What process is responsible for the formation of cosmic dust. Cosmic dust and strange balls in ancient earth layers
During 2003–2008 a group of Russian and Austrian scientists with the participation of Heinz Kohlmann, a famous paleontologist, curator of the Eisenwurzen National Park, studied the catastrophe that happened 65 million years ago, when more than 75% of all organisms died out on Earth, including dinosaurs. Most researchers believe that the extinction was due to the fall of an asteroid, although there are other points of view.
Traces of this catastrophe in geological sections are represented by a thin layer of black clay with a thickness of 1 to 5 cm. One of these sections is located in Austria, in the Eastern Alps, in the National Park not far from small town Gams, located 200 km southwest of Vienna. As a result of the study of samples from this section using a scanning electron microscope, particles of unusual shape and composition were found, which are not formed under terrestrial conditions and belong to cosmic dust.
Space dust on earth
For the first time, traces of cosmic matter on Earth were discovered in red deep-sea clays by an English expedition that explored the bottom of the World Ocean on the Challenger ship (1872–1876). They were described by Murray and Renard in 1891. At two stations in the southern part Pacific Ocean during dredging from a depth of 4300 m, samples of ferromanganese nodules and magnetic microspheres with a diameter of up to 100 microns were raised, which later received the name "cosmic balls". However, iron microspheres recovered by the Challenger expedition were studied in detail only in last years. It turned out that the balls are 90% metallic iron, 10% nickel, and their surface is covered with a thin crust of iron oxide.
Rice. 1. Monolith from the Gams 1 section, prepared for sampling. Layers of different ages are denoted by Latin letters. The transitional clay layer between the Cretaceous and Paleogene periods (about 65 million years old), in which an accumulation of metal microspheres and plates was found, is marked with the letter "J". Photo by A.F. Grachev
With the discovery of mysterious balls in deep-sea clays, in fact, the beginning of the study of cosmic matter on Earth is connected. However, an explosion of researchers' interest in this problem occurred after the first launches. spacecraft, which made it possible to select lunar soil and samples of dust particles from different parts of the solar system. The works of K.P. Florensky (1963), who studied the traces of the Tunguska catastrophe, and E.L. Krinov (1971), who studied meteoric dust at the site of the fall of the Sikhote-Alin meteorite.
The interest of researchers in metallic microspheres has led to their discovery in sedimentary rocks of different ages and origins. Metal microspheres have been found in the ice of Antarctica and Greenland, in deep ocean sediments and manganese nodules, in the sands of deserts and coastal beaches. They are often found in meteorite craters and next to them.
In the last decade, metal microspheres of extraterrestrial origin have been found in sedimentary rocks of different ages: from the Lower Cambrian (about 500 million years ago) to modern formations.
Data on microspheres and other particles from ancient deposits make it possible to judge the volumes, as well as the uniformity or unevenness of the supply of cosmic matter to the Earth, the change in the composition of particles entering the Earth from space, and the primary sources of this matter. This is important because these processes affect the development of life on Earth. Many of these questions are still far from being resolved, but the accumulation of data and their comprehensive study will undoubtedly make it possible to answer them.
It is now known that the total mass of dust circulating inside the Earth's orbit is about 1015 tons. Every year, from 4 to 10 thousand tons of cosmic matter falls on the Earth's surface. 95% of the matter falling on the Earth's surface are particles with a size of 50-400 microns. The question of how the rate of arrival of cosmic matter to the Earth changes with time remains controversial until now, despite the many studies carried out in the past 10 years.
Based on the size of cosmic dust particles, interplanetary cosmic dust with a size of less than 30 microns and micrometeorites larger than 50 microns are currently distinguished. Even earlier, E.L. Krinov suggested that the smallest fragments of a meteoroid melted from the surface be called micrometeorites.
Strict criteria for distinguishing between cosmic dust and meteorite particles have not yet been developed, and even using the example of the Hams section studied by us, it has been shown that metal particles and microspheres are more diverse in shape and composition than provided by the existing classifications. Almost perfect spherical shape, metallic luster and magnetic properties particles were considered as proof of their cosmic origin. According to geochemist E.V. Sobotovich, "the only morphological criterion for assessing the cosmogenicity of the material under study is the presence of melted balls, including magnetic ones." However, in addition to the extremely diverse form, the chemical composition of the substance is fundamentally important. The researchers found that, along with microspheres of cosmic origin, there is great amount balls of a different genesis - associated with volcanic activity, the vital activity of bacteria or metamorphism. There is evidence that ferruginous microspheres of volcanic origin are much less likely to have an ideal spherical shape and, moreover, have an increased admixture of titanium (Ti) (more than 10%).
Russian-Austrian group of geologists and film crew of the Vienna Television on the Gams section in the Eastern Alps. In the foreground - A.F. Grachev
Origin of cosmic dust
The question of the origin of cosmic dust is still a subject of debate. Professor E.V. Sobotovich believed that cosmic dust could represent the remnants of the original protoplanetary cloud, which was objected to in 1973 by B.Yu. Levin and A.N. Simonenko, believing that a finely dispersed substance could not be preserved for a long time (Earth and Universe, 1980, No. 6).
There is another explanation: the formation of cosmic dust is associated with the destruction of asteroids and comets. As noted by E.V. Sobotovich, if the amount of cosmic dust entering the Earth does not change in time, then B.Yu. Levin and A.N. Simonenko.
Despite big number studies, the answer to this fundamental question cannot be given at present, because there are very few quantitative estimates, and their accuracy is debatable. IN Lately NASA isotopic data on cosmic dust particles sampled in the stratosphere suggest the existence of particles of pre-solar origin. Minerals such as diamond, moissanite (silicon carbide) and corundum were found in this dust, which, using carbon and nitrogen isotopes, allow us to attribute their formation to the time before the formation of the solar system.
The importance of studying cosmic dust in geological section obvious. This article presents the first results of a study of cosmic matter in the transitional clay layer at the Cretaceous-Paleogene boundary (65 million years ago) from the Gams section, in the Eastern Alps (Austria).
General characteristics of the Gams section
Particles of cosmic origin were obtained from several sections of the transitional layers between the Cretaceous and Paleogene (in the German-language literature - the K / T boundary), located near the Alpine village of Gams, where the river of the same name in several places reveals this boundary.
In section Gams 1, a monolith was cut from the outcrop, in which the K/T boundary is very well expressed. Its height is 46 cm, width is 30 cm in the lower part and 22 cm in the upper part, thickness is 4 cm. ,C…W), and within each layer, the numbers (1, 2, 3, etc.) were also marked every 2 cm. The transition layer J at the K/T interface was studied in more detail, where six sublayers with a thickness of about 3 mm were identified.
The results of studies obtained in the Gams 1 section are largely repeated in the study of another section - Gams 2. The complex of studies included the study of thin sections and monomineral fractions, their chemical analysis, as well as X-ray fluorescence, neutron activation and X-ray structural analyses, isotopic analysis of helium, carbon and oxygen, determination of the composition of minerals on a microprobe, magnetomineralogical analysis.
Variety of microparticles
Iron and nickel microspheres from the transitional layer between the Cretaceous and Paleogene in the Gams section: 1 – Fe microsphere with a rough reticulate-hummocky surface (upper part of the transitional layer J); 2 – Fe microsphere with a rough longitudinally parallel surface (lower part of the transition layer J); 3 – Fe microsphere with elements of crystallographic faceting and coarse cellular-network surface texture (layer M); 4 – Fe microsphere with a thin network surface (upper part of transition layer J); 5 – Ni microsphere with crystallites on the surface (upper part of transition layer J); 6 – aggregate of sintered Ni microspheres with crystallites on the surface (upper part of transition layer J); 7 – aggregate of Ni microspheres with microdiamonds (C; upper part of the transition layer J); 8, 9—characteristic forms of metal particles from the transitional layer between the Cretaceous and Paleogene in the Gams section in the Eastern Alps.
In the transitional clay layer between the two geological boundaries - the Cretaceous and Paleogene, as well as at two levels in the overlying deposits of the Paleocene in the Gams section, many metal particles and microspheres of cosmic origin were found. They are much more diverse in shape, surface texture and chemical composition than all known so far in transitional clay layers of this age in other regions of the world.
In the Gams section, the cosmic matter is represented by finely dispersed particles of various shapes, among which the most common are magnetic microspheres ranging in size from 0.7 to 100 μm, consisting of 98% pure iron. Such particles in the form of spherules or microspherules are found in large quantities not only in layer J, but also higher, in clays of the Paleocene (layers K and M).
The microspheres are composed of pure iron or magnetite, some of them have impurities of chromium (Cr), an alloy of iron and nickel (avaruite), and pure nickel (Ni). Some Fe-Ni particles contain an admixture of molybdenum (Mo). In the transitional clay layer between the Cretaceous and Paleogene, all of them were discovered for the first time.
Never before have come across particles with a high nickel content and a significant admixture of molybdenum, microspheres with the presence of chromium and pieces of spiral iron. In addition to metallic microspheres and particles, Ni-spinel, microdiamonds with microspheres of pure Ni, as well as torn plates of Au and Cu, which were not found in the underlying and overlying deposits, were found in the transitional clay layer in Gams.
Characterization of microparticles
Metallic microspheres in the Gams section are present at three stratigraphic levels: ferruginous particles of various shapes are concentrated in the transitional clay layer, in the overlying fine-grained sandstones of layer K, and the third level is formed by siltstones of layer M.
Some spheres have a smooth surface, others have a reticulate-hilly surface, and others are covered with a network of small polygonal cracks or a system of parallel cracks extending from one main crack. They are hollow, shell-like, filled with a clay mineral, and may also have an internal concentric structure. Metal particles and Fe microspheres are found throughout the transitional clay layer, but are mainly concentrated in the lower and middle horizons.
Micrometeorites are melted particles of pure iron or Fe-Ni iron-nickel alloy (awaruite); their sizes are from 5 to 20 microns. Numerous awaruite particles are confined to the upper level of the transition layer J, while purely ferruginous particles are present in the lower and upper parts of the transition layer.
Particles in the form of plates with a transversely bumpy surface consist only of iron, their width is 10–20 µm, and their length is up to 150 µm. They are slightly arcuately curved and occur at the base of the transition layer J. In its lower part, there are also Fe-Ni plates with an admixture of Mo.
Plates made of an alloy of iron and nickel have an elongated shape, slightly curved, with longitudinal grooves on the surface, the dimensions vary in length from 70 to 150 microns with a width of about 20 microns. They are more common in the lower and middle parts of the transition layer.
Iron plates with longitudinal grooves are identical in shape and size to Ni-Fe alloy plates. They are confined to the lower and middle parts of the transition layer.
Of particular interest are particles of pure iron, having the shape of a regular spiral and bent in the form of a hook. They mainly consist of pure Fe, rarely it is an Fe-Ni-Mo alloy. Spiral iron particles occur in the upper part of the J layer and in the overlying sandstone layer (K layer). A spiral Fe-Ni-Mo particle was found at the base of the transition layer J.
In the upper part of the transition layer J, there were several grains of microdiamonds sintered with Ni microspheres. Microprobe studies of nickel balls carried out on two instruments (with wave and energy dispersive spectrometers) showed that these balls consist of almost pure nickel under a thin film of nickel oxide. The surface of all nickel balls is dotted with distinct crystallites with pronounced twins 1–2 µm in size. Such pure nickel in the form of balls with a well-crystallized surface is not found either in igneous rocks or in meteorites, where nickel necessarily contains a significant amount of impurities.
When studying a monolith from the Gams 1 section, pure Ni balls were found only in the uppermost part of the transition layer J (in its uppermost part, a very thin sedimentary layer J 6, whose thickness does not exceed 200 μm), and according to thermal magnetic analysis data, metallic nickel is present in transitional layer, starting from sublayer J4. Here, along with Ni balls, diamonds were also found. In a layer taken from a cube with an area of 1 cm2, the number of diamond grains found is in the tens (from fractions of microns to tens of microns in size), and hundreds of nickel balls of the same size.
In samples of the upper part of the transition layer, taken directly from the outcrop, diamonds were found with small particles of nickel on the grain surface. It is significant that the presence of the mineral moissanite was also revealed during the study of samples from this part of layer J. Previously, microdiamonds were found in the transitional layer at the Cretaceous-Paleogene boundary in Mexico.
Finds in other areas
Hams microspheres with concentric internal structure similar to those that were mined by the Challenger expedition in the deep-sea clays of the Pacific Ocean.
iron particles irregular shape with melted edges, as well as in the form of spirals and curved hooks and plates, they are very similar to the destruction products of meteorites falling to the Earth, they can be considered as meteoric iron. Avaruite and pure nickel particles can be assigned to the same category.
Curved iron particles are close to the various forms of Pele's tears - lava drops (lapilli) that are thrown into liquid state volcanoes from the vent during eruptions.
Thus, the transitional clay layer in Gams has a heterogeneous structure and is distinctly divided into two parts. Iron particles and microspheres predominate in the lower and middle parts, while the upper part of the layer is enriched in nickel: awaruite particles and nickel microspheres with diamonds. This is confirmed not only by the distribution of iron and nickel particles in the clay, but also by the data of chemical and thermomagnetic analyses.
Comparison of the data of thermomagnetic analysis and microprobe analysis indicates an extreme inhomogeneity in the distribution of nickel, iron, and their alloy within layer J; however, according to the results of thermomagnetic analysis, pure nickel is recorded only from layer J4. It is also noteworthy that helical iron occurs mainly in the upper part of layer J and continues to occur in the overlying layer K, where, however, there are few Fe, Fe-Ni particles of isometric or lamellar shape.
We emphasize that such a clear differentiation in terms of iron, nickel, and iridium, which is manifested in the transitional clay layer in Gamsa, also exists in other regions. Yes, in US state In New Jersey, in the transitional (6 cm) spherule layer, the iridium anomaly manifested itself sharply at its base, while impact minerals are concentrated only in the upper (1 cm) part of this layer. In Haiti, at the Cretaceous–Paleogene boundary and in the uppermost part of the spherule layer, there is a sharp enrichment in Ni and impact quartz.
Background phenomenon for the Earth
Many features of the found Fe and Fe-Ni spherules are similar to the balls discovered by the Challenger expedition in the deep-sea clays of the Pacific Ocean, in the area of the Tunguska catastrophe and the sites of the fall of the Sikhote-Alin meteorite and the Nio meteorite in Japan, as well as in sedimentary rocks of different ages from many parts of the world. Except for the areas of the Tunguska catastrophe and the fall of the Sikhote-Alin meteorite, in all other cases the formation of not only spherules, but also particles of various morphologies, consisting of pure iron (sometimes containing chromium) and nickel-iron alloy, has no connection with the impact event. We consider the appearance of such particles as a result of the fall of cosmic interplanetary dust onto the Earth's surface, a process that has been continuously ongoing since the formation of the Earth and is a kind of background phenomenon.
Many particles studied in the Gams section are close in composition to the bulk chemical composition of the meteorite substance at the site of the fall of the Sikhote-Alin meteorite (according to E.L. Krinov, these are 93.29% iron, 5.94% nickel, 0.38% cobalt).
The presence of molybdenum in some of the particles is not unexpected, as many types of meteorites include it. The content of molybdenum in meteorites (iron, stone and carbonaceous chondrites) ranges from 6 to 7 g/t. The most important was the discovery of molybdenite in the Allende meteorite as an inclusion in a metal alloy of the following composition (wt %): Fe—31.1, Ni—64.5, Co—2.0, Cr—0.3, V—0.5, P—0.1. It should be noted that native molybdenum and molybdenite were also found in the lunar dust sampled by the automatic stations Luna-16, Luna-20, and Luna-24.
The balls of pure nickel with a well-crystallized surface found for the first time are not known either in igneous rocks or in meteorites, where nickel necessarily contains a significant amount of impurities. Such a surface structure of nickel balls could have arisen in the event of an asteroid (meteorite) fall, which led to the release of energy, which made it possible not only to melt the material of the fallen body, but also to evaporate it. Metal vapors could be raised by the explosion to a great height (probably tens of kilometers), where crystallization took place.
Particles consisting of awaruite (Ni3Fe) are found together with metallic nickel balls. They belong to meteor dust, and melted iron particles (micrometeorites) should be considered as "meteorite dust" (according to the terminology of E.L. Krinov). The diamond crystals encountered together with the nickel balls probably arose as a result of the ablation (melting and evaporation) of the meteorite from the same vapor cloud during its subsequent cooling. It is known that synthetic diamonds are obtained by spontaneous crystallization from a carbon solution in a melt of metals (Ni, Fe) above the graphite–diamond phase equilibrium line in the form of single crystals, their intergrowths, twins, polycrystalline aggregates, framework crystals, needle-shaped crystals, and irregular grains. Almost all of the listed typomorphic features of diamond crystals were found in the studied sample.
This allows us to conclude that the processes of crystallization of diamond in a cloud of nickel-carbon vapor during its cooling and spontaneous crystallization from a carbon solution in a nickel melt in experiments are similar. However, the final conclusion about the nature of diamond can be made after detailed isotopic studies, for which it is necessary to obtain a sufficiently large amount of the substance.
Thus, the study of cosmic matter in the transitional clay layer at the Cretaceous–Paleogene boundary showed its presence in all parts (from layer J1 to layer J6), but signs of an impact event are recorded only from layer J4, which is 65 million years old. This layer of cosmic dust can be compared with the time of the death of dinosaurs.
A.F. GRACHEV Doctor of Geological and Mineralogical Sciences, V.A. TSELMOVICH Candidate of Physical and Mathematical Sciences, Institute of Physics of the Earth RAS (IFZ RAS), OA KORCHAGIN Candidate of Geological and Mineralogical Sciences, Geological Institute of the Russian Academy of Sciences (GIN RAS).
Magazine "Earth and Universe" № 5 2008.
Between stars and planets
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 zodiac - 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.
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 after a hot day, fog from cooled water vapor collects in the lowlands. 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 the dust?
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 galaxies, is filled with matter, flows 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 1-2% 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 - its mass 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 interstellar gas and dust forms a gas and dust layer near the plane of symmetry of the disk of the Galaxy. Its thickness in our galaxy is several hundred light-years. Most of the gas and dust in its spiral arms and core is concentrated mainly in giant molecular clouds ranging in size from 5 to 50 parsecs (16-160 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. In this case, there is a correspondence between the density and temperature of the cloud (or its individual parts) and those substances, the molecules of which are found 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. And 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, in greater or lesser quantities, 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, it is best to observe them against the background. 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 regarded 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 accumulations 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 which stars appear 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 stars are very diverse and depend on 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.
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A giant galactic molecular cloud with a size of 100 parsecs, a mass of 100,000 suns, a temperature of 50K, a density of 100 particles per cubic cm. Inside this cloud, there are large-scale condensations - diffuse gas and dust and mania (1-10 pc, 10,000 suns, 20 K, 1000 particles per cubic cm) and small condensations - gas and dust nebulae (up to 1 pc, 100-1000 suns, 20 K, 10,000 particles per cubic cm). Inside the latter, there are clusters-globules with a size of 0.1 pc, a mass of 1-10 suns and a density of 10 5 -10 6 particles / cm 3, where new stars are formed. |
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The birth of a star inside a gas and dust cloud |
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A new star with its radiation and stellar wind accelerates the surrounding gas away from itself |
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A young star enters space, clean and free of gas and dust, pushing the nebula that gave birth to it |
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Stages of "embryonic" development of a star, equal in mass to the Sun |
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The origin of a gravitationally unstable cloud 2,000,000 suns in size, with a temperature of 15 K and an initial density of 10 -19 g/cm 3 . |
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A few hundred thousand years later, 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 sun. |
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At this stage, the core with temperatures up to 2000 K shrinks sharply due to hydrogen ionization and simultaneously heats up to 20,000 K, the rate of matter falling onto the growing star reaches 100 km/s. |
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A protostar the size of two suns with a temperature at the center of 2x100000 K, and not on the surface - 3x1000 K. |
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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 in the interior of the star, thermonuclear reactions of helium synthesis from hydrogen are launched. 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. |
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Description of the stages of development of a gas and dust cloud into a star |
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 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. going on powerful explosion, 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. The explosion is accompanied by a sharp release of energy and the release of matter. A star explodes - this process is called a supernova. Ultimately, the star, depending on the mass, will turn into 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. Electronic structure The energy 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. There is not much of it by mass - 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, so does the pressure, 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 is to a large extent turned out to be 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 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's a mystery that hasn't been solved yet. 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 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.
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 point is that the surface of a dust grain 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 in flight with various atoms or molecules, especially inside a cold dense cloud, is quite high. Actually, this is what happens - this is how the shell of interstellar dust grains is formed from the met atoms and molecules 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 advantageous 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. 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 an 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 to study in detail, to 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 received 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. Spaceship equipped with special traps - collectors for collecting interstellar dust and cosmic wind particles. 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 - then 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 to 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.
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 collisions, the destruction of small solids, 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. Most bright stars, which 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's a mystery that hasn't been solved yet. 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.
Cosmic dust particles of matter in interstellar and interplanetary space. Light-absorbing condensations of the K. p. 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 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 the line of force. Thus, observing the polarized light of distant heavenly 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.
Big 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. By modern ideas, space 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: angl. 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
Books
- 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 show warm dust ( White color) 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.
Today it is already known that comets contain primordial dust, which is billions of years old, and which played leading 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.