1.
Comet
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A comet is an icy small Solar System body that, when passing close to the Sun, warms and begins to evolve gasses, a process called outgassing. This produces an atmosphere or coma, and sometimes also a tail. These phenomena are due to the effects of radiation and the solar wind acting upon the nucleus of the comet. Comet nuclei range from a few hundred metres to tens of kilometres across and are composed of collections of ice, dust. The coma may be up to 15 times the Earths diameter, if sufficiently bright, a comet may be seen from the Earth without the aid of a telescope and may subtend an arc of 30° across the sky. Comets have been observed and recorded since ancient times by many cultures, Comets usually have highly eccentric elliptical orbits, and they have a wide range of orbital periods, ranging from several years to potentially several millions of years. Short-period comets originate in the Kuiper belt or its associated scattered disc, long-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside the Kuiper belt to halfway to the nearest star. Long-period comets are set in motion towards the Sun from the Oort cloud by gravitational perturbations caused by passing stars, hyperbolic comets may pass once through the inner Solar System before being flung to interstellar space. The appearance of a comet is called an apparition, Comets are distinguished from asteroids by the presence of an extended, gravitationally unbound atmosphere surrounding their central nucleus. This atmosphere has parts termed the coma and the tail, however, extinct comets that have passed close to the Sun many times have lost nearly all of their volatile ices and dust and may come to resemble small asteroids. Asteroids are thought to have a different origin from comets, having formed inside the orbit of Jupiter rather than in the outer Solar System, the discovery of main-belt comets and active centaur minor planets has blurred the distinction between asteroids and comets. As of November 2014 there are 5,253 known comets, however, this represents only a tiny fraction of the total potential comet population, as the reservoir of comet-like bodies in the outer Solar System is estimated to be one trillion. Roughly one comet per year is visible to the eye, though many of those are faint. Particularly bright examples are called Great Comets, the word comet derives from the Old English cometa from the Latin comēta or comētēs. That, in turn, is a latinisation of the Greek κομήτης, Κομήτης was derived from κομᾶν, which was itself derived from κόμη and was used to mean the tail of a comet. The astronomical symbol for comets is ☄, consisting of a disc with three hairlike extensions. The solid, core structure of a comet is known as the nucleus, cometary nuclei are composed of an amalgamation of rock, dust, water ice, and frozen gases such as carbon dioxide, carbon monoxide, methane, and ammonia. As such, they are described as dirty snowballs after Fred Whipples model
2.
Sun
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The Sun is the star at the center of the Solar System. It is a perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99. 86% of the total mass of the Solar System. About three quarters of the Suns mass consists of hydrogen, the rest is mostly helium, with smaller quantities of heavier elements, including oxygen, carbon, neon. The Sun is a G-type main-sequence star based on its spectral class and it formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into a disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core and it is thought that almost all stars form by this process. The Sun is roughly middle-aged, it has not changed dramatically for more than four billion years and it is calculated that the Sun will become sufficiently large enough to engulf the current orbits of Mercury, Venus, and probably Earth. The enormous effect of the Sun on Earth has been recognized since prehistoric times, the synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar, which is the predominant calendar in use today. The English proper name Sun developed from Old English sunne and may be related to south, all Germanic terms for the Sun stem from Proto-Germanic *sunnōn. The English weekday name Sunday stems from Old English and is ultimately a result of a Germanic interpretation of Latin dies solis, the Latin name for the Sun, Sol, is not common in general English language use, the adjectival form is the related word solar. The term sol is used by planetary astronomers to refer to the duration of a solar day on another planet. A mean Earth solar day is approximately 24 hours, whereas a mean Martian sol is 24 hours,39 minutes, and 35.244 seconds. From at least the 4th Dynasty of Ancient Egypt, the Sun was worshipped as the god Ra, portrayed as a falcon-headed divinity surmounted by the solar disk, and surrounded by a serpent. In the New Empire period, the Sun became identified with the dung beetle, in the form of the Sun disc Aten, the Sun had a brief resurgence during the Amarna Period when it again became the preeminent, if not only, divinity for the Pharaoh Akhenaton. The Sun is viewed as a goddess in Germanic paganism, Sól/Sunna, in ancient Roman culture, Sunday was the day of the Sun god. It was adopted as the Sabbath day by Christians who did not have a Jewish background, the symbol of light was a pagan device adopted by Christians, and perhaps the most important one that did not come from Jewish traditions
3.
Perihelion and aphelion
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The perihelion is the point in the orbit of a celestial body where it is nearest to its orbital focus, generally a star. It is the opposite of aphelion, which is the point in the orbit where the body is farthest from its focus. The word perihelion stems from the Ancient Greek words peri, meaning around or surrounding, aphelion derives from the preposition apo, meaning away, off, apart. According to Keplers first law of motion, all planets, comets. Hence, a body has a closest and a farthest point from its parent object, that is, a perihelion. Each extreme is known as an apsis, orbital eccentricity measures the flatness of the orbit. Because of the distance at aphelion, only 93. 55% of the solar radiation from the Sun falls on a given area of land as does at perihelion. However, this fluctuation does not account for the seasons, as it is summer in the northern hemisphere when it is winter in the southern hemisphere and vice versa. Instead, seasons result from the tilt of Earths axis, which is 23.4 degrees away from perpendicular to the plane of Earths orbit around the sun. Winter falls on the hemisphere where sunlight strikes least directly, and summer falls where sunlight strikes most directly, in the northern hemisphere, summer occurs at the same time as aphelion. Despite this, there are larger land masses in the northern hemisphere, consequently, summers are 2.3 °C warmer in the northern hemisphere than in the southern hemisphere under similar conditions. Apsis Ellipse Solstice Dates and times of Earths perihelion and aphelion, 2000–2025 from the United States Naval Observatory
4.
Evaporation
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Evaporation is a type of vaporization of a liquid that occurs from the surface of a liquid into a gaseous phase that is not saturated with the evaporating substance. The other type of vaporization is boiling, which is characterized by bubbles of saturated vapor forming in the liquid phase, steam produced in a boiler is another example of evaporation occurring in a saturated vapor phase. Evaporation that occurs directly from the solid phase below the melting point, on average, a fraction of the molecules in a glass of water have enough heat energy to escape from the liquid. The water in the glass will be cooled by the evaporation until an equilibrium is reached where the air supplies the amount of heat removed by the evaporating water, in an enclosed environment the water would evaporate until the air is saturated. With sufficient temperature, the liquid would turn into vapor quickly, when the molecules collide, they transfer energy to each other in varying degrees, based on how they collide. Sometimes the transfer is so one-sided for a molecule near the surface that it ends up with energy to escape. Evaporation is an part of the water cycle. The sun drives evaporation of water from oceans, lakes, moisture in the soil, in hydrology, evaporation and transpiration are collectively termed evapotranspiration. Evaporation of water occurs when the surface of the liquid is exposed, allowing molecules to escape and form water vapor, when only a small proportion of the molecules meet these criteria, the rate of evaporation is low. Since the kinetic energy of a molecule is proportional to its temperature, as the faster-moving molecules escape, the remaining molecules have lower average kinetic energy, and the temperature of the liquid decreases. This phenomenon is also called evaporative cooling and this is why evaporating sweat cools the human body. Evaporation also tends to proceed quickly with higher flow rates between the gaseous and liquid phase and in liquids with higher vapor pressure. For example, laundry on a line will dry more rapidly on a windy day than on a still day. Three key parts to evaporation are heat, atmospheric pressure, on a molecular level, there is no strict boundary between the liquid state and the vapor state. Instead, there is a Knudsen layer, where the phase is undetermined, because this layer is only a few molecules thick, at a macroscopic scale a clear phase transition interface cannot be seen. It is just that the process is slower and thus significantly less visible. If evaporation takes place in an area, the escaping molecules accumulate as a vapor above the liquid. Many of the return to the liquid, with returning molecules becoming more frequent as the density
5.
Tidal force
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The tidal force is a force that is the secondary effect of the force of gravity, it is responsible for the phenomenon of tides. It arises because the force exerted by one body on another is not constant across it. Thus, the force is differential. Consider the gravitational attraction of the Moon on the oceans nearest to the Moon, the solid Earth, there is a mutual attraction between the Moon and the solid Earth, which can be considered to act on its centre of mass. However, the oceans are more strongly attracted and, especially since they are fluid, they approach the Moon slightly. The far oceans are attracted less, viewing the Earth as a whole, we see that all its mass experiences a mutual attraction with that of the Moon, but the near oceans more so than the far oceans, leading to a separation of the two. When a body is acted on by the gravity of another body, Figure 2 shows the differential force of gravity on a spherical body exerted by another body. These so-called tidal forces cause strains on both bodies and may distort them or even, in cases, break one or the other apart. These strains would not occur if the field were uniform, because a uniform field only causes the entire body to accelerate together in the same direction. In the case of a small elastic sphere, the effect of a tidal force is to distort the shape of the body without any change in volume. The sphere becomes an ellipsoid with two bulges, pointing towards and away from the other body, larger objects distort into an ovoid, and are slightly compressed, which is what happens to the Earths oceans under the action of the Moon. The Earth and Moon rotate about their center of mass or barycenter. To an observer on the Earth, very close to this barycenter, all parts of the Earth are subject to the Moons gravitational forces, causing the water in the oceans to redistribute, forming bulges on the sides near the Moon and far from the Moon. When a body rotates while subject to forces, internal friction results in the gradual dissipation of its rotational kinetic energy as heat. In the case for the Earth, and Earths Moon, the loss of kinetic energy results in a gain of about 2 milliseconds per century. If the body is enough to its primary, this can result in a rotation which is tidally locked to the orbital motion. Tidal heating produces dramatic volcanic effects on Jupiters moon Io, stresses caused by tidal forces also cause a regular monthly pattern of moonquakes on Earths Moon. Tidal forces contribute to ocean currents, which moderate global temperatures by transporting heat energy toward the poles and it has been suggested that in addition to other factors, harmonic beat variations in tidal forcing may contribute to climate changes
6.
Heinrich Kreutz
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The group is now known as the Kreutz Sungrazers, and has produced some of the brightest comets ever seen. Kreutz was born in Siegen in 1854, and obtained his PhD at the University of Bonn in 1880 on the orbit of comet C/1861 J1, in 1882 he moved to Kiel, working at the observatory and university there. In 1896 he became the editor of the Astronomische Nachrichten, the leading journal of the time. Obituary -1907, Publications of the Astronomical Society of the Pacific, v.19, p.248 Biography from SEDS
7.
Daniel Kirkwood
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Daniel Kirkwood was an American astronomer. Kirkwood was born in Harford County, Maryland to John and Agnes Kirkwood and he graduated in mathematics from the York County Academy in York, Pennsylvania in 1838. Kirkwoods most significant contribution came from his study of asteroid orbits, further, Kirkwood also suggested a similar dynamic was responsible for Cassini Division in Saturns rings, as the result of a resonance with one of Saturns moons. In the same paper, he was the first to correctly posit that the material in meteor showers is cometary debris, Kirkwood also identified a pattern relating the distances of the planets to their rotation periods, which was called Kirkwoods Law. The Law has since become discredited as new measurements of planetary rotation periods have shown that the pattern doesnt hold, in 1891, at age 77, he became a lecturer in astronomy at Stanford University. He died in Riverside, California in 1895, altogether he wrote 129 publications, including three books. The asteroid 1951 AT was named 1578 Kirkwood in his honor and so was the impact crater Kirkwood. He is buried in the Rose Hill Cemetery in Bloomington, Indiana, Kirkwood was a cousin of Iowa governor Samuel Jordan Kirkwood who became United States Secretary of the Interior under President James A. Garfield and President Chester A. Arthur. Frank K. Edmondson, Daniel Kirkwood, Dean of American Astronomers, Mercury Magazine, J. Donald Fernie 1999, The American Kepler, The New Scientist vol. Works by Daniel Kirkwood at Project Gutenberg Works by or about Daniel Kirkwood at Internet Archive Daniel Kirkwood at Find a Grave
8.
Coronagraph
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A coronagraph is a telescopic attachment designed to block out the direct light from a star so that nearby objects – which otherwise would be hidden in the stars bright glare – can be resolved. The coronagraph was introduced in 1931 by the French astronomer Bernard Lyot, since then, coronagraphs operating within Earths atmosphere suffer from scattered light in the sky itself, due primarily to Rayleigh scattering of sunlight in the upper atmosphere. At view angles close to the Sun, the sky is much brighter than the background corona even at high altitude sites on clear, dry days. Coronagraph instruments are examples of stray light rejection and precise photometry because the total brightness from the solar corona is less than one millionth the brightness of the Sun. The apparent surface brightness is even fainter because, in addition to delivering less total light, during a solar eclipse, the Moon acts as an occulting disk and any camera in the eclipse path may be operated as a coronagraph until the eclipse is over. More common is an arrangement where the sky is imaged onto a focal plane containing an opaque spot. Either way, the instrument design must take into account scattering, as an example, imaging instruments on the Hubble Space Telescope offer coronagraphic capability. A band-limited coronagraph uses a kind of mask called a band-limited mask. This mask is designed to light and also manage potangina effects caused by removal of the light. The band-limited coronagraph has served as the design for the canceled Terrestrial Planet Finder coronagraph. Band-limited masks will also be available on the James Webb Space Telescope, see also, A phase-mask coronagraph uses a transparent mask to shift the phase of the stellar light in order to create a self-destructive interference, rather than a simple opaque disc to block it. See also, An optical vortex coronagraph uses a phase-mask in which the phase-shift varies azimuthally around the center, several varieties of optical vortex coronagraphs exist, the scalar optical vortex coronagraph based on a phase ramp directly etched in a dielectric material, like fused silica. The vector vortex coronagraph employs a mask that rotates the angle of polarization of photons, a mask of this kind can be synthesized by various technologies, ranging from liquid crystal polymer, and micro-structured surfaces. Such a vector vortex coronagraph made out of liquid crystal polymers is currently in use at the 200-inch Hale telescope at the Palomar Observatory and it has recently been operated with adaptive optics to image extrasolar planets. This works with other than the sun because they are so far away their light is, for this purpose. The coronagraph using interference masks out the light along the axis of the telescope. Coronagraphs in outer space are more effective than the same instruments would be if located on the ground. This is because the absence of atmospheric scattering eliminates the largest source of glare present in a terrestrial coronagraph
9.
Great comet
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A great comet is a comet that becomes exceptionally bright. Great comets are rare, on average, only one will appear in a decade, although comets are officially named after their discoverers, great comets are sometimes also referred to by the year in which they appeared great, using the formulation The Great Comet of. The vast majority of comets are never enough to be seen by the naked eye. However, occasionally a comet may brighten to naked eye visibility, the requirements for this to occur are, a large and active nucleus, a close approach to the Sun, and a close approach to the Earth. A comet fulfilling all three of these criteria will certainly be spectacular, sometimes, a comet failing on one criterion will still be extremely impressive. For example, Comet Hale–Bopp had a large and active nucleus. Equally, Comet Hyakutake was a small comet, but appeared bright because it passed extremely close to the Earth. Cometary nuclei vary in size from a few hundreds of metres across or less to many kilometres across, when they approach the Sun, large amounts of gas and dust are ejected by cometary nuclei, due to solar heating. A crucial factor in how bright a comet becomes is how large, the sudden brightening of comet 17P/Holmes in 2007 showed the importance of the activity of the nucleus in the comets brightness. On October 23–24,2007, the comet suffered a sudden outburst which caused it to brighten by factor of about half a million. It unexpectedly brightened from an apparent magnitude of about 17 to about 2.8 in a period of only 42 hours, all these temporarily made comet 17P the largest object in the Solar System although its nucleus is estimated to be only about 3.4 km in diameter. The brightness of a simple reflective body varies with the square of its distance from the Sun. That is, if a distance from the Sun is halved. However, comets behave differently, due to their ejection of large amounts of gas which then also reflect sunlight. Their brightness varies roughly as the cube of their distance from the Sun, meaning that if a comets distance from the Sun is halved. This means that the brightness of a comet depends significantly on its distance from the Sun. For most comets, the perihelion of their orbit lies outside the Earths orbit, any comet approaching the Sun to within 0.5 AU or less may have a chance of becoming a great comet. For a comet to become spectacular, it needs to pass close to the Earth
10.
Volatility (chemistry)
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In chemistry and physics, volatility is quantified by the tendency of a substance to vaporize. Volatility is directly related to a vapor pressure. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a vapor pressure. The vapor pressure of a substance is the pressure at which its gas phase is in equilibrium with its condensed phases and it is a measure of the tendency of molecules and atoms to escape from a liquid or a solid. The higher the pressure of a liquid at a given temperature, the higher the volatility. The vapor pressure chart displays the vapor pressures dependency for a variety of liquids as a function of temperature, for example, at any given temperature, chloromethane has the highest vapor pressure of any of the liquids in the chart. It also has the lowest normal boiling point, which is where the pressure curve intersects the horizontal pressure line of one atmosphere of absolute vapor pressure
11.
Great Comet of 1680
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C/1680 V1, also called the Great Comet of 1680, Kirchs Comet, and Newtons Comet, has the distinction of being the first comet discovered by telescope. Passing 0.42 AUs from Earth on 30 November 1680, it sped around an extremely close perihelion of 0.0062 AU on 18 December 1680 and it was last observed on 19 March 1681. As of September 2012 the comet was about 253 AU from the Sun, while the Kirch Comet of 1680–1681 was discovered by—and subsequently named for—Gottfried Kirch, credit must also be given to Eusebio Kino, the Spanish Jesuit priest who charted the comet’s course. During his delayed departure for Mexico, Kino began his observations of the comet in Cádiz in late 1680, upon his arrival in Mexico City, he published his Exposisión astronómica de el cometa in which he presented his findings. Kino’s Exposisión astronómica is among the earliest scientific treatises published by a European in the New World, although it was undeniably a sungrazing comet, it was probably not part of the Kreutz family. Aside from its brilliance, it is probably most noted for being used by Isaac Newton to test, Newton later changed his mind, however, and then, with Edmond Halleys help, purloined some of Flamsteeds data to indeed verify this was the case without giving Flamsteed credit. Comet Halley Comet ISON The Great Comet of 1680 Over Rotterdam
12.
Isaac Newton
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His book Philosophiæ Naturalis Principia Mathematica, first published in 1687, laid the foundations of classical mechanics. Newton also made contributions to optics, and he shares credit with Gottfried Wilhelm Leibniz for developing the infinitesimal calculus. Newtons Principia formulated the laws of motion and universal gravitation that dominated scientists view of the universe for the next three centuries. Newtons work on light was collected in his influential book Opticks. He also formulated a law of cooling, made the first theoretical calculation of the speed of sound. Newton was a fellow of Trinity College and the second Lucasian Professor of Mathematics at the University of Cambridge, politically and personally tied to the Whig party, Newton served two brief terms as Member of Parliament for the University of Cambridge, in 1689–90 and 1701–02. He was knighted by Queen Anne in 1705 and he spent the last three decades of his life in London, serving as Warden and Master of the Royal Mint and his father, also named Isaac Newton, had died three months before. Born prematurely, he was a child, his mother Hannah Ayscough reportedly said that he could have fit inside a quart mug. When Newton was three, his mother remarried and went to live with her new husband, the Reverend Barnabas Smith, leaving her son in the care of his maternal grandmother, Newtons mother had three children from her second marriage. From the age of twelve until he was seventeen, Newton was educated at The Kings School, Grantham which taught Latin and Greek. He was removed from school, and by October 1659, he was to be found at Woolsthorpe-by-Colsterworth, Henry Stokes, master at the Kings School, persuaded his mother to send him back to school so that he might complete his education. Motivated partly by a desire for revenge against a bully, he became the top-ranked student. In June 1661, he was admitted to Trinity College, Cambridge and he started as a subsizar—paying his way by performing valets duties—until he was awarded a scholarship in 1664, which guaranteed him four more years until he would get his M. A. He set down in his notebook a series of Quaestiones about mechanical philosophy as he found it, in 1665, he discovered the generalised binomial theorem and began to develop a mathematical theory that later became calculus. Soon after Newton had obtained his B. A. degree in August 1665, in April 1667, he returned to Cambridge and in October was elected as a fellow of Trinity. Fellows were required to become ordained priests, although this was not enforced in the restoration years, however, by 1675 the issue could not be avoided and by then his unconventional views stood in the way. Nevertheless, Newton managed to avoid it by means of a special permission from Charles II. A and he was elected a Fellow of the Royal Society in 1672. Newtons work has been said to distinctly advance every branch of mathematics then studied and his work on the subject usually referred to as fluxions or calculus, seen in a manuscript of October 1666, is now published among Newtons mathematical papers
13.
Jacques Cassini
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Jacques Cassini was a French astronomer, son of the famous Italian astronomer Giovanni Domenico Cassini. Cassini was born at the Paris Observatory, admitted at the age of seventeen to membership of the French Academy of Sciences, he was elected in 1696 a fellow of the Royal Society of London, and became maître des comptes in 1706. His two separate calculations for a degree of meridian arc were 57,097 toises de Paris and 57,061 toises, giving results for Earths radius of 3,271,420 toises and 3,269,297 toises, respectively. He published the first tables of the satellites of Saturn in 1716 and he died at Thury, near Clermont, France. The asteroid 24102 Jacquescassini is named after him, Jacques Cassini married Suzanne Françoise Charpentier de Charmois. Their second son was astronomer César-François Cassini de Thury, who was known as Cassini III. This article incorporates text from a now in the public domain, Chisholm, Hugh. OConnor, John J. Robertson, Edmund F. Jacques Cassini, MacTutor History of Mathematics archive, Jacques Cassini at the Mathematics Genealogy Project
14.
Tycho Brahe
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Tycho Brahe, born Tyge Ottesen Brahe, was a Danish nobleman known for his accurate and comprehensive astronomical and planetary observations. He was born in the then Danish peninsula of Scania, well known in his lifetime as an astronomer, astrologer and alchemist, he has been described as the first competent mind in modern astronomy to feel ardently the passion for exact empirical facts. His observations were some five times more accurate than the best available observations at the time, an heir to several of Denmarks principal noble families, he received a comprehensive education. He took an interest in astronomy and in the creation of more instruments of measurement. His system correctly saw the Moon as orbiting Earth, and the planets as orbiting the Sun, furthermore, he was the last of the major naked eye astronomers, working without telescopes for his observations. In his De nova stella of 1573, he refuted the Aristotelian belief in a celestial realm. Using similar measurements he showed that comets were also not atmospheric phenomena, as previously thought, on the island he founded manufactories, such as a paper mill, to provide material for printing his results. He built an observatory at Benátky nad Jizerou, there, from 1600 until his death in 1601, he was assisted by Johannes Kepler, who later used Tychos astronomical data to develop his three laws of planetary motion. Tychos body has been exhumed twice, in 1901 and 2010, to examine the circumstances of his death, both of his grandfathers and all of his great grandfathers had served as members of the Danish kings Privy Council. His paternal grandfather and namesake Thyge Brahe was the lord of Tosterup Castle in Scania, Tychos father Otte Brahe, like his father a royal Privy Councilor, married Beate Bille, who was herself a powerful figure at the Danish court holding several royal land titles. Both parents are buried under the floor of Kågeröd Church, four kilometres east of Knutstorp, Tycho was born at his familys ancestral seat of Knutstorp Castle, about eight kilometres north of Svalöv in then Danish Scania. He was the oldest of 12 siblngs,8 of whom lived to adulthood and his twin brother died before being baptized. Tycho later wrote an ode in Latin to his dead twin, an epitaph, originally from Knutstorp, but now on a plaque near the church door, shows the whole family, including Tycho as a boy. When he was two years old Tycho was taken away to be raised by his uncle Jørgen Thygesen Brahe. It is unclear why the Otte Brahe reached this arrangement with his brother, Tycho later wrote that Jørgen Brahe raised me and generously provided for me during his life until my eighteenth year, he always treated me as his own son and made me his heir. From ages 6 to 12, Tycho attended Latin school, probably in Nykøbing, at age 12, on 19 April 1559, Tycho began studies at the University of Copenhagen. There, following his uncles wishes, he studied law, but also studied a variety of other subjects, at the University, Aristotle was a staple of scientific theory, and Tycho likely received a thorough training in Aristotelian physics and cosmology. He experienced the solar eclipse of 21 August 1560, and was impressed by the fact that it had been predicted
15.
Edmond Halley
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Edmond Halley, FRS was an English astronomer, geophysicist, mathematician, meteorologist, and physicist who is best known for computing the orbit of Halleys Comet. He was the second Astronomer Royal in Britain, succeeding John Flamsteed, Halley was born in Haggerston, in east London. His father, Edmond Halley Sr. came from a Derbyshire family and was a wealthy soap-maker in London, as a child, Halley was very interested in mathematics. He studied at St Pauls School, and from 1673 at The Queens College, while still an undergraduate, Halley published papers on the Solar System and sunspots. While at Oxford University, Halley was introduced to John Flamsteed, influenced by Flamsteeds project to compile a catalog of northern stars, Halley proposed to do the same for the Southern Hemisphere. In 1676, Halley visited the south Atlantic island of Saint Helena, while there he observed a transit of Mercury, and realised that a similar transit of Venus could be used to determine the absolute size of the Solar System. He returned to England in May 1678, in the following year he went to Danzig on behalf of the Royal Society to help resolve a dispute. Because astronomer Johannes Hevelius did not use a telescope, his observations had been questioned by Robert Hooke, Halley stayed with Hevelius and he observed and verified the quality of Hevelius observations. In 1679, Halley published the results from his observations on St. Helena as Catalogus Stellarum Australium which included details of 341 southern stars and these additions to contemporary star maps earned him comparison with Tycho Brahe, e. g. the southern Tycho as described by Flamsteed. Halley was awarded his M. A. degree at Oxford, in 1686, Halley published the second part of the results from his Helenian expedition, being a paper and chart on trade winds and monsoons. The symbols he used to represent trailing winds still exist in most modern day weather chart representations, in this article he identified solar heating as the cause of atmospheric motions. He also established the relationship between pressure and height above sea level. His charts were an important contribution to the field of information visualisation. Halley spent most of his time on lunar observations, but was interested in the problems of gravity. One problem that attracted his attention was the proof of Keplers laws of planetary motion, Halleys first calculations with comets were thereby for the orbit of comet Kirch, based on Flamsteeds observations in 1680-1. Although he was to calculate the orbit of the comet of 1682. They indicated a periodicity of 575 years, thus appearing in the years 531 and 1106 and it is now known to have an orbital period of circa 10,000 years. In 1691, Halley built a bell, a device in which the atmosphere was replenished by way of weighted barrels of air sent down from the surface
16.
Johann Franz Encke
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Johann Franz Encke was a German astronomer. Among his activities, he worked on the calculation of the periods of comets and asteroids, measured the distance from the earth to the sun, Encke was born in Hamburg, where his father was the Pastor at the St. James Church, Hamburg. He was the youngest of eight children, and at the time his father died when he was four, thanks to the financial assistance of a teacher, he was able to be educated at the Gelehrtenschule des Johanneums. In 1814 he resumed his studies at the University but after Napoleons escape from Elba he returned to the military, having returned to Göttingen in 1816, he was at once appointed by Bernhardt von Lindenau as his assistant in the observatory of Seeberg near Gotha. That comet is now called 12P/Pons-Brooks, at this time, all the known comets had an orbital period of seventy years and more, with an aphelion far beyond the orbit of Uranus. The most famous comet of this family was Comet Halley with its period of seventy-six years. So the orbit of the discovered by Pons was a sensation, because his orbit was found to have a period of 3.3 years. Encke predicted its return for 1822, but this return was only from the southern hemisphere and was seen by Carl Ludwig Christian Rümker in Australia. The comet was identified with the one seen by Pierre Méchain in 1786. Encke sent his calculations as a note to Gauss, Olbers and his former mathematics professor published this note and Encke became famous as the discoverer of the short periodic comets. The first object of this family, the Encke comet, was named after him and so it is one of the few comets not named after the discoverer, later this comet was identified as the origin of the Taurids meteor showers. The importance of the return based on the calculation by Encke was rewarded by the Royal Astronomical Society in London by presenting their Gold Medal to him in 1824. In this year Encke married Amalie Becker, daughter of author, bookseller and publisher Rudolph Zacharias Becker and they had three sons and two daughters. In 1825 he was elected a Fellow of the Royal Society, eight masterly treatises on the comets movements were published by him in the Berliner Abhandlungen. From a fresh discussion of the transits of Venus in 1761 and 1769 he deduced a solar parallax of 8.57 arcsecond and this and the corresponding distance to the sun were long accepted as authoritative. His results were published in two tracts, entitled Die Entfernung der Sonne. Mostly on the recommendation of Bessel, Encke became director of the new observatory and secretary of the Academy of Sciences, within the following time Encke was involved in the discovery and orbital parameter determination of other short periodic comets and asteroids. In 1837, Encke described a variation in the brightness of the A Ring of Saturn
17.
C/1843 D1
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The Great Comet of 1843, formally designated C/1843 D1 and 1843 I, was a long-period comet which became very bright in March 1843. It was discovered on February 5,1843 and rapidly brightened to become a great comet and it was a member of the Kreutz Sungrazers, a family of comets resulting from the breakup of a parent comet into multiple fragments in about 1106. These comets pass extremely close to the surface of the Sun—within a few solar radii—and often become very bright as a result and it was last observed on April 19,1843. At that time this comet had passed closer to the Sun than any known object. The Great Comet of 1843 developed a long tail during. At over two units in length, it was the longest known cometary tail until measurements in 1996 showed that Comet Hyakutakes tail was almost twice as long. There is a painting in the National Maritime Museum that was created by astronomer Charles Piazzi Smyth, the purpose of the painting is to show the overall brightness and size of the tail of the comet. Estimates for the period of the comet have varied from 512 ±105 years,654 ±103 years,688 years. But the comet was observed over a period of 45 days from March 5 to April 19. The Mexican composer Luis Baca composed a waltz for piano, El cometa de 1843 and it appeared as no. com Saw a comet star ablazing
18.
C/1882 R1
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The Great Comet of 1882 formally designated C/1882 R1,1882 II, and 1882b, was a comet which became very bright in September 1882. It was a member of the Kreutz Sungrazers, a family of comets which pass within 1 R☉ of the Suns photosphere at perihelion, the comet was bright enough to be visible next to the Sun in the daytime sky at its perihelion. The comet appeared in the skies of September 1882. The first astronomer to record observations of the comet was W. H. Finlay, the Chief Assistant at the Royal Observatory in Cape Town, South Africa. Finlays observation on 7 September at 16h GMT was also an independent discovery, and he reported that the comet had an apparent magnitude of about 3, the comet brightened rapidly, and within days had become an exceptionally bright object. The comet was approaching perihelion when it was first seen. At perihelion, the comet is estimated to have been only 300,000 miles or 480,000 kilometres from the Suns surface, subsequent orbital studies have determined that it was a Sungrazing comet, one which passes extremely close to the surface of the Sun. For many hours on either side of its passage, the comet was easily visible in the daytime sky next to the Sun. It reached a magnitude of −17. Shortly after perihelion was reached on 17 September, the comet transited the Sun, at the Cape, Finlay observed the comet with the aid of a neutral density filter right up until the moment of transit, when the Suns limb was boiling all about it. Finlay noted that the disappeared from view very suddenly. After its perihelion passage, the moved into dark skies. Observers reported that the brightness of the fragments varied from day to day. In mid-October, the comet developed a notable antitail, pointing towards the Sun, anti-tails are a fairly common cometary phenomenon, and result from orbital geometry giving the appearance of a tail pointing towards the Sun although material can only be driven away from the Sun. The nucleus reached its maximum apparent size in December 1882, the comet faded gradually, but despite its fragmentation it remained visible to the naked eye until February 1883. The last definite sighting of the comet was made by B. A. Gould at Córdoba on 1 June 1883. Studies of the orbit of the comet showed that the Great Comet of 1882 was moving on an almost identical path to previous great comets seen in C/1843 D1 and these comets had also suddenly appeared in the morning sky and had passed extremely close to the Sun at perihelion. One suggestion was that all three were in fact the same comet, with a period that was being drastically shortened at each perihelion passage
19.
X/1106 C1
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X/1106 C1, also known as the Great Comet of 1106, was a great comet that appeared on 2 February 1106, and was observed across the world from the beginning of February through to mid-March. It was recorded by astronomers in Wales, England, Japan, Korea, China and it is a member of the Kreutz Group, known as Subfragment I, split from an earlier comet. A brief note in the Welsh manuscript known as the Brut y Tywysogion reads, and his son, after winning the seat of the empire of Rome, was made emperor. The 1106 annal of the Peterborough Chronicle describes the comet and this star appeared in the south-west, it seemed small and dark. It was like a great Pei Kow and it appeared like a broken-up star. It was 60 in length and was 3 in breadth and its direction was to the north-east. It then entered into the clouds and was no more seen, sigebert of Gembloux mentions it in his Chronicon sive Chronographia. Comet X/1106 C1, Publication der Sternwarte in Kiel, No,6, pp. 1–66, and AN238, pp. 403–4 Historic astronomical observations in Wales SOHO-620, A Comet on the Right Track http, //cometography. com/lcomets/1106c1. html
20.
Aristotle
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Aristotle was an ancient Greek philosopher and scientist born in the city of Stagira, Chalkidice, on the northern periphery of Classical Greece. His father, Nicomachus, died when Aristotle was a child, at seventeen or eighteen years of age, he joined Platos Academy in Athens and remained there until the age of thirty-seven. Shortly after Plato died, Aristotle left Athens and, at the request of Philip II of Macedon, teaching Alexander the Great gave Aristotle many opportunities and an abundance of supplies. He established a library in the Lyceum which aided in the production of many of his hundreds of books and he believed all peoples concepts and all of their knowledge was ultimately based on perception. Aristotles views on natural sciences represent the groundwork underlying many of his works, Aristotles views on physical science profoundly shaped medieval scholarship. Their influence extended from Late Antiquity and the Early Middle Ages into the Renaissance, some of Aristotles zoological observations, such as on the hectocotyl arm of the octopus, were not confirmed or refuted until the 19th century. His works contain the earliest known study of logic, which was incorporated in the late 19th century into modern formal logic. Aristotle was well known among medieval Muslim intellectuals and revered as The First Teacher and his ethics, though always influential, gained renewed interest with the modern advent of virtue ethics. All aspects of Aristotles philosophy continue to be the object of academic study today. Though Aristotle wrote many elegant treatises and dialogues – Cicero described his style as a river of gold – it is thought that only around a third of his original output has survived. Aristotle, whose means the best purpose, was born in 384 BC in Stagira, Chalcidice. His father Nicomachus was the physician to King Amyntas of Macedon. Aristotle was orphaned at a young age, although there is little information on Aristotles childhood, he probably spent some time within the Macedonian palace, making his first connections with the Macedonian monarchy. At the age of seventeen or eighteen, Aristotle moved to Athens to continue his education at Platos Academy and he remained there for nearly twenty years before leaving Athens in 348/47 BC. Aristotle then accompanied Xenocrates to the court of his friend Hermias of Atarneus in Asia Minor, there, he traveled with Theophrastus to the island of Lesbos, where together they researched the botany and zoology of the island. Aristotle married Pythias, either Hermiass adoptive daughter or niece and she bore him a daughter, whom they also named Pythias. Soon after Hermias death, Aristotle was invited by Philip II of Macedon to become the tutor to his son Alexander in 343 BC, Aristotle was appointed as the head of the royal academy of Macedon. During that time he gave not only to Alexander
21.
Kreutz sungrazer
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The Kreutz sungrazers are a family of sungrazing comets, characterized by orbits taking them extremely close to the Sun at perihelion. They are believed to be fragments of one large comet that broke up several centuries ago and are named for German astronomer Heinrich Kreutz, several members of the Kreutz family have become great comets, occasionally visible near the Sun in the daytime sky. The most recent of these was Comet Ikeya–Seki in 1965, which may have one of the brightest comets in the last millennium. It has been suggested that another cluster of bright Kreutz system comets may begin to arrive in the inner Solar System in the few years to decades. Many hundreds of members of the family, some only a few meters across, have been discovered since the launch of the SOHO satellite in 1995. None of these smaller comets have survived its perihelion passage, larger sungrazers such as the Great Comet of 1843 and C/2011 W3 have survived their perihelion passage. Amateur astronomers have been successful at discovering Kreutz comets in the data available in time via the Internet. The first comet whose orbit had been found to take it close to the Sun was the Great Comet of 1680. This comet was found to have passed just 200,000 km above the Suns surface and it thus became the first known sungrazing comet. Its perihelion distance was just 1.3 solar radii, astronomers at the time, including Edmond Halley, speculated that this comet was a return of a bright comet seen close to the Sun in the sky in 1106. 163 years later, the Great Comet of 1843 appeared and also passed close to the Sun. Despite orbital calculations showing that it had a period of several centuries, a bright comet seen in 1880 was found to be travelling on an almost identical orbit to that of 1843, as was the subsequent Great Comet of 1882. An alternative suggestion was that the comets were all fragments of an earlier Sun-grazing comet and this idea was first proposed in 1880, and its plausibility was amply demonstrated when the Great Comet of 1882 broke up into several fragments after its perihelion passage. In 1888, Heinrich Kreutz published a paper showing that the comets of 1843,1880, the comet of 1680 proved to be unrelated to this family of comets. After another Kreutz sungrazer was seen in 1887, the one did not appear until 1945. Two further sungrazers appeared in the 1960s, Comet Pereyra in 1963 and Comet Ikeya–Seki, which became bright in 1965. The appearance of two Kreutz Sungrazers in quick succession inspired further study of the dynamics of the group, the group generally has an Inclination of roughly 140 degrees, a perihelion distance of around 0.01 AU, and a Longitude of ascending node of 340–10°. The brightest members of the Kreutz sungrazers have been spectacular, easily visible in the daytime sky, the three most impressive have been the Great Comet of 1843, the Great Comet of 1882 and Comet Ikeya–Seki
22.
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
23.
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
24.
Potassium
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Potassium is a chemical element with symbol K and atomic number 19. It was first isolated from potash, the ashes of plants, in the periodic table, potassium is one of the alkali metals. Potassium in nature only in ionic salts. It is found dissolved in sea water, and is part of many minerals, naturally occurring potassium is composed of three isotopes, of which 40K is radioactive. Traces of 40K are found in all potassium, and it is the most common radioisotope in the human body, Potassium is chemically very similar to sodium, the previous element in Group 1 of the periodic table. They have a similar energy, which allows for each atom to give up its sole outer electron. That they are different elements combine with the same anions to make similar salts was suspected in 1702. Most industrial applications of potassium exploit the high solubility in water of potassium compounds, heavy crop production rapidly depletes the soil of potassium, and this can be remedied with agricultural fertilizers containing potassium, accounting for 95% of global potassium chemical production. Potassium ions are necessary for the function of all living cells, fresh fruits and vegetables are good dietary sources of potassium. Potassium is the second least dense metal after lithium and it is a soft solid with a low melting point, and can be easily cut with a knife. Freshly cut potassium is silvery in appearance, but it begins to tarnish toward gray immediately on exposure to air, in a flame test, potassium and its compounds emit a lilac color with a peak emission wavelength of 766.5 nanometers. Neutral potassium atoms have 19 electrons, one more than the stable configuration of the noble gas argon. This process requires so little energy that potassium is readily oxidized by atmospheric oxygen, in contrast, the second ionization energy is very high, because removal of two electrons breaks the stable noble gas electronic configuration. Potassium therefore does not readily form compounds with the state of +2 or higher. Potassium is an active metal that reacts violently with oxygen in water. With oxygen it forms potassium peroxide, and with water potassium forms potassium hydroxide, the reaction of potassium with water is dangerous because of its violent exothermic character and the production of hydrogen gas. Hydrogen reacts again with atmospheric oxygen, producing water, which reacts with the remaining potassium and this reaction requires only traces of water, because of this, potassium and the liquid sodium-potassium — NaK — are potent desiccants that can be used to dry solvents prior to distillation. Because of the sensitivity of potassium to water and air, reactions with other elements are only in an inert atmosphere such as argon gas using air-free techniques
25.
Calcium
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Calcium is a chemical element with symbol Ca and atomic number 20. Calcium is a soft grayish-yellow alkaline earth metal, fifth-most-abundant element by mass in the Earths crust, the ion Ca2+ is also the fifth-most-abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, magnesium, and sulfate. Free calcium metal is too reactive to occur in nature, Calcium is produced in supernova nucleosynthesis. Calcium is a trace element in living organisms. It is the most abundant metal by mass in animals, and it is an important constituent of bone, teeth. In cell biology, the movement of the calcium ion into, Calcium carbonate and calcium citrate are often taken as dietary supplements. Calcium is on the World Health Organizations List of Essential Medicines, Calcium has a wide variety of applications, almost all of which are associated with calcium compounds and salts. Calcium metal is used as a deoxidizer, desulfurizer, and decarbonizer for production of ferrous and nonferrous alloys. In steelmaking and production of iron, Ca reacts with oxygen, Calcium carbonate is used in manufacturing cement and mortar, lime, limestone and aids in production in the glass industry. It also has chemical and optical uses as mineral specimens in toothpastes, Calcium hydroxide solution is used to detect the presence of carbon dioxide in a gas sample bubbled through a solution. The solution turns cloudy where CO2 is present, Calcium arsenate is used in insecticides. Calcium carbide is used to make acetylene gas and various plastics, Calcium chloride is used in ice removal and dust control on dirt roads, as a conditioner for concrete, as an additive in canned tomatoes, and to provide body for automobile tires. Calcium citrate is used as a food preservative, Calcium cyclamate is used as a sweetening agent in several countries. In the United States, it has been outlawed as a suspected carcinogen, Calcium gluconate is used as a food additive and in vitamin pills. Calcium hypochlorite is used as a swimming pool disinfectant, as an agent, as an ingredient in deodorant. Calcium permanganate is used in rocket propellant, textile production, as a water sterilizing agent. Calcium phosphate is used as a supplement for animal feed, fertilizer, in production for dough and yeast products, in the manufacture of glass. Calcium phosphide is used in fireworks, rodenticide, torpedoes, Calcium sulfate is used as common blackboard chalk, as well as, in its hemihydrate form, Plaster of Paris
26.
Chromium
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Chromium is a chemical element with symbol Cr and atomic number 24. It is the first element in Group 6 and it is a steely-grey, lustrous, hard and brittle metal which takes a high polish, resists tarnishing, and has a high melting point. The name of the element is derived from the Greek word χρῶμα, chrōma, meaning color, Chromium metal is of high value for its high corrosion resistance and hardness. A major development was the discovery that steel could be highly resistant to corrosion and discoloration by adding metallic chromium to form stainless steel. Stainless steel and chrome plating together comprise 85% of the commercial use, trivalent chromium ion is an essential nutrient in trace amounts in humans for insulin, sugar and lipid metabolism, although the issue is debated. While chromium metal and Cr ions are not considered toxic, hexavalent chromium is toxic and carcinogenic, abandoned chromium production sites often require environmental cleanup. Chromium is remarkable for its properties, it is the only elemental solid which shows antiferromagnetic ordering at room temperature. Above 38 °C, it changes to paramagnetic, Chromium metal left standing in air is passivated by oxidation, forming a thin, protective, surface layer. This layer is a structure only a few molecules thick. It is very dense, and prevents the diffusion of oxygen into the underlying metal and this is different from the oxide that forms on iron and carbon steel, through which elemental oxygen continues to migrate, reaching the underlying material to cause incessant rusting. Passivation can be enhanced by short contact with oxidizing acids like nitric acid, passivated chromium is stable against acids. Passivation can be removed with a reducing agent that destroys the protective oxide layer on the metal. Chromium metal treated in this way readily dissolves in weak acids, Chromium, unlike such metals as iron and nickel, does not suffer from hydrogen embrittlement. However, it suffer from nitrogen embrittlement, reacting with nitrogen from air. Chromium is the 22nd most abundant element in Earths crust with a concentration of 100 ppm. Chromium compounds are found in the environment from the erosion of chromium-containing rocks, Chromium is mined as chromite ore. About two-fifths of the ores and concentrates in the world are produced in South Africa, while Kazakhstan, India, Russia. Untapped chromite deposits are plentiful, but geographically concentrated in Kazakhstan, although rare, deposits of native chromium exist
27.
Cobalt
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Cobalt is a chemical element with symbol Co and atomic number 27. Like nickel, cobalt is found in the Earths crust only in chemically combined form, the free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal. In 1735, such ores were found to be reducible to a new metal, today, some cobalt is produced specifically from various metallic-lustered ores, for example cobaltite, but the main source of the element is as a by-product of copper and nickel mining. The copper belt in the Democratic Republic of the Congo, Central African Republic, cobalt is primarily used in the preparation of magnetic, wear-resistant and high-strength alloys. The compounds, cobalt silicate and cobalt aluminate give a deep blue color to glass, ceramics, inks, paints. Cobalt occurs naturally as only one isotope, cobalt-59. Cobalt-60 is an important radioisotope, used as a radioactive tracer. Cobalt is the center of coenzymes called cobalamins, the most common example of which is vitamin B12. As such, it is a trace dietary mineral for all animals. Cobalt in inorganic form is also a micronutrient for bacteria, algae, cobalt is a ferromagnetic metal with a specific gravity of 8.9. The Curie temperature is 1,115 °C and the moment is 1. 6–1.7 Bohr magnetons per atom. Cobalt has a relative permeability two-thirds that of iron, metallic cobalt occurs as two crystallographic structures, hcp and fcc. The ideal transition temperature between the hcp and fcc structures is 450 °C, but in practice, the difference is so small that random intergrowth of the two is common. Cobalt is a weakly reducing metal that is protected from oxidation by an oxide film. It is attacked by halogens and sulfur, heating in oxygen produces Co3O4 which loses oxygen at 900 °C to give the monoxide CoO. The metal reacts with fluorine at 520 K to give CoF3, with chlorine, bromine and iodine and it does not react with hydrogen gas or nitrogen gas even when heated, but it does react with boron, carbon, phosphorus, arsenic and sulfur. At ordinary temperatures, it reacts slowly with mineral acids, and very slowly with moist, common oxidation states of cobalt include +2 and +3, although compounds with oxidation states ranging from −3 to +5 are also known. A common oxidation state for simple compounds is +2 and these salts form the pink-colored metal aquo complex 2+ in water
28.
Manganese
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Manganese is a chemical element with symbol Mn and atomic number 25. It is not found as an element in nature, it is often found in minerals in combination with iron. Manganese is a metal with important industrial metal alloy uses, particularly in stainless steels, by the mid-18th century, Swedish chemist Carl Wilhelm Scheele had used pyrolusite to produce chlorine. Scheele and others were aware that pyrolusite contained a new element, johan Gottlieb Gahn was the first to isolate an impure sample of manganese metal in 1774, which he did by reducing the dioxide with carbon. Manganese phosphating is used for rust and corrosion prevention on steel, ionized manganese is used industrially as pigments of various colors, which depend on the oxidation state of the ions. The permanganates of alkali and alkaline earth metals are powerful oxidizers, Manganese dioxide is used as the cathode material in zinc-carbon and alkaline batteries. In biology, manganese ions function as cofactors for a variety of enzymes with many functions. Manganese enzymes are essential in detoxification of superoxide free radicals in organisms that must deal with elemental oxygen. Manganese also functions in the complex of photosynthetic plants. The element is a trace mineral for all known living organisms but is a neurotoxin. In larger amounts, and apparently with far greater effectiveness through inhalation, Manganese is a silvery-gray metal that resembles iron. It is hard and very brittle, difficult to fuse, Manganese metal and its common ions are paramagnetic. Manganese tarnishes slowly in air and oxidizes like iron in water containing dissolved oxygen, naturally occurring manganese is composed of one stable isotope, 55Mn. Eighteen radioisotopes have been isolated and described, the most stable being 53Mn with a half-life of 3.7 million years, 54Mn with a half-life of 312.3 days, and 52Mn with a half-life of 5.591 days. All of the radioactive isotopes have half-lives of less than three hours, and the majority of less than one minute. Manganese also has three meta states, Manganese is part of the iron group of elements, which are thought to be synthesized in large stars shortly before the supernova explosion. 53Mn decays to 53Cr with a half-life of 3.7 million years, because of its relatively short half-life, 53Mn is relatively rare, produced by cosmic rays impact on iron. Manganese isotopic contents are combined with chromium isotopic contents and have found application in isotope geology
29.
Copper
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Copper is a chemical element with symbol Cu and atomic number 29. It is a soft, malleable, and ductile metal with high thermal and electrical conductivity. A freshly exposed surface of copper has a reddish-orange color. Copper is one of the few metals that occur in nature in directly usable metallic form as opposed to needing extraction from an ore and this led to very early human use, from c.8000 BC. Copper used in buildings, usually for roofing, oxidizes to form a green verdigris, Copper is sometimes used in decorative art, both in its elemental metal form and in compounds as pigments. Copper compounds are used as agents, fungicides, and wood preservatives. Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the enzyme complex cytochrome c oxidase. In molluscs and crustaceans, copper is a constituent of the blood pigment hemocyanin, replaced by the hemoglobin in fish. In humans, copper is found mainly in the liver, muscle, the adult body contains between 1.4 and 2.1 mg of copper per kilogram of body weight. The filled d-shells in these elements contribute little to interatomic interactions, unlike metals with incomplete d-shells, metallic bonds in copper are lacking a covalent character and are relatively weak. This observation explains the low hardness and high ductility of single crystals of copper, at the macroscopic scale, introduction of extended defects to the crystal lattice, such as grain boundaries, hinders flow of the material under applied stress, thereby increasing its hardness. For this reason, copper is supplied in a fine-grained polycrystalline form. The softness of copper partly explains its high conductivity and high thermal conductivity. The maximum permissible current density of copper in open air is approximately 3. 1×106 A/m2 of cross-sectional area, Copper is one of a few metallic elements with a natural color other than gray or silver. Pure copper is orange-red and acquires a reddish tarnish when exposed to air, as with other metals, if copper is put in contact with another metal, galvanic corrosion will occur. A green layer of verdigris can often be seen on old structures, such as the roofing of many older buildings. Copper tarnishes when exposed to sulfur compounds, with which it reacts to form various copper sulfides. There are 29 isotopes of copper, 63Cu and 65Cu are stable, with 63Cu comprising approximately 69% of naturally occurring copper, both have a spin of 3⁄2
30.
Vanadium
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Vanadium is a chemical element with symbol V and atomic number 23. It is a hard, silvery grey, ductile, and malleable transition metal, the elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer stabilizes the free metal somewhat against further oxidation. Four years later, however, he was convinced by other scientists that erythronium was identical to chromium, both names were attributed to the wide range of colors found in vanadium compounds. Del Rios lead mineral was later renamed vanadinite for its vanadium content, in 1867 Henry Enfield Roscoe obtained the pure element. Vanadium occurs naturally in about 65 different minerals and in fossil fuel deposits and it is produced in China and Russia from steel smelter slag, other countries produce it either from the flue dust of heavy oil, or as a byproduct of uranium mining. It is mainly used to produce specialty steel alloys such as high-speed tool steels, the most important industrial vanadium compound, vanadium pentoxide, is used as a catalyst for the production of sulfuric acid. Large amounts of ions are found in a few organisms. The oxide and some salts of vanadium have moderate toxicity. Particularly in the ocean, vanadium is used by life forms as an active center of enzymes. Vanadium was discovered by Andrés Manuel del Río, a Spanish-Mexican mineralogist, Del Río extracted the element from a sample of Mexican brown lead ore, later named vanadinite. He found that its salts exhibit a variety of colors. Later, Del Río renamed the element erythronium because most of the salts turned red upon heating, Del Río accepted Collet-Descotils statement and retracted his claim. In 1831, the Swedish chemist Nils Gabriel Sefström rediscovered the element in a new oxide he found working with iron ores. Later that same year, Friedrich Wöhler confirmed del Ríos earlier work, Sefström chose a name beginning with V, which had not been assigned to any element yet. He called the element vanadium after Old Norse Vanadís, because of the many beautifully colored chemical compounds it produces, in 1831, the geologist George William Featherstonhaugh suggested that vanadium should be renamed rionium after del Río, but this suggestion was not followed. The isolation of vanadium metal proved difficult, in 1831, Berzelius reported the production of the metal, but Henry Enfield Roscoe showed that Berzelius had in fact produced the nitride, vanadium nitride. Roscoe eventually produced the metal in 1867 by reduction of chloride, VCl2. In 1927, pure vanadium was produced by reducing vanadium pentoxide with calcium, the first large-scale industrial use of vanadium was in the steel alloy chassis of the Ford Model T, inspired by French race cars
31.
Solwind
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P78-1 or Solwind was a United States satellite launched aboard an Atlas F rocket from Vandenberg Air Force Base in California on February 24,1979. The satellite operated until it was destroyed in orbit on September 13,1985 to test the ASM-135 ASAT anti-satellite missile, the satellites Orbiting Solar Observatory platform included a solar-oriented sail and a rotating wheel section. Ball Aerospace was the contractor for design and construction, and provided the attitude control. The X-ray monitor, designated NRL-608 or XMON, was a collaboration between the Naval Research Laboratory and Los Alamos National Laboratory, the white-light coronagraph and the ultraviolet imager were combined in a single package, designated NRL-401 or SOLWIND, which was built by the Naval Research Laboratory. The coronagraph was the spare of the white-light coronagraph on the OSO-7 satellite. The ultraviolet imager used a CCD imager, one of the first uses of a CCD in space, p78-1 was the first satellite in space to discover a comet in general and a sungrazing comet in particular. Its perihelion distance of 0.1051 AU was at least ten times larger than that of the previously found true sungrazers, by 1985, the satellites batteries were degrading. This caused more and more frequent under-voltage cutoffs, a condition where the satellite detected a low main bus voltage and automatically shut down all non-vital systems. In addition, the last of the three tape recorders failed in the spring of 1985, so data collection could only occur while the spacecraft was in contact with a ground station, a normal contact lasted only about 15 minutes, so this was a serious impediment. Special arrangements could be made to string several contacts together, as a result of these failures, an ever-increasing amount of time and network resources were spent reconfiguring the satellite for normal operation. Data collection from the few remaining payloads was severely limited, because of the additional burden on the Air Force Satellite Control Network, discussions were already underway to terminate the mission. This led to the satellite being chosen as a test target for an ASM-135 ASAT anti-satellite missile, the mission was extended for several weeks solely to support the test. During this final phase, the satellite was often allowed to remain in the condition for several days at a time. On September 13,1985, the satellite was destroyed in orbit at 2043 UTC at 35°N 126°W with an altitude of 525 kilometres by an ASM-135 ASAT launched from a US Air Force F-15 Eagle fighter aircraft, the test resulted in 285 cataloged pieces of orbital debris. 1 piece of debris remained in orbit to at least May 2004, but had deorbited by 2008
32.
Solar Maximum Mission
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The Solar Maximum Mission satellite was designed to investigate Solar phenomena, particularly solar flares. It was launched on February 14,1980, the Solar Maximum Mission ended on December 2,1989, when the spacecraft re-entered the atmosphere and burned up. In November 1980, the second of four fuses in SMMs attitude control system failed, in this mode, only three of the seven instruments on board were usable, as the others required the satellite to be accurately pointed at the Sun. The use of the satellites magnetorquers prevented the satellite from being used in a stable position, three attempts to grapple the satellite using the TPAD failed. The TPAD jaws could not lock onto Solar Max because of an obstructing grommet on the satellite not included in its blueprints and this led to an improvised plan which nearly ended the satellites mission. The improvisation had the astronaut use his hands to hold of a solar array. Instead, this attempt induced higher rates and in multiple axes, SMM Operations Control Center engineers shut down all non-essential satellite subsystems and with a bit of luck were able to recover the satellite minutes before total failure. The ground support engineers then stabilized the satellite and nulled its rotation rates for capture with the Shuttles robotic arm and this proved to be a much better plan. The satellite had been fitted with one of the grapple fixtures so that the robotic arm was able to capture. Their successful work added five years to the lifespan of the satellite. The mission was depicted in the 1985 IMAX movie The Dream Is Alive, significantly, the SMMs ACRIM instrument package showed that contrary to expectations, the Sun is actually brighter during the sunspot cycle maximum. This is because sunspots are surrounded by bright features called faculae, the major scientific findings from the SMM are presented in several review articles in a monograph. The SMM discovered ten sungrazing comets between 1987 and 1989
33.
Solar and Heliospheric Observatory
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It began normal operations in May 1996. It is a joint project of cooperation between the European Space Agency and NASA. Originally planned as a mission, SOHO continues to operate after over 20 years in space. In June 2013, a mission lasting until December 2016 was approved. In addition to its mission, it is the main source of near-real-time solar data for space weather prediction. Rather it lies in the plane passes through L1 and is perpendicular to the line connecting the Sun. It stays in this plane, tracing out an elliptical lissajous orbit centered about L1 and it orbits L1 once every six months, while L1 itself orbits the Sun every 12 months as it is coupled with the motion of the Earth. This keeps SOHO at a position for communication with Earth at all times. In normal operation the spacecraft transmits a continuous 200 kbit/s data stream of photographs, SOHOs data about solar activity are used to predict coronal mass ejection arrival times at earth, so electrical grids and satellites can be protected from their damaging effects. CMEs directed toward the earth may produce geomagnetic storms, which in turn produce geomagnetically induced currents, in the most extreme cases creating black-outs, etc. In 2003 ESA reported the failure of the antenna Y-axis stepper motor, necessary for pointing the high-gain antenna, at the time, it was thought that the antenna anomaly might cause two- to three-week data-blackouts every three months. The SOHO Mission Interruption sequence of events began on June 24,1998, while the SOHO Team was conducting a series of spacecraft gyroscope calibrations and maneuvers. Operations proceeded until 23,16 UTC when SOHO lost lock on the Sun, the SOHO Team attempted to recover the observatory, but SOHO entered the emergency mode again on June 2502,35 UTC. Recovery efforts continued, but SOHO entered the emergency mode for the last time at 04,38 UTC, all contact with SOHO was lost, and the mission interruption had begun. SOHO was spinning, losing power, and no longer pointing at the Sun. Expert ESA personnel were dispatched from Europe to the United States to direct operations. Days passed without contact from SOHO, on July 23, the Arecibo Observatory and Goldstone Solar System Radar combined to locate SOHO with radar, and to determine its location and attitude. SOHO was close to its position, oriented with its side versus the usual front Optical Surface Reflector panel pointing toward the Sun
34.
Naked eye
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Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying or light-collecting optical device, such as a telescope or microscope. Vision corrected to normal acuity using corrective lenses is considered naked, in astronomy, the naked eye may be used to observe events that can be viewed without equipment, such as an astronomical conjunction, the passage of a comet, or a meteor shower. Sky lore and various tests demonstrate a wealth of phenomena that can be seen with the unaided eye. The basic accuracies of the eye are, Quick autofocus from distances of 25 cm to 50 cm to infinity. Angular resolution, about 1 arcminute, approximately 0. 02° or 0.0003 radians, field of view, simultaneous visual perception in an area of about 160° × 175°. Faint stars up to +8 magnitude under a dark sky. Photometry to ±10% or 1% of intensity – in a range between night and day of 1,10,000,000,000, symmetries of 10–20, see the measurements of Tycho Brahe and the Egyptians. Even a few hundred kilometers away from an area where the sky can appear to be very dark. For most people, these are likely to be the best observing conditions within their reach, under such typical dark sky conditions, the naked eye can see stars with an apparent magnitude up to +6m. Under perfect dark sky conditions where all light pollution is absent, the angular resolution of the naked eye is about 1′, however, some people have sharper vision than that. There is anecdotal evidence that people had seen the Galilean moons of Jupiter before telescopes were invented, Uranus, when discovered in 1781, was the first planet discovered using technology rather than being spotted by the naked eye. In practice, the extinction and dust reduces this number somewhat. In the center of a city, where the limiting magnitude due to extreme amounts of light pollution can be +4m or less. Colors can be seen but this is limited by the fact that the eye uses rods instead of cones to view fainter stars, the visibility of diffuse objects such as star clusters and galaxies is much more strongly affected by light pollution than is that of planets and stars. Under typical dark conditions only a few objects are visible. The Triangulum Galaxy is a difficult averted vision object and only visible at all if it is higher than 50° in the sky, the globular clusters M3 in Canes Venatici and M92 in Hercules are also visible with the naked eye under such conditions. Under really dark sky conditions, however, M33 is easy to see, many other Messier objects are also visible under such conditions. The most distant objects that have seen by the naked eye are nearby bright galaxies such as Centaurus A, Bodes Galaxy, Sculptor Galaxy
35.
Apparent magnitude
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The apparent magnitude of a celestial object is a number that is a measure of its brightness as seen by an observer on Earth. The brighter an object appears, the lower its magnitude value, the Sun, at apparent magnitude of −27, is the brightest object in the sky. It is adjusted to the value it would have in the absence of the atmosphere, furthermore, the magnitude scale is logarithmic, a difference of one in magnitude corresponds to a change in brightness by a factor of 5√100, or about 2.512. The measurement of apparent magnitudes or brightnesses of celestial objects is known as photometry, apparent magnitudes are used to quantify the brightness of sources at ultraviolet, visible, and infrared wavelengths. An apparent magnitude is measured in a specific passband corresponding to some photometric system such as the UBV system. In standard astronomical notation, an apparent magnitude in the V filter band would be denoted either as mV or often simply as V, the scale used to indicate magnitude originates in the Hellenistic practice of dividing stars visible to the naked eye into six magnitudes. The brightest stars in the sky were said to be of first magnitude, whereas the faintest were of sixth magnitude. Each grade of magnitude was considered twice the brightness of the following grade and this rather crude scale for the brightness of stars was popularized by Ptolemy in his Almagest, and is generally believed to have originated with Hipparchus. This implies that a star of magnitude m is 2.512 times as bright as a star of magnitude m +1 and this figure, the fifth root of 100, became known as Pogsons Ratio. The zero point of Pogsons scale was defined by assigning Polaris a magnitude of exactly 2. However, with the advent of infrared astronomy it was revealed that Vegas radiation includes an Infrared excess presumably due to a disk consisting of dust at warm temperatures. At shorter wavelengths, there is negligible emission from dust at these temperatures, however, in order to properly extend the magnitude scale further into the infrared, this peculiarity of Vega should not affect the definition of the magnitude scale. Therefore, the scale was extrapolated to all wavelengths on the basis of the black body radiation curve for an ideal stellar surface at 11000 K uncontaminated by circumstellar radiation. On this basis the spectral irradiance for the zero magnitude point, with the modern magnitude systems, brightness over a very wide range is specified according to the logarithmic definition detailed below, using this zero reference. In practice such apparent magnitudes do not exceed 30, astronomers have developed other photometric zeropoint systems as alternatives to the Vega system. The AB magnitude zeropoint is defined such that an objects AB, the dimmer an object appears, the higher the numerical value given to its apparent magnitude, with a difference of 5 magnitudes corresponding to a brightness factor of exactly 100. Since an increase of 5 magnitudes corresponds to a decrease in brightness by a factor of exactly 100, each magnitude increase implies a decrease in brightness by the factor 5√100 ≈2.512. Inverting the above formula, a magnitude difference m1 − m2 = Δm implies a brightness factor of F2 F1 =100 Δ m 5 =100.4 Δ m ≈2.512 Δ m
36.
Amorphous solid
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In condensed matter physics and materials science, an amorphous or non-crystalline solid is a solid that lacks the long-range order that is characteristic of a crystal. In some older books, the term has been used synonymously with glass, nowadays, glassy solid or amorphous solid is considered to be the overarching concept, and glass the more special case, A glass is an amorphous solid that exhibits a glass transition. Other types of solids include gels, thin films. Amorphous materials have a structure made of interconnected structural blocks. Even amorphous materials have some shortrange order at the length scale due to the nature of chemical bonding. Furthermore, in small crystals a large fraction of the atoms are the crystal, relaxation of the surface and interfacial effects distort the atomic positions. Amorphous phases are important constituents of thin films, which are layers of a few nm to some tens of µm thickness deposited upon a substrate. For higher values, the diffusion of deposited atomic species would allow for the formation of crystallites with long range atomic order. Regarding their applications, amorphous metallic layers played an important role in the discussion of a suspected superconductivity in amorphous metals, today, optical coatings made from TiO2, SiO2, Ta2O5 etc. and combinations of them in most cases consist of amorphous phases of these compounds. Much research is carried out into thin films as a gas separating membrane layer. Also, hydrogenated amorphous silicon, a-Si, H in short, is of significance for thin film solar cells. In case of a-Si, H the missing long-range order between silicon atoms is partly induced by the presence by hydrogen in the percent range, the occurrence of amorphous phases turned out as a phenomenon of particular interest for studying thin film growth. Remarkably, the growth of polycrystalline films is used and preceded by an initial amorphous layer. The most investigated example is represented by thin multicrystalline silicon films, an initial amorphous layer was observed in many studies. The phenomenon has been interpreted in the framework of Ostwalds rule of stages that predicts the formation of phases to proceed with increasing condensation time towards increasing stability. Experimental studies of the phenomenon require a clearly defined state of the substrate surface, the Physics of Structurally Disordered Matter, An Introduction. Amorphous Solids and the Liquid State
37.
Olivine
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The mineral olivine is a magnesium iron silicate with the formula 2SiO4. Thus it is a type of nesosilicate or orthosilicate and it is a common mineral in the Earths subsurface but weathers quickly on the surface. The ratio of magnesium and iron varies between the two endmembers of the solid solution series, forsterite and fayalite, compositions of olivine are commonly expressed as molar percentages of forsterite and fayalite. Forsterite has a high melting temperature at atmospheric pressure, almost 1,900 °C. The melting temperature varies smoothly between the two endmembers, as do other properties, olivine incorporates only minor amounts of elements other than oxygen, silicon, magnesium and iron. Manganese and nickel commonly are the elements present in highest concentrations. Olivine gives its name to the group of minerals with a structure which includes tephroite, monticellite and kirschsteinite. It has a structure similar to magnetite but uses one quadravalent. Olivine gemstones are called peridot and chrysolite, olivine is named for its typically olive-green color, though it may alter to a reddish color from the oxidation of iron. Translucent olivine is sometimes used as a gemstone called peridot, some of the finest gem-quality olivine has been obtained from a body of mantle rocks on Zabargad island in the Red Sea. Olivine occurs in mafic and ultramafic igneous rocks and as a primary mineral in certain metamorphic rocks. Mg-rich olivine crystallizes from magma that is rich in magnesium and low in silica and that magma crystallizes to mafic rocks such as gabbro and basalt. Ultramafic rocks such as peridotite and dunite can be left after extraction of magmas. Olivine and high pressure structural variants constitute over 50% of the Earths upper mantle, the metamorphism of impure dolomite or other sedimentary rocks with high magnesium and low silica content also produces Mg-rich olivine, or forsterite. In contrast, Mg-rich olivine does not occur stably with silica minerals, Mg-rich olivine is stable to pressures equivalent to a depth of about 410 km within Earth. Mg-rich olivine has also discovered in meteorites, on the Moon and Mars, falling into infant stars. Such meteorites include chondrites, collections of debris from the early Solar System, the spectral signature of olivine has been seen in the dust disks around young stars. The tails of comets often have the signature of olivine
38.
Sublimation (phase transition)
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Sublimation is the phase transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase. Sublimation is a process that occurs at temperatures and pressures below a substances triple point in its phase diagram. The reverse process of sublimation is deposition or desublimation, in which a substance directly from a gas to a solid phase. Sublimation has also used as a generic term to describe a solid-to-gas transition followed by a gas-to-solid transition. At normal pressures, most chemical compounds and elements possess three different states at different temperatures, in these cases, the transition from the solid to the gaseous state requires an intermediate liquid state. The pressure referred to is the pressure of the substance. So, all solids that possess an appreciable vapor pressure at a temperature usually can sublimate in air. The term sublimation refers to a change of state and is not used to describe transformation of a solid to a gas in a chemical reaction. For example, the dissociation on heating of ammonium chloride into hydrogen chloride and ammonia is not sublimation. Similarly the combustion of candles, containing paraffin wax, to carbon dioxide and water vapor is not sublimation, sublimation requires additional energy and is an endothermic change. The enthalpy of sublimation can be calculated by adding the enthalpy of fusion, solid carbon dioxide sublimes everywhere along the line below the triple point, whereas its melting into liquid CO2 can occur only along the line at pressures and temperatures above the triple point. Snow and ice sublime, although more slowly, at temperatures below the freezing/melting point temperature line at 0 °C for most pressures, in freeze-drying, the material to be dehydrated is frozen and its water is allowed to sublime under reduced pressure or vacuum. The loss of snow from a snowfield during a spell is often caused by sunshine acting directly on the upper layers of the snow. Ablation is a process that includes sublimation and erosive wear of glacier ice, naphthalene, an organic compound commonly found in pesticide such as mothball also sublimes. It sublimes easily because it is made of molecules and has van der Waals intermolecular forces. Naphthalene is a solid that sublimes at atmospheric temperature with the sublimation point at around 80˚C or 176˚F. At low temperature, its pressure is high enough,1 mmHg at 53˚C. On the cool surface, the sublimated vapour will be solidified to form a needle-like crystal, iodine produces fumes on gentle heating
39.
Pyroxene
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The pyroxenes are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes are silicon-aluminum oxides with Ca, Na, Fe, Mg, Zn, Mn, Li substituting for Si, although aluminium substitutes extensively for silicon in silicates such as feldspars and amphiboles, the substitution occurs only to a limited extent in most pyroxenes. They share a structure consisting of single chains of silica tetrahedra. The name pyroxene is derived from the Ancient Greek words for fire, however, they are simply early-forming minerals that crystallized before the lava erupted. The upper mantle of Earth is composed mainly of olivine and pyroxene, a piece of the mantle is shown at right and is dominated by olivine, typical for common peridotite. Pyroxene and feldspar are the minerals in basalt and gabbro. Pyroxene minerals are named according to the chemical species occupying the X site, the Y site, cations in Y site are closely bound to 6 oxygens in octahedral coordination. Cations in the X site can be coordinated with 6 to 8 oxygen atoms, twenty mineral names are recognised by the International Mineralogical Associations Commission on New Minerals and Mineral Names and 105 previously used names have been discarded. A typical pyroxene has mostly silicon in the site and predominately ions with a charge of +2 in both the X and Y sites, giving the approximate formula XYT2O6. The names of the common calcium – iron – magnesium pyroxenes are defined in the pyroxene quadrilateral shown in Figure 2, the enstatite-ferrosilite series contain up to 5 mol. % calcium and exists in three polymorphs, orthorhombic orthoenstatite and protoenstatite and monoclinic clinoenstatite. Increasing the calcium content prevents the formation of the orthorhombic phases, there is not complete solid solution in calcium content and Mg-Fe-Ca pyroxenes with calcium contents between about 15 and 25 mol. % are not stable with respect to a pair of exolved crystals. This leads to a miscibility gap between pigeonite and augite compositions, there is an arbitrary separation between augite and the diopside-hedenbergite solid solution. The divide is taken at >45 mol. % Ca, as the calcium ion cannot occupy the Y site, pyroxenes with more than 50 mol. % calcium are not possible. A related mineral wollastonite has the formula of the hypothetical calcium end member, magnesium, calcium and iron are by no means the only cations that can occupy the X and Y sites in the pyroxene structure. A second important series of minerals are the sodium-rich pyroxenes. The inclusion of sodium, which has a charge of +1, in jadeite and aegirine this is added by the inclusion of a +3 cation on the Y site. Table 1 shows the range of other cations that can be accommodated in the pyroxene structure. For example, Na and Al give the jadeite composition, coupled substitution of a 1+ ion on the X site and a mixture of equal numbers of 2+ and 4+ ions on the Y site
40.
C/2011 W3 (Lovejoy)
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Comet Lovejoy, formally designated C/2011 W3, is a long-period comet and Kreutz Sungrazer. It was discovered in November 2011 by Australian amateur astronomer Terry Lovejoy, the comets perihelion took it through the Suns corona on 16 December 2011, after which it emerged intact, though greatly impacted by the event. Comet Lovejoy was discovered on 27 November 2011 by Terry Lovejoy of Thornlands, Queensland, during a survey using a 20 cm Schmidt–Cassegrain telescope. It is the comet discovered by Terry Lovejoy. He reported that it was a rapidly moving fuzzy object of 13th magnitude, upon confirmation, an official report was made to the Central Bureau for Astronomical Telegrams, and the comets existence was announced by the Minor Planet Center on 2 December. It is the first Kreutz-group comet discovered by ground-based observation in 40 years, further refinements were published during subsequent days, including one on 5 December, estimating perihelion at 0.0056 AU just before midnight on 15 December. On 11 December the first elliptical orbit was published, estimating perihelion at 0.0055 AU just after midnight on 16 December, in space, the comet first became visible to the STEREO-A spacecraft on 3 December, and to the SOHO spacecraft on 14 December. As the comet approached the Sun it was observed by eighteen instruments on six satellites, STEREO-A and -B, SOHO, SDO, Hinode, a small companion comet was detected in SOHO images on 14 December by Zhijian Xu, and later spotted by the twin STEREO spacecraft. It is believed to be a fragment of Comet Lovejoy that broke away several decades ago and this discovery was not unexpected, as Kreutz-group comets are often found with smaller companions. At its brightest, Comet Lovejoy had an apparent magnitude of between –3 and –4, which is about as bright as the planet Venus. It is the brightest sungrazing comet observed by SOHO, and the brightest comet to appear since Comet McNaught of 2007. Nevertheless, Lovejoy was largely invisible to the eye during its peak brightness due to its proximity to the Sun. Comet Lovejoy reached perihelion on 16 December 2011 at 00,17 UTC, as it passed approximately 140,000 kilometres above the Suns surface at a speed of 536 km/s, or 0. 18% the speed of light. It was not expected to survive the encounter due to conditions in the corona, such as temperatures reaching more than one million kelvins. However, the Solar Dynamics Observatory, as well as other Sun-monitoring spacecraft, the STEREO and SOHO spacecraft continued to observe the comet as it moved away from the Sun. Before perihelion, the nucleus of Comet Lovejoy had been estimated to be between 100 and 200 metres in diameter, since the comet survived perihelion, it is thought that the nucleus must have been larger, perhaps up to 500 metres. During the coronal passage, it is believed that a significant fraction of the mass was burned off. The first ground-based observation of Comet Lovejoy post-perihelion occurred on 16 December at 19,55 UTC, Baldridge estimated the comet at magnitude −1
41.
Full moon
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A full moon is the lunar phase that occurs when the Moon is completely illuminated as seen from Earth. This occurs when Earth is located directly between the Sun and the Moon and this means that the hemisphere of the Moon that is facing Earth is almost fully illuminated by the Sun and appears round. On some occasions at the time of full moon there is also a lunar eclipse so the face appears reddish due to the rayleigh scattering of blue light in Earths atmosphere. Lunar eclipses can occur only at full moon, where the Moons orbit allows it to pass through Earths shadow, Lunar eclipses do not occur every month because the Moon usually passes above or below Earths shadow. Lunar eclipses can only when the full moon occurs near the two nodes of the orbit, either the ascending or descending node. This causes eclipses to occur about every 6 months. The time interval between similar lunar phases—the synodic month—averages about 29.53 days, therefore, in those lunar calendars in which each month begins on the new moon, the full moon falls on either the 14th or 15th of the lunar month. Because calendar months have a number of days, lunar months may be either 29 or 30 days long. A full moon is thought of as an event of a full nights duration. This is somewhat misleading because the Moon seen from Earth is continuously becoming larger and/or smaller and its absolute maximum size occurs at the moment expansion has stopped. For any given location, about half of these absolute maximum full moons will be visible, as the other half occur during the day. Many almanacs list full moons not just by date, but by their time as well. Typical monthly calendars that include phases of the Moon may be offset by one day if intended for use in a different time zone, Full moons are generally a poor time to conduct astronomical observations, because the bright reflected sunlight from the Moon overwhelms the dimmer light from stars. On 12 December 2008, the moon occurred closer to the Earth than it had been at any time for the previous 15 years. On 19 March 2011, another full moon occurred, closer to the Earth than at any time for the previous ~18 years. On 14 November 2016, a full moon occurred closer to the Earth than at any time for the previous 68 years. The true time of a full moon may differ from this approximation by up to about 14.5 hours as a result of the non-circularity of the moons orbit, see New moon for an explanation of the formula and its parameters. The age and apparent size of the full moon vary in a cycle of just under 14 synodic months, Full moons are traditionally associated with temporal insomnia, insanity and various magical phenomena such as lycanthropy
42.
Comet ISON
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Comet ISON, formally known as C/2012 S1, was a sungrazing comet discovered on 21 September 2012 by Vitaly Nevsky and Artyom Novichonok. The discovery was made using the 0. 4-meter reflector of the International Scientific Optical Network near Kislovodsk, data processing was carried out by automated asteroid-discovery program CoLiTec. Precovery images by the Mount Lemmon Survey from 28 December 2011, follow-up observations were made on 22 September by a team from Remanzacco Observatory in Italy using the iTelescope network. The discovery was announced by the Minor Planet Center on 24 September, observations by Swift in January 2013 suggested that Comet ISONs nucleus was around 5 kilometers in diameter. Later estimates were that the nucleus was only about 2 kilometers in diameter, Mars Reconnaissance Orbiter observations suggested the nucleus was smaller than 0.8 kilometers in diameter. Shortly after Comet ISONs discovery, the media reported that it might become brighter than the full Moon, however, as events transpired, it never became bright enough to be readily visible to the naked eye. Furthermore, it broke apart as it passed close to the Sun, reports on 28 November 2013 indicated that Comet ISON had partially or completely disintegrated due to the Suns heat and tidal forces. However, later that day CIOC members discovered a coma-like feature, on 29 November 2013, the coma dimmed to an apparent magnitude of 5. By the end of 30 November 2013, the coma had further faded to below naked-eye visibility at magnitude 7, on 1 December, the coma continued to fade even further as it finished traversing the Solar and Heliospheric Observatorys view. On 2 December 2013, the CIOC announced that Comet ISON had fully disintegrated, the Hubble Space Telescope failed to detect fragments of ISON on 18 December 2013. On 8 May 2014, an examination of the disintegration was published. The team used ISONs 0. 4-meter reflector near Kislovodsk, Russia, shortly after their session, Nevski processed data using CoLiTec, an automated asteroid discovery software program. In analysis he noted an unusually bright object with slow apparent movement, at the time of discovery, the objects apparent magnitude ranged from 19.1 to as bright as 18.8. The group reported their discovery to the Central Bureau for Astronomical Telegrams as an asteroidal object, however, the group later reported that the object had a cometary appearance with a coma approximately 8 arcseconds across. Comet ISON was precovered in analysis of Mount Lemmon Observatory imagery by G. V. Williams, precovery images from Mount Lemmon were first taken on 28 December 2011 and indicated that the comet had an estimated apparent magnitude ranging from 19.5 to 19.9. Images from Pan-STARRS were taken on 28 January 2012 and in those images the comet had an apparent magnitude ranging from 19.8 to 20.6. Comet ISON came to perihelion on 28 November 2013 at a distance of 0.0124 AU from the point of the Sun. Accounting for the radius of 695,500 km, Comet ISON passed approximately 1,165,000 km above the Suns surface
43.
96P/Machholz
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On June 6,1986, comet 96P/Machholz passed 0.40373 AU from the Earth. Comet 96P/Machholz last came to perihelion on July 14,2012, 96P/Machholz has an estimated diameter of around 6.4 km. Machholz 1 is unusual among comets in several respects and its highly eccentric 5.2 year orbit has the smallest perihelion distance known among numbered/regular short-period comets, bringing it considerably closer to the Sun than the orbit of Mercury. It is also the only known short-period comet with both high orbital inclination and high eccentricity, in 2007, Machholz 1 was found to be both carbon-depleted and cyanogen-depleted, a chemical composition nearly unique among comets with known compositions. The chemical composition implies a different and possible extrasolar origin, the orbit of Machholz 1 corresponds to the Arietids and the Marsden and Kracht Comet groups. Its Tisserand parameter with respect to Jupiter, TJ, is 1.94, orbital integrations indicate that TJ was greater than 2 about 2500 years ago. Machholz 1 is currently in a 9,4 orbital resonance with Jupiter, 96P will not make another close approach to the Earth until 2028, when it will pass at a distance of 0.31972 AU. During the 2002 passage the comet brightened to magnitude −2, and was impressive as seen by SOHO. During the comets last perihelion passage in 2007, it appeared in SOHOs LASCO C3s field of view from April 2 to 6, peaking in brightness on April 4,2007, around magnitude +2. In these observations, its coma was substantially smaller than the Sun in volume, the most recent opportunity to observe Machholz 1 was when it returned to perihelion in 2012. Between July 12–17,2012, comet Machholz was visible in the SOHO LASCO/C3 field of view, two small faint fragments of Comet Machholz were detected in the SOHO C2 images. The fragments were 5 hours ahead of Comet Machholz, and probably fragmented from the comet during the 2007 perihelion passage, spectrographic analysis of the coma of Machholz 1 was made during its 2007 apparition, as part of the Lowell Observatory comet composition long-term observing program. These other comets had on average 72 times as much cyanogen as Machholz 1, the only comet previously seen with similar depletion both in carbon-chain molecules and cyanogens is Yanaka, but it has a substantially different orbit. There are currently three hypotheses to explain the composition of Machholz 1. One hypothesis for the difference is that Machholz 1 was a comet from outside the Solar System and was captured by the Sun. Other possibilities are that it formed in a cold region of the Solar System. Given how close it approaches the Sun at perihelion, repeated baking by the Sun has stripped most of its cyanogen
44.
Meteoroid
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A meteoroid is a small rocky or metallic body in outer space. Meteoroids are significantly smaller than asteroids, and range in size from small grains to 1 meter-wide objects, objects smaller than this are classified as micrometeoroids or space dust. Most are fragments from comets or asteroids, whereas others are collision impact debris ejected from bodies such as the Moon or Mars and this phenomenon is called a meteor or shooting star. A series of many meteors appearing seconds or minutes apart and appearing to originate from the fixed point in the sky is called a meteor shower. If that object withstands ablation from its passage through the atmosphere as a meteor and impacts with the ground, an estimated 15,000 tonnes of meteoroids, micrometeoroids and different forms of space dust enter Earths atmosphere each year. In 1995, Beech and Steel, writing in the Quarterly Journal of the Royal Astronomical Society, according to Rubin and Grossman, the minimum size of an asteroid is given by what can be discovered from Earth-bound telescopes, so the distinction between meteoroid and asteroid is fuzzy. Some of the smallest asteroids discovered are 2008 TS26 with H =33.2 and 2011 CQ1 with H =32.1 both with a size of 1 meter. Objects smaller than meteoroids are classified as micrometeoroids and cosmic dust, the Minor Planet Center does not use the term meteoroid. Almost all meteoroids contain extraterrestrial nickel and iron and they have three main classifications, iron, stone, and stony-iron. Some stone meteoroids contain grain-like inclusions known as chondrules and are called chondrites, stoney meteoroids without these features are called achondrites, which are typically formed from extraterrestrial igneous activity, they contain little or no extraterrestrial iron. The composition of meteoroids can be inferred as they pass through Earths atmosphere from their trajectories and their effects on radio signals also give information, especially useful for daytime meteors, which are otherwise very difficult to observe. From these trajectory measurements, meteoroids have been found to have many different orbits, some clustering in streams associated with a parent comet. Debris from meteoroid streams may eventually be scattered into other orbits, the study of meteorites also gives insights into the composition of non-ephemeral meteoroids. Most meteoroids come from the belt, having been perturbed by the gravitational influences of planets. Some meteoroids are pieces of planets or moons, such as Mars or our moon, meteoroids travel around the Sun in a variety of orbits and at various velocities. The fastest ones move at about 42 kilometers per second through space in the vicinity of Earths orbit, Earth travels at about 29.6 kilometers per second. Thus, when meteoroids meet Earths atmosphere head-on, the speed may reach about 71 kilometers per second. Meteoroids moving through Earths orbital space average about 20 km/s, on January 17,2013 at 05,21 PST, a 1 meter-sized comet from the Oort cloud entered Earth atmosphere over a wide area in California and Nevada
45.
Arietids
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The Arietids are a strong meteor shower that lasts from May 22 to July 2 each year, and peaks on June 7. The Arietids, along with the Zeta Perseids, are the most intense daylight meteor showers of the year, the source of the shower is unknown, but scientists suspect that they come from the asteroid 1566 Icarus, although the orbit also corresponds similarly to 96P/Machholz. However, because both constellations are so close to the Sun when these showers reach their peak, the showers are difficult to view with the naked eye, some of the early meteors are visible in the very early hours of the morning, usually an hour before dawn. The meteors strike Earths atmosphere at speeds around 39 km/s
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