Ecology of knowledge. Science and discoveries: The Universe is infinite, and there are no number of stars in it. In the center of the forest, which is smaller than the Universe, and there are not as many trees as stars, you cannot see the gaps - the field of view is blocked by trunks and leaves. Why then is the night sky not full of stars? This is the Olbers paradox, or photometric paradox. Today we will find a solution for him.
The Universe is infinite, and there are no number of stars in it. In the center of the forest, which is smaller than the Universe, and there are not as many trees as stars, you cannot see the gaps - the field of view is blocked by trunks and leaves.
Why then is the night sky not full of stars? This is the Olbers paradox, or photometric paradox. Today we will find a solution for him.
A powerful telescope can see so many stars in a small square of the sky. The point is that there should be even more of them.
Science vs. Logics
The mystery of why there are so few stars in the night sky tormented astronomers even in the scientifically mature 19th century. Through telescopes, it is true, scientists have seen much more luminaries - but fewer than are burning in the endless Universe. Under the arches of learned foreheads, logic insisted that the night sky should look something like the animation next to it.
The solution to the paradox turned out to be even simpler than the formulation.
Invisible stars
Let's start with the fact that the stargazers of the last millennium were not so wrong. The photo below was taken by the Hubble Orbital Telescope (an incredibly cool device). Depicted here is a piece measuring 1/13,000,000 of the entire celestial sphere.
Sky according to Olbers' Paradox
All these colored stars are galaxies that are invisible to the eye. In order to take this picture, the telescope had to go into space, use ultra-sensitive matrices and hold the frame for more than 11 days! Such technologies appeared only at the end of the last century.
Hubble Ultra Deep Field
If a person could see everything that an orbiting telescope can, the night sky would be as bright as the center of the arm of our Milky Way! However, there are still black gaps that Olbers' paradox denies. The answer to these voids lies in the same reason why galaxies are hidden from the naked eye.
The universe is expanding too fast
We have already discussed together how and why the world around us is inflating. In short, light from distant galaxies travels a greater distance to us than it did when it left home. This creates a redshift effect - the frequency and energy of rays from distant stars decreases.
What follows from this? There are such distant stars, the rays from which will fade away even before they reach the Earth. Therefore, there is light in the black abysses of space - we just never see it.
Redshift
By the way, distance is the main source of the photometric paradox. More on this below.
It takes time for light to reach Earth. It travels 149,600,000 kilometers from the Sun to us in 8.3 minutes, and 81360544648396 kilometers from the star Sirius in 8.6 years. The greater the distance, the longer the light travels, everything is clear here.
Our Universe is about 13.8 billion years old. But the dimensions of space are infinite! The most powerful telescopes were able to detect light from a distance-time of 12-13 billion years. This means that the galaxy gap remains invisible - they are so far away that the radiation physically did not have time to reach even in the form of elusive neutrinos!
The event horizon has a lot to do with why black holes are black.
As the Universe expands, light has to travel even greater distances. And someday, on the outskirts of the world, the expansion will become equal to the speed of light - this will establish the so-called event horizon. It will move closer and closer to us until even the closest stars are no longer visible.
This will happen only if the expansion continues, and then after many billions of years. We recently wrote about large-scale space disasters - even catching them is easier than waiting for the event horizon at your doorstep.
Finally
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It turns out that Olbers’ riddle is not a paradox at all - it’s just that the laws of physics do not allow all the stars to blind our eyes at once. However, this cannot stop scientists, and they continue to discover new stars. published
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Our Universe consists of several trillion galaxies. The solar system is located inside a fairly large galaxy, the total number of which in the Universe is limited to several tens of billions of units.
Our galaxy contains 200-400 billion stars. 75% of them are faint red dwarfs, and only a few percent of the stars in the galaxy are similar to yellow dwarfs, the spectral type of star to which ours belongs. For an earthly observer, our Sun is 270 thousand times closer to the nearest star (). At the same time, luminosity decreases in direct proportion to the decrease in distance, so the visible brightness of the Sun in the earth's sky is 25 magnitudes or 10 billion times greater than the visible luminosity of the nearest star (). In this regard, due to the blinding light of the Sun, stars are not visible in the daytime sky. A similar problem occurs when trying to photograph exoplanets around nearby stars. In addition to the Sun during the day, you can see the International Space Station (ISS) and flares of satellites of the first constellation Iridium. This is explained by the fact that the Moon, some and artificial satellites (artificial satellites of the Earth) in the earth’s sky look much brighter than the brightest stars. For example, the apparent brightness of the Sun is -27 magnitudes, for the Moon in full phase -13, for flares of satellites of the first constellation Iridium -9, for the ISS -6, for Venus -5, for Jupiter and Mars -3, for Mercury -2 , Sirius (the brightest star) has -1.6.
The magnitude scale for the apparent brightness of various astronomical objects is logarithmic: a difference in the apparent brightness of astronomical objects of one magnitude corresponds to a difference of 2.512 times, and a difference of 5 magnitudes corresponds to a difference of 100 times.
Why can't you see the stars in the city?
In addition to the problems of observing stars in the daytime sky, there is the problem of observing stars in the night sky in populated areas (near large cities and industrial enterprises). Light pollution in this case is caused by artificial radiation. Examples of such radiation include street lighting, illuminated advertising posters, gas torches of industrial enterprises, and spotlights for entertainment events.
In February 2001, an amateur astronomer from the United States, John E. Bortle, created a light scale for assessing light pollution in the sky and published it in the Sky&Telescope magazine. This scale consists of nine divisions:
1. Completely dark sky
With such a night sky, not only is it clearly visible, but individual clouds of the Milky Way cast clear shadows. Also visible in detail is the zodiacal light with counterradiance (reflection of sunlight from dust particles located on the other side of the Sun-Earth line). Stars up to magnitude 8 are visible to the naked eye in the sky; the background brightness of the sky is 22 magnitudes per square arcsecond.
2. Natural dark sky
With such a night sky, the Milky Way is clearly visible in detail and the zodiacal light along with the counter-radiance. The naked eye shows stars with apparent brightness up to 7.5 magnitudes, the background sky brightness is close to 21.5 magnitudes per square arcsecond.
3. Country sky
With such a sky, the zodiacal light and the Milky Way continue to be clearly visible with a minimum of detail. The naked eye shows stars up to magnitude 7, the background sky brightness is close to 21 magnitude per square arcsecond.
4. The sky of the transitional area between villages and suburbs
With such a sky, the Milky Way and the zodiacal light continue to be visible with a minimum of detail, but only partially - high above the horizon. The naked eye shows stars up to magnitude 6.5, the background sky brightness is close to 21 magnitude per square arcsecond.
5. Sky surrounding cities
With such skies, the zodiacal light and the Milky Way are rarely visible, under ideal weather and seasonal conditions. The naked eye shows stars up to magnitude 6, the background sky brightness is close to 20.5 magnitude per square arcsecond.
6. Sky of city suburbs
With such a sky, the zodiacal light is not observed under any conditions, and the Milky Way is hardly visible only at the zenith. The naked eye shows stars up to magnitude 5.5, the background sky brightness is close to magnitude 19 per square arcsecond.
7. The transitional sky between suburbs and cities
In such a sky, under no circumstances is either the zodiacal light or the Milky Way visible. The naked eye only shows stars up to magnitude 5, the background sky brightness is close to magnitude 18 per square arcsecond.
8. City sky
In such a sky, only a few of the brightest open star clusters can be seen with the naked eye. The naked eye only shows stars up to magnitude 4.5, the background sky brightness is less than 18 magnitudes per square arcsecond.
9. The sky of the central part of cities
In such a sky, only star clusters can be seen. The naked eye, at best, shows stars up to magnitude 4.
Light pollution from residential, industrial, transport and other economic facilities of modern human civilization leads to the need to create the largest astronomical observatories in high mountain areas, which are as remote as possible from the economic facilities of human civilization. In these places, special rules are observed to limit street lighting, minimize traffic at night, and build residential buildings and transport infrastructure. Similar rules apply in special protected zones of the oldest observatories, which are located near large cities. For example, in 1945, a protective park zone was organized within a radius of 3 km around the Pulkovo Observatory near St. Petersburg, in which large-scale residential or industrial production was prohibited. In recent years, attempts to organize the construction of residential buildings in this protective zone have become more frequent due to the high cost of land near one of the largest metropolises in Russia. A similar situation is observed around astronomical observatories in Crimea, which are located in a region extremely attractive for tourism.
The image from NASA clearly shows that the most heavily illuminated areas are Western Europe, the eastern part of the continental United States, Japan, coastal China, the Middle East, Indonesia, India, and the southern coast of Brazil. On the other hand, a minimal amount of artificial light is typical for the polar regions (especially Antarctica and Greenland), areas of the World Ocean, the basins of the tropical Amazon and Congo rivers, the high-mountainous Tibetan plateau, desert regions of northern Africa, central Australia, northern regions of Siberia and the Far East.
In June 2016, the journal Science published a detailed study on the topic of light pollution in various regions of our planet (“The new world atlas of artificial night sky brightness”). The study found that more than 80% of the world's inhabitants and more than 99% of people in the United States and Europe live in conditions of severe light pollution. More than a third of the planet's inhabitants are deprived of the opportunity to observe the Milky Way, including 60% of Europeans and almost 80% of North Americans. Extreme light pollution affects 23% of the earth's surface between 75 degrees north latitude and 60 degrees south latitude, as well as 88% of the surface of Europe and almost half of the surface of the United States. In addition, the study notes that energy-saving technologies for converting street lighting from incandescent lamps to LED lamps will lead to an increase in light pollution by approximately 2.5 times. This is due to the fact that the maximum light emission from LED lamps with an effective temperature of 4 thousand Kelvin falls on blue rays, where the retina of the human eye has maximum light sensitivity.
According to the study, maximum light pollution is observed in the Nile Delta in the Cairo region. This is due to the extremely high population density of the Egyptian metropolis: 20 million Cairo residents live in an area of half a thousand square kilometers. This means an average population density of 40 thousand people per square kilometer, which is about 10 times the average population density in Moscow. In some areas of Cairo, the average population density exceeds 100 thousand people per square kilometer. Other areas with maximum exposure are in the Bonn-Dortmund metropolitan areas (near the border between Germany, Belgium and the Netherlands), in the Padanian Plain in northern Italy, between the US cities of Boston and Washington, around the English cities of London, Liverpool and Leeds, and in area of the Asian megacities Beijing and Hong Kong. For residents of Paris, you must travel at least 900 km to Corsica, central Scotland or the Cuenca province of Spain to see dark skies (light pollution levels less than 8% of natural light). And in order for a resident of Switzerland to see an extremely dark sky (the level of light pollution is less than 1% of natural light), he will have to travel more than 1,360 km to the north-western part of Scotland, Algeria or Ukraine.
The maximum degree of dark sky absence is found in 100% of Singapore, 98% of Kuwait, 93% of the United Arab Emirates (UAE), 83% of Saudi Arabia, 66% of South Korea, 61% of Israel, 58% of Argentina, 53% of Libya and 50% Trinidad and Tobago. The opportunity to observe the Milky Way is absent from all residents of the small states of Singapore, San Marino, Kuwait, Qatar and Malta, as well as from 99%, 98% and 97% of residents of the UAE, Israel and Egypt, respectively. Countries with the largest share of territory where there is no opportunity to observe the Milky Way are Singapore and San Marino (100 each), Malta (89%), West Bank (61%), Qatar (55%), Belgium and Kuwait (51 each). %), Trinidad and Tobago, the Netherlands (43% each) and Israel (42%).
On the other hand, Greenland (only 0.12% of its territory has a darkened sky), the Central African Republic (CAR) (0.29%), the Pacific territory of Niue (0.45%), Somalia (1.2%) and Mauritania (1.4%) have minimal light pollution.
Despite the ongoing growth of the global economy, along with an increase in energy consumption, there is also an increase in the astronomical education of the population. A striking example of this was the annual international Earth Hour event where the majority of the population turns off the lights on the last Saturday of March. Initially, this action was conceived by the World Wildlife Fund (WWF) as an attempt to popularize energy saving and reduce greenhouse gas emissions (combat global warming). However, at the same time, the astronomical aspect of the action also gained popularity - the desire to make the skies of megacities more suitable for amateur observations, at least for a short time. The campaign was first carried out in Australia in 2007, and the following year it spread throughout the world. Every year the event attracts an increasing number of participants. If in 2007 400 cities from 35 countries took part in the event, then in 2017 more than 7 thousand cities from 187 countries took part.
At the same time, one can note the disadvantages of the promotion, which consist in an increased risk of accidents in the world's energy systems due to the sudden simultaneous switching off and switching on of a huge number of electrical appliances. In addition, statistics show a strong correlation between the lack of street lighting and an increase in injuries, street crime and other emergency incidents.
Why are stars not visible in images from the ISS?
The photo clearly shows the lights of Moscow, the greenish glow of the aurora on the horizon, and the absence of stars in the sky. The huge difference between the brightness of the Sun and even the brightest stars makes it impossible to observe stars not only in the daytime sky from the surface of the Earth, but also from space. This fact clearly shows how large the role of “light pollution” from the Sun is compared to the influence of the earth’s atmosphere on astronomical observations. However, the fact that there were no stars in the sky photographs during manned flights to the Moon became one of the key “evidence” of the conspiracy theory about the absence of NASA astronauts flying to the Moon.
Why are stars not visible in photographs of the Moon?
If the difference between the visible luminosity of the Sun and the brightest star - Sirius in the earth's sky is about 25 magnitudes or 10 billion times, then the difference between the visible luminosity of the full Moon and the brightness of Sirius decreases to 11 magnitudes or about 10 thousand times.
In this regard, the presence of a full Moon does not lead to the disappearance of stars in the entire night sky, but only makes it difficult to see them near the lunar disk. However, one of the first ways to measure the diameter of stars was to measure the duration of the lunar disk covering the bright stars of the zodiacal constellations. Naturally, such observations tend to be carried out at the minimum phase of the Moon. A similar problem of detecting dim sources near a bright light source exists when trying to photograph planets around nearby stars (the apparent brightness of the Jupiter analogue in nearby stars due to reflected light is approximately 24 magnitudes, while the Earth analogue is only about 30 magnitudes). In this regard, astronomers have so far been able to photograph only young massive planets during observations in the infrared: young planets are very hot after the planet formation process. Therefore, in order to learn how to detect exoplanets around nearby stars, two technologies are being developed for space telescopes: coronagraphy and null interferometry. According to the first technology, a bright source is covered by an eclipsed disk (artificial eclipse); according to the second technology, the light of a bright source is “nullified” using special wave interference techniques. A striking example of the first technology was, which since 1995 has been monitoring solar activity from the first libration point. Images from the space observatory's 17-degree coronagraph camera show stars up to magnitude 6 (a difference of 30 magnitudes, or a trillion times).
A black hole is a product of gravity. Therefore, the prehistory of the discovery of black holes can begin from the time of I. Newton, who discovered the law of universal gravitation - the law governing the force to which absolutely everything is subject. Neither in the time of I. Newton, nor today, centuries later, has another such universal force been discovered. All other types of physical interaction are associated with specific properties of matter. For example, an electric field acts only on charged bodies, and neutral bodies are completely indifferent to it. And only gravity absolutely reigns in nature. The gravitational field affects everything: light particles and heavy ones (and under the same initial conditions, in exactly the same way), even light. The fact that light is attracted by massive bodies was already assumed by I. Newton. From this fact, from the understanding that light is also subject to gravitational forces, the prehistory of black holes begins, the history of predictions of their amazing properties.
One of the first to do this was the famous French mathematician and astronomer P. Laplace.
The name of P. Laplace is well known in the history of science. First of all, he is the author of a huge five-volume work, “Treatise on Celestial Mechanics.” In this work, published from 1798 to 1825, he presented the classical theory of the motion of bodies in the solar system, based only on Newton's law of universal gravitation. Before this work, some observed features of the motion of the planets, the Moon, and other bodies of the Solar System were not fully explained. It even seemed that they contradicted Newton's law. P. Laplace, with a subtle mathematical analysis, showed that all these features are explained by the mutual attraction of celestial bodies, the influence of the planets' gravity on each other. Only one force reigns in the heavens, he proclaimed, and that is the force of gravity. “Astronomy, considered from the most general point of view, is a great problem of mechanics,” wrote P. Laplace in the preface to his “Treatise.” By the way, the very term “celestial mechanics”, which has become so firmly established in science, was first used by him.
P. Laplace was also one of the first to understand the need for a historical approach to explaining the properties of systems of celestial bodies. He, following I. Kant, proposed a hypothesis of the origin of the Solar system from initially rarefied matter.
The main idea of Laplace's hypothesis is about the condensation of the Sun and planets from a gas nebula and still serves as the basis for modern theories of the origin of the Solar system...
Much has been written about all this in the literature and in textbooks, just like the proud words of P. Laplace, who, in response to Napoleon’s question: why is God not mentioned in his “Celestial Mechanics”? - said: “I don’t need this hypothesis.”
But what little was known about until recently was his prediction of the possibility of the existence of invisible stars.
The prediction was made in his book Exposition of the Systems of the World, published in 1795. In this book, which we would call popular today, the famous mathematician never once resorted to formulas and drawings. P. Laplace’s deep conviction that gravity acts on light in the same way as on other bodies allowed him to write the following significant words: “A luminous star with a density equal to the density of the Earth and a diameter 250 times greater than the diameter of the Sun does not give not a single ray of light can reach us due to its gravity; Therefore, it is possible that the brightest celestial bodies in the Universe turn out to be invisible for this reason.”
The book provided no evidence for this claim. It was published by him several years later.
How did P. Laplace reason? He calculated, using Newton's theory of gravity, the value that we now call the second escape velocity on the surface of the star. This is the speed that must be given to any body so that it, having overcome gravity, forever flies away from a star or planet into outer space. If the initial speed of the body is less than the second cosmic speed, then the gravitational forces will slow down and stop the movement of the body and force it to fall again towards the gravitating center. In our time of space flights, everyone knows that the second escape velocity on the surface of the Earth is 11 kilometers per second. The greater the mass and the smaller the radius of this body, the greater the second escape velocity on the surface of a celestial body. This is understandable: after all, with increasing mass, gravity increases, and with increasing distance from the center it weakens.
On the surface of the Moon, the second escape velocity is 2.4 kilometers per second, on the surface of Jupiter 61, on the Sun - 620, and on the surface of the so-called neutron stars, which are approximately the same in mass as the Sun, but have a radius of only ten kilometers, this speed reaches half the speed of light - 150 thousand kilometers per second.
Let us imagine, reasoned P. Laplace, that we take a celestial body on the surface of which the second cosmic velocity already exceeds the speed of light. Then the light from such a star will not be able to fly into space due to the action of gravity, will not be able to reach a distant observer, and we will not see the star, despite the fact that it emits light!
If you increase the mass of a celestial body by adding matter with the same average density to it, then the second cosmic velocity increases as much as the radius or diameter increases.
Now the conclusion made by P. Laplace is clear: in order for gravity to delay light, it is necessary to take a star with a substance of the same density as the Earth, and with a diameter 250 times greater than that of the Sun, that is, 27 thousand times greater than that of the Earth. Indeed, the second escape velocity on the surface of such a star will also be 27 thousand times greater than on the surface of the Earth, and will be approximately equal to the speed of light: the star will cease to be visible.
This was a brilliant insight into one of the properties of a black hole - not letting out light, being invisible. To be fair, it should be noted that P. Laplace was not the only scientist and formally not even the very first who made such a prediction. Relatively recently, it turned out that in 1783, an English priest and geologist, one of the founders of scientific seismology, J. Michell, made a similar statement. His argumentation was very similar to that of P. Laplace.
Now between the French and the British there is sometimes a half-joking, and sometimes a serious debate: who should be considered the discoverer of the possibility of the existence of invisible stars - the Frenchman P. Laplace or the Englishman J. Michell? In 1973, the famous English theoretical physicists S. Hawking and G. Ellis, in a book devoted to modern special mathematical issues of the structure of space and time, cited the work of the Frenchman P. Laplace with proof of the possibility of the existence of black stars; At that time, the work of J. Michell was not yet known. In the fall of 1984, the famous English astrophysicist M. Riess, speaking at a conference in Toulouse, said that although it is not very convenient to speak on the territory of France, he must emphasize that the Englishman J. Michell was the first to predict invisible stars, and showed a snapshot of the first page of the corresponding his works. This historic remark was met with applause and smiles from those present.
How can one not recall the discussions between the French and the British about who predicted the position of the planet Neptune from disturbances in the movement of Uranus: the Frenchman W. Le Verrier or the Englishman J. Adams? As is known, both scientists independently correctly indicated the position of the new planet. Then the Frenchman W. Le Verrier was luckier. This is the fate of many discoveries. Often they are done almost simultaneously and independently by different people. Usually priority is given to those who have penetrated deeper into the essence of the problem, but sometimes this is simply the whims of fortune.
But the prediction of P. Laplace and J. Michell was not yet a real prediction of a black hole. Why?
The fact is that in the time of P. Laplace it was not yet known that nothing in nature could move faster than light. It is impossible to outrun the light in emptiness! This was established by A. Einstein in the special theory of relativity already in our century. Therefore, for P. Laplace, the star he was considering was only black (non-luminous), and he could not know that such a star would lose the ability to “communicate” with the outside world in any way, to “report” anything to distant worlds about the events taking place on it . In other words, he did not yet know that this was not only a “black”, but also a “hole” into which one could fall, but it was impossible to get out. Now we know that if light cannot come out of some region of space, then nothing at all can come out, and we call such an object a black hole.
Another reason why P. Laplace’s reasoning cannot be considered rigorous is that he considered gravitational fields of enormous strength, in which falling bodies are accelerated to the speed of light, and the emerging light itself can be delayed, and applied the law of gravity Newton.
A. Einstein showed that Newton’s theory of gravity is inapplicable for such fields, and created a new theory that is valid for superstrong, as well as rapidly changing fields (for which Newton’s theory is also inapplicable!), and called it the general theory of relativity. It is the conclusions of this theory that must be used to prove the possibility of the existence of black holes and to study their properties.
General relativity is an amazing theory. She is so deep and slender that she evokes a feeling of aesthetic pleasure in everyone who gets to know her. Soviet physicists L. Landau and E. Lifshitz in their textbook “Field Theory” called it “the most beautiful of all existing physical theories.” German physicist Max Born said of the discovery of the theory of relativity: “I admire it as a work of art.” And the Soviet physicist V. Ginzburg wrote that it evokes “... a feeling... akin to that experienced when looking at the most outstanding masterpieces of painting, sculpture or architecture.”
Numerous attempts at popular presentation of Einstein's theory can, of course, give a general impression of it. But, frankly speaking, it is as little similar to the delight of knowing the theory itself as acquaintance with a reproduction of the “Sistine Madonna” differs from the experience that arises when examining the original created by the genius of Raphael.
And yet, when there is no opportunity to admire the original, you can (and should!) get acquainted with available reproductions, preferably good ones (and there are all kinds).
To understand the incredible properties of black holes, we need to briefly talk about some consequences of Einstein's general theory of relativity.
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It is believed that the very first stars were powered by dark matter. It is possible that these invisible giants, which originated almost 13 billion years ago, still exist in the Universe. It's possible they simply don't emit visible light, making them difficult to detect.
Initially, researcher Paolo Gondolo, a professor of particle astrophysics at the University of Utah (USA), who is working on this problem, wanted to name a new, theoretically existing type of invisible stars - "brown giants", like brown dwarfs, which have the approximate size of Jupiter, but, accordingly, much larger massive. However, his colleagues insisted on calling them "dark stars", after the song of the same name, which was first performed in 1967 by the beloved rock band the Grateful Dead.
According to scientists, “dark stars” should be 200-400 thousand times larger in diameter than our Sun, and 500-1000 times larger than supermassive black holes.
Born almost 13 billion years ago, "dark stars" may still exist today, although they do not emit visible light. The fact is that it is difficult for astronomers to detect these mysterious giants, since in order to become visible, they must emit gamma rays, neutrons and antimatter. Moreover, they should be shrouded in clouds of cold molecular hydrogen gas, which is currently not enough to fuel the energetic particles of such objects.
If scientists manage to detect them, it will help find and identify dark matter. Then it will be possible to find out why black holes form so quickly.
Scientists believe that invisible and as yet unidentified dark matter makes up approximately 95 percent of the entire universe. They are convinced that it exists - there is a lot of evidence for this. For example, galaxies rotate much faster than they should if we consider only those objects that have been discovered within our line of sight to date.
According to scientists, dark matter particles may be so-called WIMPs, or weakly interacting massive particles. Researchers consider neutrinos involved in gravitational interaction to be one of the studied varieties of WIMP. Such particles can destroy each other, producing high temperatures.
Dark matter particles also produce quarks (the hypothetical fundamental elements from which, according to modern ideas, all elementary particles involved in the strong force are composed), as well as copies of antimatter - antiquarks, which, upon collision, emit gamma rays, neutrinos and antimatter, such as positrons and antiprotons.
The researchers calculated that in the newborn Universe, approximately 80-100 million years after the Big Bang occurred, the destroyed proto-stellar clouds of hydrogen and helium cooled and contracted, while remaining hot and massive.
As a result of these processes, dark stars could form, powered by dark matter instead of nuclear energy (as in ordinary stars). They were composed largely of ordinary matter, mainly hydrogen and helium, but were significantly more massive and larger in volume than the Sun and most other modern stars.
“This is a completely new type of star that has a new source of energy,” says researcher Katherine Freese, a theoretical physicist at the University of Michigan.
The Invisible Woman stood on the very edge of the rock and watched as the muddy-brown, dirty water with twigs, withered leaves and roots floating in it splashed, meandering, around her paws. And no matter how the cat peered at her, she could not even discern the stones at the bottom of the river, let alone the reflections on the backs of the fish, which previously always betrayed the presence of prey. She leaned down to touch the surface of the water with her tongue. Bitter and dirty.
Not at all like before, right? - Spotted Star, standing nearby, noted sadly. Mistyfoot raised her head to look at her leader. The previously shining golden fur faded in the gray dawn twilight, and the dark spots that gave it its name became so dim during the last moon that it was no longer possible to distinguish them. - When the water returned, I decided that now everything would be just like before. - Spotted Star sighed and, lowering her paw into the water, moved it a little from side to side. Then she straightened it, watching how dirt dripped from her claws onto the stone.
The fish will be back soon,” the Invisible Man meowed. - After all, the streams are full again. Why would fish avoid them?
But Spotted Star looked at the rippling water and did not seem to hear the words of the herald.
So many fish died during the drought,” she sighed again. - What if the lake remains empty? What will we eat?
The Invisible Man moved closer to her, touched her shoulder, and with horror felt the sharp ribs protruding from under the skin.
“Everything will be fine,” she muttered. - The beavers’ home was destroyed, and after the rain the drought ended. It was a difficult season, but we have already survived it.
Black Claw, Catfish and Primrose - no,” the leader bared her teeth in response. - Three dead elders for one Green Leaves! I am forced to watch my people die. And all because there is nothing left in the lake except dirt! And Scalefish? He was brave, like the rest of the cats who went up the river - so why didn't he deserve the opportunity to return? Maybe only because he went too far, to where StarClan couldn’t see anything?
The Invisible Woman helplessly stroked her back with her tail.
The scalefish died saving the lake, the tribes and all of us. We will always honor his memory.
Leopard Star turned around in irritation and began to climb up the bank.
“He paid too much,” the cat growled without turning around. “And if the fish don’t return to the lake, his sacrifice will be in vain.”
The leader stumbled, and the Invisible One rushed forward, ready to support her. But she only hissed irritably and continued to climb up, stumbling and staggering.
The Invisible Man settled down behind her, several tails away, not wanting to fuss around the proud golden cat. She knew that now Leopard Star was constantly in pain, which even all of Mothwing's herbs could not drown out, despite the fact that this illness was not at all unusual - just a withering thirst, a sharp loss of weight, constant hunger and growing weakness that dulled her hearing. and vision. Mistyfoot only felt relief when her leader squeezed through the ferns surrounding RiverClan's camp and disappeared inside.
And suddenly from there, from the depths, a muffled scream was heard.
Leopard Star? - internally growing cold, the cat rushed upstairs. The leader lay on the ground, eyes wide in pain and desperately trying to breathe.
Don’t move,” the Invisible Man ordered. - I'll bring help.
She broke through the ferns and fell into a clearing in the center of the camp.
Mothwing, hurry up! Spotted Star has fallen!
The heavy patter of paws on the ground was heard, then the sandy fur of Mothwing flashed, and finally she herself appeared on the threshold of the tent. Then she stopped and shook her head, not knowing where to go.
Here! - the Invisible Woman shouted to her.
Side by side, the cats squeezed between the green stems to their leader. Leopard Star closed her eyes tiredly, the air bubbled in her throat with every breath. Mothwing leaned over her, sniffing the fur. The Invisible Woman also came closer, but recoiled when she felt the stale smell coming from the sick cat. Up close, she saw the dirt on Leopard Star's fur, as if she hadn't been licked for a whole moon.
“Bring Myatnik and Reedworm,” the healer quietly asked her, turning over her shoulder. “They haven’t gone on patrol yet and will help carry Spotted Star to her tent.”
Feeling relieved that she now had a reason to leave and guilty for wanting to do so, Mistyfoot nodded silently, backed away and rushed back into the clearing. She returned with Myatnik and Kamyshinnik. The leader helped Mothwing get up, and she leaned heavily on the warriors. The herald walked ahead, parting the ferns and lightly holding their leaves in front of the tribesmen who were either leading or dragging the sick cat.
Is Leopard Star dead? - the ringing voice of one of Dusk’s kittens was heard.
Of course not, my dear,” the queen answered in a whisper. - She's just very tired.
The Invisible Woman remained standing on the threshold of the leader's tent, watching as Reed Man raked moss under the head of the lying cat. This is more than exhaustion. The cave seemed to have become dark, shadows gathered in the corners, as if the Star Ancestors were already ready to appear and greet the departing leader of the River Tribe. The mint pushed past the heralds, fragrant with the scent of ferns.
“Let me know if there’s anything else I can do for her,” he said quietly, and Mistyfoot nodded. The Reedtail also came out, lowering its head and dragging its tail behind it, leaving a long trail in the dust.
Mothwing shifted Leopardstar's paw slightly into a more comfortable position and straightened up.
“I need to get some herbs from my tent,” she announced. “Stay here, so that she understands that you are nearby,” the healer looked back at the motionless cat, then came closer and whispered in her ear, “Be strong, my friend.”
After she left, there was dead silence in the tent. Spotted Star's breathing became shallow, her wheezes barely moving the moss next to her muzzle. The Invisible Woman sank down next to her and stroked the leader’s bony side with her tail.
“Sleep well,” she purred softly. - Now everything will be all right. The moth will soon bring herbs and you will feel better.
To her surprise, Leopard Star began to stir.
“It’s late,” she rasped, without opening her eyes. - The star ancestors are close, I feel them next to me. The time has come for me to leave.
Do not say that! - Invisible Man hissed at her. - Your ninth life has just begun! Mothwing will cure you, you'll see!
Mothwing is a good healer, but she can’t always help. Let me go quietly. I won’t fight this final battle, and I don’t want you to try,” Leopard Star tried to grin, but all he could do was wheeze.
But I don't want to lose you! - The Invisible Man was indignant.
Is it true? - the leader croaked, opening one eye. A searching amber gaze looked at her from head to toe. - After everything I did to your brother? With all the half-breeds?
For a moment, Mistyfoot again felt trapped in that terrible black hole, reeking of rabbit, near the old RiverClan camp. Then Leopardstar and Tigerstar united to create TigerClan, and, in an attempt to purify the blood of the warriors, they captured all the half-bloods. Mistyfoot and Rock, who was then RiverClan's herald, had just learned that their mother was Bluestar. In the eyes of the leaders, this was enough for a sentence, and Spotted Star allowed Blackfoot to kill Stone in cold blood. His sister was saved by Firestar, and he brought her to ThunderClan, where she remained until his power, along with Tigerstar’s nine lives, ended in the battle with BloodClan.