time it would take for light to travel over one year. Let us remember that one light second is equal to almost 300 thousand km. Therefore, when converted to the usual kilometers, a light year turns out to be approximately equal to 10 thousand billion. It is impossible to imagine, therefore the scale of the Universe is unimaginable for humans. If you need to indicate the distance between neighboring galaxies, then a light year is not enough. An even larger value is needed. It turned out to be a parsec, which is equal to 3.26 light years.

How does the Galaxy work?

It is a giant formation consisting of stars and nebulae. A small part of them is visible every night in the sky. The structure of our Galaxy is very complex. It can be considered a highly compressed ellipsoid of revolution. Moreover, it has an equatorial part and a center. Galaxy Equator for the most part made up of gaseous nebulae and hot massive stars. In the Milky Way, this part is located in its central region.

The solar system is no exception to the rule. It is also located near the equator of the Galaxy. By the way, the main part of the stars forms a huge disk, the diameter of which is 100 thousand and the thickness is 1500. If we return to the scale that was used to represent the Solar System, then the size of the Galaxy will be commensurate. This is an incredible figure. Therefore, the Sun and the Earth turn out to be crumbs in the Galaxy.

What objects exist in the Universe?

Let's list the most important ones:

• Stars are massive self-luminous balls. They arise from an environment consisting of a mixture of dust and gases. Most of them are hydrogen and helium.
• CMB radiation. They are those spreading in space. Its temperature is 270 degrees Celsius. Moreover, this radiation is the same in all directions. This property is called isotropy. In addition, some mysteries of the Universe are associated with it. For example, it became clear that it arose at the moment of the big bang. That is, it exists from the very beginning of the existence of the Universe. It also confirms the idea that it is expanding equally in all directions. Moreover, this statement is true not only for the present time. It was like that at the very beginning.
• That is, hidden mass. These are those objects of the Universe that cannot be studied by direct observation. In other words, they do not emit electromagnetic waves. But they have a gravitational effect on other bodies.
• Black holes. They have not been sufficiently studied, but are very well known. This happened due to the massive description of such objects in science fiction works. Essentially, a black hole is a body from which it cannot spread electromagnetic radiation due to the fact that the second cosmic velocity on it is equal to It is worth remembering that it is the second cosmic velocity that must be communicated to the object in order for it to leave the space object.

In addition, there are quasars and pulsars in the Universe.

Mysterious Universe

It is full of things that have not yet been fully discovered or studied. And what has been discovered often raises new questions and related mysteries of the Universe. These can even include the well-known theory “ big bang" It is really only a conditional doctrine, since humanity can only guess at how it happened.

The second mystery is the age of the Universe. It can be calculated approximately by the already mentioned relict radiation, observation of globular clusters and other objects. Today, scientists agree that the age of the Universe is approximately 13.7 billion years. Another mystery - if there is life on other planets? After all, it was not only in the solar system that suitable conditions arose and the Earth appeared. And the Universe is most likely filled with similar formations.

One?

What is outside the Universe? What is there where the human gaze has not penetrated? Is there something beyond this border? If so, how many universes are there? These are questions that scientists have yet to find answers to. Our world is like a box of surprises. It once seemed to consist only of the Earth and the Sun, with a few stars in the sky. Then the worldview expanded. Accordingly, the boundaries have expanded. It is not surprising that many bright minds have long come to the conclusion that the Universe is only part of an even larger formation.

20. Radio communications between civilizations located on different planetary systems

21. Possibility of interstellar communication using optical methods

22. Communication with alien civilizations using automatic probes

23. Probability-theoretical analysis of interstellar radio communications. Character of signals

24. On the possibility of direct contacts between alien civilizations

25. Remarks on the pace and nature of technological development of mankind

II. Is communication with intelligent beings on other planets possible?

Part one ASTRONOMICAL ASPECT OF THE PROBLEM

1. The scale of the Universe and its structure If professional astronomers constantly and tangibly imagined the monstrous magnitude of cosmic distances and time intervals of the evolution of celestial bodies, it is unlikely that they could successfully develop the science to which they devoted their lives. The space-time scales familiar to us since childhood are so insignificant compared to cosmic ones that when it comes to consciousness, it literally takes your breath away. When dealing with any problem in space, an astronomer either solves a certain mathematical problem (this is most often done by specialists in celestial mechanics and theoretical astrophysicists), or improves instruments and observation methods, or builds in his imagination, consciously or unconsciously, some small model the space system under study. In this case, the main importance is a correct understanding of the relative sizes of the system being studied (for example, the ratio of the sizes of parts of a given space system, the ratio of the sizes of this system and others similar or dissimilar to it, etc.) and time intervals (for example, the ratio of the flow rate of a given process to the rate of occurrence of any other). The author of this book dealt quite a lot, for example, with the solar corona and the Galaxy. And they always seemed to him irregular shape spheroidal bodies of approximately the same size - something around 10 cm... Why 10 cm? This image arose subconsciously, simply because too often, while thinking about one or another issue of solar or galactic physics, the author drew the outlines of the objects of his thoughts in an ordinary notebook (in a box). I drew, trying to adhere to the scale of the phenomena. On one very interesting question, for example, it was possible to draw an interesting analogy between the solar corona and the Galaxy (or rather, the so-called “galactic corona”). Of course, the author of this book knew very well, so to speak, “intellectually,” that the dimensions of the galactic corona are hundreds of billions of times larger than the dimensions of the solar corona. But he calmly forgot about it. And if in a number of cases the large dimensions of the galactic corona acquired some fundamental significance (this also happened), this was taken into account formally and mathematically. And still, visually, both “crowns” seemed equally small... If the author, in the process of this work, had indulged philosophical reflections about the enormity of the size of the Galaxy, about the unimaginable rarefaction of the gas that makes up the galactic corona, about the insignificance of our little planet and our own existence, and about other other equally correct subjects, work on the problems of the solar and galactic coronas would stop automatically... Let him forgive me reader this" lyrical digression"I have no doubt that other astronomers had the same thoughts when they were working on their problems. It seems to me that sometimes it is useful to become more familiar with the “kitchen” of scientific work ... If we want to discuss exciting issues in the pages of this book about the possibility of intelligent life in the Universe, then, first of all, it will be necessary to form a correct idea of ​​​​its spatio-temporal scale. Until relatively recently, the globe seemed huge to man. It took over three years for the brave companions of Magellan to, 465 years ago, at the cost of incredible hardships, accomplish first trip around the world. A little over 100 years have passed since the resourceful hero fantasy novel Jules Verne made, using the latest technological advances of that time, a trip around the world in 80 days. And only 26 years have passed since those memorable days for all mankind, when the first Soviet cosmonaut Gagarin flew around on the legendary spaceship"Vostok" globe in 89 minutes. And people’s thoughts involuntarily turned to the vast expanses of space in which the small planet Earth was lost... Our Earth is one of the planets of the solar system. Compared to other planets, it is located quite close to the Sun, although it is not the closest. The average distance from the Sun to Pluto, the most distant planet in the solar system, is 40 times greater than the average distance from Earth to the Sun. It is currently unknown whether there are planets in the solar system that are even more distant from the Sun than Pluto. One can only say that if such planets exist, they are relatively small. Conventionally, the size of the Solar System can be taken to be 50-100 astronomical units *, or about 10 billion km. By our earthly scale, this is a very large value, approximately 1 million greater than the diameter of the Earth.

Rice. 1. Planets of the Solar System

We can more clearly imagine the relative scale of the solar system as follows. Let the Sun be represented by a billiard ball with a diameter of 7 cm. Then the planet closest to the Sun - Mercury - is located on this scale at a distance of 280 cm. The Earth is at a distance of 760 cm, the giant planet Jupiter is at a distance of about 40 m, and the farthest planet - in many respects, Pluto is still mysterious - at a distance of about 300m. The dimensions of the globe on this scale are slightly more than 0.5 mm, the lunar diameter is slightly more than 0.1 mm, and the Moon’s orbit has a diameter of about 3 cm. Even the closest star to us, Proxima Centauri, is so far away from us that compared to it, interplanetary distances within the solar system seem like mere trifles. Readers, of course, know that a unit of length such as a kilometer is never used to measure interstellar distances**). This unit of measurement (as well as centimeter, inch, etc.) arose from the needs practical activities humanity on Earth. It is completely unsuitable for estimating cosmic distances that are too large compared to a kilometer. IN popular literature, and sometimes in science, to estimate interstellar and intergalactic distances, the “light year” is used as a unit of measurement. This is the distance that light, moving at a speed of 300 thousand km/s, travels in a year. It is easy to see that a light year is equal to 9.46 x 10 12 km, or about 10,000 billion km. In the scientific literature, a special unit called the “parsec” is usually used to measure interstellar and intergalactic distances;

1 parsec (pc) is equal to 3.26 light years. A parsec is defined as the distance from which the radius of the Earth's orbit is visible at an angle of 1 second. arcs. This is a very small angle. Suffice it to say that from this angle a one-kopeck coin is visible from a distance of 3 km.

Rice. 2. Globular cluster 47 Tucanae

None of the stars - the closest neighbors of the Solar System - are closer to us than 1 pc. For example, the mentioned Proxima Centauri is located at a distance of about 1.3 pc from us. On the scale in which we depicted the Solar System, this corresponds to 2 thousand km. All this well illustrates the great isolation of our Solar system from surrounding stellar systems; some of these systems may have many similarities with it. But the stars surrounding the Sun and the Sun itself constitute only an insignificant part of the gigantic group of stars and nebulae, which is called the “Galaxy”. We see this cluster of stars on clear moonless nights as a stripe of the Milky Way crossing the sky. The galaxy has a rather complex structure. In the first, roughest approximation, we can assume that the stars and nebulae of which it consists fill a volume shaped like a highly compressed ellipsoid of revolution. Often in popular literature the shape of the Galaxy is compared to a biconvex lens. In reality, everything is much more complicated, and the picture drawn is too rough. In fact, it turns out that different types of stars concentrate in completely different ways towards the center of the Galaxy and towards its “equatorial plane”. For example, gaseous nebulae, as well as very hot massive stars, are strongly concentrated towards the equatorial plane of the Galaxy (in the sky this plane corresponds to a large circle passing through the central parts of the Milky Way). However, they do not show a significant concentration towards the galactic center. On the other hand, some types of stars and star clusters (the so-called “globular clusters”, Fig. 2) show almost no concentration towards the equatorial plane of the Galaxy, but are characterized by a huge concentration towards its center. Between these two extreme types of spatial distribution (which astronomers call "flat" and "spherical") are all the intermediate cases. However, it turns out that the bulk of the stars in the Galaxy are located in a giant disk, the diameter of which is about 100 thousand light years and the thickness is about 1500 light years. This disk contains slightly more than 150 billion stars of the most various types. Our Sun is one of these stars, located on the periphery of the Galaxy close to its equatorial plane (more precisely, “only” at a distance of about 30 light years - a value quite small compared to the thickness of the stellar disk). The distance from the Sun to the core of the Galaxy (or its center) is about 30 thousand light years. Stellar density in the Galaxy is very uneven. It is highest in the region of the galactic core, where, according to the latest data, it reaches 2 thousand stars per cubic parsec, which is almost 20 thousand times more than the average stellar density in the vicinity of the Sun ***. In addition, stars tend to form separate groups or clusters. A good example of such a cluster is the Pleiades, which is visible in our winter sky (Figure 3). The Galaxy also contains structural details on a much larger scale. Research in recent years has proven that nebulae, as well as hot massive stars, are distributed along the branches of the spiral. The spiral structure is especially clearly visible in other star systems - galaxies (with a small letter, in contrast to our star system - Galaxies). One of these galaxies is shown in Fig. 4. Establishing the spiral structure of the Galaxy in which we ourselves find ourselves has proven extremely difficult.

Rice. 3. Photo of the Pleiades star cluster

Rice. 4. Spiral galaxy NGC 5364

Stars and nebulae within the Galaxy move in quite complex ways. First of all, they participate in the rotation of the Galaxy around an axis perpendicular to its equatorial plane. This rotation is not the same as that of a solid body: different parts of the Galaxy have different periods of rotation. Thus, the Sun and the stars surrounding it in a huge area several hundred light years in size complete a full revolution in about 200 million years. Since the Sun, together with its family of planets, has apparently existed for about 5 billion years, during its evolution (from birth from a gas nebula to its current state) it has made approximately 25 revolutions around the axis of rotation of the Galaxy. We can say that the age of the Sun is only 25 “galactic years”; let’s face it, it’s a blooming age... The speed of movement of the Sun and its neighboring stars in their almost circular galactic orbits reaches 250 km/s ****. Superimposed on this regular motion around the galactic core are the chaotic, disorderly movements of stars. The speeds of such movements are much lower - about 10-50 km/s, and for objects different types they are different. The speeds are lowest for hot massive stars (6-8 km/s); for solar-type stars they are about 20 km/s. The lower these velocities, the more “flat” the distribution of a given type of star is. On the scale that we used to visually represent the Solar System, the size of the Galaxy will be 60 million km - a value already quite close to the distance from the Earth to the Sun. From here it is clear that as we penetrate into increasingly more distant regions of the Universe, this scale is no longer suitable, since it loses clarity. Therefore, we will take a different scale. Let us mentally reduce the earth's orbit to the size of the innermost orbit of the hydrogen atom in the classical Bohr model. Let us recall that the radius of this orbit is 0.53x10 -8 cm. Then the nearest star will be at a distance of approximately 0.014 mm, the center of the Galaxy will be at a distance of about 10 cm, and the dimensions of our star system will be about 35 cm. The diameter of the Sun will have microscopic dimensions : 0.0046 A (angstrom unit of length equal to 10 -8 cm).

We have already emphasized that the stars are located at enormous distances from each other, and are thus practically isolated. In particular, this means that stars almost never collide with each other, although the motion of each of them is determined by the gravitational field created by all the stars in the Galaxy. If we consider the Galaxy as a certain region filled with gas, and the role of gas molecules and atoms is played by stars, then we must consider this gas to be extremely rarefied. In the solar vicinity, the average distance between stars is about 10 million times greater than the average diameter of stars. Meanwhile, under normal conditions in ordinary air, the average distance between molecules is only several tens of times more sizes the latter. To achieve the same degree of relative rarefaction, the air density would have to be reduced by at least 1018 times! Note, however, that in the central region of the Galaxy, where stellar density is relatively high, collisions between stars will occur from time to time. Here we should expect approximately one collision every million years, while in the “normal” regions of the Galaxy there have been virtually no collisions between stars in the entire history of the evolution of our stellar system, which is at least 10 billion years old (see Chapter 9). ).

We have briefly outlined the scale and most general structure of the star system to which our Sun belongs. At the same time, the methods with the help of which, over the course of many years, several generations of astronomers, step by step, recreated a majestic picture of the structure of the Galaxy, were not considered at all. Other books are devoted to this important problem, to which we refer interested readers (for example, B.A. Vorontsov-Velyaminov “Essays on the Universe”, Yu.N. Efremov “Into the Depths of the Universe”). Our task is to give only the most big picture structure and development of individual objects of the Universe. This picture is absolutely necessary for understanding this book.

Rice. 5. Andromeda Nebula with satellites

For several decades now, astronomers have been persistently studying other star systems that are more or less similar to ours. This area of ​​research is called "extragalactic astronomy." She now plays almost the leading role in astronomy. Over the past three decades, extragalactic astronomy has made astonishing advances. Little by little, the grandiose contours of the Metagalaxy began to emerge, of which our stellar system is included as a small particle. We still don’t know everything about the Metagalaxy. The enormous remoteness of objects creates very specific difficulties, which are resolved by using the most powerful means of observation in combination with in-depth theoretical research. Yet the general structure of the Metagalaxy in last years mostly became clear. We can define a Metagalaxy as a collection of star systems - galaxies moving in the vast spaces of the part of the Universe we observe. The galaxies closest to our star system are the famous Magellanic Clouds, clearly visible in the sky southern hemisphere as two large spots of approximately the same surface brightness as the Milky Way. The distance to the Magellanic Clouds is “only” about 200 thousand light years, which is quite comparable to the total extent of our Galaxy. Another galaxy “close” to us is the nebula in the constellation Andromeda. It is visible to the naked eye as a faint speck of light of 5th magnitude *****. In fact, this is a huge star world, in terms of the number of stars and total mass three times greater than our Galaxy, which in turn is a giant among galaxies. The distance to the Andromeda nebula, or, as astronomers call it, M 31 (this means that in the well-known catalog of Messier nebulae it is listed as No. 31), is about 1800 thousand light years, which is about 20 times the size of the Galaxy. The M 31 nebula has a clearly defined spiral structure and in many of its characteristics is very similar to our Galaxy. Next to it are its small ellipsoidal satellites (Fig. 5). In Fig. Figure 6 shows photographs of several galaxies relatively close to us. Noteworthy is the wide variety of their forms. Along with spiral systems (such galaxies are designated by the symbols Sа, Sb and Sс depending on the nature of the development of the spiral structure; if there is a “bridge” passing through the core (Fig. 6a), the letter B is placed after the letter S), there are spheroidal and ellipsoidal ones, devoid of any traces spiral structure, as well as “irregular” galaxies, a good example of which are the Magellanic Clouds. A huge number of galaxies are observed in large telescopes. If there are about 250 galaxies brighter than the visible 12th magnitude, then there are already about 50 thousand brighter than the 16th. The faintest objects that can be photographed at the limit by a reflecting telescope with a mirror diameter of 5 m are 24.5th magnitude. It turns out that among the billions of such faint objects, the majority are galaxies. Many of them are distant from us at distances that light travels over billions of years. This means that the light that caused the plate to blacken was emitted by such a distant galaxy long before the Archean period geological history Earth!.

Rice. 6a. Cross spiral galaxy

Rice. 6b. Galaxy NGC 4594

Rice. 6s. Galaxies Magellanic clouds

Sometimes among the galaxies you come across amazing objects, for example, “radio galaxies”. These are star systems that emit huge amounts of energy in the radio range. For some radio galaxies, the flux of radio emission is several times higher than the flux of optical radiation, although in the optical range their luminosity is very high - several times greater than the total luminosity of our Galaxy. Let us recall that the latter consists of the radiation of hundreds of billions of stars, many of which, in turn, radiate much stronger than the Sun. Classic example such a radio galaxy is the famous object Cygnus A. In the optical range, these are two insignificant specks of light of the 17th magnitude (Fig. 7). In fact, their luminosity is very high, about 10 times greater than that of our Galaxy. This system seems weak because it is located at a huge distance from us - 600 million light years. However, the flux of radio emission from Cygnus A at meter waves is so great that it even exceeds the flux of radio emission from the Sun (during periods when there are no sunspots on the Sun). But the Sun is very close - the distance to it is “only” 8 light minutes; 600 million years - and 8 minutes! But radiation fluxes, as is known, are inversely proportional to the squares of the distances! The spectra of most galaxies resemble the sun; in both cases, individual dark absorption lines are observed against a fairly bright background. This is not unexpected, since the radiation of galaxies is the radiation of the billions of stars that comprise them, more or less similar to the Sun. Careful study of the spectra of galaxies many years ago led to a discovery of fundamental importance. The fact is that by the nature of the shift in the wavelength of any spectral line in relation to the laboratory standard, one can determine the speed of movement of the emitting source along the line of sight. In other words, it is possible to determine at what speed the source is approaching or moving away.

Rice. 7. Radio galaxy Cygnus A

If the light source approaches, the spectral lines shift towards shorter wavelengths; if it moves away, towards longer ones. This phenomenon is called the "Doppler effect". It turned out that galaxies (with the exception of a few closest to us) have spectral lines that are always shifted to the long-wavelength part of the spectrum (“red shift” of the lines), and the greater the distance the galaxy is from us, the greater the magnitude of this shift. This means that all galaxies are moving away from us, and the speed of “expansion” increases as the galaxies move away. It reaches enormous values. For example, the recession speed of the radio galaxy Cygnus A, found from the red shift, is close to 17 thousand km/s. Twenty-five years ago, the record belonged to the very faint (in optical rays of the 20th magnitude) radio galaxy 3S 295. In 1960, its spectrum was obtained. It turned out that the well-known ultraviolet spectral line belonging to ionized oxygen is shifted to the orange region of the spectrum! From here it is easy to find that the speed of removal of this amazing star system is 138 thousand km/s, or almost half the speed of light! Radio galaxy 3S 295 is distant from us at a distance that light travels in 5 billion years. Thus, astronomers studied the light that was emitted when the Sun and planets were formed, and maybe even “a little” earlier... Since then, even more distant objects have been discovered (Chapter 6). We will not touch upon the reasons for the expansion of a system consisting of a huge number of galaxies here. This complex question is the subject of modern cosmology. However, the very fact of the expansion of the Universe has great importance to analyze the development of life in it (chapter 7). Superimposed on the overall expansion of the galaxy system are the erratic velocities of individual galaxies, typically several hundred kilometers per second. This is why the galaxies closest to us do not exhibit a systematic redshift. After all, the speeds of random (so-called “peculiar”) movements for these galaxies are greater than the regular redshift speed. The latter increases as the galaxies move away by approximately 50 km/s, for every million parsecs. Therefore, for galaxies whose distances do not exceed several million parsecs, the random velocities exceed the receding velocity due to the redshift. Among nearby galaxies, there are also those that are approaching us (for example, the Andromeda nebula M 31). Galaxies are not uniformly distributed in metagalactic space, i.e. with constant density. They show a pronounced tendency to form separate groups or clusters. In particular, a group of about 20 galaxies close to us (including our Galaxy) forms the so-called “local system”. In turn, the local system is part of a large cluster of galaxies, the center of which is in that part of the sky onto which the Virgo constellation is projected. This cluster has several thousand members and is among the largest. In Fig. Figure 8 shows a photograph of the famous galaxy cluster in the constellation Corona Borealis, numbering hundreds of galaxies. In the space between clusters, the density of galaxies is tens of times less than inside the clusters.

Rice. 8. Cluster of galaxies in the constellation Corona Borealis

Noteworthy is the difference between clusters of stars that form galaxies and clusters of galaxies. In the first case, the distances between cluster members are enormous compared to the sizes of the stars, while the average distances between galaxies in galaxy clusters are only several times larger than the sizes of the galaxies. On the other hand, the number of galaxies in clusters cannot be compared with the number of stars in galaxies. If we consider a collection of galaxies as a kind of gas, where the role of molecules is played by individual galaxies, then we must consider this medium to be extremely viscous.

Table 1

Big Bang
Formation of galaxies (z~10)
Formation of the Solar System
Earth Education
The emergence of life on Earth
Education ancient rocks on the ground
The appearance of bacteria and blue-green algae
The emergence of photosynthesis
The first cells with a nucleus

Sunday	Monday	Tuesday	Wednesday	Thursday	Friday	Saturday
	The emergence of an oxygen atmosphere on Earth				Violent volcanic activity on Mars
		The first worms		Ocean plankton Trilobites	Ordovician The first fish	Silur Plants colonize land
Devonian The first insects Animals colonize land	The first amphibians and winged insects	Carbon The first trees The first reptiles	Permian The first dinosaurs	Beginning of the Mesozoic	Triassic First mammals	Yura The first birds
Chalk First flowers	Tertiary period First primates	First hominids	Quaternary period First People (~22:30)

What does the Metagalaxy look like in our model, where the earth's orbit is reduced to the size of the first orbit of a Bohr atom? On this scale, the distance to the Andromeda nebula will be slightly more than 6 m, the distance to the central part of the Virgo galaxy cluster, which includes our local galaxy system, will be about 120 m, and the size of the cluster itself will be of the same order. The radio galaxy Cygnus A will now be removed at a distance of 2.5 km, and the distance to the radio galaxy 3S 295 will reach 25 km... We met in the very general view with the main structural features and with the scale of the Universe. It's like a frozen frame of her development. She was not always the way we see her now. Everything in the Universe changes: stars and nebulae appear, develop and “die”, the Galaxy develops in a natural way, the very structure and scale of the Metagalaxy change (if only because of the red shift). Therefore, the drawn static picture of the Universe must be supplemented with a dynamic picture of the evolution of individual cosmic objects from which it is formed, and the entire Universe as a whole. As for the evolution of individual stars and nebulae that form galaxies, this will be discussed in Chapter. 4 . Here we will only say that stars are born from the interstellar gas and dust medium, quietly emit for some time (depending on the mass), after which they “die” in a more or less dramatic way. The discovery of “relict” radiation in 1965 (see Chapter 7) clearly showed that at the very early stages of evolution the Universe was qualitatively different from its current state. The main thing is that then there were no stars, no galaxies, no heavy elements. And, of course, there was no life. We are observing a grandiose process of evolution of the Universe from simple to complex. The same direction evolution has also the development of life on Earth. In the Universe, the rate of evolution in the beginning was much higher than in modern era. It seems, however, that the opposite pattern is observed in the development of life on Earth. This is clearly seen from the “cosmic chronology” model presented in Table 1, proposed by the American planetary scientist Sagan. Above, we developed in some detail the spatial model of the Universe, based on the choice of one or another linear scale. Essentially speaking, the same method is used in table. 1. The entire existence of the Universe (which, for definiteness, is taken to be equal to 15 billion real “earthly” years, and here an error of several tens of percent is possible) is modeled by some imaginary “cosmic year”. It is not difficult to verify that one second of a “cosmic” year is equal to 500 very real years. With this scale, each epoch of the development of the Universe is assigned a certain date (and time of day) of the “cosmic” year. It is easy to see that this table in its main part is purely “anthropocentric”: the dates and moments of the cosmic calendar after “September” and, especially, the entire specially designated “December”, reflect certain stages in the development of life on Earth. This calendar would look completely different for the inhabitants of some planet orbiting “their” star in some distant galaxy. Nevertheless, the very comparison of the pace of cosmic and terrestrial evolution is extremely impressive.

• * Astronomical unit - the average distance from the Earth to the Sun, equal to 149,600 thousand km.
• ** Perhaps, only the speeds of stars and planets in astronomy are expressed in units of “kilometers per second”.
• *** In the very center of the galactic core, in a region 1 pc across, there are apparently several million stars.
• **** It is useful to remember a simple rule: a speed of 1 pc in 1 million years is almost equal to a speed of 1 km/s. We leave it to the reader to verify this.
• ***** The flux of radiation from stars is measured by so-called “stellar magnitudes”. By definition, the flux from an (i+1)th magnitude star is 2.512 times less than from i-th stars quantities. Stars fainter than 6th magnitude are not visible to the naked eye. The brightest stars have a negative magnitude (for example, Sirius has a magnitude of -1.5).