Universe distance scale
As the universe expands, the question of distances to very distant galaxies is difficult to answer. Everything depends on your point of view.
Omega Nebula
Eagle Nebula
Antlia cluster
Here's the problem with determining distances in an expanding universe: Two galaxies are next to each other when the universe is only 1 billion years old. The first galaxy emits a light pulse. The second galaxy does not perceive this impulse until the Universe is 14 billion years old.
By this time, these galaxies are separated by about 26 billion light years; a light pulse has been on its way for 13 billion years; and the picture that people get in the second galaxy is an image of the first galaxy at a time when it was only one billion years old and when it was only 2 billion light years away.
In cosmology, four different distance scales are generally accepted:
(1) Photometric distance - DL
In an expanding universe, distant galaxies are much harder to see than one might expect, as photons of light are stretched out and spread out over a wide area. This is why huge telescopes are required to see very distant galaxies. The most distant galaxies seen through the Hubble Space Telescope are so faint that they appear to be about 350 billion light-years away, even though they are much closer.
The photometric scale does not represent actual distance, but it is used to determine how dim we see very distant galaxies.
(2) Angular diameter distance - DA
In an expanding universe, we see galaxies at the edge of the visible universe when they were very young, about 14 billion years ago, because light took about 14 billion years to reach us.
However, the galaxies at that time were not only young, but also located much closer to us.
The most faintly visible galaxies seen by the Hubble Space Telescope were only a few billion light-years away from us when the light was emitted.
This means that very distant galaxies look much larger than you might expect, as if they are on the order of 2 or 3 billion light years away from us (Although they also look very, very dim - see "Photometric distance").
Angular diameter distance is a good indicator (especially in a flat galaxy like ours) of how close a particular galaxy was to us when it emitted the light we currently see.
(3) Follow distance - DC
The comoving distance scale expands with the universe. It gives us an idea of where galaxies are currently located, despite the fact that we are observing a distant galaxy as it was when it was much younger and smaller. On this scale, the outermost edge of the visible universe is currently 47 billion light-years away from us, although the most distant galaxies seen through the Hubble Space Telescope would be about 32 billion light-years away.
The comoving distance is the opposite of the angular diameter distance.
This distance shows where the galaxies are at the moment, not where they were when they emitted the light that we see now.
(4) Aberration distance - DT
Aberration distance refers to the amount of time it takes light from distant galaxies to reach us. This is what is meant when they say that visible universe has a radius of 14 billion light years.
The meaning of this statement: the age of the Universe is about 14 billion years, but the light from more distant galaxies did not have enough time to reach us.
The aberration distance is equally a measure of time and a measure of distance. The main use of this scale is that it gives us an idea of the age of the image of a given galaxy that we currently see.
For small distances (of the order of 2 billion light years or less), all four distance scales are combined and repeat one another, so it is much easier to determine the distances to galaxies in the local Universe surrounding us.
Below are all four distance scales superimposed on redshift. Redshift is a measure of the stretching of light caused by the expansion of the universe: a galaxy with high level redshift is further away than a low redshift galaxy. The most distant galaxies seen through the Hubble Space Telescope have a redshift of 10, while the most distant protogalaxies in the universe probably have a redshift of 15. The boundary of the visible universe has a redshift of infinity. For comparison: a typical portable telescope does not allow viewing objects with a redshift much higher than 0.1 (about 1.3 billion light years).
The photometric distance (DL ) shows why distant galaxies are so hard to see: a very young and distant galaxy with a redshift of 15 appears to be 560 billion light-years away, although the angular diameter distance (DA ) shows that at the time the galaxy emits light , which we see now, she was actually about 2.2 billion light years. The aberration distance (DT) shows that the light from a given galaxy has traveled 13.6 billion years from its emission to the present. The comoving distance (DC) shows that the same galaxy today, if we could see it, would be 35 billion light-years away from us.
If our universe were not expanding and the speed of light was approaching infinity, the questions “can we see the entire universe?” or "how far can we see the universe?" would not make sense. We'd be in live» would see everything that happens in any corner of outer space.
But, as you know, the speed of light is finite, and our Universe is expanding, and it does so with acceleration. If the expansion rate is constantly increasing, then there are regions escaping from us at superluminal speed, which, according to logic, we cannot see. But how is this possible? Doesn't this contradict the Theory of Relativity? AT this case no: after all, space itself is expanding, while objects inside it still have sub-light velocities. For clarity, we can imagine our universe in the form balloon, and the button glued to the ball will play the role of a galaxy. Try to inflate the balloon: the button galaxy will start moving away from you along with the expansion of the space of the balloon-Universe, although the own speed of the button galaxy will remain zero.
It turns out that there must be an area inside which there are objects escaping from us at a speed lower than the speed of light, and the radiation of which we can fix in our telescopes. This area is called Hubble sphere. It ends with a boundary where the speed of removal of distant galaxies will coincide with the speed of their photons that fly in our direction (ie the speed of light). This border is called Particle Horizon. Obviously, objects beyond the Particle Horizon will have a speed higher than the speed of light and their radiation cannot reach us. Or can it still?
Let's imagine that galaxy X was in the Hubble Sphere and emitted light that reached the Earth without any problems. But due to the accelerating expansion of the Universe, the X galaxy has gone beyond the Particle Horizon, and is already moving away from us at a speed faster than the speed of light. But its photons, emitted at the moment of being in the Hubble Sphere, are still flying in the direction of our planet, and we continue to fix them, i.e. we observe an object that is currently moving away from us at a speed exceeding the speed of light.
But what if galaxy Y has never been in the Hubble Sphere and at the moment of the beginning of the radiation immediately had a superluminal speed? It turns out that not a single photon of its existence has ever visited our part of the Universe. But that doesn't mean it won't happen in the future! We must not forget that the Hubble Sphere is also expanding (along with the entire Universe), and its expansion is greater than the speed at which a photon of galaxy Y is moving away from us (we found the speed of removal of a photon of galaxy Y by subtracting the speed of light from the escape velocity of galaxy Y). While doing given condition someday the Hubble Sphere will catch up with these photons, and we will be able to detect the Y galaxy. This process is clearly demonstrated in the diagram below.
A space that includes Hubble sphere and Particle horizon, is called Metagalaxy or visible universe.
But is there anything beyond the Metagalaxy? Some cosmic theories suggest the existence of a so-called Event Horizon. You may have already heard this name from the description of black holes. The principle of its operation remains the same: we will never see what is outside the Event Horizon, since objects outside the Event Horizon will have a photon escape velocity greater than the expansion velocity of the Hubble Sphere, so their light will always run away from us.
But for an Event Horizon to exist, the Universe must be expanding at an accelerating rate (which is consistent with modern ideas about the world order). Eventually, all the galaxies surrounding us will go beyond the Event Horizon. It will look like time has stopped in them. We will see them go out of sight endlessly, but we will never see them completely hidden.
It is interesting: if instead of galaxies we observed through a telescope big clock with the dial, and leaving the Event Horizon would indicate the position of the hands at 12:00, then they would slow down indefinitely at 11:59:59, and the image would become more fuzzy, because fewer and fewer photons would reach us.
But if scientists are wrong, and in the future the expansion of the Universe begins to slow down, then this immediately cancels the existence of the Event Horizon, since the radiation of any object will sooner or later exceed its escape velocity. It will only be necessary to wait hundreds of billions of years...
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The portal site is an information resource where you can get a lot of useful and interesting knowledge related to the Cosmos. First of all, we will talk about our and other Universes, about celestial bodies, black holes and phenomena in the depths of outer space.
The totality of everything that exists, matter, individual particles and the space between these particles is called the Universe. According to scientists and astrologers, the age of the universe is approximately 14 billion years. By size visible part The universe spans about 14 billion light years. And some argue that the universe extends over 90 billion light-years. For greater convenience, in calculating such distances, it is customary to use the parsec value. One parsec is equal to 3.2616 light years, that is, a parsec is the distance over which the average radius of the Earth's orbit is viewed at an angle of one arc second.
Armed with these indicators, you can calculate the cosmic distance from one object to another. For example, the distance from our planet to the Moon is 300,000 km, or 1 light second. Consequently, this distance to the Sun increases to 8.31 light minutes.
Throughout its history, people have tried to solve the mysteries associated with the Cosmos and the Universe. In the articles of the portal site you can learn not only about the Universe, but also about modern scientific approaches to its study. All material is based on the most advanced theories and facts.
It should be noted that the Universe includes a large number known to people various objects. The most widely known among them are planets, stars, satellites, black holes, asteroids and comets. The planets are the most understood at the moment, since we live on one of them. Some planets have their own moons. So, the Earth has its own satellite - the Moon. In addition to our planet, there are 8 more that revolve around the sun.
There are many stars in the Cosmos, but each of them is not similar to each other. They have different temperatures, sizes and brightness. Since all stars are different, they are classified as follows:
white dwarfs;
Giants;
Supergiants;
neutron stars;
Quasars;
Pulsars.
The densest substance known to us is lead. In some planets, the density of their own substance can be thousands of times greater than the density of lead, which poses many questions for scientists.
All the planets revolve around the sun, but it also does not stand still. Stars can gather into clusters, which, in turn, also revolve around a center that is not yet known to us. These clusters are called galaxies. Our galaxy is called the Milky Way. All studies conducted so far say that most of the matter that galaxies create is still invisible to humans. Because of this, it was called dark matter.
The centers of galaxies are considered the most interesting. Some astronomers believe that a black hole is the possible center of the galaxy. This is a unique phenomenon formed as a result of the evolution of a star. But for now, these are just theories. It is not yet possible to conduct experiments or study such phenomena.
In addition to galaxies, the Universe contains nebulae (interstellar clouds consisting of gas, dust and plasma), relic radiation that permeates the entire space of the Universe, and many other little-known and even generally unknown objects.
The circulation of the ether of the universe
Symmetry and balance of material phenomena is main principle structural organization and interaction in nature. Moreover, in all forms: stellar plasma and matter, world and released ethers. The whole essence of such phenomena consists in their interactions and transformations, most of which are represented by the invisible ether. It is also called relic radiation. It's a microwave space background radiation, which has a temperature of 2.7 K. There is an opinion that it is this oscillating ether that is the fundamental principle for everything that fills the Universe. The anisotropy of the distribution of the ether is connected with the directions and intensity of its movement in different areas of the invisible and visible space. The whole difficulty of studying and researching is quite comparable with the difficulties of studying turbulent processes in gases, plasmas and liquids of matter.
Why do many scientists believe that the universe is multidimensional?
After conducting experiments in laboratories and in the Cosmos itself, data were obtained from which it can be assumed that we live in a Universe in which the location of any object can be characterized by time and three spatial coordinates. Because of this, the assumption arises that the universe is four-dimensional. However, some scientists, developing theories of elementary particles and quantum gravity, may come to the conclusion that the existence a large number measurements are essential. Some models of the Universe do not exclude such a number as 11 dimensions.
It should be taken into account that the existence of a multidimensional Universe is possible with high-energy phenomena - black holes, big bang, bursters. At least, this is one of the ideas of leading cosmologists.
The model of the expanding Universe is based on the general theory of relativity. It was proposed to adequately explain the redshift structure. The expansion began at the same time as the Big Bang. Its state is illustrated by the surface of an inflated rubber ball, on which dots were applied - extragalactic objects. When such a balloon is inflated, all its points move away from each other, regardless of position. According to the theory, the Universe can either expand indefinitely or contract.
Baryon asymmetry of the Universe
The significant increase in the number of elementary particles observed in the Universe over the entire number of antiparticles is called baryon asymmetry. Baryons include neutrons, protons, and some other short-lived elementary particles. This disproportion happened in the era of annihilation, namely, three seconds after the Big Bang. Up to this point, the number of baryons and antibaryons corresponded to each other. During the mass annihilation of elementary antiparticles and particles, most of them paired up and disappeared, thereby giving rise to electromagnetic radiation.
Age of the Universe on the portal website
Modern scientists believe that our universe is about 16 billion years old. According to estimates, the minimum age can be 12-15 billion years. The minimum is repelled by the oldest stars in our galaxy. Its real age can be determined only with the help of Hubble's law, but real does not mean exact.
visibility horizon
A sphere with a radius equal to the distance that light travels during the entire existence of the Universe is called its visibility horizon. The existence of the horizon is directly proportional to the expansion and contraction of the universe. According to Friedman's cosmological model, the Universe began to expand from a singular distance about 15-20 billion years ago. For all the time, light travels a residual distance in the expanding universe, namely 109 light years. Because of this, each observer of the moment t0 after the start of the expansion process can view only a small part, bounded by a sphere, which at that moment has radius I. Those bodies and objects that are beyond this border at that moment are, in principle, not observable. The light reflected from them simply does not have time to reach the observer. This is not possible even if the light came out at the moment the expansion process began.
Due to absorption and scattering in the early Universe, given the high density, photons could not propagate in a free direction. Therefore, the observer is able to fix only the radiation that appeared in the era of the Universe transparent to radiation. This epoch is determined by the time t»300,000 years, the density of matter r»10-20 g/cm3, and the moment of hydrogen recombination. It follows from the foregoing that the closer the source is in the galaxy, the greater the redshift will be for it.
The moment the universe began is called the Big Bang. This concept is based on the fact that initially there was a point (singularity point), in which all energy and all matter were present. The basis of the characteristic is considered to be a high density of matter. What happened before this singularity is unknown.
Regarding the events and conditions that occurred before the onset of the moment 5 * 10-44 seconds (the moment of the end of the 1st time quantum), there is no exact information. In the physical sense of that era, one can only assume that then the temperature was approximately 1.3 * 1032 degrees with a matter density of approximately 1096 kg / m 3. These values are the limits for the application. existing ideas. They appear due to the ratio of the gravitational constant, the speed of light, the Boltzmann and Planck constants and are referred to as "Planck".
Those events that are associated with 5 * 10-44 to 10-36 seconds reflect the "inflationary Universe" model. The moment of 10-36 seconds is attributed to the "hot universe" model.
In the period from 1-3 to 100-120 seconds, helium nuclei were formed and a small amount of nuclei of other lungs chemical elements. From that moment, the ratio began to be established in the gas - hydrogen 78%, helium 22%. Before one million years, the temperature in the Universe began to drop to 3000-45000 K, the era of recombination began. Before, free electrons began to combine with light protons and atomic nuclei. Helium atoms, hydrogen atoms, and a small number of lithium atoms began to appear. The substance became transparent, and the radiation, which is still observed, detached from it.
The next billion years of the existence of the Universe was marked by a decrease in temperature from 3000-45000 K to 300 K. Scientists called this period for the Universe the “Dark Age” due to the fact that no sources of electromagnetic radiation have yet appeared. During the same period, the inhomogeneities of the initial gas mixtures were condensed due to the effect of gravitational forces. Having simulated these processes on a computer, astronomers saw that this irreversibly led to the appearance of giant stars, exceeding the mass of the Sun by millions of times. Due to such a large mass, these stars heated up to unthinkable high temperatures and evolved over a period of tens of millions of years, after which they exploded as supernovae. Heating up to high temperatures, the surfaces of such stars created strong fluxes of ultraviolet radiation. Thus, a period of reionization began. The plasma that was formed as a result of such phenomena began to strongly scatter electromagnetic radiation in its spectral short-wavelength ranges. In a sense, the universe began to sink into a dense fog.
These huge stars became the first sources in the universe of chemical elements that are much heavier than lithium. Space objects of the 2nd generation began to form, which contained the nuclei of these atoms. These stars began to form from mixtures of heavy atoms. A repeated type of recombination of most of the atoms of intergalactic and interstellar gases took place, which, in turn, led to a new transparency of space for electromagnetic radiation. The universe has become exactly what we can observe now.
The observed structure of the universe on the portal site
The observed part is spatially inhomogeneous. Most clusters of galaxies and individual galaxies form its cellular or honeycomb structure. They construct cell walls that are a couple of megaparsecs thick. These cells are called "voids". They are characterized big size, in tens of megaparsecs, and at the same time they do not contain matter with electromagnetic radiation. About 50% of the total volume of the Universe falls to the share of "voids".
Doctor of Pedagogical Sciences E. LEVITAN, full member of the Russian Academy of Natural Sciences
Science and life // Illustrations
One of the best modern astrophysical observatories is the European Southern Observatory (Chile). In the picture: a unique instrument of this observatory - the New Technologies Telescope (NTT).
Photo reverse side 3.6-meter primary mirror of the Telescope of New Technologies.
Spiral galaxy NGC 1232 in the constellation Eridani (about 100 million light-years away). Size - 200 light years.
Before you is a huge gas disk, possibly heated to hundreds of millions of degrees Kelvin (its diameter is about 300 light years).
Seemingly strange question. Of course, we also see Milky Way and other stars of the universe closer to us. But the question posed in the title of the article is actually not so simple, and therefore we will try to figure it out.
The bright Sun during the day, the Moon and the scattering of stars in the night sky have always attracted the attention of a person. Judging by rock paintings, on which the most ancient painters captured the figures of the most conspicuous constellations, even then people, at least the most inquisitive of them, peered into the mysterious beauty of the starry sky. And of course, they showed interest in the rising and setting of the Sun, in the mysterious changes in the appearance of the Moon ... Probably, this is how "primitive-contemplative" astronomy was born. This happened many thousands of years before writing arose, the monuments of which have already become documents for us, testifying to the origin and development of astronomy.
At first, the heavenly bodies, perhaps, were only an object of curiosity, then they were deified, and, finally, they began to help people, acting as a compass, calendar, and clock. A serious reason for philosophizing about possible device The discovery of "wandering stars" (planets) could become the universe. Attempts to unravel the incomprehensible loops that describe the planets against the background of supposedly fixed stars led to the construction of the first astronomical pictures or models of the world. Their apotheosis is rightfully considered geocentric system the world of Claudius Ptolemy (II century AD). Ancient astronomers tried (mostly unsuccessfully) to determine (but not yet prove!) What place the Earth occupies in relation to the seven then known planets (these were considered the Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn). And only Nicholas Copernicus (1473-1543) finally succeeded.
Ptolemy is called the creator of the geocentric, and Copernicus - the heliocentric system of the world. But fundamentally, these systems differed only in their ideas about the location of the Sun and the Earth in relation to the true planets (Mercury, Venus, Mars, Jupiter, Saturn) and to the Moon.
Copernicus, in essence, discovered the Earth as a planet, the Moon took its proper place as a satellite of the Earth, and the Sun turned out to be the center of circulation of all the planets. The sun and six planets moving around it (including the Earth) - this was the solar system as it was represented in the 16th century.
The system, as we now know, is far from complete. Indeed, in addition to the six planets known to Copernicus, it also includes Uranus, Neptune, Pluto. The latter was discovered in 1930 and turned out to be not only the most distant, but also the smallest planet. In addition, the solar system includes about a hundred satellites of the planets, two asteroid belts (one between the orbits of Mars and Jupiter, the other, recently discovered - the Kuiper belt - in the region of the orbits of Neptune and Pluto) and many comets with different orbital periods. The hypothetical "Cloud of Comets" (something like their habitat) is, according to various estimates, at a distance of about 100-150 thousand astronomical units from the Sun. The boundaries of the solar system have accordingly expanded many times over.
In early 2002, American scientists "talked" to their automatic interplanetary station Pioneer-10, which was launched 30 years ago and managed to fly away from the Sun at a distance of 12 billion kilometers. The answer to the radio signal sent from the Earth came in 22 hours 06 minutes (at a speed of propagation of radio waves of about 300,000 km/sec). Given the above, Pioneer-10 will have to fly to the "boundaries" of the solar system for a long time (of course, quite conditional!). And then he will fly to the nearest star in his path Aldebaran (the most bright Star in the constellation Taurus). Pioneer-10 will probably rush there and deliver the messages of the earthlings embedded in it only after 2 million years ...
At least 70 light years separate us from Aldebaran. And the distance to the star closest to us (in the a Centauri system) is only 4.75 light years. Today, even schoolchildren should know what a "light year", "parsec" or "megaparsec" is. These are already questions and terms of stellar astronomy, which not only in the time of Copernicus, but much later, simply did not exist.
It was assumed that the stars were distant luminaries, but their nature was unknown. True, Giordano Bruno, developing the ideas of Copernicus, ingeniously suggested that the stars are distant suns, and, possibly, with their own planetary systems. The correctness of the first part of this hypothesis became quite obvious only in the 19th century. And the first dozens of planets around other stars were discovered only in the most last years recently ended 20th century. Before the birth of astrophysics and before applications in astronomy spectral analysis it was simply impossible to approach the scientific solution to the nature of stars. So it turned out that the stars in the previous systems of the world played almost no role. The starry sky was a kind of stage on which the planets "performed", but they did not particularly think about the nature of the stars themselves (sometimes they were mentioned as ... about "silver carnations" stuck into the firmament of heaven). The "sphere of stars" was a kind of boundary of the Universe both in geocentric and in heliocentric system peace. The whole Universe, of course, was considered visible, and what is beyond it is the "kingdom of heaven" ...
Today we know that only a tiny fraction of the stars are visible to the naked eye. The whitish band stretching across the entire sky (the Milky Way) turned out to be, as some ancient Greek philosophers guessed, a lot of stars. Galileo (at the beginning of the 17th century) distinguished the brightest of them even with the help of his very imperfect telescope. As the size of telescopes increased and they improved, astronomers were able to gradually penetrate into the depths of the Universe, as if probing it. But it did not immediately become clear that the stars observed in different directions sky, have something to do with the stars of the Milky Way. One of the first who managed to prove this was the English astronomer and optician W. Herschel. Therefore, the discovery of our Galaxy is associated with his name (it is sometimes called the Milky Way). However, it is apparently not given to a mere mortal to see our Galaxy in its entirety. Of course, it is enough to look into an astronomy textbook to find clear diagrams there: a view of the Galaxy "from above" (with a distinct spiral structure, with arms consisting of stars and gas-dust matter) and a view "from the side" (in this perspective, our stellar island resembles biconvex lens, if you do not go into some details of the structure of the central part of this lens). Schemes, schemes... And where is at least one photograph of our Galaxy?
Gagarin was the first earthling who saw our planet from outer space. Now, probably, everyone has seen photographs of the Earth from space, transmitted from the board of artificial satellites of the Earth, from automatic interplanetary stations. Forty-one years have passed since the flight of Gagarin, and 45 years since the launch of the first satellite - the beginning of the space age. But to this day, no one knows whether a person will ever be able to see the Galaxy, going beyond its limits ... For us, this is a question from the realm of fantasy. So let's get back to reality. But only at the same time, please think about the fact that just a hundred years ago, the current reality could seem like the most incredible fantasy.
So, the Solar System and our Galaxy were discovered, in which the Sun is one of the trillions of stars (about 6,000 stars are visible to the naked eye in the entire celestial sphere), and the Milky Way is a projection of a part of the Galaxy onto the celestial sphere. But just as in the 16th century, earthlings realized that our Sun is the most ordinary star, we now know that our Galaxy is one of the many other galaxies now discovered. Among them, as in the world of stars, there are giants and dwarfs, "ordinary" and "unusual" galaxies, relatively calm and extremely active. They are at great distances from us. Light from the closest of them rushes to us for almost two million three hundred thousand years. But we can see this galaxy even with the naked eye, it is in the constellation Andromeda. This is a very large spiral galaxy, similar to our own, and therefore its photographs "compensate" to some extent for the lack of photographs of our Galaxy.
Almost all discovered galaxies can only be seen in photographs taken with modern ground-based giant telescopes or space telescopes. The use of radio telescopes and radio interferometers helped to significantly supplement the optical data. Radio astronomy and extra-atmospheric X-ray astronomy have lifted the curtain on the secret of the processes occurring in the nuclei of galaxies and in quasars (the most distant objects of our Universe known today, almost indistinguishable from stars in photographs taken with optical telescopes).
In the extremely huge and practically hidden from the eyes mega-world (or in the Metagalaxy), it was possible to discover its important regularities and properties: expansion, large-scale structure. All this is somewhat reminiscent of another, already open and largely unraveled microcosm. They study very close to us, but also invisible building blocks of the universe (atoms, hadrons, protons, neutrons, mesons, quarks). Having learned the structure of atoms and the patterns of interaction of their electron shells, scientists literally "revived" Periodic system elements of D. I. Mendeleev.
The most important thing is that a person turned out to be able to discover and cognize worlds of various scales (mega-world and micro-world) that are not directly perceived by him.
In this context, astrophysics and cosmology do not seem to be original. But here we are approaching the most interesting.
The "curtain" of long-known constellations has opened, taking with it the last attempts of our "centrism": geocentrism, heliocentrism, galaxy centrism. We ourselves, like our Earth, like the Solar System, like the Galaxy, are just "particles" of the unimaginable in terms of everyday scale and complexity of the structure of the Universe, called the "Metagalaxy". It includes many systems of galaxies of varying complexity (from "double" to clusters and superclusters). Agree that, at the same time, awareness of the scale of one’s own insignificant size in the vast mega world does not humiliate a person, but, on the contrary, elevates the power of his Mind, capable of discovering all this and understanding what was discovered earlier.
It would seem that it is time to calm down, because modern painting structure and evolution of the Metagalaxy in general terms created. However, firstly, it contains a lot of fundamentally new, previously unknown to us, and secondly, it is possible that, in addition to our Metagalaxy, there are other mini-universes that form the still hypothetical Big Universe...
Maybe this is worth stopping for now. Because we would now, as they say, deal with our universe. The fact is that at the end of the 20th century it presented astronomy with a big surprise.
Those who are interested in the history of physics know that at the beginning of the 20th century it seemed to some great physicists that their titanic work was over, because everything important in this science had already been discovered and explored. True, a couple of strange "clouds" remained on the horizon, but few imagined that they would soon "turn into" the theory of relativity and quantum mechanics... Is something similar awaiting astronomy?
It is quite likely, because our Universe, observed with the help of all the power of modern astronomical instruments and seemingly already quite thoroughly studied, may turn out to be only the tip of the universal iceberg. Where is the rest of it? How could such a daring assumption about the existence of something else huge, material and completely hitherto unknown?
Let us turn again to the history of astronomy. One of its triumphant pages was the discovery of the planet Neptune "at the tip of a pen." The gravitational effect of some mass on the movement of Uranus prompted scientists to think about the existence of an as yet unknown planet, allowed talented mathematicians to determine its location in solar system, and then tell astronomers exactly where to look for it on the celestial sphere. And in the future, gravity provided astronomers with similar services: it helped to discover various "outlandish" objects - white dwarfs, black holes. So now, the study of the motion of stars in galaxies and galaxies in their clusters has led scientists to the conclusion that there is a mysterious invisible ("dark") substance (or perhaps some form of matter unknown to us), and the reserves of this "substance" must be colossal.
According to the most ambitious estimates, everything that we observe and take into account in the Universe (stars, gas-dust complexes, galaxies, etc.) is only 5 percent of the mass that "should be" according to calculations based on the laws of gravity. These 5 percent include the entire megaworld known to us, from dust grains and hydrogen atoms common in space to superclusters of galaxies. Some astrophysicists include here even all-penetrating neutrinos, believing that, despite their small rest mass, neutrinos, by their countless number, make a certain contribution to the same 5 percent.
But, perhaps, "invisible matter" (or at least a part of it, unevenly distributed in space) is a mass of extinct stars or galaxies, or such invisible space objects as black holes? To some extent, such an assumption makes sense, although the missing 95 percent (or, according to other estimates, 60-70 percent) cannot be made up. Astrophysicists and cosmologists are forced to sort through various other, mostly hypothetical, possibilities. The most fundamental ideas boil down to the fact that a significant part of the "hidden mass" is a "dark matter" consisting of elementary particles unknown to us.
Further research in the field of physics will show which elementary particles, apart from those that consist of quarks (baryons, mesons, etc.) or are structureless (for example, muons), can exist in nature. Unraveling this riddle will probably be easier if we combine the forces of physicists, astronomers, astrophysicists, and cosmologists. Much hope is placed on the data that can be obtained in the coming years in the event of successful launches of specialized spacecraft. For example, it is planned to launch a space telescope (8.4 meters in diameter). It will be able to register a huge number of galaxies (up to the 28th magnitude; we recall that the luminaries up to the 6th magnitude are visible to the naked eye), and this will allow us to build a map of the distribution of "hidden mass" throughout the sky. Certain information can also be extracted from ground-based observations, since the "hidden matter", having a large gravity, should bend the rays of light coming to us from distant galaxies and quasars. By processing images of such light sources on computers, it is possible to register and evaluate the invisible gravitating mass. Surveys of this kind of individual parts of the sky have already been made. (See the article by Academician N. Kardashev "Cosmology and problems of SETI", recently published in the popular scientific journal of the Presidium of the Russian Academy of Sciences "Earth and Universe", 2002, No. 4.)
In conclusion, let us return to the question formulated in the title of this article. It seems that after all that has been said, it is hardly possible to confidently give a positive answer to it ... The oldest of the most ancient sciences - astronomy is just beginning.
