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Where does cosmic dust come from? Our planet is surrounded by a dense air shell - the atmosphere. The composition of the atmosphere, in addition to the gases known to all, also includes solid particles - dust.
Basically, it consists of soil particles rising up under the influence of wind. During volcanic eruptions, powerful dust clouds are often observed. Entire "dust caps" hang over large cities, reaching a height of 2-3 km. The number of dust particles in one cube. cm of air in cities reaches 100 thousand pieces, while in the clean mountain air they contain only a few hundred. However, dust of terrestrial origin rises to relatively small heights - up to 10 km. Volcanic dust can reach a height of 40-50 km.
Origin of cosmic dust
The presence of dust clouds at a height significantly exceeding 100 km has been established. These are the so-called "silver clouds", consisting of cosmic dust.
The origin of cosmic dust is extremely diverse: it includes the remains of decayed comets, and particles of matter ejected by the Sun and brought to us by the force of light pressure.
Naturally, under the influence of gravity, a significant part of these cosmic dust particles slowly settles to the earth. The presence of such cosmic dust has been detected on high snowy peaks.
meteorites
In addition to this slowly settling cosmic dust, hundreds of millions of meteors burst into the confines of our atmosphere every day - what we call "shooting stars". Flying at an cosmic speed of hundreds of kilometers per second, they burn out from friction against air particles before they reach the surface of the earth. The products of their combustion also settle on the ground.
However, among the meteors there are exceptionally large specimens that reach the surface of the earth. Thus, the fall of the large Tunguska meteorite at 5 am on June 30, 1908 is known, accompanied by a number of seismic phenomena noted even in Washington (9 thousand km from the place of impact) and indicating the power of the explosion during the fall of the meteorite. Professor Kulik, who examined the meteorite impact site with exceptional courage, found a thicket of windbreak surrounding the impact site within a radius of hundreds of kilometers. Unfortunately, the meteorite was not found. An employee of the British Museum Kirpatrick made a special trip to the USSR in 1932, but did not even get to the place where the meteorite fell. However, he confirmed the assumption of Professor Kulik, who estimated the mass of the fallen meteorite at 100-120 tons.
Space dust cloud
The hypothesis of academician V. I. Vernadsky is interesting, who considered it possible that not a meteorite could fall, but a huge cloud of cosmic dust moving at an enormous speed.
Academician Vernadsky confirmed his hypothesis by the appearance these days of a large number of luminous clouds moving at high altitude at a speed of 300-350 km per hour. This hypothesis could also explain the fact that the trees surrounding the meteorite crater remained standing, while those located further were knocked down by the blast wave.
In addition to the Tunguska meteorite, a number of craters of meteorite origin are also known. The first of these surveyed craters can be called the Arizona crater in the "Devil's Canyon". Interestingly, not only fragments of an iron meteorite were found near it, but also small diamonds formed from carbon from high temperature and pressure during the fall and explosion of a meteorite.
In addition to these craters, which testify to the fall of huge meteorites weighing tens of tons, there are also smaller craters: in Australia, on Ezel Island and a number of others.
In addition to large meteorites, quite a lot of smaller ones fall annually - weighing from 10-12 grams to 2-3 kilograms.
If the Earth were not protected by a dense atmosphere, every second we would be bombarded by the smallest cosmic particles, rushing at a speed exceeding the speed of a bullet.
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 nucleus, 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. In conditions 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.
Cosmic dust, its composition and properties are little known to a person who is not associated with the study of extraterrestrial space. However, such a phenomenon leaves its traces on our planet! Let us consider in more detail where it comes from and how it affects life on Earth.
The concept of space dust
Cosmic dust on Earth is most often found in certain layers of the ocean floor, ice sheets of the polar regions of the planet, peat deposits, hard-to-reach places in the desert and meteorite craters. The size of this substance is less than 200 nm, which makes its study problematic.
Usually the concept of cosmic dust includes the delimitation of the interstellar and interplanetary varieties. However, all this is very conditional. The most convenient option for studying this phenomenon is the study of dust from space at the edges of the solar system or beyond.
The reason for this problematic approach to the study of the object is that the properties of extraterrestrial dust change dramatically when it is near a star such as the Sun.
Theories on the origin of cosmic dust
Streams of cosmic dust constantly attack the surface of the Earth. The question arises where this substance comes from. Its origin gives rise to many discussions among specialists in this field.
There are such theories of the formation of cosmic dust:
- Decay of celestial bodies. Some scientists believe that space dust is nothing more than the result of the destruction of asteroids, comets and meteorites.
- The remnants of a protoplanetary type cloud. There is a version according to which cosmic dust is referred to as microparticles of a protoplanetary cloud. However, such an assumption raises some doubts due to the fragility of a finely dispersed substance.
- The result of the explosion on the stars. As a result of this process, according to some experts, there is a powerful release of energy and gas, which leads to the formation of cosmic dust.
- Residual phenomena after the formation of new planets. The so-called construction "garbage" has become the basis for the occurrence of dust.
The main types of cosmic dust
A specific classification of types of cosmic dust on this moment does not exist. Subspecies can be distinguished by visual characteristics and location of these microparticles.
Consider seven groups of cosmic dust in the atmosphere, different in external indicators:
- gray wreckage irregular shape. These are residual phenomena after the collision of meteorites, comets and asteroids no larger than 100-200 nm in size.
- Particles of slag-like and ash-like formation. Such objects are difficult to identify solely by outward signs, because they have undergone changes, having passed through the atmosphere of the Earth.
- The grains are round in shape, which are similar in parameters to black sand. Outwardly, they resemble powder of magnetite (magnetic iron ore).
- Small black circles with a characteristic sheen. Their diameter does not exceed 20 nm, which makes their study a painstaking task.
- Larger balls of the same color with a rough surface. Their size reaches 100 nm and makes it possible to study their composition in detail.
- Balls of a certain color with a predominance of black and white tones with inclusions of gas. These microparticles of cosmic origin consist of a silicate base.
- Spheres of heterogeneous structure made of glass and metal. Such elements are characterized by microscopic dimensions within 20 nm.
- Dust found in intergalactic space. This view can distort the size of distances in certain calculations and is able to change the color of space objects.
- Formations within the Galaxy. The space within these limits is always filled with dust from the destruction of cosmic bodies.
- Matter concentrated between stars. It is most interesting due to the presence of a shell and a core of a solid consistency.
- Dust located near a certain planet. It is usually located in the ring system of a celestial body.
- Clouds of dust around the stars. They circle the orbital path of the star itself, reflecting its light and creating a nebula.
- metal group. Members of this subspecies have specific gravity more than five grams per cubic centimeter, and their basis consists mainly of iron.
- silicate group. The base is clear glass with a specific gravity of approximately three grams per cubic centimeter.
- Mixed group. The very name of this association indicates the presence of both glass and iron in the structure of microparticles. The base also includes magnetic elements.
- Spherules with hollow filling. This species is often found in places where meteorites fall.
- Spherules of metal formation. This subspecies has a core of cobalt and nickel, as well as a shell that has oxidized.
- Spheres of uniform addition. Such grains have an oxidized shell.
- Balls with a silicate base. The presence of gas inclusions gives them the appearance of ordinary slags, and sometimes foam.
It should be remembered that these classifications are very arbitrary, but they serve as a certain guideline for designating types of dust from space.
Composition and characteristics of the components of cosmic dust
Let's take a closer look at what cosmic dust is made of. There is a problem in determining the composition of these microparticles. Unlike gaseous substances, solids have a continuous spectrum with relatively few bands that are blurred. As a result, the identification of cosmic dust grains is difficult.
The composition of cosmic dust can be considered on the example of the main models of this substance. These include the following subspecies:
- Ice particles, the structure of which includes a core with a refractory characteristic. The shell of such a model consists of light elements. In particles of large size there are atoms with elements of magnetic properties.
- Model MRN, the composition of which is determined by the presence of silicate and graphite inclusions.
- Oxide space dust, which is based on diatomic oxides of magnesium, iron, calcium and silicon.
- Balls with a metallic nature of education. The composition of such microparticles includes such an element as nickel.
- Metal balls with the presence of iron and the absence of nickel.
- Circles on a silicone basis.
- Irregular-shaped iron-nickel balls.
Soils are fertile for the presence of cosmic material. A particularly large number of spherules were found in the places where meteorites fell. They were based on nickel and iron, as well as various minerals such as troilite, cohenite, steatite and other components.
Glaciers also hide aliens from outer space in the form of dust in their blocks. Silicate, iron and nickel serve as the basis for the found spherules. All mined particles were classified into 10 clearly demarcated groups.
Difficulties in determining the composition of the studied object and differentiating it from impurities of terrestrial origin leave this issue open for further research.
The influence of cosmic dust on life processes
The influence of this substance has not been fully studied by specialists, which provides great opportunities in terms of further activities in this direction. At a certain height, using rockets, they discovered a specific belt consisting of cosmic dust. This gives grounds to assert that such an extraterrestrial substance affects some of the processes occurring on planet Earth.
Influence of cosmic dust on the upper atmosphere
Recent studies suggest that the amount of cosmic dust can affect the change in the upper atmosphere. This process is very significant, because it leads to certain fluctuations in climatic characteristic planet Earth.
A huge amount of dust from the collision of asteroids fills the space around our planet. Its amount reaches almost 200 tons per day, which, according to scientists, cannot but leave its consequences.
The most susceptible to this attack, according to the same experts, is the northern hemisphere, whose climate is predisposed to cold temperatures and dampness.
The impact of cosmic dust on cloud formation and climate change is not well understood. New research in this area gives rise to more and more questions, the answers to which have not yet been received.
Influence of dust from space on the transformation of oceanic silt
Irradiation of cosmic dust by the solar wind leads to the fact that these particles fall to the Earth. Statistics show that the lightest of the three isotopes of helium in large quantities falls through dust particles from space into oceanic silt.
The absorption of elements from space by minerals of ferromanganese origin served as the basis for the formation of unique ore formations on the ocean floor.
At the moment, the amount of manganese in areas that are close to the Arctic Circle is limited. All this is due to the fact that cosmic dust does not enter the World Ocean in those areas due to ice sheets.
Influence of cosmic dust on the composition of the ocean water
If we consider the glaciers of Antarctica, they amaze with the number of meteorite remains found in them and the presence of cosmic dust, which is a hundred times higher than the usual background.
An excessively high concentration of the same helium-3, valuable metals in the form of cobalt, platinum and nickel, makes it possible to assert with certainty the fact of the intervention of cosmic dust in the composition of the ice sheet. At the same time, the substance of extraterrestrial origin remains in its original form and not diluted by the waters of the ocean, which in itself is a unique phenomenon.
According to some scientists, the amount of cosmic dust in such peculiar ice sheets over the past million years is on the order of several hundred trillion formations of meteorite origin. During the period of warming, these covers melt and carry elements of cosmic dust into the World Ocean.
Watch a video about space dust:
This cosmic neoplasm and its influence on some factors of the vital activity of our planet have not yet been studied enough. It is important to remember that a substance can affect climate change, the structure of the ocean floor and the concentration of certain substances in the waters of the oceans. Photographs of cosmic dust testify to how many more mysteries these microparticles are fraught with. All this makes the study of this interesting and relevant!
There are billions of stars and planets in the universe. And if a star is a flaming sphere of gas, then planets like Earth are made up of solid elements. Planets form in clouds of dust that swirl around a newly formed star. In turn, the grains of this dust are composed of elements such as carbon, silicon, oxygen, iron and magnesium. But where do cosmic dust particles come from? A new study from the Niels Bohr Institute in Copenhagen shows that not only can dust grains form in giant supernova explosions, they can also survive the subsequent shock waves of various explosions that impact the dust.
Computer generated image of how cosmic dust is formed in supernova explosions. Source: ESO/M. Kornmesser
How cosmic dust was formed has long been a mystery to astronomers. The dust elements themselves are formed in the glowing hydrogen gas in stars. Hydrogen atoms combine with each other to form heavier and heavier elements. As a result, the star begins to emit radiation in the form of light. When all the hydrogen is exhausted and it is no longer possible to extract energy, the star dies, and its shell flies into outer space, which forms various nebulae in which young stars can again be born. Heavy elements are formed primarily in supernovae, the progenitors of which are massive stars that die in a giant explosion. But how single elements stick together to form cosmic dust has remained a mystery.
“The problem was that even if the dust was formed along with the elements in supernova explosions, the event itself is so strong that these small grains simply should not have survived. But cosmic dust exists, and its particles can be of completely different sizes. Our study sheds light on this problem,” says Professor Jens Hjort, head of the Center for Dark Cosmology at the Niels Bohr Institute.
Hubble telescope image of an unusual dwarf galaxy in which the bright supernova SN 2010jl originated. The image was taken before its appearance, so the arrow shows its progenitor star. The exploding star was very massive, about 40 solar masses. Source: ESO
In cosmic dust studies, scientists observe supernovae using the X-shooter astronomical instrument at the Very Large Telescope (VLT) complex in Chile. It has amazing sensitivity, and the three spectrographs included in it. can observe the entire light spectrum at once, from ultraviolet and visible to infrared. Hjort explains that at first they were expecting a "proper" supernova explosion. And that's when it happened, the surveillance campaign began. The observed star was extraordinarily bright, 10 times brighter than a typical average supernova, and its mass was 40 times that of the sun. In total, the observation of the star took the researchers two and a half years.
“Dust absorbs light, and using our data, we were able to calculate a function that could tell us about the amount of dust, its composition and grain size. In the results, we found something really exciting,” Christa Gol.
The first step in the formation of cosmic dust is a mini explosion in which a star ejects material containing hydrogen, helium and carbon into space. This gas cloud becomes a kind of shell around the star. A few more of these flashes and the shell becomes denser. Finally, the star explodes, and a dense gas cloud completely envelops its core.
“When a star explodes, the shock wave hits the dense gas cloud like a brick hitting the concrete wall. All this happens in the gas phase at incredible temperatures. But the place where the explosion hit becomes dense and cools down to 2000 degrees Celsius. At this temperature and density, the elements can nucleate and form solid particles. We found dust grains as small as one micron, which is a very large value for these elements. At this size, they should be able to survive their future journey through the galaxy.”
Thus, scientists believe that they have found the answer to the question of how cosmic dust is formed and lives.
COSMIC DUST, solid particles with characteristic sizes from about 0.001 microns to about 1 microns (and possibly up to 100 microns or more in the interplanetary medium and protoplanetary disks), found in almost all astronomical objects: from the solar system to very distant galaxies and quasars . Dust characteristics (particle concentration, chemical composition, particle size, etc.) vary significantly from one object to another, even for objects of the same type. Cosmic dust scatters and absorbs incident radiation. Scattered radiation with the same wavelength as the incident radiation propagates in all directions. The radiation absorbed by the dust grain is transformed into thermal energy, and the particle usually radiates in the longer wavelength region of the spectrum compared to the incident radiation. Both processes contribute to extinction - the attenuation of the radiation of celestial bodies by dust located on the line of sight between the object and the observer.
Dust objects are studied in almost the entire range of electromagnetic waves - from X-ray to millimeter. Electric dipole radiation from rapidly rotating ultrafine particles appears to make some contribution to microwave radiation at frequencies of 10-60 GHz. An important role is played by laboratory experiments in which they measure the refractive indices, as well as the absorption spectra and scattering matrices of particles - analogues of cosmic dust particles, simulate the processes of formation and growth of refractory dust grains in the atmospheres of stars and protoplanetary disks, study the formation of molecules and the evolution of volatile dust components under conditions similar to those found in dark interstellar clouds.
Cosmic dust, which is in various physical conditions, is directly studied in the composition of meteorites that fell on the Earth's surface, in the upper layers of the Earth's atmosphere (interplanetary dust and the remains of small comets), during spacecraft flights to planets, asteroids and comets (near planetary and cometary dust) and beyond. limits of the heliosphere (interstellar dust). Ground and space remote observations of cosmic dust cover solar system(interplanetary, circumplanetary and cometary dust, dust near the Sun), the interstellar medium of our Galaxy (interstellar, circumstellar and nebular dust) and other galaxies (extragalactic dust), as well as very distant objects (cosmological dust).
Cosmic dust particles mainly consist of carbonaceous substances (amorphous carbon, graphite) and magnesium-iron silicates (olivines, pyroxenes). They condense and grow in the atmospheres of stars of late spectral classes and in protoplanetary nebulae, and then are ejected into the interstellar medium by radiation pressure. In interstellar clouds, especially dense ones, refractory particles continue to grow as a result of the accretion of gas atoms, as well as when particles collide and stick together (coagulation). This leads to the appearance of shells of volatile substances (mainly ice) and to the formation of porous aggregate particles. The destruction of dust grains occurs as a result of dispersion in shock waves arising after supernova explosions, or evaporation in the process of star formation that began in the cloud. The remaining dust continues to evolve near the formed star and later manifests itself in the form of an interplanetary dust cloud or cometary nuclei. Paradoxically, dust around evolved (old) stars is “fresh” (recently formed in their atmosphere), and around young stars it is old (evolved as part of the interstellar medium). It is assumed that cosmological dust, possibly existing in distant galaxies, condensed in the ejecta of matter after the explosions of massive supernovae.
Lit. see at st. Interstellar dust.
