1.
Asteroid
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Asteroids are minor planets, especially those of the inner Solar System. The larger ones have also been called planetoids and these terms have historically been applied to any astronomical object orbiting the Sun that did not show the disc of a planet and was not observed to have the characteristics of an active comet. As minor planets in the outer Solar System were discovered and found to have volatile-based surfaces that resemble those of comets, in this article, the term asteroid refers to the minor planets of the inner Solar System including those co-orbital with Jupiter. There are millions of asteroids, many thought to be the remnants of planetesimals. The large majority of known asteroids orbit in the belt between the orbits of Mars and Jupiter, or are co-orbital with Jupiter. However, other orbital families exist with significant populations, including the near-Earth objects, individual asteroids are classified by their characteristic spectra, with the majority falling into three main groups, C-type, M-type, and S-type. These were named after and are identified with carbon-rich, metallic. The size of asteroids varies greatly, some reaching as much as 1000 km across, asteroids are differentiated from comets and meteoroids. In the case of comets, the difference is one of composition, while asteroids are composed of mineral and rock, comets are composed of dust. In addition, asteroids formed closer to the sun, preventing the development of the aforementioned cometary ice, the difference between asteroids and meteoroids is mainly one of size, meteoroids have a diameter of less than one meter, whereas asteroids have a diameter of greater than one meter. Finally, meteoroids can be composed of either cometary or asteroidal materials, only one asteroid,4 Vesta, which has a relatively reflective surface, is normally visible to the naked eye, and this only in very dark skies when it is favorably positioned. Rarely, small asteroids passing close to Earth may be visible to the eye for a short time. As of March 2016, the Minor Planet Center had data on more than 1.3 million objects in the inner and outer Solar System, the United Nations declared June 30 as International Asteroid Day to educate the public about asteroids. The date of International Asteroid Day commemorates the anniversary of the Tunguska asteroid impact over Siberia, the first asteroid to be discovered, Ceres, was found in 1801 by Giuseppe Piazzi, and was originally considered to be a new planet. In the early half of the nineteenth century, the terms asteroid. Asteroid discovery methods have improved over the past two centuries. This task required that hand-drawn sky charts be prepared for all stars in the band down to an agreed-upon limit of faintness. On subsequent nights, the sky would be charted again and any moving object would, hopefully, the expected motion of the missing planet was about 30 seconds of arc per hour, readily discernible by observers
2.
Albedo
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Albedo is a measure for reflectance or optical brightness. It is dimensionless and measured on a scale from zero to one, surface albedo is defined as the ratio of radiation reflected to the radiation incident on a surface. The proportion reflected is not only determined by properties of the surface itself and these factors vary with atmospheric composition, geographic location and time. While bi-hemispherical reflectance is calculated for an angle of incidence. The temporal resolution may range from seconds to daily, seasonal or annual averages, unless given for a specific wavelength, albedo refers to the entire spectrum of solar radiation. Due to measurement constraints, it is given for the spectrum in which most solar energy reaches the surface. This spectrum includes visible light, which explains why surfaces with a low albedo appear dark, albedo is an important concept in climatology, astronomy, and environmental management. The term albedo was introduced into optics by Johann Heinrich Lambert in his 1760 work Photometria, any albedo in visible light falls within a range of about 0.9 for fresh snow to about 0.04 for charcoal, one of the darkest substances. Deeply shadowed cavities can achieve an effective albedo approaching the zero of a black body, when seen from a distance, the ocean surface has a low albedo, as do most forests, whereas desert areas have some of the highest albedos among landforms. Most land areas are in a range of 0.1 to 0.4. The average albedo of Earth is about 0.3 and this is far higher than for the ocean primarily because of the contribution of clouds. Earths surface albedo is regularly estimated via Earth observation satellite sensors such as NASAs MODIS instruments on board the Terra, thereby, the BRDF allows to translate observations of reflectance into albedo. Earths average surface temperature due to its albedo and the effect is currently about 15 °C. If Earth were frozen entirely, the temperature of the planet would drop below −40 °C. If only the land masses became covered by glaciers, the mean temperature of the planet would drop to about 0 °C. In contrast, if the entire Earth was covered by water — a so-called aquaplanet — the average temperature on the planet would rise to almost 27 °C, hence, the actual albedo α can then be given as, α = α ¯ + D α ¯ ¯. Directional-hemispherical reflectance is sometimes referred to as black-sky albedo and bi-hemispherical reflectance as white-sky albedo and these terms are important because they allow the albedo to be calculated for any given illumination conditions from a knowledge of the intrinsic properties of the surface. The albedos of planets, satellites and asteroids can be used to infer much about their properties, the study of albedos, their dependence on wavelength, lighting angle, and variation in time comprises a major part of the astronomical field of photometry
3.
Nickel
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Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a golden tinge. Nickel belongs to the metals and is hard and ductile. Meteoric nickel is found in combination with iron, a reflection of the origin of elements as major end products of supernova nucleosynthesis. An iron–nickel mixture is thought to compose Earths inner core, use of nickel has been traced as far back as 3500 BCE. Nickel was first isolated and classified as an element in 1751 by Axel Fredrik Cronstedt. The elements name comes from a mischievous sprite of German miner mythology, Nickel, an economically important source of nickel is the iron ore limonite, which often contains 1–2% nickel. Nickels other important ore minerals include garnierite, and pentlandite, major production sites include the Sudbury region in Canada, New Caledonia in the Pacific, and Norilsk in Russia. Nickel is slowly oxidized by air at room temperature and is considered corrosion-resistant, historically, it has been used for plating iron and brass, coating chemistry equipment, and manufacturing certain alloys that retain a high silvery polish, such as German silver. About 6% of world production is still used for corrosion-resistant pure-nickel plating. Nickel-plated objects sometimes provoke nickel allergy, Nickel has been widely used in coins, though its rising price has led to some replacement with cheaper metals in recent years. Nickel is one of four elements that are ferromagnetic around room temperature, alnico permanent magnets based partly on nickel are of intermediate strength between iron-based permanent magnets and rare-earth magnets. The metal is valuable in modern times chiefly in alloys, about 60% of world production is used in nickel-steels, other common alloys and some new superalloys comprise most of the remainder of world nickel use, with chemical uses for nickel compounds consuming less than 3% of production. As a compound, nickel has a number of chemical manufacturing uses. Nickel is a nutrient for some microorganisms and plants that have enzymes with nickel as an active site. Nickel is a metal with a slight golden tinge that takes a high polish. It is one of four elements that are magnetic at or near room temperature. Its Curie temperature is 355 °C, meaning that bulk nickel is non-magnetic above this temperature, the unit cell of nickel is a face-centered cube with the lattice parameter of 0.352 nm, giving an atomic radius of 0.124 nm
4.
Iron
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Iron is a chemical element with symbol Fe and atomic number 26. It is a metal in the first transition series and it is by mass the most common element on Earth, forming much of Earths outer and inner core. It is the fourth most common element in the Earths crust, like the other group 8 elements, ruthenium and osmium, iron exists in a wide range of oxidation states, −2 to +6, although +2 and +3 are the most common. Elemental iron occurs in meteoroids and other low oxygen environments, but is reactive to oxygen, fresh iron surfaces appear lustrous silvery-gray, but oxidize in normal air to give hydrated iron oxides, commonly known as rust. Unlike the metals that form passivating oxide layers, iron oxides occupy more volume than the metal and thus flake off, Iron metal has been used since ancient times, although copper alloys, which have lower melting temperatures, were used even earlier in human history. Pure iron is soft, but is unobtainable by smelting because it is significantly hardened and strengthened by impurities, in particular carbon. A certain proportion of carbon steel, which may be up to 1000 times harder than pure iron. Crude iron metal is produced in blast furnaces, where ore is reduced by coke to pig iron, further refinement with oxygen reduces the carbon content to the correct proportion to make steel. Steels and iron alloys formed with metals are by far the most common industrial metals because they have a great range of desirable properties. Iron chemical compounds have many uses, Iron oxide mixed with aluminium powder can be ignited to create a thermite reaction, used in welding and purifying ores. Iron forms binary compounds with the halogens and the chalcogens, among its organometallic compounds is ferrocene, the first sandwich compound discovered. Iron plays an important role in biology, forming complexes with oxygen in hemoglobin and myoglobin. Iron is also the metal at the site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants. A human male of average height has about 4 grams of iron in his body and this iron is distributed throughout the body in hemoglobin, tissues, muscles, bone marrow, blood proteins, enzymes, ferritin, hemosiderin, and transport in plasma. The mechanical properties of iron and its alloys can be evaluated using a variety of tests, including the Brinell test, Rockwell test, the data on iron is so consistent that it is often used to calibrate measurements or to compare tests. An increase in the content will cause a significant increase in the hardness. Maximum hardness of 65 Rc is achieved with a 0. 6% carbon content, because of the softness of iron, it is much easier to work with than its heavier congeners ruthenium and osmium. Because of its significance for planetary cores, the properties of iron at high pressures and temperatures have also been studied extensively
5.
Iron meteorite
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Iron meteorites are meteorites that consist overwhelmingly of an iron–nickel alloy known as meteoric iron that usually consists of two mineral phases, kamacite and taenite. Iron meteorites originate from planetary cores of planetesimals, the iron found in iron meteorites was one of the earliest sources of usable iron available to humans, before the development of smelting that signaled the beginning of the iron age. Although they are rare compared to the stony meteorites, comprising only about 5. 7% of witnessed falls. This is due to several factors, They are easily recognized as unusual even by laymen, modern-day searches for meteorites in deserts and Antarctica yield a much more representative sample of meteorites overall. They are much more resistant to weathering and they are much more likely to survive atmospheric entry, and are more resistant to the resulting ablation. Hence, they are likely to be found as large pieces. They are able to be even when buried by use of surface metal detecting equipment. Because they are denser than stony meteorites, iron meteorites also account for almost 90% of the mass of all known meteorites. All the largest known meteorites are of type, including the largest—the Hoba meteorite. Iron meteorites have been linked to M-type asteroids because both have similar characteristics in the visible and near-infrared. Iron meteorites are thought to be the fragments of the cores of larger ancient asteroids that have been shattered by impacts, the IIE iron meteorites may be a notable exception, in that they probably originate from the crust of S-type asteroid 6 Hebe. Chemical and isotope analysis indicates that at least about 50 distinct parent bodies were involved and this implies that there were once at least this many large, differentiated, asteroids in the asteroid belt – many more than today. The overwhelming bulk of these consists of the FeNi-alloys kamacite and taenite. Minor minerals, when occurring, often form rounded nodules of troilite or graphite, schreibersite and troilite also occur as plate shaped inclusions, which show up on cut surfaces as cm-long and mm-thick lamellae. The troilite plates are called Reichenbach lamellae, the chemical composition is dominated by the elements Fe, Ni and Co, which make up more than 95%. Ni is always present, the concentration is always higher than 5%. Iron meteorites were historically used for their meteoric iron, which was forged into cultural objects, with the advent of smelting and the beginning of the iron age the importance of iron meteorites as a resource decreased, at least in those cultures that developed those techniques. The Inuit used the Cape York meteorite for a longer time
6.
22 Kalliope
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22 Kalliope is a large M-type asteroid from the asteroid belt discovered by J. R. Hind on November 16,1852. It is named after Calliope, the Greek Muse of epic poetry and it is orbited by a small moon named Linus. Kalliope is somewhat elongated, approximately 166 km in diameter, and slightly asymmetric and this new diameter, which was measured by observing mutual eclipses of Kalliope and Linus, is 8% smaller than that calculated from IRAS observations. The spectrum of Kalliope is an M-type, indicating that its surface may be composed of iron–nickel metal. The asteroids density is about 3.4 g/cm3, spectroscopic studies have shown, however, evidence of hydrated minerals and silicates, which indicate rather a stony surface composition. Kalliope also has a low albedo, which is inconsistent with a purely metallic surface. Lightcurve analysis indicates that Kalliopes pole most likely points towards ecliptic coordinates = with a 10° uncertainty, Kalliopes rotation is then slightly retrograde. Kalliope has one natural satellite, Linus, or Kalliope I Linus. It is quite large, being about 28 km in diameter and it orbits about 1100 km from the center of Kalliope, equivalent to about 13.2 Kalliope radii. Linus was discovered on August 29,2001 by Jean-Luc Margot and Michael E. Brown, based on more than 5 years of regular observations of Kalliope binary system using adaptive optics systems on ground-based telescopes. The observed chords of Linus give an opportunity to estimate the size of the moonlet which was estimated to 20–28 km. Lightcurve plot of 22 Kalliope, Palmer Divide Observatory, B. D,22 Kalliope at the JPL Small-Body Database Discovery · Orbit diagram · Orbital elements · Physical parameters
7.
21 Lutetia
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21 Lutetia is a large asteroid in the asteroid belt of an unusual spectral type. It measures about 100 kilometers in diameter and it was discovered in 1852 by Hermann Goldschmidt, and is named after Lutetia, the Latin name of Paris. Lutetia has a shape and is heavily cratered, with the largest impact crater reaching 45 km in diameter. The surface is heterogeneous and is intersected by a system of grooves and scarps. It has an average density, meaning that it is made of metal-rich rock. The Rosetta probe passed within 3,162 km of Lutetia in July 2010 and it was the largest asteroid visited by a spacecraft until Dawn arrived at Vesta in July 2011. Lutetia was discovered on November 15,1852, by Hermann Goldschmidt from the balcony of his apartment in Paris, a preliminary orbit for the asteroid was computed in November–December 1852 by German astronomer Georg Rümker and others. In 1903, it was photographed at opposition by Edward Pickering at Harvard College Observatory and he computed an opposition magnitude of 10.8. There have been two reported stellar occultations by Lutetia, observed from Malta in 1997 and Australia in 2003, with one chord each. On July 10,2010, the European Rosetta space probe flew by Lutetia at a distance of 3168 ±7.5 km at a velocity of 15 kilometres per second on its way to the comet 67P/Churyumov-Gerasimenko. The flyby provided images of up to 60 meters per pixel resolution and covered about 50% of the surface, the 462 images were obtained in 21 narrow- and broad-band filters extending from 0.24 to 1 μm. Lutetia was also observed by the imaging spectrometer VIRTIS, and measurements of the magnetic field. Lutetia orbits the Sun at the distance of approximately 2.4 AU in the asteroid belt. Its orbit lies almost in the plane of ecliptic and is moderately eccentric, the orbital period of Lutetia is 3.8 years. The Rosetta flyby demonstrated that the mass of Lutetia is ×1018 kg and it has one of the highest densities seen before in asteroids at 3.4 ±0.3 g/cm3. Taking into account possible porosity of 10–15%, the density of Lutetia exceeds that of a typical stony meteorite. The composition of Lutetia has puzzled astronomers for some time, while classified among the M-type asteroids, most of which are metallic, Lutetia is one of the anomalous members that do not display much evidence of metal on their surface. The Rosetta probe actually found that the asteroid has a red spectrum in the visible light
8.
Silicate
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A silicate is a compound containing an anionic silicon compound. The great majority of the silicates are oxides, but hexafluorosilicate, orthosilicate is the anion SiO4−4 or its compounds. Related to orthosilicate are families of anions with the formula 2n−, important members are the cyclic and single chain silicates n and the sheet-forming silicates n. Silicates constitute the majority of Earths crust, as well as the terrestrial planets, rocky moons. Sand, Portland cement, and thousands of minerals are examples of silicates, silicate compounds, including the minerals, consist of silicate anions whose charge is balanced by various cations. Myriad silicate anions can exist, and each can form compounds with many different cations, hence this class of compounds is very large. Both minerals and synthetic materials fit in this class, in the vast majority of silicates, including silicate minerals, the Si occupies a tetrahedral environment, being surrounded by 4 oxygen centres. In these structures, the bonds to silicon conform to the octet rule. These tetrahedra sometimes occur as isolated SiO4−4 centres, but most commonly, commonly the silicate anions are chains, double chains, sheets, and three-dimensional frameworks. All these such species have negligible solubility in water at normal conditions, silicates are well characterized as solids, but are less commonly observed in solution. The anion SiO4−4 is the base of silicic acid, Si4. Instead, solutions of silicates are usually observed as mixtures of condensed, the nature of soluble silicates is relevant to understanding biomineralization and the synthesis of aluminosilicates, such as the industrially important catalysts called zeolites. Although the tetrahedron is the coordination geometry for silicon compounds. A well-known example of such a high number is hexafluorosilicate. Octahedral coordination by 6 oxygen centres is observed, at very high pressure, even SiO2 adopts this geometry in the mineral stishovite, a dense polymorph of silica found in the lower mantle of the Earth. This structure is formed by shock during meteorite impacts. In geology and astronomy, the silicate is used to denote types of rock that consist predominantly of silicate minerals. On Earth, a variety of silicate minerals occur in an even wider range of combinations as a result of the processes that form
