We are all made of cosmic dust, scientists have proven. Cosmic dust and strange balls in ancient earth layers What kind of light absorbs particles of cosmic dust

Cosmic dust

particles of matter in interstellar and interplanetary space. Light-absorbing clumps of cosmic rays are visible as dark spots in photographs of the Milky Way. Weakening of light due to the influence of K. p. interstellar absorption, or extinction, is not the same for electromagnetic waves of different lengths λ , resulting in reddening of the stars. In the visible region, extinction is approximately proportional to λ-1, while in the near ultraviolet region it almost does not depend on the wavelength, but there is an additional absorption maximum near 1400 Å. Much of the extinction is due to the scattering of light rather than its absorption. This follows from observations of reflective nebulae that contain condensate fields and are visible around B-type stars and some other stars bright enough to illuminate the dust. A comparison of the brightness of the nebulae and the stars illuminating them shows that the dust albedo is high. The observed extinction and albedo lead to the conclusion that the C.P. consists of dielectric particles with an admixture of metals with a size slightly less than 1 µm. The ultraviolet extinction maximum can be explained by the fact that inside the dust grains there are graphite flakes about 0.05 × 0.05 × 0.01 µm. Due to the diffraction of light by a particle whose dimensions are comparable to the wavelength, the light scatters predominantly forward. Interstellar absorption often leads to polarization of light, which is explained by the anisotropy of the properties of dust grains (the prolate shape of dielectric particles or the anisotropy of graphite conductivity) and their ordered orientation in space. The latter is explained by the action of a weak interstellar field, which orients dust grains with their long axis perpendicular to the line of force. Thus, by observing the polarized light of distant celestial bodies, one can judge the orientation of the field in interstellar space.

The relative amount of dust is determined from the value of the average absorption of light in the plane of the Galaxy - from 0.5 to several magnitudes per kiloparsec in the visual region of the spectrum. The mass of dust is about 1% of the mass of interstellar matter. Dust, like gas, is distributed inhomogeneously, forming clouds and denser formations - Globules. In globules, dust is a cooling factor, screening the light of stars and emitting in the infrared range the energy received by the dust grain from inelastic collisions with gas atoms. On the surface of dust, atoms combine into molecules: dust is a catalyst.

S. B. Pikelner.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what "Space dust" is in other dictionaries:

Particles of condensed matter in interstellar and interplanetary space. According to modern concepts, cosmic dust consists of particles approx. 1 µm with graphite or silicate core. In the galaxy, cosmic dust forms ... ... Big Encyclopedic Dictionary

COSMIC DUST, very small particles of solid matter found in any part of the universe, including meteoritic dust and interstellar matter that can absorb starlight and form dark nebulae in galaxies. Spherical… … Scientific and technical encyclopedic dictionary

COSMIC DUST- meteor dust, as well as the smallest particles of matter that form dust and other nebulae in interstellar space ... Great Polytechnic Encyclopedia

cosmic dust- Very small particles of solid matter present in world space and falling to Earth... Geography Dictionary

Particles of condensed matter in interstellar and interplanetary space. According to modern ideas, cosmic dust consists of particles about 1 micron in size with a core of graphite or silicate. In the galaxy, cosmic dust forms ... ... encyclopedic Dictionary

Formed in space by particles ranging in size from a few molecules to 0.1 mm. 40 kilotons of cosmic dust settles on planet Earth every year. Cosmic dust can also be distinguished by its astronomical position, for example: intergalactic dust, ... ... Wikipedia

cosmic dust- kosminės dulkės statusas T sritis fizika atitikmenys: engl. cosmic dust; interstellar dust; space dust vok. interstellarer Staub, m; kosmische Staubteilchen, m rus. cosmic dust, f; interstellar dust, f pranc. poussière cosmique, f; poussière… … Fizikos terminų žodynas

cosmic dust- kosminės dulkės statusas T sritis ekologija ir aplinkotyra apibrėžtis Atmosferoje susidarančios meteorinės dulkės. atitikmenys: engl. space dust vok. kosmischer Staub, m rus. cosmic dust, f ... Ekologijos terminų aiskinamasis žodynas

Particles condensed in va in interstellar and interplanetary space. According to modern to representations, K. the item consists of particles in the size apprx. 1 µm with graphite or silicate core. In the Galaxy, cosmic rays form clusters of clouds and globules. Summons… … Natural science. encyclopedic Dictionary

Particles of condensed matter in interstellar and interplanetary space. Composed of particles about 1 micron in size with a core of graphite or silicate, it forms clouds in the Galaxy that cause the light emitted by stars to weaken and ... ... Astronomical dictionary

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99 secrets of astronomy, Serdtseva N. 99 secrets of astronomy are hidden in this book. Open it and learn about how the Universe works, what cosmic dust is made of and where black holes come from. . Funny and simple lyrics...

The science

Scientists have noticed a large cloud of cosmic dust created by a supernova explosion.

Cosmic dust may provide answers to questions about how life appeared on earth- whether it originated here or was brought with comets that fell to the Earth, whether there was water here from the very beginning, or whether it was also brought from space.

A recent snapshot of a cloud of cosmic dust that occurred after a supernova explosion proves thatsupernovaeable to produce enough space dust to create planets like our Earth.

Moreover, scientists believe that this dust is enough to create thousands suchplanets like earth.

Telescope data shows warm dust (white) that survived inside the supernova remnant. Supernova remnant cloud Sagittarius A East shown in blue. Radio emission (red) indicates an expanding shock wave colliding with surrounding interstellar clouds (green).

It is worth noting that cosmic dust participated in the creation of both our planet and many other cosmic bodies. Sheconsists of small particles up to 1 micrometer in size.

It is now known that comets contain primordial dust that is billions of years old and played a major role in the formation of the solar system. By examining this dust, you can learn a lot abouthow the universe and our solar system began to be createdin particular, as well as learn more about the composition of the first organic matter and water.

According to Ryan Lau of Cornell University in Ithaca, New York,flash,recentlyphotographed by a telescope, occurred 10,000 years ago, resulting in a cloud of dust large enough togot 7,000 planets similar to the Earth.

Observations of a supernova (Supernova)

By using Stratospheric Observatory for Infrared Astronomy (SOFIA), scientists studied the intensity of radiation, and were able to calculate the total mass of cosmic dust in the cloud.

It is worth noting that SOFIA is a joint a project of NASA and the German Air and Space Center. The aim of the project is to create and use a Cassegrain telescope aboard a Boeing 474.

During the flight at an altitude of 12-14 kilometers, a telescope with a circumference of 2.5 meters is able to create photographs of space that are close in quality to photographs taken by space observatories.

Led by Lau, the team used the SOFIA telescope with a special cameraFORCAST on boardto take infrared pictures of the cosmic dust cloud, also known as the supernova remnant Sagittarius A Vostok. FORCAST isinfrared camera for detecting low-contrast objects.

Hello. In this lecture, we will talk to you about dust. But not about the one that accumulates in your rooms, but about cosmic dust. What is it?

Space dust is very small particles of solid matter found in any part of the universe, including meteoritic dust and interstellar matter that can absorb starlight and form dark nebulae in galaxies. Spherical dust particles about 0.05 mm in diameter are found in some marine sediments; it is believed that these are the remains of those 5,000 tons of cosmic dust that annually fall on the globe.

Scientists believe that cosmic dust is formed not only from the collision, the destruction of small solid bodies, but also due to the thickening of interstellar gas. Cosmic dust is distinguished by its origin: dust is intergalactic, interstellar, interplanetary and circumplanetary (usually in a ring system).

Cosmic dust grains arise mainly in the slowly outflowing atmospheres of red dwarf stars, as well as in explosive processes on stars and in the rapid ejection of gas from the nuclei of galaxies. Other sources of cosmic dust are planetary and protostellar nebulae, stellar atmospheres, and interstellar clouds.

Entire clouds of cosmic dust, which are in the layer of stars that form the Milky Way, prevent us from observing distant star clusters. A star cluster like the Pleiades is completely submerged in a dust cloud. The brightest stars that are in this cluster illuminate the dust, as a lantern illuminates the fog at night. Cosmic dust can only shine by reflected light.

Blue rays of light passing through cosmic dust are attenuated more than red ones, so the light of stars reaching us appears yellowish and even reddish. Entire regions of world space remain closed to observation precisely because of cosmic dust.

Interplanetary dust, at least in comparative proximity to the Earth, is a fairly well-studied matter. Filling the entire space of the solar system and concentrated in the plane of its equator, it was born for the most part as a result of random collisions of asteroids and the destruction of comets approaching the Sun. The composition of dust, in fact, does not differ from the composition of meteorites falling to the Earth: it is very interesting to study it, and there are still many discoveries to be made in this area, but it seems that there is no particular intrigue here. But thanks to this particular dust, in fine weather in the west immediately after sunset or in the east before sunrise, you can admire a pale cone of light above the horizon. This is the so-called zodiacal - sunlight scattered by small cosmic dust particles.

Much more interesting is interstellar dust. Its distinctive feature is the presence of a solid core and shell. The core appears to consist mainly of carbon, silicon, and metals. And the shell is mainly made of gaseous elements frozen on the surface of the nucleus, crystallized in the conditions of “deep freezing” of interstellar space, and this is about 10 kelvins, hydrogen and oxygen. However, there are impurities of molecules in it and more complicated. These are ammonia, methane, and even polyatomic organic molecules that stick to a grain of dust or form on its surface during wanderings. Some of these substances, of course, fly away from its surface, for example, under the action of ultraviolet radiation, but this process is reversible - some fly away, others freeze or are synthesized.

If the galaxy has formed, then where does the dust come from - in principle, scientists understand. Its most significant sources are novae and supernovae, which lose part of their mass, "dumping" the shell into the surrounding space. In addition, dust is also born in the expanding atmosphere of red giants, from where it is literally swept away by radiation pressure. In their cool, by the standards of stars, atmosphere (about 2.5 - 3 thousand kelvins) there are quite a lot of relatively complex molecules.
But here is a mystery that has not yet been solved. It has always been believed that dust is a product of the evolution of stars. In other words, stars must be born, exist for some time, grow old and, say, produce dust in the last supernova explosion. What came first, the egg or the chicken? The first dust necessary for the birth of a star, or the first star, which for some reason was born without the help of dust, grew old, exploded, forming the very first dust.
What was in the beginning? After all, when the Big Bang happened 14 billion years ago, there were only hydrogen and helium in the Universe, no other elements! It was then that the first galaxies, huge clouds, and in them the first stars began to emerge from them, which had to go a long way in life. Thermonuclear reactions in the cores of stars were supposed to “weld” more complex chemical elements, turn hydrogen and helium into carbon, nitrogen, oxygen, and so on, and only after that the star had to throw it all into space, exploding or gradually dropping the shell. Then this mass had to cool, cool down and, finally, turn into dust. But already 2 billion years after the Big Bang, in the earliest galaxies, there was dust! With the help of telescopes, it was discovered in galaxies that are 12 billion light years away from ours. At the same time, 2 billion years is too short a period for the full life cycle of a star: during this time, most stars do not have time to grow old. Where the dust came from in the young Galaxy, if there should be nothing but hydrogen and helium, is a mystery.

Looking at the time, the professor smiled slightly.

But you will try to unravel this mystery at home. Let's write the task.

Homework.

1. Try to reason about what appeared first, the first star or is it still dust?

Additional task.

1. Report about any kind of dust (interstellar, interplanetary, circumplanetary, intergalactic)

2. Composition. Imagine yourself as a scientist assigned to investigate space dust.

3. Pictures.

homemade task for students:

1. Why is dust needed in space?

Additional task.

1. Report about any kind of dust. Former students of the school remember the rules.

2. Composition. Disappearance of cosmic dust.

3. Pictures.

Interstellar dust is a product of various intensity processes occurring in all corners of the Universe, and its invisible particles even reach the surface of the Earth, flying in the atmosphere around us.

A repeatedly confirmed fact - nature does not like emptiness. Interstellar outer space, which seems to us to be vacuum, is actually filled with gas and microscopic dust particles, 0.01-0.2 microns in size. The combination of these invisible elements gives rise to objects of enormous size, a kind of clouds of the Universe, capable of absorbing some types of spectral radiation from stars, sometimes completely hiding them from earthly researchers.

What is interstellar dust made of?

These microscopic particles have a core, which is formed in the gaseous envelope of stars and depends entirely on its composition. For example, graphite dust is formed from grains of carbon luminaries, and silicate dust is formed from oxygen ones. This is an interesting process that lasts for decades: when the stars cool down, they lose their molecules, which, flying into space, combine into groups and become the basis of the core of a dust grain. Further, a shell of hydrogen atoms and more complex molecules is formed. At low temperatures, interstellar dust is in the form of ice crystals. Wandering around the Galaxy, little travelers lose part of the gas when heated, but new molecules take the place of the departed molecules.

Location and properties

The main part of the dust that falls on our Galaxy is concentrated in the region of the Milky Way. It stands out against the background of stars in the form of black stripes and spots. Despite the fact that the weight of dust is negligible compared to the weight of gas and is only 1%, it is able to hide celestial bodies from us. Although the particles are separated from each other by tens of meters, but even in such an amount, the densest regions absorb up to 95% of the light emitted by stars. The sizes of gas and dust clouds in our system are really huge, they are measured in hundreds of light years.

Impact on observations

Thackeray globules obscure the region of the sky behind them

Interstellar dust absorbs most of the radiation from stars, especially in the blue spectrum, it distorts their light and polarity. Short waves from distant sources receive the greatest distortion. Microparticles mixed with gas are visible as dark spots on the Milky Way.

In connection with this factor, the core of our Galaxy is completely hidden and is available for observation only in infrared rays. Clouds with a high concentration of dust become almost opaque, so the particles inside do not lose their icy shell. Modern researchers and scientists believe that it is they who stick together to form the nuclei of new comets.

Science has proven the influence of dust granules on the processes of star formation. These particles contain various substances, including metals, which act as catalysts for numerous chemical processes.

Our planet increases its mass every year due to falling interstellar dust. Of course, these microscopic particles are invisible, and in order to find and study them, they explore the ocean floor and meteorites. The collection and delivery of interstellar dust has become one of the functions of spacecraft and missions.

When entering the Earth's atmosphere, large particles lose their shell, and small ones invisibly circle around us for years. Cosmic dust is ubiquitous and similar in all galaxies, astronomers regularly observe dark lines on the face of distant worlds.

By mass, solid particles of dust make up a negligible part of the Universe, but it is thanks to interstellar dust that stars, planets and people studying space and simply admiring the stars have arisen and continue to appear. What kind of substance is this cosmic dust? What makes people equip expeditions into space worth the annual budget of a small state in the hope of only, and not in firm certainty, to extract and bring to Earth at least a tiny handful of interstellar dust?

Between stars and planets

Dust in astronomy is called small, fractions of a micron in size, solid particles flying in outer space. Cosmic dust is often conditionally divided into interplanetary and interstellar, although, obviously, interstellar entry into interplanetary space is not prohibited. Just finding it there, among the “local” dust, is not easy, the probability is low, and its properties near the Sun can change significantly. Now, if you fly away, to the borders of the solar system, there the probability of catching real interstellar dust is very high. The ideal option is to go beyond the solar system altogether.

Dust is interplanetary, in any case, in comparative proximity to the Earth - the matter is quite studied. Filling the entire space of the solar system and concentrated in the plane of its equator, it was born for the most part as a result of random collisions of asteroids and the destruction of comets approaching the Sun. The composition of dust, in fact, does not differ from the composition of meteorites falling to the Earth: it is very interesting to study it, and there are still many discoveries to be made in this area, but it seems that there is no particular intrigue here. But thanks to this particular dust, in fine weather in the west immediately after sunset or in the east before sunrise, you can admire a pale cone of light above the horizon. This is the so-called zodiacal sunlight, scattered by small cosmic dust particles.

Now, in the space between stars or near them, of course, not chemical, but physical, that is, spectroscopic, methods have already been found: water, oxides of carbon, nitrogen, sulfur and silicon, hydrogen chloride, ammonia, acetylene, organic acids, such as formic and acetic, ethyl and methyl alcohols, benzene, naphthalene. They even found the amino acid glycine!

It would be interesting to catch and study the interstellar dust penetrating the solar system and probably falling to the Earth. The problem of "catching" it is not easy, because few interstellar dust particles manage to keep their ice "coat" in the sun, especially in the Earth's atmosphere. Large ones heat up too much their cosmic speed cannot be quickly extinguished, and the dust particles “burn”. Small ones, however, plan in the atmosphere for years, retaining part of the shell, but here the problem arises of finding and identifying them.

There is another very intriguing detail. It concerns the dust, the nuclei of which are composed of carbon. Carbon synthesized in the cores of stars and leaving into space, for example, from the atmosphere of aging (like red giants) stars, flying out into interstellar space, cools and condenses in much the same way as fog from cooled water vapor collects in the lowlands after a hot day. Depending on the crystallization conditions, layered structures of graphite, diamond crystals (just imagine whole clouds of tiny diamonds!) and even hollow balls of carbon atoms (fullerenes) can be obtained. And in them, perhaps, like in a safe or a container, particles of the atmosphere of a very ancient star are stored. Finding such dust particles would be a huge success.

Where is space dust found?

It must be said that the very concept of cosmic vacuum as something completely empty has long remained only a poetic metaphor. In fact, the entire space of the Universe, both between stars and between galaxies, is filled with matter, flows of elementary particles, radiation and fields - magnetic, electric and gravitational. All that can be touched, relatively speaking, is gas, dust and plasma, whose contribution to the total mass of the Universe, according to various estimates, is only about 12% with an average density of about 10-24 g/cm 3 . Gas in space is the most, almost 99%. This is mainly hydrogen (up to 77.4%) and helium (21%), the rest account for less than two percent of the mass. And then there is dust in terms of mass, it is almost a hundred times less than gas.

Although sometimes the emptiness in interstellar and intergalactic space is almost ideal: sometimes there is 1 liter of space for one atom of matter! There is no such vacuum either in terrestrial laboratories or within the solar system. For comparison, we can give the following example: in 1 cm 3 of the air we breathe, there are approximately 30,000,000,000,000,000,000 molecules.

This matter is distributed in interstellar space very unevenly. Most of the interstellar gas and dust forms a gas and dust layer near the plane of symmetry of the Galactic disk. Its thickness in our Galaxy is several hundred light years. Most of the gas and dust in its spiral branches (arms) and core are concentrated mainly in giant molecular clouds ranging in size from 5 to 50 parsecs (16160 light years) and weighing tens of thousands and even millions of solar masses. But even within these clouds, the matter is also distributed inhomogeneously. In the main volume of the cloud, the so-called fur coat, mainly from molecular hydrogen, the particle density is about 100 pieces per 1 cm 3. In densifications inside the cloud, it reaches tens of thousands of particles per 1 cm 3 , and in the cores of these densifications, in general, millions of particles per 1 cm 3 . It is this unevenness in the distribution of matter in the Universe that owes the existence of stars, planets and, ultimately, ourselves. Because it is in molecular clouds, dense and relatively cold, that stars are born.

What is interesting: the higher the density of the cloud, the more diverse it is in composition. At the same time, there is a correspondence between the density and temperature of the cloud (or its individual parts) and those substances whose molecules meet there. On the one hand, this is convenient for studying clouds: by observing their individual components in different spectral ranges along the characteristic lines of the spectrum, for example, CO, OH or NH 3, you can "look" into one or another part of it. On the other hand, data on the composition of the cloud allow us to learn a lot about the processes taking place in it.

In addition, in interstellar space, judging by the spectra, there are also substances whose existence under terrestrial conditions is simply impossible. These are ions and radicals. Their chemical activity is so high that they immediately react on Earth. And in the rarefied cold space of space, they live long and quite freely.

In general, gas in interstellar space is not only atomic. Where it is colder, no more than 50 kelvins, the atoms manage to stay together, forming molecules. However, a large mass of interstellar gas is still in the atomic state. This is mainly hydrogen, its neutral form was discovered relatively recently in 1951. As you know, it emits radio waves with a length of 21 cm (frequency 1420 MHz), the intensity of which determined how much it is in the Galaxy. Incidentally, it is distributed inhomogeneously in the space between the stars. In clouds of atomic hydrogen, its concentration reaches several atoms per 1 cm3, but between clouds it is orders of magnitude less.

Finally, near hot stars, gas exists in the form of ions. Powerful ultraviolet radiation heats and ionizes the gas, and it begins to glow. That is why areas with a high concentration of hot gas, with a temperature of about 10,000 K, look like luminous clouds. They are called light gas nebulae.

And in any nebula, to a greater or lesser extent, there is interstellar dust. Despite the fact that nebulae are conditionally divided into dusty and gaseous, there is dust in both of them. And in any case, it is dust that apparently helps stars form in the depths of nebulae.

fog objects

Among all space objects, nebulae are perhaps the most beautiful. True, dark nebulae in the visible range look just like black blobs in the sky - they are best observed against the background of the Milky Way. But in other ranges of electromagnetic waves, such as infrared, they are visible very well and the pictures are very unusual.

Nebulae are isolated in space, connected by gravitational forces or external pressure, accumulations of gas and dust. Their mass can be from 0.1 to 10,000 solar masses, and their size can be from 1 to 10 parsecs.

At first, astronomers were annoyed by nebulae. Until the middle of the 19th century, the discovered nebulae were considered as an annoying hindrance that prevented observing stars and searching for new comets. In 1714, the Englishman Edmond Halley, whose name the famous comet bears, even compiled a “black list” of six nebulae so that they would not mislead the “comet catchers”, and the Frenchman Charles Messier expanded this list to 103 objects. Fortunately, musician Sir William Herschel, his sister and son, who was in love with astronomy, became interested in nebulae. Observing the sky with their own built telescopes, they left behind a catalog of nebulae and star clusters, with information about 5,079 space objects!

The Herschels practically exhausted the possibilities of optical telescopes of those years. However, the invention of photography and the long exposure time made it possible to find very faintly luminous objects. A little later, spectral methods of analysis, observations in various ranges of electromagnetic waves made it possible in the future not only to detect many new nebulae, but also to determine their structure and properties.

An interstellar nebula looks bright in two cases: either it is so hot that its gas itself glows, such nebulae are called emission nebulae; or the nebula itself is cold, but its dust scatters the light of a nearby bright star this is a reflection nebula.

Dark nebulae are also interstellar collections of gas and dust. But unlike light gaseous nebulae, sometimes visible even with strong binoculars or a telescope, such as the Orion Nebula, dark nebulae do not emit light, but absorb it. When the light of a star passes through such nebulae, the dust can completely absorb it, converting it into infrared radiation invisible to the eye. Therefore, such nebulae look like starless dips in the sky. V. Herschel called them "holes in the sky." Perhaps the most spectacular of these is the Horsehead Nebula.

However, dust particles may not completely absorb the light of stars, but only partially scatter it, while selectively. The fact is that the size of interstellar dust particles is close to the wavelength of blue light, so it is scattered and absorbed more strongly, and the “red” part of the light of stars reaches us better. By the way, this is a good way to estimate the size of dust grains by how they attenuate light of different wavelengths.

star from the cloud

The reasons for the formation of stars have not been precisely established there are only models that more or less reliably explain the experimental data. In addition, the ways of formation, properties and further fate of stars are very diverse and depend on very many factors. However, there is a well-established concept, or rather, the most developed hypothesis, the essence of which, in the most general terms, is that stars are formed from interstellar gas in areas with an increased density of matter, that is, in the depths of interstellar clouds. Dust as a material could be ignored, but its role in the formation of stars is enormous.

This happens (in the most primitive version, for a single star), apparently, like this. First, a protostellar cloud condenses from the interstellar medium, which may be due to gravitational instability, but the reasons may be different and are not yet fully understood. One way or another, it contracts and attracts matter from the surrounding space. The temperature and pressure at its center rise until the molecules at the center of this shrinking ball of gas begin to disintegrate into atoms and then into ions. Such a process cools the gas, and the pressure inside the core drops sharply. The core is compressed, and a shock wave propagates inside the cloud, discarding its outer layers. A protostar is formed, which continues to shrink under the influence of gravitational forces until thermonuclear fusion reactions begin in its center - the conversion of hydrogen into helium. Compression continues for some time, until the forces of gravitational compression are balanced by the forces of gas and radiant pressure.

It is clear that the mass of the formed star is always less than the mass of the nebula that "produced" it. Part of the matter that did not have time to fall onto the nucleus is “swept out” by the shock wave, radiation and particle flows simply into the surrounding space during this process.

The process of formation of stars and stellar systems is influenced by many factors, including the magnetic field, which often contributes to the "break" of the protostellar cloud into two, less often three fragments, each of which is compressed into its own protostar under the influence of gravity. This is how, for example, many binary star systems arise - two stars that revolve around a common center of mass and move in space as a single whole.

As the "aging" of the nuclear fuel in the bowels of stars gradually burns out, and the faster, the larger the star. In this case, the hydrogen cycle of reactions is replaced by helium, then, as a result of nuclear fusion reactions, increasingly heavier chemical elements are formed, up to iron. In the end, the nucleus, which does not receive more energy from thermonuclear reactions, sharply decreases in size, loses its stability, and its substance, as it were, falls on itself. A powerful explosion occurs, during which the substance can heat up to billions of degrees, and the interactions between the nuclei lead to the formation of new chemical elements, up to the heaviest ones. The explosion is accompanied by a sharp release of energy and the release of matter. A star explodes, a process called a supernova explosion. Ultimately, the star, depending on the mass, will turn into a neutron star or a black hole.

This is probably what actually happens. In any case, there is no doubt that young, that is, hot, stars and their clusters are most of all just in nebulae, that is, in areas with an increased density of gas and dust. This is clearly seen in photographs taken by telescopes in different wavelength ranges.

Of course, this is nothing more than the crudest summary of the sequence of events. For us, two points are fundamentally important. First, what is the role of dust in the formation of stars? And the second where, in fact, does it come from?

Universal coolant

In the total mass of cosmic matter, dust itself, that is, atoms of carbon, silicon and some other elements combined into solid particles, is so small that, in any case, as a building material for stars, it would seem that they can not be taken into account. However, in fact, their role is great it is they who cool the hot interstellar gas, turning it into that very cold dense cloud, from which stars are then obtained.

The fact is that interstellar gas cannot cool itself. The electronic structure of the hydrogen atom is such that it can give up excess energy, if any, by emitting light in the visible and ultraviolet regions of the spectrum, but not in the infrared range. Figuratively speaking, hydrogen cannot radiate heat. In order to cool down properly, it needs a “refrigerator”, the role of which is precisely played by particles of interstellar dust.

During a collision with dust grains at high speed unlike heavier and slower dust grains, gas molecules fly quickly they lose speed and their kinetic energy is transferred to the dust grain. It also heats up and gives off this excess heat to the surrounding space, including in the form of infrared radiation, while itself cools down. So, taking on the heat of interstellar molecules, the dust acts as a kind of radiator, cooling the gas cloud. Its mass is not much - about 1% of the mass of the entire substance of the cloud, but this is enough to remove excess heat over millions of years.

When the temperature of the cloud drops, the pressure also drops, the cloud condenses and stars can already be born from it. The remnants of the material from which the star was born are, in turn, the source for the formation of planets. Here, dust particles are already included in their composition, and in larger quantities. Because, having been born, the star heats up and accelerates all the gas around it, and the dust remains to fly nearby. After all, it is able to cool and is attracted to a new star much stronger than individual gas molecules. In the end, next to the newborn star is a dust cloud, and on the periphery, dust-saturated gas.

Gas planets such as Saturn, Uranus and Neptune are born there. Well, solid planets appear near the star. We have Mars, Earth, Venus and Mercury. It turns out a fairly clear division into two zones: gas planets and solid ones. So the Earth turned out to be largely made of interstellar dust particles. Metallic dust particles have become part of the planet's core, and now the Earth has a huge iron core.

Mystery of the young universe

If a galaxy has formed, then where does the dust come from? In principle, scientists understand. Its most significant sources are novae and supernovae, which lose part of their mass, "dumping" the shell into the surrounding space. In addition, dust is also born in the expanding atmosphere of red giants, from where it is literally swept away by radiation pressure. In their cool, by the standards of stars, atmosphere (about 2.5 3 thousand kelvins) there are quite a lot of relatively complex molecules.

But here is a mystery that has not yet been solved. It has always been believed that dust is a product of the evolution of stars. In other words, stars must be born, exist for some time, grow old and, say, produce dust in the last supernova explosion. But what came first, the egg or the chicken? The first dust necessary for the birth of a star, or the first star, which for some reason was born without the help of dust, grew old, exploded, forming the very first dust.

What was in the beginning? After all, when the Big Bang happened 14 billion years ago, there were only hydrogen and helium in the Universe, no other elements! It was then that the first galaxies, huge clouds, and in them the first stars began to emerge from them, which had to go a long way in life. Thermonuclear reactions in the cores of stars were supposed to “weld” more complex chemical elements, turn hydrogen and helium into carbon, nitrogen, oxygen, and so on, and only after that the star had to throw it all into space, exploding or gradually dropping the shell. Then this mass had to cool, cool down and, finally, turn into dust. But already 2 billion years after the Big Bang, in the earliest galaxies, there was dust! With the help of telescopes, it was discovered in galaxies that are 12 billion light years away from ours. At the same time, 2 billion years is too short a period for the full life cycle of a star: during this time, most stars do not have time to grow old. Where did the dust come from in the young Galaxy, if there should be nothing but hydrogen and helium, a mystery.

Mote reactor

Not only does interstellar dust act as a kind of universal refrigerant, it is perhaps thanks to dust that complex molecules appear in space.

The fact is that the surface of a grain of dust can simultaneously serve as a reactor in which molecules are formed from atoms, and as a catalyst for the reactions of their synthesis. After all, the probability that many atoms of different elements will collide at once at one point, and even interact with each other at a temperature slightly above absolute zero, is unimaginably small. On the other hand, the probability that a grain of dust will sequentially collide with various atoms or molecules in flight, especially inside a cold dense cloud, is quite high. Actually, this is what happens this is how a shell of interstellar dust grains is formed from atoms and molecules encountered frozen on it.

On a solid surface, atoms are side by side. Migrating over the surface of a dust grain in search of the most energetically favorable position, atoms meet and, being in close proximity, get the opportunity to react with each other. Of course, very slowly in accordance with the temperature of the dust grain. The surface of particles, especially those containing a metal in the core, can exhibit the properties of a catalyst. Chemists on Earth are well aware that the most effective catalysts are just particles a fraction of a micron in size, on which molecules are assembled and then react, which, under normal conditions, are completely “indifferent” to each other. Apparently, molecular hydrogen is also formed in this way: its atoms “stick” to a grain of dust, and then fly away from it, but already in pairs, in the form of molecules.

It is very possible that small interstellar dust grains, having retained in their shells a few organic molecules, including the simplest amino acids, brought the first "seeds of life" to Earth about 4 billion years ago. This, of course, is nothing more than a beautiful hypothesis. But in its favor is the fact that the amino acid glycine was found in the composition of cold gas and dust clouds. Maybe there are others, just so far the capabilities of telescopes do not allow them to be detected.

Hunting for dust

It is possible, of course, to study the properties of interstellar dust at a distance with the help of telescopes and other instruments located on the Earth or on its satellites. But it is much more tempting to catch interstellar dust particles, and then study them in detail, find out not theoretically, but practically, what they consist of, how they are arranged. There are two options here. You can get to the depths of space, collect interstellar dust there, bring it to Earth and analyze it in all possible ways. Or you can try to fly out of the solar system and analyze the dust along the way right on board the spacecraft, sending the data to Earth.

The first attempt to bring samples of interstellar dust, and in general the substance of the interstellar medium, was made by NASA several years ago. The spacecraft was equipped with special traps - collectors for collecting interstellar dust and cosmic wind particles. In order to catch dust particles without losing their shell, the traps were filled with a special substance, the so-called airgel. This very light foamy substance (whose composition is a trade secret) resembles jelly. Once in it, dust particles get stuck, and then, as in any trap, the lid slams shut to be open already on Earth.

This project was called Stardust Stardust. His program is great. After launching in February 1999, the equipment on board will eventually collect samples of interstellar dust and, separately, dust in the immediate vicinity of comet Wild-2, which flew near the Earth in February last year. Now with containers filled with this most valuable cargo, the ship is flying home to land on January 15, 2006 in Utah, near Salt Lake City (USA). That's when astronomers will finally see with their own eyes (with the help of a microscope, of course) those very dust particles, the models of the composition and structure of which they have already predicted.

And in August 2001, Genesis flew for samples of matter from deep space. This NASA project was aimed mainly at capturing solar wind particles. After spending 1,127 days in outer space, during which it flew about 32 million km, the ship returned and dropped a capsule with the obtained samples onto Earth - traps with ions, particles of the solar wind. Alas, a misfortune happened the parachute did not open, and the capsule flopped on the ground with all its might. And crashed. Of course, the wreckage was collected and carefully studied. However, in March 2005, at a conference in Houston, a participant in the program, Don Barnetty, stated that four collectors with solar wind particles were not affected, and scientists are actively studying their contents, 0.4 mg of captured solar wind, in Houston.

However, now NASA is preparing a third project, even more grandiose. This will be the Interstellar Probe space mission. This time the spacecraft will move away at a distance of 200 AU. e. from the Earth (a. e. the distance from the Earth to the Sun). This ship will never return, but will be "stuffed" with a wide variety of equipment, including and for analyzing samples of interstellar dust. If all goes well, interstellar dust particles from deep space will finally be captured, photographed and analyzed automatically, right on board the spacecraft.

Formation of young stars

1. A giant galactic molecular cloud with a size of 100 parsecs, a mass of 100,000 suns, a temperature of 50 K, a density of 10 2 particles / cm 3. Inside this cloud there are large-scale condensations diffuse gas and dust nebulae (110 pc, 10,000 suns, 20 K, 10 3 particles/cm 4 particles/cm3). Inside the latter, there are clusters of globules with a size of 0.1 pc, a mass of 110 suns and a density of 10 10 6 particles / cm 3, where new stars are formed

2. The birth of a star inside a gas and dust cloud

3. A new star with its radiation and stellar wind accelerates the surrounding gas away from itself

4. A young star enters space, clean and free of gas and dust, pushing the nebula that gave birth to it

Stages of the "embryonic" development of a star, equal in mass to the Sun

5. The origin of a gravitationally unstable cloud 2,000,000 suns in size, with a temperature of about 15 K and an initial density of 10 -19 g/cm 3

6. After several hundred thousand years, this cloud forms a core with a temperature of about 200 K and a size of 100 suns, its mass is still only 0.05 of the solar

7. At this stage, the core with temperatures up to 2,000 K shrinks sharply due to hydrogen ionization and simultaneously heats up to 20,000 K, the velocity of matter falling onto a growing star reaches 100 km/s

8. A protostar the size of two suns with a temperature at the center of 2x10 5 K, and on the surface 3x10 3 K

9. The last stage in the pre-evolution of a star is slow compression, during which lithium and beryllium isotopes burn out. Only after the temperature rises to 6x10 6 K, thermonuclear reactions of helium synthesis from hydrogen start in the interior of the star. The total duration of the birth cycle of a star like our Sun is 50 million years, after which such a star can quietly burn for billions of years

Olga Maksimenko, Candidate of Chemical Sciences