Cosmic dust
particles of matter in interstellar and interplanetary space. Light-absorbing condensations of photons are visible as dark spots in photographs. Milky Way. Attenuation of light due to the influence of K. p. - so-called. interstellar absorption, or extinction, is not the same for electromagnetic waves different lengths λ
, as a result of which reddening of stars is observed. In the visible region, extinction is approximately proportional to λ -1, in the near ultraviolet region it is almost independent of wavelength, but around 1400 Å there is an additional absorption maximum. Most of the extinction is due to light scattering rather than absorption. This follows from observations of reflection nebulae containing cosmic particles, visible around stars of spectral class B and some other stars bright enough to illuminate the dust. A comparison of the brightness of nebulae and the stars that illuminate them shows that the albedo of dust is high. The observed extinction and albedo lead to the conclusion that the crystal structure 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 measuring about 0.05 × 0.05 × 0.01 µm. Due to the diffraction of light by a particle whose dimensions are comparable to the wavelength, light is scattered predominantly forward. Interstellar absorption often leads to polarization of light, which is explained by the anisotropy of the properties of dust grains (the elongated shape of dielectric particles or the anisotropy of the conductivity of graphite) 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 power line. 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 average absorption of light in the Galactic plane - from 0.5 to several stellar magnitudes per 1 kiloParsec in the visual region of the spectrum. The mass of dust makes up about 1% of the mass of interstellar matter. Dust, like gas, is distributed non-uniformly, forming clouds and denser formations - Globules. In globules, dust acts as a cooling factor, shielding the light of stars and emitting in the infrared the energy received by the dust grain from inelastic collisions with gas atoms. On the surface of the dust, atoms combine into molecules: the dust is a catalyst. S. B. Pikelner.
Big Soviet encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .
See what “Cosmic dust” is in other dictionaries:
Particles of condensed matter in interstellar and interplanetary space. According to modern concepts, cosmic dust consists of particles measuring approx. 1 µm with a graphite or silicate core. In the Galaxy, cosmic dust forms... ... Big Encyclopedic Dictionary
SPACE DUST, very fine particles solid, located in any part of the Universe, including meteorite dust and interstellar matter, capable of absorbing starlight and forming dark NEBULAs in galaxies. Spherical... ... Scientific and technical encyclopedic dictionary
COSMIC DUST- meteoric dust, as well as the smallest particles of matter that form dust and other nebulae in interstellar space... Big Polytechnic Encyclopedia
cosmic dust- Very small particles of solid matter present in outer space and falling to the Earth... Dictionary of Geography
Particles of condensed matter in interstellar and interplanetary space. According to modern concepts, 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
It is formed in space by particles ranging in size from several molecules to 0.1 mm. 40 kilotons of cosmic dust settle 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. cosmic dust vok. kosmischer Staub, m rus. cosmic dust, f... Ekologijos terminų aiškinamasis žodynas
Particles condensed into va in interstellar and interplanetary space. According to modern According to the ideas, K. p. consists of particles measuring approx. 1 µm with a graphite or silicate core. In the Galaxy, the cosmos forms condensations of clouds and globules. Calls... ... Natural science. Encyclopedic Dictionary
Particles of condensed matter in interstellar and interplanetary space. Consists of particles about 1 micron in size with a core of graphite or silicate, in the Galaxy it forms clouds that cause a weakening of the light emitted by stars and... ... Astronomical Dictionary
Books
- Children about space and astronauts, G. N. Elkin. This book introduces amazing world space. On its pages, the child will find answers to many questions: what are stars, black holes, where do comets and asteroids come from, what is...
Cosmic X-ray background
Oscillations and waves: Characteristics of various oscillatory systems (oscillators).
Rupture of the Universe
Dust circumplanetary complexes: fig4
Properties of cosmic dust
| S. V. Bozhokin St. Petersburg State Technical University | Content |
Introduction
Many people admire with delight the beautiful spectacle of the starry sky, one of greatest creations nature. In a clear autumn sky, it is clearly visible how a faintly luminous stripe runs across the entire sky, called Milky Way, having irregular outlines with different widths and brightness. If we examine the Milky Way, which forms our Galaxy, through a telescope, it will turn out that this bright strip breaks up into many faintly luminous stars, which for the naked eye merge into a continuous glow. It is now established that the Milky Way consists not only of stars and star clusters, but also of gas and dust clouds.
Huge interstellar clouds of luminous rarefied gases got the name gaseous diffuse nebulae. One of the most famous is the nebula in Orion constellation, which is visible even to the naked eye near the middle of the three stars that form the “sword” of Orion. The gases that form it glow with cold light, re-emitting the light of neighboring hot stars. The composition of gaseous diffuse nebulae consists mainly of hydrogen, oxygen, helium and nitrogen. Such gaseous or diffuse nebulae serve as a cradle for young stars, which are born in the same way as ours was once born. solar system. The process of star formation is continuous, and stars continue to form today.
IN interstellar space Diffuse dust nebulae are also observed. These clouds are made up of tiny solid grains of dust. If there is a bright star near the dust nebula, then its light is scattered by this nebula and the dust nebula becomes directly observable(Fig. 1). Gas and dust nebulae can generally absorb the light of the stars behind them, so in sky photographs they are often visible as black, gaping holes against the background of the Milky Way. Such nebulae are called dark nebulae. There is one very large dark nebula in the sky of the southern hemisphere, which navigators nicknamed the Coal Sack. There is no clear boundary between gas and dust nebulae, so they are often observed together as gas and dust nebulae.
Diffuse nebulae are only densifications in that extremely rarefied interstellar matter, which was named interstellar gas. Interstellar gas is detected only when observing the spectra of distant stars, causing additional gas in them. Indeed, over a long distance, even such rarefied gas can absorb the radiation of stars. Emergence and rapid development radio astronomy made it possible to detect this invisible gas by the radio waves it emits. The vast, dark clouds of interstellar gas are composed primarily of hydrogen, which even when low temperatures ah emits radio waves at a length of 21 cm. These radio waves pass unhindered through gas and dust. It was radio astronomy that helped us study the shape of the Milky Way. Today we know that gas and dust mixed with large clusters of stars form a spiral, the branches of which, emerging from the center of the Galaxy, wrap around its middle, creating something similar to a cuttlefish with long tentacles caught in a whirlpool.
Currently, a huge amount of matter in our Galaxy is in the form of gas and dust nebulae. Interstellar diffuse matter is concentrated relatively thin layer V equatorial plane our star system. Clouds of interstellar gas and dust block the center of the Galaxy from us. Due to clouds of cosmic dust, tens of thousands of open star clusters remain invisible to us. Fine cosmic dust not only weakens the light of stars, but also distorts them spectral composition. The fact is that when light radiation passes through cosmic dust, it not only weakens, but also changes color. The absorption of light by cosmic dust depends on the wavelength, so of all optical spectrum of a star Blue rays are absorbed more strongly and photons corresponding to red are absorbed more weakly. This effect leads to the phenomenon of reddening of the light of stars passing through the interstellar medium.
For astrophysicists, it is of great importance to study the properties of cosmic dust and determine the influence that this dust has when studying physical characteristics of astrophysical objects. Interstellar absorption and interstellar polarization of light, infrared radiation of neutral hydrogen regions, deficiency chemical elements in the interstellar medium, issues of the formation of molecules and the birth of stars - in all these problems, a huge role belongs to cosmic dust, the properties of which are discussed in this article.
Origin of cosmic dust
Cosmic dust grains arise mainly in the slowly expiring atmospheres of stars - red dwarfs, as well as during explosive processes on stars and violent ejections of gas from the cores of galaxies. Other sources of cosmic dust formation are planetary and protostellar nebulae , stellar atmospheres and interstellar clouds. In all processes of the formation of cosmic dust grains, the gas temperature drops as the gas moves outward and at some point passes through the dew point, at which condensation of vapors of substances, forming the nuclei of dust grains. The centers of formation of a new phase are usually clusters. Clusters are small groups of atoms or molecules that form a stable quasi-molecule. When colliding with an already formed dust grain nucleus, atoms and molecules can join it, or enter into chemical reactions with atoms of a dust grain (chemisorption), or completing the formation of a cluster. In the densest regions of the interstellar medium, the concentration of particles in which is cm -3, the growth of dust grains can be associated with coagulation processes, in which dust grains can stick together without being destroyed. Coagulation processes, depending on the surface properties of dust grains and their temperatures, occur only when collisions between dust grains occur at low relative collision velocities.
In Fig. Figure 2 shows the process of growth of cosmic dust clusters using the addition of monomers. The resulting amorphous cosmic dust particle may be a cluster of atoms with fractal properties. Fractals are called geometric objects: lines, surfaces, spatial bodies that have a highly rugged shape and have the property of self-similarity. Self-similarity means the immutability of the basic geometric characteristics fractal object when changing the scale. For example, images of many fractal objects appear very similar when the resolution of a microscope increases. Fractal clusters are highly branched porous structures formed under highly nonequilibrium conditions when solid particles of similar sizes combine into one whole. Under terrestrial conditions, fractal aggregates are obtained when vapor relaxation metals in nonequilibrium conditions, during the formation of gels in solutions, during the coagulation of particles in smoke. The model of a fractal cosmic dust particle is shown in Fig. 3. Note that the processes of coagulation of dust grains occurring in protostellar clouds and gas and dust disks, are significantly enhanced by turbulent motion interstellar matter.
The nuclei of cosmic dust grains, consisting of refractory elements, hundreds of microns in size, are formed in the shells of cold stars during the smooth outflow of gas or during explosive processes. Such dust grain nuclei are resistant to many external influences.
Interstellar dust is a product of processes of varying intensity occurring in all corners of the Universe, and its invisible particles even reach the surface of the Earth, flying in the atmosphere around us.
It has been proven many times that nature does not like emptiness. Interstellar space, which appears to us as a vacuum, is actually filled with gas and microscopic, 0.01-0.2 microns in size, dust particles. The combination of these invisible elements gives rise to objects of enormous size, a kind of clouds of the Universe, capable of absorbing certain 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 that is formed in the gas envelope of stars and is completely dependent on its composition. For example, graphite dust is formed from grains of carbon stars, and silicate dust is formed from oxygen particles. This is an interesting process that lasts for decades: as stars cool, they lose their molecules, which, flying into space, join into groups and become the basis of the core of a dust grain. Next, a shell of hydrogen atoms and more complex molecules is formed. At low temperatures, interstellar dust occurs in the form of ice crystals. Wandering around the Galaxy, little travelers lose some of the gas when heated, but new molecules take the place of the departed molecules.
Location and properties
The bulk of the dust that falls on our Galaxy is concentrated in the Milky Way region. 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 capable of hiding celestial bodies from us. Although the particles are separated from each other by tens of meters, even in this quantity the densest regions absorb up to 95% of the light emitted by the stars. The size of the gas and dust clouds in our system is truly enormous, measured in hundreds of light years.
Impact on observations
Thackeray's globules make the area of the sky behind them invisible
Interstellar dust absorbs most of the radiation from stars, especially in the blue spectrum, and it distorts their light and polarity. The greatest distortion is experienced by short waves from distant sources. Microparticles mixed with gas are visible as dark spots on the Milky Way.
Due to this factor, the core of our Galaxy is completely hidden and accessible to 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, when sticking together, that 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 to find and study them, they study the ocean floor and meteorites. The collection and delivery of interstellar dust has become one of the functions of spacecraft and missions.
When large particles enter the Earth's atmosphere, they lose their shell, and small particles circle around us invisibly for years. Cosmic dust is ubiquitous and similar in all galaxies; astronomers regularly observe dark features on the faces of distant worlds.
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 deserts and meteorite craters. The size of this substance is less than 200 nm, which makes its study problematic.
Typically, the concept of cosmic dust includes a distinction between interstellar and interplanetary varieties. However, all this is very conditional. Most convenient option To study such a phenomenon, they consider studying dust from space at the boundaries solar system or beyond.
The reason for this problematic approach to studying the object is that the properties of extraterrestrial dust change dramatically when it is near a star such as the Sun.
Theories of the origin of cosmic dust
Streams of cosmic dust constantly attack the Earth's surface. The question arises where this substance comes from. Its origins give rise to much debate among experts in the field.
The following theories of the formation of cosmic dust are distinguished:
- Decay celestial bodies . Some scientists believe that cosmic dust is nothing more than the result of the destruction of asteroids, comets and meteorites.
- Remnants of a protoplanetary type cloud. There is a version according to which cosmic dust is classified as microparticles of a protoplanetary cloud. However, this assumption raises some doubts due to the fragility of the finely dispersed substance.
- The result of an explosion on the stars. As a result of this process, according to some experts, a powerful release of energy and gas occurs, 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 emergence of dust.
The main types of cosmic dust
There is currently no specific classification of cosmic dust types. Subspecies can be distinguished by visual characteristics and location of these microparticles.
Let's consider seven groups of cosmic dust in the atmosphere, different in external indicators:
- Gray debris 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 external signs, because they underwent changes after passing through the Earth's atmosphere.
- Grains round shape, which is similar in parameters to black sand. Outwardly, they resemble magnetite powder (magnetic iron ore).
- Small black circles with a characteristic shine. Their diameter does not exceed 20 nm, which makes studying them 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 cosmic origin consist of a silicate base.
- Balls of heterogeneous structure made of glass and metal. Such elements are characterized by microscopic sizes within 20 nm.
- Dust found in intergalactic space. This type can distort the dimensions of distances during certain calculations and is capable of changing 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 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 along the orbital path of the star itself, reflecting its light and creating a nebula.
- Metal band. Representatives of this subspecies have specific gravity more than five grams per cubic centimeter, and their base consists mainly of iron.
- Silicate-based group. Basis - 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 microparticles in the structure. The base also includes magnetic elements.
- Spherules with hollow filling. This species is often found in meteorite crash sites.
- Spherules of metallic formation. This subspecies has a core of cobalt and nickel, as well as a shell that has oxidized.
- Balls of homogeneous build. Such grains have an oxidized shell.
- Balls with a silicate base. The presence of gas inclusions gives them the appearance of ordinary slag, and sometimes foam.
It should be remembered that these classifications are very arbitrary, but serve as a certain guideline for designating the types of dust from space.
Composition and characteristics of cosmic dust components
Let's take a closer look at what cosmic dust consists of. There is a certain problem in determining the composition of these microparticles. Unlike gaseous substances, solids have a continuous spectrum with a relatively small presence of bands that are blurred. As a result, the identification of cosmic dust grains becomes difficult.
The composition of cosmic dust can be considered using the example of the main models of this substance. These include the following subspecies:
- Ice particles whose structure includes a core with a refractory characteristic. The shell of such a model consists of light elements. Large particles contain atoms with magnetic elements.
- The MRN model, the composition of which is determined by the presence of silicate and graphite inclusions.
- Oxide cosmic dust, which is based on diatomic oxides of magnesium, iron, calcium and silicon.
- Balls with metallic nature of formation. The composition of such microparticles includes an element such as nickel.
- Metal balls with the presence of iron and the absence of nickel.
- Silicone based circles.
- Iron-nickel balls of irregular shape.
The soils are fertile for the presence of cosmic material. A particularly large number of spherules were found in places where meteorites fell. The basis for them was nickel and iron, as well as various minerals such as troilite, cohenite, steatite and other components.
Glaciers also melt aliens from outer space in the form of dust in their blocks. Silicate, iron and nickel serve as the basis for the spherules found. All mined particles were classified into 10 clearly defined groups.
Difficulties in determining the composition of the object under study 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 for further activities in this direction. At a certain altitude, with the help of rockets, they discovered a specific belt consisting of cosmic dust. This gives grounds to assert that such extraterrestrial matter affects some processes occurring on planet Earth.
The influence of cosmic dust on the upper atmosphere
Recent studies indicate that the amount of cosmic dust can influence changes in upper layers atmosphere. This process is very significant because it leads to certain fluctuations in the climatic characteristics of planet Earth.
A huge amount of dust resulting from asteroid collisions fills the space around our planet. Its amount reaches almost 200 tons per day, which, according to scientists, cannot but leave its consequences.
Most susceptible to this attack, according to the same experts, is the northern hemisphere, whose climate is prone to cold temperatures and dampness.
The impact of cosmic dust on cloud formation and climate change has not yet been sufficiently studied. New research in this area raises more and more questions, the answers to which have not yet been obtained.
The influence of dust from space on the transformation of oceanic silt
Irradiation of cosmic dust by the solar wind causes these particles to fall to Earth. Statistics show that the lightest of the three isotopes of helium enters ocean silt in huge quantities through dust grains from space.
The absorption of elements from outer 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.
The influence of cosmic dust on the composition of the water of the World Ocean
If we look at the glaciers of Antarctica, they are striking in the number of meteorite remains found in them and the presence of cosmic dust, which is a hundred times higher than the normal background.
The excessively increased concentration of the same helium-3, valuable metals in the form of cobalt, platinum and nickel allows us to confidently assert the fact of the interference 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 ocean waters, which in itself is a unique phenomenon.
According to some scientists, the amount of cosmic dust in such peculiar ice sheets over the last million years is on the order of several hundred trillion formations of meteorite origin. During the warming period, these covers melt and carry elements of cosmic dust into the World Ocean.
Watch a video about cosmic dust:
This cosmic neoplasm and its influence on some factors of life on our planet have not yet been studied enough. It is important to remember that the substance can influence climate change, the structure of the ocean floor and the concentration of certain substances in the waters of the World Ocean. Photos of cosmic dust indicate how many more mysteries these microparticles conceal. All this makes studying this interesting and relevant!
Supernova SN2010jl Photo: NASA/STScI
For the first time, astronomers observed in real time the formation of cosmic dust in the immediate vicinity of a supernova, which allowed them to explain this mysterious phenomenon that occurs in two stages. The process begins soon after the explosion, but continues for many years, the researchers write in the journal Nature.
We are all made of stardust, of the elements that are building material for new celestial bodies. Astronomers have long assumed that this dust is formed when stars explode. But how exactly this happens and how dust particles are not destroyed in the vicinity of galaxies where active activity is taking place has remained a mystery until now.
This question was first clarified by observations made using the Very Large Telescope at the Paranal Observatory in northern Chile. An international research team led by Christa Gall from the Danish University of Aarhus examined a supernova that occurred in 2010 in a galaxy 160 million light years away. Researchers spent months and early years observing catalog number SN2010jl in visible and infrared light using the X-Shooter spectrograph.
“When we combined the observational data, we were able to make the first measurement of the absorption of different wavelengths in the dust around the supernova,” Gall explains. “This allowed us to learn more about this dust than was previously known.” Thus, it became possible to study in more detail various sizes dust particles and their formation.
Dust in the immediate vicinity of a supernova occurs in two stages. Photo: © ESO/M. Kornmesser
As it turns out, dust particles larger than a thousandth of a millimeter form in the dense material around the star relatively quickly. The sizes of these particles are surprisingly large for cosmic dust grains, making them resistant to destruction by galactic processes. “Our evidence of the formation of large dust particles shortly after the supernova explosion means that there must be a rapid and effective way their formation," adds co-author Jens Hjorth from the University of Copenhagen. "But we don't yet understand exactly how this happens."
However, astronomers already have a theory based on their observations. Based on it, dust formation occurs in 2 stages:
- The star pushes material into its surroundings shortly before exploding. Then the supernova shock wave comes and spreads, behind which a cool and dense shell of gas is created - environment, into which dust particles from previously ejected material can condense and grow.
- In the second stage, several hundred days after the supernova explosion, material that was ejected by the explosion itself is added and an accelerated process of dust formation occurs.
“Recently, astronomers have discovered a lot of dust in the remnants of supernovae that arose after the explosion. However, they also found evidence of a small amount of dust that actually originated from the supernova itself. New observations explain how this apparent contradiction may be resolved,” writes Christa Gall in conclusion.
