1.
Prague
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Prague is the capital and largest city of the Czech Republic. It is the 14th largest city in the European Union and it is also the historical capital of Bohemia. Situated in the north-west of the country on the Vltava river, the city has a temperate climate, with warm summers and chilly winters. Prague has been a political, cultural, and economic centre of central Europe with waxing and waning fortunes during its history and it was an important city to the Habsburg Monarchy and its Austro-Hungarian Empire. Prague is home to a number of cultural attractions, many of which survived the violence. Main attractions include the Prague Castle, the Charles Bridge, Old Town Square with the Prague astronomical clock, since 1992, the extensive historic centre of Prague has been included in the UNESCO list of World Heritage Sites. The city has more than ten major museums, along with theatres, galleries, cinemas. An extensive modern public transportation system connects the city, also, it is home to a wide range of public and private schools, including Charles University in Prague, the oldest university in Central Europe. Prague is classified as an Alpha- global city according to GaWC studies, Prague ranked sixth in the Tripadvisor world list of best destinations in 2016. Its rich history makes it a popular tourist destination, and the city more than 6.4 million international visitors annually. Prague is the fifth most visited European city after London, Paris, Istanbul, the region was settled as early as the Paleolithic age. In the last century BC, the Celts were slowly driven away by Germanic tribes, around the area where present-day Prague stands, the 2nd century map of Ptolemaios mentioned a Germanic city called Casurgis. In the following century, the Czech tribes built several fortified settlements in the area, most notably in Levý Hradec, Butovice and in the Šárka valley. The construction of what came to be known as the Prague Castle began near the end of the 9th century, the first masonry under Prague Castle dates from the year 885 at the latest. The other prominent Prague fort, the Přemyslid fort Vyšehrad, was founded in the 10th century, Prague Castle is dominated by the cathedral, which was founded in 1344, but completed in the 20th century. The legendary origins of Prague attribute its foundation to the 8th century Czech duchess and prophetess Libuše and her husband, Přemysl, legend says that Libuše came out on a rocky cliff high above the Vltava and prophesied, I see a great city whose glory will touch the stars. She ordered a castle and a town called Praha to be built on the site, a 17th century Jewish chronicler David Solomon Ganz, citing Cyriacus Spangenberg, claimed that the city was founded as Boihaem in c.1306 BC by an ancient king, Boyya. The region became the seat of the dukes, and later kings of Bohemia, under Roman Emperor Otto II the area became a bishopric in 973
2.
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
3.
Halley's Comet
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Halleys Comet or Comet Halley, officially designated 1P/Halley, is a short-period comet visible from Earth every 75–76 years. Halley is the only known short-period comet that is visible to the naked eye from Earth. Halley last appeared in the parts of the Solar System in 1986. Halleys returns to the inner Solar System have been observed and recorded by astronomers since at least 240 BC, clear records of the comets appearances were made by Chinese, Babylonian, and medieval European chroniclers, but were not recognized as reappearances of the same object at the time. The comets periodicity was first determined in 1705 by English astronomer Edmond Halley, Comet Halley is commonly pronounced /ˈhæli/, rhyming with valley, or /ˈheɪli/, rhyming with daily. Spellings of Edmond Halleys name during his lifetime included Hailey, Haley, Hayley, Halley, Hawley, Halley was the first comet to be recognized as periodic. Until the Renaissance, the consensus on the nature of comets. This idea was disproved in 1577 by Tycho Brahe, who used parallax measurements to show that comets must lie beyond the Moon, many were still unconvinced that comets orbited the Sun, and assumed instead that they must follow straight paths through the Solar System. In 1687, Sir Isaac Newton published his Philosophiæ Naturalis Principia Mathematica, in which he outlined his laws of gravity and his work on comets was decidedly incomplete. Halley thus concluded that all three comets were, in fact, the same object returning every 76 years, a period that has since been amended to every 75–76 years. After a rough estimate of the perturbations the comet would sustain from the attraction of the planets. Halley died in 1742 before he could observe this himself, Halleys prediction of the comets return proved to be correct, although it was not seen until 25 December 1758, by Johann Georg Palitzsch, a German farmer and amateur astronomer. It did not pass through its perihelion until 13 March 1759 and this effect was computed prior to its return by a team of three French mathematicians, Alexis Clairaut, Joseph Lalande, and Nicole-Reine Lepaute. The confirmation of the return was the first time anything other than planets had been shown to orbit the Sun. It was also one of the earliest successful tests of Newtonian physics, the comet was first named in Halleys honour by French astronomer Nicolas Louis de Lacaille in 1759. Some scholars have proposed that first-century Mesopotamian astronomers already had recognized Halleys Comet as periodic and this theory notes a passage in the Bavli Talmud that refers to a star which appears once in seventy years that makes the captains of the ships err. It was necessary to use ancient Chinese comet observations to constrain their calculations, Halleys orbital period over the last 3 centuries has been between 75–76 years, although it has varied between 74–79 years since 240 BC. Its orbit around the Sun is highly elliptical, with an eccentricity of 0.967
4.
Rotterdam
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Rotterdam is a city in the Netherlands, located in South Holland, within the Rhine–Meuse–Scheldt river delta at the North Sea. Its history goes back to 1270 when a dam was constructed in the Rotte river by people settled around it for safety, in 1340 Rotterdam was granted city rights by the Count of Holland and slowly grew into a major logistic and economic centre. Nowadays it is home to Europes largest port and has a population of 633,471, ranking second in the Netherlands, just behind Amsterdam. The Greater Rijnmond area is home to approximately 1.4 million people, Rotterdam is part of the yet larger Randstad conurbation with a total population of 7,100,000. The city of Rotterdam is known for the Erasmus University, riverside setting, lively cultural life, the near-complete destruction of Rotterdams city centre during World War II has resulted in a varied architectural landscape including sky-scrapers, which are an uncommon sight in other Dutch cities. Rotterdam is home to some world-famous architecture from renowned architects like Rem Koolhaas, Piet Blom, Ben van Berkel and others. Recently Rotterdam was listed eighth in The Rough Guide Top 10 Cities to Visit, the port of Rotterdam is the largest cargo port in Europe and the 10th largest in the world. Rotterdams logistic success is based on its location on the North Sea. The rivers Rhine, Meuse, and Scheldt give waterway access into the heart of Western Europe, the extensive distribution system including rail, roads, and waterways have earned Rotterdam the nickname Gateway to Europe, and, conversely, Gateway to the World in Europe. The settlement at the end of the fen stream Rotte dates from at least 900 CE. A dam on the Rotte or Rotterdam was built in the 1260s and was located at the present-day Hoogstraat, on 7 July 1340, Count Willem IV of Holland granted city rights to Rotterdam, which then had approximately 2,000 inhabitants. The port of Rotterdam grew slowly but steadily into a port of importance, becoming the seat of one of the six chambers of the Vereenigde Oostindische Compagnie, the greatest spurt of growth, both in port activity and population, followed the completion of the Nieuwe Waterweg in 1872. The city and harbor started to expand on the bank of the river. The Witte Huis or White House skyscraper, inspired by American office buildings and built in 1898 in the French Château-style, is evidence of Rotterdams rapid growth, when completed, it was the tallest office building in Europe, with a height of 45 m. During World War I the city was the worlds largest spy centre because of Dutch neutrality, many spies who were arrested and executed in Britain were led by German secret agents operating from Rotterdam. MI6 had its main European office on de Boompjes, from there the British coordinated espionage in Germany and occupied Belgium. In WWI an average of 25,000 Belgian refugees lived in the city, as well as hundreds of German deserters, during World War II, the German army invaded the Netherlands on 10 May 1940. Adolf Hitler had hoped to conquer the country in just one day, the Dutch army was finally forced to capitulate on 15 May 1940, following Hitlers bombing of Rotterdam on 14 May and threatening to bomb other Dutch cities
5.
Lieve Verschuier
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Lieve Pietersz Verschuier was a Dutch Golden Age painter of maritime subjects. He was born in Rotterdam, and is documented in Amsterdam in 1651 and he traveled to Rome in 1653 as a young man with Jan Vermeer van Utrecht and became friends with Willem Drost and Johann Carl Loth. On his return he settled in Rotterdam in 1667 where he remained, painting marine scenes and his maritime works are valued today for their historical value illustrating the art of shipbuilding in the 17th century
6.
Solar System
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The Solar System is the gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly. Of those objects that orbit the Sun directly, the largest eight are the planets, with the remainder being significantly smaller objects, such as dwarf planets, of the objects that orbit the Sun indirectly, the moons, two are larger than the smallest planet, Mercury. The Solar System formed 4.6 billion years ago from the collapse of a giant interstellar molecular cloud. The vast majority of the mass is in the Sun. The four smaller inner planets, Mercury, Venus, Earth and Mars, are terrestrial planets, being composed of rock. The four outer planets are giant planets, being more massive than the terrestrials. All planets have almost circular orbits that lie within a flat disc called the ecliptic. The Solar System also contains smaller objects, the asteroid belt, which lies between the orbits of Mars and Jupiter, mostly contains objects composed, like the terrestrial planets, of rock and metal. Beyond Neptunes orbit lie the Kuiper belt and scattered disc, which are populations of trans-Neptunian objects composed mostly of ices, within these populations are several dozen to possibly tens of thousands of objects large enough that they have been rounded by their own gravity. Such objects are categorized as dwarf planets, identified dwarf planets include the asteroid Ceres and the trans-Neptunian objects Pluto and Eris. In addition to two regions, various other small-body populations, including comets, centaurs and interplanetary dust clouds. Six of the planets, at least four of the dwarf planets, each of the outer planets is encircled by planetary rings of dust and other small objects. The solar wind, a stream of charged particles flowing outwards from the Sun, the heliopause is the point at which pressure from the solar wind is equal to the opposing pressure of the interstellar medium, it extends out to the edge of the scattered disc. The Oort cloud, which is thought to be the source for long-period comets, the Solar System is located in the Orion Arm,26,000 light-years from the center of the Milky Way. For most of history, humanity did not recognize or understand the concept of the Solar System, the invention of the telescope led to the discovery of further planets and moons. The principal component of the Solar System is the Sun, a G2 main-sequence star that contains 99. 86% of the known mass. The Suns four largest orbiting bodies, the giant planets, account for 99% of the mass, with Jupiter. The remaining objects of the Solar System together comprise less than 0. 002% of the Solar Systems total mass, most large objects in orbit around the Sun lie near the plane of Earths orbit, known as the ecliptic
7.
Astronomer
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An astronomer is a scientist in the field of astronomy who concentrates their studies on a specific question or field outside of the scope of Earth. They look at stars, planets, moons, comets and galaxies, as well as other celestial objects — either in observational astronomy. Examples of topics or fields astronomers work on include, planetary science, solar astronomy, there are also related but distinct subjects like physical cosmology which studies the Universe as a whole. Astronomers usually fit into two types, Observational astronomers make direct observations of planets, stars and galaxies, and analyze the data, theoretical astronomers create and investigate models of things that cannot be observed. They use this data to create models or simulations to theorize how different celestial bodies work, there are further subcategories inside these two main branches of astronomy such as planetary astronomy, galactic astronomy or physical cosmology. Today, that distinction has disappeared and the terms astronomer. Professional astronomers are highly educated individuals who typically have a Ph. D. in physics or astronomy and are employed by research institutions or universities. They spend the majority of their time working on research, although quite often have other duties such as teaching, building instruments. The number of astronomers in the United States is actually quite small. The American Astronomical Society, which is the organization of professional astronomers in North America, has approximately 7,000 members. This number includes scientists from other such as physics, geology. The International Astronomical Union comprises almost 10,145 members from 70 different countries who are involved in research at the Ph. D. level. Before CCDs, photographic plates were a method of observation. Modern astronomers spend relatively little time at telescopes usually just a few weeks per year, analysis of observed phenomena, along with making predictions as to the causes of what they observe, takes the majority of observational astronomers time. Astronomers who serve as faculty spend much of their time teaching undergraduate and graduate classes, most universities also have outreach programs including public telescope time and sometimes planetariums as a public service to encourage interest in the field. Those who become astronomers usually have a background in maths, sciences. Taking courses that teach how to research, write and present papers are also invaluable, in college/university most astronomers get a Ph. D. in astronomy or physics. Keeping in mind how few there are it is understood that graduate schools in this field are very competitive
8.
Comet nucleus
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The nucleus is the solid, central part of a comet, popularly termed a dirty snowball or an icy dirtball. A cometary nucleus is composed of rock, dust, and frozen gases, when heated by the Sun, the gases sublimate and produce an atmosphere surrounding the nucleus known as the coma. The force exerted on the coma by the Suns radiation pressure and solar wind cause an enormous tail to form, a typical comet nucleus has an albedo of 0.04. This is blacker than coal, and may be caused by a covering of dust, comets, or their precursors, formed in the outer Solar System, possibly millions of years before planet formation. How and when formed is debated, with distinct implications for Solar System formation, dynamics. Three-dimensional computer simulations indicate the structural features observed on cometary nuclei can be explained by pairwise low velocity accretion of weak cometesimals. The currently favored creation mechanism is that of the nebular hypothesis, astronomers think that comets originate in both the Oort cloud and the scattered disk. Most cometary nuclei are thought to be no more than about 10 miles across, the largest comets that have come inside the orbit of Saturn are C/2002 VQ94, Hale–Bopp, 29P, 109P/Swift–Tuttle, and 28P/Neujmin. The potato-shaped nucleus of Halleys comet contains equal amounts of ice, during a flyby in September 2001, the Deep Space 1 spacecraft observed the nucleus of Comet Borrelly and found it to be about half the size of the nucleus of Halleys Comet. Borrellys nucleus was also potato-shaped and had a black surface. Like Halleys Comet, Comet Borrelly only released gas from small areas where holes in the crust exposed the ice to sunlight, the nucleus of comet Hale–Bopp was estimated to be 60 ±20 km in diameter. Hale-Bopp appeared bright to the eye because its unusually large nucleus gave off a great deal of dust. The nucleus of P/2007 R5 is probably only 100–200 meters in diameter, the largest centaurs are estimated to be 250 km to 300 km in diameter. Three of the largest would include 10199 Chariklo,2060 Chiron, known comets have been estimated to have an average density of 0.6 g/cm3. Below is a list of comets that have had estimated sizes, densities, about 80% of the Halleys Comet nucleus is water ice, and frozen carbon monoxide makes up another 15%. Much of the remainder is carbon dioxide, methane. Scientists think that comets are chemically similar to Halleys Comet. The nucleus of Halleys Comet is also a dark black
9.
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
10.
Earth
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Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, thus, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, politically, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe. It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, originally, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun
11.
Comet Hyakutake
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Comet Hyakutake is a comet, discovered on 31 January 1996, that passed very close to Earth in March of that year. It was dubbed The Great Comet of 1996, its passage near the Earth was one of the closest cometary approaches of the previous 200 years, Hyakutake appeared very bright in the night sky and was widely seen around the world. The comet temporarily upstaged the much anticipated Comet Hale–Bopp, which was approaching the inner Solar System at the time, scientific observations of the comet led to several discoveries. The Ulysses spacecraft unexpectedly crossed the tail at a distance of more than 500 million kilometres from the nucleus. Before its most recent passage through the Solar System, its period was about 17,000 years. The comet was discovered on 31 January 1996, by Yuji Hyakutake and he had been searching for comets for years and had moved to Kagoshima Prefecture partly for the dark skies in nearby rural areas. He was using a set of binoculars with 150 mm objective lenses to scan the skies on the night of the discovery. This comet was actually the second Comet Hyakutake, Hyakutake had discovered comet C/1995 Y1 several weeks earlier, while re-observing his first comet and the surrounding patch of sky, Hyakutake was surprised to find another comet in almost the same position as the first had been. Hardly believing a second discovery so soon after the first, Hyakutake reported his observation to the National Astronomical Observatory of Japan the following morning, later that day, the discovery was confirmed by independent observations. At the time of its discovery, the comet was shining at magnitude 11.0 and had a coma approximately 2.5 arcminutes across and it was approximately 2 astronomical units from the Sun. Later, an image of the comet was found on a photograph taken on January 1. When the first calculations of the orbit were made, scientists realized that it was going to pass just 0.1 AU from Earth on 25 March. Only four comets in the century had passed closer. Comet Hale–Bopp was already being discussed as a great comet. Moreover, Comet Hyakutakes orbit meant that it had last been to the inner Solar System approximately 17,000 years earlier. Comets entering the inner Solar System for the first time may brighten rapidly before fading as they near the Sun and this was the case with Comet Kohoutek in 1973, it was initially touted as potentially spectacular, but only appeared moderately bright. Older comets show a more consistent brightening pattern, thus, all indications suggested Comet Hyakutake would be bright. This would be an unusual occurrence, because most comets are close to the Sun in the sky when the comets are at their brightest, Hyakutake became visible to the naked eye in early March 1996
12.
Gas
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Gas is one of the four fundamental states of matter. A pure gas may be made up of atoms, elemental molecules made from one type of atom. A gas mixture would contain a variety of pure gases much like the air, what distinguishes a gas from liquids and solids is the vast separation of the individual gas particles. This separation usually makes a colorless gas invisible to the human observer, the interaction of gas particles in the presence of electric and gravitational fields are considered negligible as indicated by the constant velocity vectors in the image. One type of commonly known gas is steam, the gaseous state of matter is found between the liquid and plasma states, the latter of which provides the upper temperature boundary for gases. Bounding the lower end of the temperature scale lie degenerative quantum gases which are gaining increasing attention, high-density atomic gases super cooled to incredibly low temperatures are classified by their statistical behavior as either a Bose gas or a Fermi gas. For a comprehensive listing of these states of matter see list of states of matter. The only chemical elements which are stable multi atom homonuclear molecules at temperature and pressure, are hydrogen, nitrogen and oxygen. These gases, when grouped together with the noble gases. Alternatively they are known as molecular gases to distinguish them from molecules that are also chemical compounds. The word gas is a neologism first used by the early 17th-century Flemish chemist J. B. van Helmont, according to Paracelsuss terminology, chaos meant something like ultra-rarefied water. An alternative story is that Van Helmonts word is corrupted from gahst and these four characteristics were repeatedly observed by scientists such as Robert Boyle, Jacques Charles, John Dalton, Joseph Gay-Lussac and Amedeo Avogadro for a variety of gases in various settings. Their detailed studies ultimately led to a relationship among these properties expressed by the ideal gas law. Gas particles are separated from one another, and consequently have weaker intermolecular bonds than liquids or solids. These intermolecular forces result from interactions between gas particles. Like-charged areas of different gas particles repel, while oppositely charged regions of different gas particles attract one another, transient, randomly induced charges exist across non-polar covalent bonds of molecules and electrostatic interactions caused by them are referred to as Van der Waals forces. The interaction of these forces varies within a substance which determines many of the physical properties unique to each gas. A comparison of boiling points for compounds formed by ionic and covalent bonds leads us to this conclusion, the drifting smoke particles in the image provides some insight into low pressure gas behavior
13.
Dust
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Dust is fine particles of matter. It generally consists of particles in the atmosphere that come from sources such as soil, dust lifted by weather, volcanic eruptions. House dust mites are present indoors wherever humans live, positive tests for dust mite allergies are extremely common among people with asthma. Dust mites are microscopic arachnids whose primary food is dead skin cells. They and their feces and other allergens they produce are major constituents of house dust and they are generally found on the floor and other surfaces until disturbed. It could take somewhere between twenty minutes and two hours for dust mites to settle back down out of the air, Dust mites are a nesting species that prefers a dark, warm, and humid climate. They flourish in mattresses, bedding, upholstered furniture, and carpets and their feces include enzymes that are released upon contact with a moist surface, which can happen when a person inhales, and these enzymes can kill cells within the human body. House dust mites did not become a problem until humans began to use textiles, such as western style blankets and clothing. Atmospheric or wind-borne dust, also known as aeolian dust, comes from arid and dry regions where high velocity winds are able to remove mostly silt-sized material, Dust in the atmosphere is produced by saltation and sandblasting of sand-sized grains, and it is transported through the troposphere. This airborne dust is considered an aerosol and once in the atmosphere, saharan dust in particular can be transported and deposited as far as the Caribbean and the Amazon basin, and may affect air temperatures, cause ocean cooling, and alter rainfall amounts. Dust in the Middle East has been a historic phenomenon, recently, because of climate change and the escalating process of desertification, the problem has worsened dramatically. As a multi-factor phenomenon, there is not yet a consensus on the sources or potential solutions to the problem. In Iran, the dust is already affecting more than 5 million people directly, in the province of Khuzestan it has led to the severe reduction of air quality. The amount of pollutants in the air has surpassed more than 50 times the normal level several times in a year, recently, initiatives such as Project-Dust have been established to directly study the Middle Eastern dust. Dust kicked up by vehicles traveling on roads may make up 33% of air pollution, road dust consists of deposits of vehicle exhausts and industrial exhausts, particles from tire and brake wear, dust from paved roads or potholes, and dust from construction sites. Road dust is a significant source contributing to the generation and release of particulate matter into the atmosphere. Control of road dust is a significant challenge in urban areas, road dust may be suppressed by mechanical methods like street sweeper vehicles equipped with vacuum cleaners, vegetable oil sprays, or with water sprayers. Improvements in automotive engineering have reduced the amount of PM10s produced by road traffic, coal dust is responsible for the lung disease known as pneumoconiosis, including black lung disease that occurs among coal miners
14.
Comet Holmes
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Comet Holmes is a periodic comet in the Solar System, discovered by the British amateur astronomer Edwin Holmes on November 6,1892. It also briefly became the largest object in the Solar System, Comet Holmes was discovered by Edwin Holmes on November 6,1892, while he was conducting regular observations of the Andromeda Galaxy. The comets discovery was confirmed by Edward Walter Maunder, William Henry Maw, independent discoveries were made by Thomas David Anderson on November 8 and by Mike Brown and by John Ewen Davidson on November 9. The first calculations of the orbit of 17P/Holmes were done independently by Heinrich Kreutz. Additional orbits eventually established the date as June 13 and the orbital period as 6.9 years. These calculations proved that the comet was not a return of Bielas Comet, the 1899 and 1906 appearances were observed, but the comet was lost after 1906 until it was recovered on July 16,1964, by Elizabeth Roemer. Aided by the predictions of Brian G. Marsden, the comet has been observed on every subsequent return. During its 2007 return, Holmes unexpectedly brightened from a magnitude of about 17 to about 2.8 in a period of only 42 hours and this represents a change of brightness by a factor of about half a million and is the largest known outburst by a comet. The outburst took place from October 23 to 24,2007, the first person reportedly to notice a change was J. A. Henríquez Santana on Tenerife in the Canary Islands, minutes later, Ramón Naves in Barcelona noticed the comet at magnitude 7.3. It became easily visible to the eye as a bright yellow star in Perseus. Although large telescopes had already shown fine-scale cometary details, naked-eye observers saw Holmes as merely star-like until October 26, after that date, 17P/Holmes began to appear more comet-like to naked-eye observers. Based on orbital computations and luminosity before the 2007 outburst, the nucleus was estimated at 3.4 km. Comet Holmes not only became brighter, but it also swelled in size as its coma expanded, in late October 2007 the comas apparent diameter increased from 3.3 arcminutes to over 13 arcminutes, about half the diameter of the Moon in the sky. At a distance of around 2 AU, this means that the diameter of the coma had swelled to over 1 million km. By comparison, the Moon is 380,000 km from Earth, therefore, during the 2007 outburst of Comet Holmes the coma was a sphere wider than the diameter of the Moons orbit around Earth. On 2007 November, the coma had dispersed to a larger than the Sun. The cause of the outburst is not definitely known, the huge cloud of gas and dust may have resulted from a collision with a meteoroid, or, more probably, from a build-up of gas inside the comets nucleus that eventually broke through the surface. Energy from the Sun – insolation – was stored in the dust cover, the comet remained visible in February 2008 though it had become a challenging target at about magnitude +5 in the constellation Perseus
15.
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
16.
Inverse-square law
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The fundamental cause for this can be understood as geometric dilution corresponding to point-source radiation into three-dimensional space. Newtons law of gravitation follows an inverse-square law, as do the effects of electric, magnetic, light, sound. The inverse-square law generally applies when some force, energy, or other conserved quantity is evenly radiated outward from a point source in three-dimensional space, hence, the intensity of radiation passing through any unit area is inversely proportional to the square of the distance from the point source. Gausss law is applicable, and can be used with any physical quantity that acts in accord to the inverse-square relationship. Gravitation is the attraction of two objects with mass, the force is always attractive and acts along the line joining them. If the distribution of matter in each body is spherically symmetric, then the objects can be treated as point masses without approximation, as shown in the shell theorem. Otherwise, if we want to calculate the attraction between bodies, we need to add all the point-point attraction forces vectorially and the net attraction might not be exact inverse square. As the law of gravitation, this law was suggested in 1645 by Ismael Bullialdus, but Bullialdus did not accept Kepler’s second and third laws, nor did he appreciate Christiaan Huygens’s solution for circular motion. Indeed, Bullialdus maintained the suns force was attractive at aphelion, robert Hooke and Giovanni Alfonso Borelli both expounded gravitation in 1666 as an attractive force. By 1679, Hooke thought gravitation had inverse square dependence and communicated this in a letter to Isaac Newton, the deviation of the exponent from 2 is less than one part in 1015. More generally, the irradiance, i. e. the intensity, for non-isotropic radiators such as parabolic antennas, headlights, and lasers, the effective origin is located far behind the beam aperture. If you are close to the origin, you dont have to go far to double the radius, so the signal drops quickly. When you are far from the origin and still have a signal, like with a laser, you have to travel very far to double the radius. This means you have a signal or have antenna gain in the direction of the narrow beam relative to a wide beam in all directions of an isotropic antenna. In photography and stage lighting, the law is used to determine the fall off or the difference in illumination on a subject as it moves closer to or further from the light source. The fractional reduction in electromagnetic fluence for indirectly ionizing radiation with increasing distance from a point source can be calculated using the inverse-square law, since emissions from a point source have radial directions, they intercept at a perpendicular incidence. The area of such a shell is 4πr 2 where r is the distance from the center. At large distances from the source, this power is distributed over larger and larger spherical surfaces as the distance from the source increases
17.
Fluorescence
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Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence, in most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. Fluorescent materials cease to glow immediately when the radiation source stops, unlike phosphorescence, Fluorescence also occurs frequently in nature in some minerals and in various biological states in many branches of the animal kingdom. An early observation of fluorescence was described in 1560 by Bernardino de Sahagún and it was derived from the wood of two tree species, Pterocarpus indicus and Eysenhardtia polystachya. The chemical compound responsible for this fluorescence is matlaline, which is the product of one of the flavonoids found in this wood. The name was derived from the fluorite, some examples of which contain traces of divalent europium. In a key experiment he used a prism to isolate ultraviolet radiation from sunlight, the specific frequencies of exciting and emitted light are dependent on the particular system. S0 is called the state of the fluorophore, and S1 is its first excited singlet state. A molecule in S1 can relax by various competing pathways and it can undergo non-radiative relaxation in which the excitation energy is dissipated as heat to the solvent. Excited organic molecules can also relax via conversion to a triplet state, relaxation from S1 can also occur through interaction with a second molecule through fluorescence quenching. Molecular oxygen is an extremely efficient quencher of fluorescence just because of its unusual triplet ground state, in most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation, this phenomenon is known as the Stokes shift. The emitted radiation may also be of the wavelength as the absorbed radiation. Molecules that are excited through light absorption or via a different process can transfer energy to a second sensitized molecule, the fluorescence quantum yield gives the efficiency of the fluorescence process. It is defined as the ratio of the number of photons emitted to the number of photons absorbed, Φ = Number of photons emitted Number of photons absorbed The maximum fluorescence quantum yield is 1.0, each photon absorbed results in a photon emitted. Compounds with quantum yields of 0.10 are still considered quite fluorescent, thus, if the rate of any pathway changes, both the excited state lifetime and the fluorescence quantum yield will be affected. Fluorescence quantum yields are measured by comparison to a standard, the quinine salt quinine sulfate in a sulfuric acid solution is a common fluorescence standard. The fluorescence lifetime refers to the time the molecule stays in its excited state before emitting a photon. This is an instance of exponential decay, various radiative and non-radiative processes can de-populate the excited state
18.
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
19.
Astronomical unit
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The astronomical unit is a unit of length, roughly the distance from Earth to the Sun. However, that varies as Earth orbits the Sun, from a maximum to a minimum. Originally conceived as the average of Earths aphelion and perihelion, it is now defined as exactly 149597870700 metres, the astronomical unit is used primarily as a convenient yardstick for measuring distances within the Solar System or around other stars. However, it is also a component in the definition of another unit of astronomical length. A variety of symbols and abbreviations have been in use for the astronomical unit. In a 1976 resolution, the International Astronomical Union used the symbol A for the astronomical unit, in 2006, the International Bureau of Weights and Measures recommended ua as the symbol for the unit. In 2012, the IAU, noting that various symbols are presently in use for the astronomical unit, in the 2014 revision of the SI Brochure, the BIPM used the unit symbol au. In ISO 80000-3, the symbol of the unit is ua. Earths orbit around the Sun is an ellipse, the semi-major axis of this ellipse is defined to be half of the straight line segment that joins the aphelion and perihelion. The centre of the sun lies on this line segment. In addition, it mapped out exactly the largest straight-line distance that Earth traverses over the course of a year, knowing Earths shift and a stars shift enabled the stars distance to be calculated. But all measurements are subject to some degree of error or uncertainty, improvements in precision have always been a key to improving astronomical understanding. Improving measurements were continually checked and cross-checked by means of our understanding of the laws of celestial mechanics, the expected positions and distances of objects at an established time are calculated from these laws, and assembled into a collection of data called an ephemeris. NASAs Jet Propulsion Laboratory provides one of several ephemeris computation services, in 1976, in order to establish a yet more precise measure for the astronomical unit, the IAU formally adopted a new definition. Equivalently, by definition, one AU is the radius of an unperturbed circular Newtonian orbit about the sun of a particle having infinitesimal mass. As with all measurements, these rely on measuring the time taken for photons to be reflected from an object. However, for precision the calculations require adjustment for such as the motions of the probe. In addition, the measurement of the time itself must be translated to a scale that accounts for relativistic time dilation
20.
Periodic comet
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Periodic comets are comets having orbital periods of less than 200 years or that have been observed during more than a single perihelion passage. Periodic comet is sometimes used to mean any comet with a periodic orbit. Periodic comets receive a permanent number prefix usually after the perihelion passage. In nearly all cases, comets are named after their discoverer, even so, quite a few comets were lost because their orbits are also affected by non-gravitational effects such as the release of gas and other material that forms the comets coma and tail. Unlike a long-period comet, the perihelion passage of a numbered periodic comet can be predicted with a high degree of accuracy. Periodic comets sometimes bear the same name repeatedly, the IAU system distinguishes between them either through the prefix or by the full designation. In the literature, a numbering system is applied to periodic comets, thus 181P and 192P are known as Comet Shoemaker–Levy 6 and Comet Shoemaker–Levy 1. Non-periodic Shoemaker–Levy comets are interleaved in this sequence, C/1991 B1 between 2 and 3, C/1991 T2 between 5 and 6, C/1993 K1 and C/1994 E2 after Shoemaker–Levy 9. In comet nomenclature, the letter before the / is either C, P, D, X, or A for an object that was identified as a comet. Some lists retain the C prefix for comets of periods larger than about 30 years until their return is confirmed
21.
Caesar's Comet
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Caesars Comet – also known as Comet Caesar and the Great Comet of 44 BC – was perhaps the most famous comet of antiquity. Its seven-day visitation was interpreted by Romans as a sign of the deification of recently assassinated dictator, Caesars Comet is one of only five comets known to have had a negative absolute magnitude and may have been the brightest daylight comet in recorded history. It was not periodic and may have disintegrated, the parabolic orbital solution estimates that the comet would now be more than 800 AU from the Sun. Caesars Comet was known to ancient writers as the Sidus Iulium or Caesaris astrum, the dating has recently been revised to a July occurrence in the same year, some four months after the assassination of Julius Caesar, as well as Caesars own birth month. According to Suetonius, as celebrations were getting underway, a comet shone for seven days, rising about the eleventh hour. The Comet became a symbol in the political propaganda that launched the career of Caesars great-nephew Augustus. The Temple of Divus Iulius was built and dedicated by Augustus for purposes of fostering a cult of the comet. In 1997, two scholars at the University of Illinois at Chicago – John T. Ramsey and A. Lewis Licht – published a book comparing astronomical/astrological evidence from both Han China and Rome. The poet Virgil writes in his ninth eclogue that the star of Caesar has appeared to gladden the fields. Virgil later writes of the period following Julius Caesar’s assassination, “Never did fearsome comets so often blaze. ”Gurval interestingly points out that this passage in no way links a comet to Caesar’s divine status, but rather links comets to his death. It is Ovid, however, who makes the assertion of the comet’s role in Julius Caesar’s deification. As she carried it, she felt it glow and take fire, and loosed it from her breast, it climbed higher than the moon and it has been argued recently that the idea of Augustuss use of the comet for his political aims largely stems from this passage. In Shakespeare’s Julius Caesar, Caesars wife remarks on the morning of her husbands murder. The heavens themselves blaze forth the death of princes, tracing the coinage from 44 BC through the developing rule of Augustus reveals the changing relationship of Julius Caesar to the Sidus Iulium. Robert Gurval notes that the status of Caesar’s comet in the coinage follows a definite pattern. Representations of the deified Julius Caesar as a star appeared relatively quickly, about twenty years passed, however, before the star completed its transformation into a comet. Starting in 44 BC, a maker named P. Sepullius Macer created coins with the front displaying Julius Caesar crowned with a wreath. On the back, Venus, the goddess of the Julian family
22.
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
23.
Great Comet of 1264
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The Great Comet of 1264 was one of the brightest comets on record. It appeared in July 1264 and remained visible to the end of September, the comet of 1264 was described to have been an object of great size and brilliancy. The comets splendor was greatest at the end of August and the beginning of September. At that time, when the head was just visible above the horizon in the morning sky. It was said that the prodigy of a star had brought upon his illness. This comet was observed in China, and the descriptions agree with the statements of the European historians. The astronomers speculated that the Great Comet of 1556 and the Great comet of 1264 are the same comet. The comet of 1264, says Pingré, is probably the same as that of 1556, its periodical revolution is about 292 years. Sir Isaac Newton showed that a controlled by the Sun moves in a conic section—that is, an ellipse. Because the latter two are open curves, a comet which pursued such a path would go off into space never to reappear, a derangement of orbit from closed to open curve has doubtless happened often
24.
Great Comet of 1556
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The Great Comet of 1556 is a famous comet that first appeared in February 1556. Cornelius Gemma says, the head of the comet, when it first appeared, was fully as large as Jupiter, the course of the comet of 1556 was observed by Paul Fabricius, a mathematician and physician at the court of Charles V, Holy Roman Emperor. The Great Comet of 1556 is called the comet of Charles V, when the Emperor first caught sight of it he stood aghast, and exclaimed, By this dread sign my fates do summon me. Charles had long meditated about retiring from the world he had conquered and crushed, regarding the comet as a sign of Heavens command to do so, he hastened towards the peaceful monastery of St. Juste, Placentia. In his 1569 book he wondered if the comet was a sign of calamities not just for China, but for the entire world - and could be even the sign of the birth of Antichrist. was that of 1264 returned. At any rate, he found a degree of probability in favor of the conclusion at which he had arrived. Hence he concluded that a return to perihelion might be looked for about the middle of this century,1848 to 1850. So far no observed comet has matched the orbital elements of either comet and this article incorporates text from On the expected return of the great comet of 1264 and 1556, by John Russell Hind, a publication from 1848 now in the public domain in the United States. This article incorporates text from The Anglo-Saxon review, Volume 6, by Lady Randolph Spencer Churchill, a publication from 1900 now in the public domain in the United States
25.
Great Comet of 1577
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The Great Comet of 1577 was a comet that passed close to Earth during the year 1577 AD. It was viewed by all over Europe, including the famous Danish astronomer Tycho Brahe. From his observations of the comet, Brahe was able to discover that comets, the best fit using JPL Horizons suggests that the comet is currently about 320 AU from the Sun. Sketches found in one of Brahes notebooks seem to indicate that the comet may have travelled close to Venus. These sketches depict the Earth at the centre of the Solar System, with the Sun and moon in orbit and the planets revolving around the Sun. Brahes discovery that the comets coma faced away from the Sun was also significant and it was discovered that, while the comet was in approximately the same place for both of them, the Moon was not, and this meant that the comet was much further out. Galileo claimed that comets were optical phenomena, and that made their parallaxes impossible to measure. However, his hypothesis was not accepted, five other observers of the comet — Taqi al-Din Muhammad ibn Maruf, Helisaeus Roeslin, William IV, Landgrave of Hesse-Kassel, Cornelius Gemma, and Michael Mästlin — also identified it as superlunary. The most complex of the representations of the Great Comet, described as an interesting, though crude, attempt. The literature resulting from the passing of the comet was prolific, however, the idea that comets were heavenly objects became a respected theory, and many took this concept to be true. Artwork inspired by the event was also made—artist Jiri Daschitzky made an engraving that was inspired by the passing of the comet over Prague on November 12,1577, cornelis Ketel painted the portrait of Richard Goodricke around 1578. Goodricke had reached adulthood in 1577 and apparently saw the comet as an omen and had it included in the painting and this comet was mentioned in the book entitled Sêfer Chazionot - The Book Of Visions - By Rabbi Chayim Vital,1577. Rosh Hodesh Kislev, after sunrise, a star with a long tail. Part of the tail was also pointing eastward and it lingered there for three hours. Then it sank in the west behind the hills of Safed and this continued for more than fifty nights. On the fifteenth of Kislev, I went to live in Jerusalem and this star was seen in every part of the west of Europe, and it was wondered at by all universally. R. Lang, Kenneth, Charles Allen Whitney, history of Physical Astronomy, from the Earliest Ages to the Middle of the 19th Century
26.
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
27.
Great Comet of 1744
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It was discovered independently in late November 1743 by Jan de Munck, in the second week of December by Dirk Klinkenberg, and, four days later, by Jean-Philippe de Chéseaux. It became visible with the eye for several months in 1744 and displayed dramatic. Its absolute magnitude — or intrinsic brightness — of 0.5 was the sixth highest in recorded history and its apparent magnitude may have reached as high as -7, leading it to be classified among what are called the Great Comets. This comet is noted especially for developing a fan of six tails after reaching its perihelion, Chéseaux said it lacked a tail and resembled a nebulous star of the third magnitude, he measured the coma as five minutes across. The comet brightened steadily as it approached perihelion, by February 18,1744, it reportedly was as bright as the planet Venus and at this time displayed a double tail. The comet reached perihelion about March 1,1744, when it was 0.2 astronomical units from the Sun, at about this time it was bright enough to be observed in daylight with the naked eye. As it moved away from perihelion, a spectacular tail developed — extending well above the horizon while the head remained invisible due to the morning twilight. In early March 1744, Chéseaux and several other observers reported an unusual phenomenon — a fan of six separate tails rose above the horizon. The tail structure was a puzzle to astronomers for many years, although other comets had displayed multiple tails on occasion, the 1744 comet was unique by having six. It has been suggested that the fan of tails was generated by as many as three active sources on the nucleus, exposed in turn to solar radiation as the nucleus rotated. It also has proposed that the tail phenomenon was a very prominent example of the dust striae seen in the tails of some comets, such as Comet West. The comet was not seen after April 22,1744, the comet also was noted in Japanese astronomical records in the Nihon Odai Ichiran of the Kanpō era. Among those who saw the comet was the thirteen-year-old Charles Messier, on whom it had a profound and he went on to become a significant figure in astronomy, and later discovered many comets during his observations. Catherine the Great, then Sophia, also observed the brilliant comet as a girl as she was travelling to Russia to be wedded. Orbit Diagram, C/1743 X1 NASA Jet Propulsion Laboratory
28.
Great Comet of 1811
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The Great Comet of 1811, formally designated C/1811 F1, is a comet that was visible to the naked eye for around 260 days, a record it held until the appearance of Comet Hale–Bopp in 1997. In October 1811, at its brightest, it displayed an apparent magnitude of 0, the comet was discovered March 25,1811 by Honoré Flaugergues at 2.7 AU from the Sun in the now-defunct constellation of Argo Navis. After being obscured for several days by moonlight, it was found by Jean-Louis Pons on April 11, while Franz Xaver. The first provisional orbit was computed in June by Johann Karl Burckhardt, based on these calculations, Heinrich Wilhelm Matthäus Olbers made a prediction that the comet would go on to become extremely bright later that year. From May to August, the position made it difficult to spot because of its low altitude. By September, in Ursa Major, it was becoming an object in the evening sky as it approached perihelion. By January 1812, the brightness had faded. The Great Comet of 1811 was thought to have had an exceptionally large coma, the comets nucleus was later estimated at 30–40 km in diameter and the orbital period was calculated at 3,757 years. In many ways the comet was quite similar to Comet Hale–Bopp, it became spectacular without passing particularly close to either the Earth or the Sun, astronomers also found the comet a memorable sight. The comet was visible during the New Madrid earthquakes in December,1811. It was the coming of the first steamboat to where Cairo now is—the New Orleans, Capt. Roosevelt and it was the severest day of the great throes of the New Madrid earthquake, at the same time, a fiery comet was rushing athwart the horizon. The Great Comet of 1811 seems to have had a impact on non-astronomers. The artists John Linnell and William Blake both witnessed it, the former producing several sketches and the latter possibly incorporating it in his famous panel The Ghost of a Flea. Such is the fact, and philosophers may make of it what they may, —remembering that I was then nine years old, and with remarkably good eyes. At the midpoint of War and Peace, Tolstoy describes the character of Pierre observing this enormous and brilliant comet which was said to all kinds of woes. The comet was popularly thought to have portended Napoleons invasion of Russia, when asked why the comet made it into the title of the show, Malloy responded for cosmic epicness. The year 1811 turned out to be fine for wine production. The film stars Penelope Ann Miller, Tim Daly and French film actor Louis Jourdan
29.
Great Comet of 1843
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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
30.
Comet Donati
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There are three Donati comets, C/1855 L1, C/1858 L1, and C/1864 R1. Comet Donati, or Donatis Comet, formally designated C/1858 L1 and 1858 VI, is a comet named after the Italian astronomer Giovanni Battista Donati who first observed it on June 2,1858. After the Great Comet of 1811, it was the most brilliant comet that appeared in the 19th century and it was also the first comet to be photographed. Donati first observed the comet on 2 June from the Florence Observatory, by mid-August it had brightened sufficiently to be visible to the naked eye. In September it passed into Ursa Major, for much of its apparition it occupied a unique position in the sky and was particularly well placed for Northern Hemisphere viewers. It was nearest the Earth on October 10,1858, and for much of October was a brilliant object with a long, scimitar-like dust tail and it remained a naked-eye object until November for Southern Hemisphere observers. The final observation was by William Mann, chief assistant at the Royal Observatory, Cape of Good Hope, during its apparition the comet was particularly closely studied by the astronomer George Phillips Bond and his father William Cranch Bond. Usherwoods photograph, which has not survived, showed the region around the comets nucleus. Bond also successfully photographed the comet on September 28 at Harvard College Observatory and he made several attempts with increasing exposure times, finally achieving a discernible image. He later wrote, only the nucleus and a little nebulosity 15 in diameter acted on the plate in an exposure of six minutes, the definitive orbits for the comet were calculated by Friedrich Emil von Asten and George William Hill, the latters based on nearly 1000 positions. The comet had an inclination of 116. 9°. Donati himself, an obscure figure, was propelled to the status of an astronomical hero. Donatis Comet appears as a streak and star in the evening sky of a painting by William Dyce, Pegwell Bay. It was featured in a number of sketches and at least one painting by William Turner of Oxford, the Comet at Yellham, a 1902 poem by Thomas Hardy, was inspired by his recollections of Donatis Comet. C/1857 V1, Comet Donati-van Arsdale C/1864 O1, Comet Donati-Toussaint Orbital simulation from JPL / Horizons Ephemeris
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C/1861 J1
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The Great Comet of 1861 formally designated C/1861 J1 and 1861 II, is a long-period comet that was visible to the naked eye for approximately 3 months. It was categorized as a Great Comet, one of the eight greatest comets of the 19th century and it was discovered by John Tebbutt of Windsor, New South Wales, Australia, on May 13,1861, with an apparent magnitude of +4, a month before perihelion. It was not visible in the northern hemisphere until June 29, on June 29,1861, comet C/1861 J1 passed 11.5 degrees from the Sun. On the following day, June 30,1861, the comet made its closest approach to the Earth at a distance of 0.1326 AU, during the Earth close approach the comet was estimated to be between magnitude 0 and −2 with a tail of over 90 degrees. As a result of forward scattering C/1861 J1 even cast shadows at night. During the night of 1861 June 30 – July 1, the famed comet observer J. F. Julius Schmidt watched in awe as the great comet C/1861 J1 cast shadows on the walls of the Athens Observatory. The comet may have interacted with the Earth in an almost unprecedented way, for two days, when the comet was at its closest, the Earth was actually within the comets tail, and streams of cometary material converging towards the distant nucleus could be seen. By the middle of August the comet was no longer visible to the naked eye, an elliptical orbit with a period of about 400 years was calculated, which would indicate a previous appearance about the middle of the 15th century, and a return in the 23rd century. Hasegawa and S. Nakano suggest that this comet is identical with C/1500 H1 that came to perihelion on 1500 April 20, by 1992 this Great Comet had traveled more than 100 AU from the Sun, making it even farther away than dwarf planet Eris. It will come to aphelion around 2063 and it is possible that C/1861 G1 and this comet are related, and that in a previous perihelion and that C/1861 G1 broke off of this comet, as the two comets have many similar orbital characteristics. In his Astronomical Memoirs Tebbutt gave an account of his discovery, the entry reads as follows, Saw a huge comet last night in the northwest. Its tail reached half across the heavens and it has probably been visible for sometime, but as it has been cloudy lately I had not observed it before. June 30 July 1 July 5,1861, I awoke in the night at 1 o’clock, when I had a glorious sight of the largest comet I ever beheld. It was a most wonderful sight, james Riley Robinson, on the schooner Conchita, in the Mexican harbor of Agiabampo. C/1861 J1 on Cometography. com The Comet of 1861, Gallery of Natural Phenomena JPL DASTCOM Comet Orbital Elements Orbital simulation from JPL / Ephemeris
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C/1874 H1
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C/1874 H1 is a famous non-periodic comet, which in the summer of 1874 could be seen by naked eye observation. On the basis of its brightness, the comet has been called the Great Comet of 1874, the astronomer Jérôme Eugène Coggia discovered this comet on 17 April 1874 at the Marseille Observatory. In mid-May telescopes revealed the development of a faint tail, in early June the comet became visible to the naked eye and by the end of June its brightness reached magnitude 4. By the beginning of July the tail had grown to 6°, the tail was straight and narrow, stretching across from 1° to 2° of the sky at the tails end. Reports indicate that the length was about 60° to 70°. On 23 July in Athens, Schmidt made the last observation of the comet from the northern hemisphere, on July 27 the comet became visible in the southern hemisphere, with observations made in South Africa and by Robert L. J. Ellery in Australia. According to a report from pre-dawn observations by H. C. Russell on July 29, The nucleus was as bright as a first magnitude star. John Tebbutt in Windsor, New South Wales made observations of the comet from 1 August to 7 October, on 19 October, John M. Thome at Córdoba, Argentina made the last observation of Comet Coggia. On the evening of July 21 with a first quarter moon, saw the comets tail shortening and extending, lightening up and extinguishing like the rays of certain auroras. Extended undulations, rapid vibrations, ran along it in succession from the horizon to its extremity, the pulsations and waves of light were of unequal duration, some being rapid, while others lasted a longer time. From May to July 1874, Huggins, Secchi, Lockyer, Rayet, at first only a continuum was found, but by mid-June the three typical comet spectral bands were found. According to Huggins, Comet Coggia was the first bright comet which has appeared since the since the spectroscope has become an instrument of scientific research. Using 638 observations of Comet Coggia made over a period of 185 days, on 9 July 1874 the comet reached perihelion at about.6758 AU from the Sun. On 23 July the comet made its closest approach to planet Earth at about.29 AU, gerard Manley Hopkins wrote on 13 July 1874 a journal entry concerning Coggia’s comet. THE BRIGHT-COMET CHRONICLES by John E. Bortle,1998 Coggias Comet, State Historical Society, Official Nebraska Government Website two pictures from The world of comets by Amédée Guillemin, trans. & ed. by James Glaisher Coggias Comet,1874, seen from the Pont-Neuf, Paris Fig.59. —Coggias Comet on July 13,1874, according to M. G. Rayet
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Great Comet of 1882
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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
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Great Comet of 1901
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The Great Comet of 1901, sometimes known as Comet Viscara, formally designated C/1901 G1, was a comet which became bright in the spring of 1901. Visible exclusively from the hemisphere, it was discovered on the morning of April 12,1901 as a naked-eye object of second magnitude with a short tail. On the day of perihelion passage, the head was reported as deep yellowish in color. It was last seen by the eye on May 23. In the pre-dawn of 12 April 1901 there was a discovery of the comet by Viscara. On April 24 the comet was observed at Cape Leeuwin in Western Australia. At the Sydney Observatory on April 25, H. C. Russell found the tail to be about 2° long. When the comets brightness reached a maximum on May 5, the tail had fanned out with a weak plasma tail about 45° long, on May 5 the comets brightness reached magnitude 1 or perhaps brighter. According to some observers the brightness might have reached magnitude −1.5, from naked-eye observations on May 5 there were at least two reports of aurora-like undulations in the tail. The comet was visible to the naked eye until about May 20. Using 160 observations over 43 days, Charles J. Merfield could calculate only a parabolic orbit, the comet travelled in a retrograde orbit relative to the planetary orbits. The comet was on April 10 about.56 AU from Venus, on April 24 the comet reached perihelion at about.245 AU from the Sun. On April 30 the comet made its closest approach to planet Earth at about.83 AU, bortle,1998 D. W. Hamacher, R. P. Norris, Comets in Australian Aboriginal Astronomy. In, Journal for Astronomical History & Heritage,1,2011, S. 31–40 Ref Book With Milner in S. Africa. Pp219 3rd May 1901 Looking out of the windows we saw a great comet dropping down the sky like a great shuttlecock. on return to Johannesburg
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Great January Comet of 1910
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The Great January Comet of 1910, formally designated C/1910 A1 and often referred to as the Daylight Comet, was a comet which appeared in January 1910. It was already visible to the eye when it was first noticed. At its brightest, it outshone the planet Venus, and was possibly the brightest comet of the 20th century, the comet brightened rather suddenly, and was initially visible from the southern hemisphere only. The year 1910 saw considerable media interest in the return of Halleys Comet. List of Solar System objects by greatest aphelion Great comet Media related to Comet C/1910 A1 at Wikimedia Commons JPL Orbit Simulator Donald Yeomans, the Great Daylight Comet of 1910, by John W. Bortle, Sky and Telescope
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Comet West
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There is another long-period comet West, C/1978 A1. Comet West, formally designated C/1975 V1,1976 VI, and it is often described as a great comet. It was discovered photographically by Richard M. West, of the European Southern Observatory, the comet came to perihelion on February 25,1976. During perihelion the comet had a solar elongation of 6. 4°. From February 25 through the 27th, observers reported that the comet was bright enough to study during full daylight, despite its brightness, Comet West went largely unreported in the popular media. With a nearly parabolic trajectory, estimates for the period of this comet have varied from 254,000 to 558,000 years. Computing the best-fit orbit for this comet is made more difficult since it underwent a splitting event which may have caused a non-gravitational perturbation of the orbit. The 2008 SAO Catalog of Cometary Orbits shows 195 observations for C/1975 V1 and 135 for C/1975 V1-A, Comet C/1999 F1 has a similar period. Aphelion is estimated at 70,000 AU, but orbital periods of millions of years are very unstable as they are subject to perturbations by passing stars and the galactic tide. Before the perihelion passage, and using 28 positions obtained between 1975 August 10 and 1976 January 27, Comet West was estimated to have a period of about 254,000 years. As the comet passed within 30 million km of the Sun, the first report of the split came around 7 March 197612, 30UT, when reports were received that the comet had broken into two pieces. Astronomer Steven OMeara, using the 9-inch Harvard Refractor, reported that two additional fragments had formed on the morning of 18 March, more recently, comets Schwassmann-Wachmann-3, C/1999 S4 LINEAR, and 57/P du Toit-Neujmin-Delporte, have been observed to disintegrate during their passage close to the Sun. The comet has been more than 50AU from the Sun since 2003, in the nomenclature of the time, it was known as Comet 1976 VI or Comet 1975n, but the modern nomenclature is C/1975 V1. List of Solar System objects by greatest aphelion
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C/2006 P1
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It was the brightest comet in over 40 years, and was easily visible to the naked eye for observers in the Southern Hemisphere in January and February 2007. With an estimated magnitude of −5.5, the comet was the second brightest since 1935. Around perihelion on 12 January, it was visible worldwide in broad daylight and its tail measured an estimated 35 degrees in length at its peak. The brightness of C/2006 P1 near perihelion was enhanced by forward scattering, the comet was discovered in Ophiuchus, shining very dimly at a magnitude of about +17. From August through November 2006, the comet was imaged and tracked as it moved through Ophiuchus and Scorpius, brightening as high as magnitude +9, then, for most of December, the comet was lost in the glare of the Sun. Upon recovery, it became apparent that the comet was brightening very fast and it was visible to northern hemisphere observers, in Sagittarius and surrounding constellations, until about 13 January. Perihelion was 12 January at a distance of 0.17 AU and this was close enough to the Sun to be observed by the space-based Solar and Heliospheric Observatory. The comet entered SOHOs LASCO C3 cameras field of view on 12 January, the comet left SOHOs field of view on 16 January. Due to its proximity to the Sun, the Northern Hemisphere ground-based viewers had a window for viewing. As it reached perihelion on 12 January, it became the brightest comet since Comet Ikeya-Seki in 1965, the comet was dubbed the Great Comet of 2007 by Space. com. On 13 and 14 January 2007, the comet attained a maximum apparent magnitude of −5.5. The comet was visible in daylight about 5°–10° southeast of the Sun from 12 to 14 January, perigee was 15 January 2007, at a distance of 0.82 AU. After passing the Sun, McNaught became visible in the Southern hemisphere, on 15 January the comet was observed at Perth Observatory with an estimated apparent magnitude of −4.0. The Ulysses spacecraft made a pass through the tail of the comet on 3 February 2007. Evidence of the encounter was published in the 1 October 2007 issue of the Astrophysical Journal, Ulysses flew through McNaughts ion tail 260 million kilometers from the comets core and instrument readings showed that there was complex chemistry in the region. The Solar Wind Ion Composition Spectrometer aboard Ulysses measured the composition of Comet McNaughts tail and it was the first time that O3+ oxygen ions were detected near a comet. This suggested that the solar wind ions, which did not originally have most of their electrons, gained some electrons while passing through the comets atmosphere. SWICS also measured the speed of the wind, and found that even at 260 million kilometers from the comets nucleus
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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
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Winter
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Winter is the coldest season of the year in polar and temperate climates, between autumn and spring. Winter is caused by the axis of the Earth in that hemisphere being oriented away from the Sun, different cultures define different dates as the start of winter, and some use a definition based on weather. When it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere, in many regions, winter is associated with snow and freezing temperatures. The moment of winter solstice is when the elevation with respect to the North or South Pole is at its most negative value, meaning this day will have the shortest day. The English word winter comes from the Proto-Indo-European root wend, relating to water, the tilt of the Earths axis relative to its orbital plane plays a large role in the formation of weather. The Earth is tilted at an angle of 23. 44° to the plane of its orbit, when it is winter in the Northern Hemisphere, the Southern Hemisphere faces the Sun more directly and thus experiences warmer temperatures than the Northern Hemisphere. Conversely, winter in the Southern Hemisphere occurs when the Northern Hemisphere is tilted more toward the Sun, from the perspective of an observer on the Earth, the winter Sun has a lower maximum altitude in the sky than the summer Sun. During winter in either hemisphere, the altitude of the Sun causes the sunlight to hit that hemisphere at an oblique angle. In regions experiencing winter, the amount of solar radiation is spread out over a larger area. This effect is compounded by the distance that the light must travel through the atmosphere. Compared with these effects, the changes in the distance of the earth from the sun are negligible, the manifestation of the meteorological winter in the northerly snow–prone parallels is highly variable depending on elevation, position versus marine winds and the amount of precipitation. A case in point is Canada, a country associated with tough winters. Winnipeg on the Great Plains at a distance from large bodies of water has a January high of −11.3 °C. In comparison, Vancouver on the coast with an influence from moderating Pacific winds has a January low of 1.4 °C with days well above freezing at 6.9 °C. Both areas are on the 49th parallel north and in the western half of the continent. Winter is often defined by meteorologists to be the three months with the lowest average temperatures. This corresponds to the months of December, January and February in the Northern Hemisphere, the coldest average temperatures of the season are typically experienced in January or February in the Northern Hemisphere and in June, July or August in the Southern Hemisphere. Blizzards often develop and cause many transportation delays, diamond dust, also known as ice needles or ice crystals, forms at temperatures approaching −40 °F due to air with slightly higher moisture from aloft mixing with colder, surface based air
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International Standard Book Number
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The International Standard Book Number is a unique numeric commercial book identifier. An ISBN is assigned to each edition and variation of a book, for example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, the method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering created in 1966, the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108. Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure, however, this can be rectified later. Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines, the ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker and in 1968 in the US by Emery Koltay. The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108, the United Kingdom continued to use the 9-digit SBN code until 1974. The ISO on-line facility only refers back to 1978, an SBN may be converted to an ISBN by prefixing the digit 0. For example, the edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has SBN340013818 -340 indicating the publisher,01381 their serial number. This can be converted to ISBN 0-340-01381-8, the check digit does not need to be re-calculated, since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland European Article Number EAN-13s. An ISBN is assigned to each edition and variation of a book, for example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, a 13-digit ISBN can be separated into its parts, and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts of a 10-digit ISBN is also done with either hyphens or spaces, figuring out how to correctly separate a given ISBN number is complicated, because most of the parts do not use a fixed number of digits. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for country or territory regardless of the publication language. Some ISBN registration agencies are based in national libraries or within ministries of culture, in other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded. In Canada, ISBNs are issued at no cost with the purpose of encouraging Canadian culture. In the United Kingdom, United States, and some countries, where the service is provided by non-government-funded organisations. Australia, ISBNs are issued by the library services agency Thorpe-Bowker
41.
Gary W. Kronk
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Gary W. Kronk is an American amateur astronomer and writer. Kronk was born in Granite City, Illinois, United States and this interest was focused even more by Comet Kohoutek. Kronk first observed this comet on November 30,1973, when he was a senior in high school and this observation provided the encouragement to research and write a paper about this comet and other great comets of the past for school. The teacher liked the paper so much, she submitted it to the local paper and he has been observing, researching, and writing about comets ever since. Kronk received a bachelor of degree in journalism from Southern Illinois University Edwardsville in 1981. He was then just shy of spending seven years in college as he struggled to find a major, in the end, he had a minor in English and extended studies in mathematics, physics, and psychology. Kronk is known as a observer, researcher, and writer. His latest book project is Cometography, which is a series being published by Cambridge University Press. His knowledge of the history of comets has led to the linking of several comets to older apparitions, Kronks comet research is also strongly aligned to meteor shower research, because of the relationship between the two fields. Charles P. Olivier Award, American Meteor Society,1999, the asteroid 48300 Kronk was named in his honor. Comets, A Descriptive Catalog, Enslow Publishers, Inc, Meteor Showers, Enslow Publishers, Inc. http, //meteorshowersonline. com Gary W. Kronks Bio Page Gary W. Kronk in libraries
42.
Coma (cometary)
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The coma is the nebulous envelope around the nucleus of a comet, formed when the comet passes close to the Sun on its highly elliptical orbit, as the comet warms, parts of it sublimes. This gives a comet a fuzzy appearance when viewed in telescopes and distinguishes it from stars, the word coma comes from the Greek kome, which means hair and is the origin of the word comet itself. The coma is generally made of ice and comet dust, water dominates up to 90% of the volatiles that outflow from the nucleus when the comet is within 3-4 AU of the Sun. The parent molecule is destroyed primarily through photodissociation and to a smaller extent photoionization. The solar wind plays a role in the destruction of water compared to photochemistry. Larger dust particles are left along the orbital path while smaller particles are pushed away from the Sun into the comets tail by light pressure. Comas typically grow in size as comets approach the Sun, and they can be as large as the diameter of Jupiter, about a month after an outburst in October 2007, comet 17P/Holmes briefly had a tenuous dust atmosphere larger than the Sun. The Great Comet of 1811 also had a coma roughly the diameter of the Sun, even though the coma can become quite large, its size can actually decrease about the time it crosses the orbit of Mars around 1.5 AU from the Sun. At this distance the solar wind becomes strong enough to blow the gas and dust away from the coma, Comets were found to emit X-rays in late-March 1996. This surprised researchers, because X-ray emission is associated with very high-temperature bodies. This ripping off leads to the emission of X-rays and far ultraviolet photons, with basic Earth-surface based telescope and some technique, the size of the Coma can be calculated. Called the drift method, one locks the telescope in position and that time multiplied by the cosine of comets declination, times.25 should equal the comas diameter in arcminutes. If the distance to the comet is known, then the apparent size of the coma can be determined. In 2015, it was noted that the ALICE instrument on the ESA Rosetta spacecraft to comet 67/P, detected hydrogen, oxygen, carbon and nitrogen in the Coma, which they also called the Comets atmosphere. Alice is a spectrograph, and it found that electrons created by UV light were colliding and breaking up molecules of water. OAO-2 discovered large halos of hydrogen gas around comets, space probe Giotto detected hydrogen ions at distance of 7.8 million km away from Halley when it did close flyby of the comet in 1986. A hydrogen gas halo was detected to be 15 times the diameter of Sun and this triggered NASA to point the Pioneer Venus mission at the Comet, and it was determined that the Comet emitting 12 tons of water per second. The hydrogen gas emission has not been detected from Earths surface because those wavelengths are blocked by the atmosphere, the process by which water is broken down into hydrogen and oxygen was studied by the ALICE instrument aboard the Rosetta spacecraft
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