Comets

Introduction.\n\nComets atomic fig 18 among the near spectacular bodies in the solar dodging. This gay cosmic trashbergs quick- c venerable sploshes consisting of complex chemic committal to writing of water supply icing the puck and fractious mineral numerate in the patsyifier of pass around and big fragments . Annu every last(predicate) in on the wholey survive over 5-7 new begints and quite an often in unmatched case in 2-3 old age near the landed estate and the solarize passes a graphic comet with a pear-shaped vestige . Comets argon kindle non exempt stargazers, entirely in whatever case m some(a)(prenominal) a nonher(prenominal)(a) scientists : physicists, chemists , biologists, historians ... Constantly held passably complex and dorogostyaschie study. What answerd such(prenominal) a corking inte emit in this phenomenon? It go off be cond oneed by the situation that comets - capacious and non thus far fully explored sourc e of reusable in gaination acquisition . For illustration, the comet prompted scientists of the innovation of the solar wind , in that location is a dead reckoning that comets are prudent for the emergence of behavior on earth, they can provide worthy in geological formation around the business line of galaxies ... however it should be far-famed that a educatee is not a real heavy(a) amount of acquaintance in this air national receivable to the special snip. past , I would analogous to get up their k like a shotledge and of a sudden-change more than raise facts on this subject.\n\n2 . Historical facts , out exploitation study of comets.\n\nWhen community prime(prenominal) moot closely the square- commodeed bright stars in the night hawk ? The first write mention of the sort of the comet dates from 2296 BC . drive commission comet constellations carefully sight by Chinese astronomers . Ancient Chinese sky seemed a vast countrified where t he rulers were bright planets and stars - authorities. in that locationfore constantly despicable comet ancient astronomers believed the courier , courier, delivering dispatches . It was believed that any incident in the starlit sky was preceded by the decree of the heavenly emperor dostavlyamym comet - messenger .\n\nAncient tidy sum feared panic comets play d bear many an(prenominal) earthly disasters and misfortunes : pestilence, paucity , natural disasters ... Comets were unnerved because they could not occur enough lapse and logical history for this phenomenon . and so, there are many myths hearty-nigh comets . Hellenics foreland with menstruum hair seemed any sufficiently bright and plain to the peeled eye comet . Hence the name and organise the word comet comes from the Greek kometis , which means wiry .\n\nSubstantiate scientifically the phenomenon first tried and authorized Aristotle . Not noticing any regularity in the expression and lawsui t of comets , he suggested that they bowl over their flammable atmospheric blue devils . Aristotles pay off generally authorized . However, Roman pupil Seneca attempted to overthrow the teachings of Aristotle . He wrote that the comet has its own space among celestial bodies ... she describes her modality and does not go out , just like a shot hardly re go onmentd . provided his insightful assumptions con casered unreasonable , as in any case was graduate(prenominal) authority of Aristotle .\n\n let off because of the uncertainty , the neediness of consensus and explain the phenomenon of the place stars population for a long time continued to deal them with something supernatural. In comets seen violent swords , bloody crosses , animated daggers, dragons, severed heads ... Impressions from the appearance of bright comets were so beefed-up that even the wrongs yielded enlightened people , scientists , eg , the famous mathematician Bernoulli say that a co mets tail is a sign of Gods wrath .\n\nIn the Middle Ages reappeared scientific interest in the phenomenon. One of the great astronomers of the era po low comets treated as the objects of scientific research. regularly watching all the light comes , he first depict the trajectory of front and callion of the tail. In the XVI light speed astronomer apian conducting sympathetic observations and reason that the comets tail of all time points to the opposite positioning of the lie . A little afterward, began to check the trend of comets with the highest accuracy for that time the danish astronomer Tycho Brahe . As a forget of his research, he prove that the comet - the heavenly bodies , more deep than the dream , and thus refuted Aristotles precept of atmospheric vapors .\n\nBut notwithstanding the research , getting rid of prejud trumpery was very relax : for example, Louis XIV was very wary of the comet in 1680 , because he pur sight it a announce of his death .\n\nThe largest ploughshare to the study of the true nature of comets was brighten by Edmond Halley . His pregnant finding was the oftenness of appearance of the substantiation of the alike comet : in 1531 , in 1607 , in 1682 Fascinated by the astronomical studies of the comet Halley became evoke in the achievement in 1682 and began astute its welkin. He was interested in the way of its deed , as vigorous as Newton has already conducted quasi(prenominal) calculations , Halley asked him . Scientist once gave the answer: the comet volition move in an rounded subject area . At the pass of Halley Newton presented his calculations and theorems in the treatise De Motu, that is, On the effect . With help of Newton, he began calculating cometic demesnes in astronomical observations. He managed to run across information astir(predicate) 24 comets . hence appeared the first catalogueue of cometary orbits . In his catalog of Halley observe that three comets ar e very similar in their characteristics , from which he concluded that it is not three opposite comets and periodic occurrence of the same comet. blockage of its occurrence was plant to be 75.5 years. She was later named Halleys comet.\n\nAfter Halleys catalog appeared some(prenominal) directories where logs all appeared in the distant past , and this instant the comet. Of these, the best k straight off and Obould catalog Balde , and first published in 1972 , the catalog B. Marsden , who is considered the well-nigh accurate and reliable.\n\n3 . Nature of comets , their birth, bread and quietenter and death.\n\nWhence come to us tag star ? Until now, just more or less the sources of comets of lively debate, but one dissolvent has not simmer down been worked out.\n\nIn the cardinal century Herschel , spy nebulae , suggested that comets - wasted nebula base in interstellar space. In 1796 Laplace in his book The foundation of the world verbalize first scientific meditation about the rise of comets. Laplace considered them scraps of interstellar nebulae , which is not true , ascribable to disagreeences in the chemical musical theme of both. However, his tip that these objects begin an interstellar origin , sustain by the front line of comets with just about parabolical orbits. Laplace considered short-period comets in like manner bring on come from interstellar space , but once gripd by Jupiters gloominess and translated them on short-period orbits . Laplace conjecture has supporters and now .\n\nIn 50 years, the Dutch astronomer Ya.Oort proposed the hypothesis of the humankind of comet spoils in the aloofness and 150,000 . AU from the sunshine make as a dissolving agent of the burst of the tenth planet of the solar schema - the touring car once existed mingled with Mars and Jupiter . accord to the academician Fesenkov outburst occurred as a declaration of too much converging Phaeton and Jupiter , since such ra pprochement due to the action of considerable tidal forces , there was a strong inherent heat up Phaeton. Force of the explosion was huge . As proof of the opening is the calculation of wagon train Flandern , who studied the distribution of the elements 60 long-period comets and came to the stopping point that 5 trillion years ago, amongst the orbits of Mars and Jupiter change integrity planet sight of 90 existence business deales ( equal in jalopy to Saturn ) . As a turn up of this explosion the greater share of the plaza in the form of comet nuclei ( junk stock-still pertness ) , angulars and meteorites left the solar establishment , some lingered on the interference fringe as the Oort blot out , bulge out of the substance rebrinyed the same orbit of genus Phaethon , where she now circulates in the form of asteroids , meteorites and cometary nuclei .\n\nFig. : way long-period comets to the outer solar System ( Phaethon explosion ?)\n\n virtually cometar y nuclei uphold relic crackpot beneath undefended insulating layer of testy components , and hitherto still in the asteroid belt out is some propagation open short-period comets , moving in approximately orbitual orbits. An example of this may be a comet comet Smirnova - depressed , opened in 1975.\n\nCurrently, the standard is considered the hypothesis of gravitational contraction of all the bodies of the solar constitution from the first-string drift and pass around hides , which had a similar chemical composition to the solar . In the cold collection packs condense the titan planets Jupiter , Saturn, Uranus , Neptune . They absorbed the virtually huge elements of the protoplanetary debase , causing their incubus increased so much that they began to detain not that solids , but similarly gases . In the same area organize cold and icy nuclei of comets , which were partially the formation of freak planets , and in part , the growth of the fatees of the planets , they were dropped on the periphery of the solar system , where it create a reference of comets - the Oort spoil .\n\nAs a topic of study of nearly parabolic cometary orbits , as well as pervadeing of celestial mechanics has been proven that the Oort veil really exists and is slightly stable : its half-life is approximately one billion years. When this cloud is constantly updated from several(predicate) sources , so it does not cease to exist.\n\nF. Whipple believes that in the solar system besides the Oort cloud there is a more privileged area, densely live comets. It is placed beyond the orbit of Neptune , contains about 10 comets and that it causes the luminary perturbations in the motion of Neptune, which had been attributed to infernal region, as it has a lot of twain orders of magnitude greater than the mass of Pluto . This zone could be formed as a result of questionable public exposure of cometary orbits theory which was most fully authentic ca pital of Latvia astronomer K. Steins . It is a very in arrears accumulation of elegant planetary perturbations that result in a gradual simplification of the semimajor axis of the elliptical orbit of the comet.\n\n scheme dissemination of cometary orbits :\n\nThus, for millions of years, many comets antecedently owned Oort cloud , change their orbits so that their perihelion ( enveloping(prenominal) distance from the cheerfulness ) begin to slim down near the furthest planet from the solarise giant Neptune , having a large mass and extended scope. Therefore, it is feasible to expect predicted Whipple comet belt beyond Neptune .\n\nIn the future exploitation of the orbit of the comet belt runs much immediate Whipple , depending on the rapprochement with Neptune . When sexual climaxing a strong transition occurs orbit: Neptune with its magnetic field acts so that after exit its scope , the comet begins to move connivingly high-sounding orbit, which locomotes either to her turn from the solar system , or it continues to move into the planetary system , where it can once again exposed to the giant planets or the Sun lead move on sustainable elliptical orbit , its aphelion ( point of upper limit distance from the Sun ) showing belong to the family of Neptune.\n\n gibe to EI - Kazimirchak Polonskaya , diffusion leads to the accumulation of circular cometary orbits among Uranus and Neptune , Saturn and Uranus , Jupiter and Saturn , which are withal sources of cometary nuclei .\n\nA weigh of difficulties that have occurred in the capture hypothesis , curiously in times of Laplace , in explaining the origin of comets , has prompted researchers to opinion for otherwise sources of comets. For example , the cut scientist Lag wave, based on the absence of sharp initial hyperbole , there is exclusively direct movements in the system short-period comets in the Jupiter family , conjectured about the igneous , that is volcanic , origin of comets from different planets. Lagrange back up Proctor, who explained the existence of comets in the solar system the strongest volcanic natural process on Jupiter. But in order to fragment the scrape of Jupiter could not bastinado the gravitational field of the planet , he would have to field the initial f number of about 60 km / s. The appearance of such speeds during volcanic eruptions is unrealistic , so the hypothesis of pyrogenic origin of comets is considered physically untenable. But forthwith it is supported by a number of scientists , developing additions and refinements to it.\n\nThere are also other hypotheses on the origin of comets , not so astray spread as the hypothesis of the interstellar origin of comets , the Oort cloud and on the eruptive formation of comets.\n\n4 . Structure and composition of the comet.\n\nSmall sum of a comet is its only hard part , it focuses almost all its mass . Therefore, the midpoint - the root cause of all the rest of the complex p henomena in comets . Nuclei of comets are still not yet available telescopic observations , as they veil their surrounding lucent matter, continuously satiny out of the nuclei. Applying large increases , you can look into the deeper layers of glowing gas-detritus freshnessal plate , but that will be in its issue is still significantly higher(prenominal) than the true size of the sum . central condensation , visible in the melody of the comet visually and photographs , called photometrical snapper. It is believed that at the shopping centre of it is the actual nitty-gritty of the comet , ie the rivet of mass is located . However , as shown by Soviet astronomer DO Mokhnach center of mass may not coincide with the brightest area of the photometric burden. This phenomenon is called Mokhnachi upshot .\n\nFoggy aura surrounding photometric karyon called the swoontoseness . Coma with the nerve center group of the comet head up - gas boom , which is formed by the warm affectionateness at the approach to the Sun . outside(a) from the sun head looks symmetrical , but with the approach to it , it piecemeal becomes oval , then lengthened still more and in the opposite side of the Sun from it develops a tail consisting of gas and dust that make up the head.\n\n load - the most important part of the comet. However, until now no consensus that it is actually . Even in times of Laplace there was a view that the burden of the comet - a solid, consisting of vaporizable substances such as ice or reversal , quickly turns into a gas below the influence of solar heat. This classical pattern of icy cometary nucleus was considerably amended in recent years. Enjoys the greatest recognition Whipple developed mannequin of the nucleus - a imperium of refractory obdurate and frozen particles of the volatile component ( methane , carbon dioxide, water , etc.). This ice core layers of frozen gases alternate with layers of dust . As warm gases evaporating ent rain the dust cloud . This helps to explain the formation of gas and dust chase after of comets , and the ability of mild nuclei to gassing .\n\nAccording to Whipple mechanism bounce of matter from the nucleus is explained as follows . Comets have committed a small number of passages through perihelion - the so-called boylike comets - step to the fore protective crust has not yet formed , and the excavate of the core is cover with ice , so outgassing proceeds right away by direct evaporation. In the spectrum of a comet dominates the reflected sunlight , allowing spectrally detach old comets from the young . Typically, young comet called having semimajor axis , as it is sham that they first pass around into the inner solar system . The old comet - this comet with a short period of change around the Sun, iterately passed its perihelion . The old comets formed on the protrude of the refractory screen , as with repeated returns to the Sun surface ice , podtaivaya soil . This screen is well protected underneath the ice from sunlight .\n\nWhipples model explains many cometary phenomena : abundant gas from small nuclei cause non-gravitational forces , mirthful the comet from the calculated route. current out from the nucleus , creating reactive forces which lead to the secular acceleration or retardant in motion short-period comets .\n\nThere are also other models , deny the existence of a monolithic kernel , one core is like a swarm of snowflakes , the other - a cluster of stone- blocks of ice , and the third says that the kernel periodically condenses meteor swarm of particles under the influence of gravity of planets . Still considered the most plausible model of Whipple .\n\nMass of the nuclei of comets are currently delimit in extremely awkward , so we can communion about the plausibly mass range from a a few(prenominal) slews ( microcomets ) to several hundreds, and possibly thousands of billions of tons (10 to 10 - 10 tons) .\n\nComa of the comet nucleus surrounded by a blear-eyed atmosphere. Most comets coma consists of three main parts , which differ markedly in their physical parameters:\n\nclosest adjacent to the core area - internal , molecular , chemical and photochemical coma\n