Meteors Case Study Essay

jibe leadingites ar rocks from home, which land on commonwealth, attracted by her gravitational force. The shoot stars that you cypher at night, ar actu totallyy burning meteoroids that happen upon on globe from bring extracurricular topographic point This is the eldest of more(prenominal) interesting facts that argon going to follow. wherefore do meteorites fall? For the a a a a interchangeable(p)(p) reason why anything falls on country Gravity. precise(prenominal) few dirty dog escape it shooting starites pass their arrive atset in out around space. They be relatively microscopical pieces of distri neverthe littlee and detritus, unremarkably left down in the wake of a get along witht. Meteorites, that ar colossal in size of it, ca-ca their origin in space, as angulates.They atomic number 18 left over pieces of out muster from formation of the solar transcription, which could not clump in concert to form a major major major planet l ike our priming coat. on that read/write head is a sonorous strike of much(prenominal) angulates outside the rotate of the planet impair, called the Asteroid thrill. Asteroids be huge in size and their lengths batch number to kilometers Once in a tour, rocknroll-broken pieces of rock or spit, come into value of grounds gravitative get by and fall on globe as barb stars. An angulate dislodged from its trajectory and falling on basis is too called a meteorite. However, an star-shaped lastence huge in size, runs a cataclysmic explosion on footing on strike.OriginMeteor and Meteorite facts be interchangeable terms and we shall discipline why they atomic number 18 so. When these rocks and pieces of frame atomic number 18 floating in space, they atomic number 18 called Meteoroids. When they make a blazing opening into landed estates aureole, they argon called Meteors. Finally, if they survive the burning entry into Earths atmospheric state and f all on Earth, they be called Meteorites. So a meteorite could originate from comet debris called shooting stars or pear-shapedr tendencyive lenss called angulars here atomic number 18 any(prenominal)what basic facts n unlike(a) meteorites, meteors and meteoroids. Comets leave tons of dust and debris in their trail as they fail along long range of a functions round the temperateness. When Earth, go revolving tumefy-nigh the Sun, passes by whatsoever(prenominal) patches of this comet debris, it drop offs the Earths standard pressure causing meteor rain squanders.Meteor squanders ar hebdomadal aftermaths. genius back see thousands of meteors or shooting stars, as they are called, during much(prenominal) a shower. The most popular meteor showers are Perseids (which peak most August 12) and Leonids (which peak sightly near 17 November). During these showers, you crowd out observe a shooting star at the rate of 1 meteor per minute on an average. A fal ling meteor can give-up the ghost at speed of as lots as 44 miles per second One of the facts is that they retain whatever of the erst composition(a)est rocks in the solar ashes among them. They could be elderly than the Earth and date from the stop when Sun was forming all day, mingy to 4 gazillion meteoroids fall on EarthMajority of them are precise diminutive and at that short letterfore do not in rankect much harm. If a meteorite is detect age falling and healed from the air of fall, its called a fall meteorite. If a meteorite is not discover while falling, moreover lay out from any location, its called a scrape up. Till cc6, t make believeher wee been roughly 1,050 witnessed falls while at that place are virtuallywhat 30,000 documented Finds. Falling meteors which are round in size, can create an animated electro magnetized pulse, which temporarily disrupt radio conversation in the region of fall With a in good order designed radio antenna, you ca n actually catch out meteorites falling as radio noise.Types and CompositionHere are both(prenominal) facts rough their guinea pigs and composition, that you should know about. regain meteorites are classified into leash main(prenominal) categories which are Chondrites (Make about 86% of all re make do meteorites), Achondrites (8%) and press meteorites (6 %). The name Chondrites comes from features called Chrondules, which are melted silicate stuff and nonsenses from their past. Chondrites are about 4.55 billion long clipping old and are the display cases of rocks from which our take planet create Certain chondrite meteorites fallen from outer space contain traces of amino acids and organic function, bolstering the scheme that life-time w profitethorn wee been place on Earth This is champion of the most astounding facts. Achronidtes are relatively younger meteorites of the igneous rock typewrite and are pieces of asteroids, the stagnate and ruin Iron meteorite s are undisturbed of iron-nickel alloys and silicate materials. They are as well thought to be pieces of asteroidsE genuinely(prenominal) iodin of these meteor facts are intriguing. Earth has been pounded by the impact of many meteorites, ranging from the precise footling to gigantic meteorites. The meteorites impact volcanic craters that are strand on earth are testimony to this. It is time for the drop dead of our facts. One gigantic meteorite impact occurred billions of long time ago on Earth which brought on the experimental extinction of dinosaurs One question that may come to your mind is, Where do meteorites fall?. They could fall anywhere on Earth. Meteors befuddle been order all over the innovation. The recent findings hit been mostly in Africa and accessible character references of Antarctica. If you could find 1, you are bound to be rich as private collectors and museums pay trillions of dollars for them The reason is that they are very rare and are make up of minerals, which are never put together on Earth So keep looking You may never know, when unity might pop out of the sky, making you rich. So its actually profitable to know any(prenominal) meteor facts. Originating in the outer space, an object r apiecees Earth and gets a place in the list of meteorites.There befuddle been many instances of extraterrestrial bodies impacting the Earths come along while some impart unless passed by the Earths atmosphere in the for the offshoot time place they were abateed. Meteorites have been arousing interest of the masses as there is an element of mystery that surrounds them. Where do they originate? What makes some of them lay the Earths atmosphere? How solemn can they get? Space research and astronomy have revealed some interesting information about some of these questions and researched thoroughly on the different types of meteorites. nigh of the meteorites disintegrate forward reaching Earth while some reach the plan ets surface. commodious meteorites form craters on Earth while the littler ones involve less danger. Meteorites containing miniature round particles are cognize as chondrites and form about 86% of those falling on Earth. Those correspondent in demeanor to trivial igneous rocks are called achondrites and be prevaricationved as creation the crustal material of asteroids.Meteorites originating from the core of asteroids are known as iron meteorites and form about 5% of the meteorites, which fall. score has recorded a number of instances of meteorites impacting the Earth. ALH 84001 It was found in the Allan Hills, Antarctica in December 1984. Meteorite hunters of the unite States work on ASMNET project sight this meteorite. When discovered, its mass was 1.93 kilograms and its rock was reportly one of the oldest forms. This meteorite was supposititious to have come from Mars. later(prenominal) it was believed to live of some traces of the life on Mars and this made ALH 84 001 to a greater extent famous than ever. Hoba This meteorite lies on the uprise Hoba West in Namibia and has never been locomote elsewhere be engender of its butionally great mass.With a mass of about 60 tons, it is the life-sizest meteorite known to mankind. It is tabloid in operate and composed of metal. It is believed to have landed on Earth about 80,000 years ago. In 1955, it was declared as a national monument and has since wherefore been attracting visitors from different part of the world. Tunguska Event The Tunguska explosion took place in June 1908 near Tunguska River, now a part of Russia. more or less probably, the air burst of a large meteorite caused this explosion. The strength emitted from this explosion was about 1000 times greater than that of the bomb b croak of Hiroshima. consort to the eyewitnesses of this explosion, the event started with a flash of glimmery blue sapless and a sanitary originating from east and moving northward. Later the sound w as accompanied by shock waves that broke windows miles out. This was one of the famous disintegrating meteorites that remain in the list of worlds most famous meteorites.Willamette Meteorite This is an iron-nickel meteorite that was discovered in the coupled States near Oregon. It is the largest of the meteorites found in the United Sates as also the sixth largest in the world. probably the meteorite had landed in the region, which is now known as Canada. This meteorite weighing about 15.5 tons is one of the very large meteorites of the world. Orgueil This meteorite dismiss in France in 1864 and is a relatively older meteorite. The fall of this meteorite consisted of small stones that covered a massive area.This is one of those eight meteorites that drop dead to the CL chondrite group. A striking feature of this type of meteorite it that its composition is similar to that of the Sun. This meteorite is one of the most researched ones. For purposes of lateer national of the co mposition of this meteorite, it was split into pieces. Currently, it exists in the form of pieces unplowed in different museums in atomic number 63 and the United States. These were some of the famous meteorites of the world. They have constantly been a subject of interest for researchers some the world.Meteor showersA meteor shower is a supernal event wherein it is detect that a group of meteors radiate from anyone point in the sky. This phenomenon is also known as Meteor Storm or Meteor Outburst. The meteors that are establish in the showers are actually cosmic debris that enter the Earth atmosphere at very laid-back speed and vaporizationize very quickly collectible(p) to friction leaving arsehole a streak of light which is known as the meteor shower. An identified meteor shower is usually an annual affair as the Earth get out encounter the uniform meteors at approximately the same time and same speed every year.CausesMeteor showers are a result of inter fulfill that t akes place amidst the planet Earth and a comet. Comets consist of glass and rocks ( a good deal termed dirty ice balls) that champaign around the sun like planets. Every time the comet gets shutting to the sun, some of the ice present in the comet melts which cites a large mensuration of debris. This debris moves past from the comet and renders a part of its pursue which is open part of the comet.The inviolable move of the tail are the meteoroids and they spread along the entire orbit of the comet which is termed as a meteoroid teem. As the Earth orbits around the sun, its path may cross the meteoroid stream and a meteor shower follows. When the meteoroid stream is particularly dense, then we get to witness the meteor storm and having witnessed one myself, I can guarantee that the sight is actually spectacular.People Behind the C at a timeptIt is believed that Irish astronomer George Johnstone Clooney collaborating with the British astronomer Arthur Matthew Weld Downi ng and Adolf Berberich belong to the Royal Astronomical Computation Institute in Berlin, Germany offered the very outgrowth idea of the meteoroid stream in the 1890. They were able to send as to how the meteoroids once freed from the comet would travel at low speeds when compared to the comet itself would start drifting after completing one orbit. This set was attributed to unsubdivided orbital wherein the materials drift laterally outside(a) from the comet as some particles make a bigr orbit when compared to some proterozoic(a) particles. The gravitational pull of the Earths atmosphere would decide where the dust trails would pass the Earths atmosphere. It is a fair possibility that some years, the dust particles can completely miss the Earths orbit.Major Meteor ShowersIf you want to watch meteor showers then the outdo time of the year is the night of January 3. The shower has been named Quadrantids and this particular shower can produce over a reason out to 140 meteor s per hr. The seminal fluid of this shower is not a comet but a minor planet, 2003 EH1 which suffered a ruinous breakup in 1490. However, the showers are very faint and the peak hours last only for a few hours. Hence, you lead have to be in a good morsel and at an ideal point to watch the shower in all its glory and the crush place to watch this particular shower is from the Northern Hemisphere. moreover people in sulfurern Hemisphere subscribe to not be disappointed.As a bet of fact, they get to witness a meteor shower termed Eta Aquarids which consists of debris from the famous Halleys Comet. This shower peaks on the night of May 5 and the rate of meteors is about 30 per hour. The meteor shower Geminids is considered to be the best annual shower. It peaks around the night of December 13 and the rate of meteor is around 70 per hour. The root of this shower is also a minor planet, 3200 Phaethon. It is best visible from the Northern Hemisphere and it is believed that paya ble to the complete cold conditions, the air tends to be more innocent and this is the reason as to why this particular shower is spectacular.Sporadic Meteor ShowersWhen the meteoroids collide with each otherwise and can bring forth a part of the noncontinuous meteors background. They form isolated meteors and are not a part of any shower.AsteroidsAsteroids are considered to be remnants of an primeval broken planet of the solar dodging. Asteroids have no fixed shape and are too small to be spherical in shape. They are ellipsoids ( cardinal dimensional figure), dumbbell or irregularly shaped. As they have different shapes, they also vary in their size. The first asteroid wrap, discovered in January clxxx1 by Italian astronomer Giuseppe Piazzi, is the largest known asteroid and is 940 km in diameter. any(prenominal) of the smallest asteroids are full 6 meters in diameter. The mass of all the asteroids added together, is believed to lesser than the mass of the Moon. only if 200,000 asteroids have been discovered so off the beaten track(predicate), but billion more undiscovered asteroids s public treasury exit in our solar system.Asteroid Belt nigh asteroids lie in the asteroid sing amid Mars and Jupiter, however there are more belts in the solar system, namely the ones beyond Neptunes orbit. The belt itself has interesting origination theories. about astronomers believe that the belt is a broken planet, while some order that the belt is primordial material that never change integrity into a planet because of Jupiters gravitational pull. The asteroid belt lies between the orbits of Mars and Jupiter and contains more than 200 asteroids big than 100 km in diameter, and more than 750,000 asteroids with diameters larger than 1 km.Most asteroids are found in this belt because of the gravitational interaction between the solar system and the airy bodies in it. As opposed to the fiction made popular by various depictions of the asteroid belt, it is no t at all dense. The region is so considerable that asteroids are hundreds of thousands of kilometers away from their close neighbor. The asteroids are so small and far away from each other that they pop out as faint stars, and except for Ceres, are not bright enough to be seen without some telescopic aid. all told the asteroid Vesta, on rare occasions of an exceedingly clear dark sky can become visible to the naked eye.What are Asteroids Composed Of?Asteroids are made of different minerals and substances. This depends on the planet they broke away from in a contact, as well as the chemical reactions they might have experient while orbiting in the solar system. The asteroids surrounding(prenominal) to the Sun are mostly deoxycytidine monophosphateiferous and the ones further away are composed of silicate rock. The metallic asteroids are made of 70-80% iron and the remaining is nickel with many other metals such as iridium mixed in. Some are also made of half silicate and half metallic. The asteroid Ceres is composed of a stony core covered by an icy mantle, whereas Vesta has a nickel-iron core, basaltic crust and a covering of atomic number 12 iron silicate (olivine mantle). Asteroids composition has been classified as the future(a) C class asteroids They are found in the Earths outer belt and are darker and more carbonaceous than the ones found in the S class. D class asteroids They are also known as Trojan asteroids of Jupiter and are dark and carbonaceous in composition. S class asteroidsThey are found in the Earths inner belt, proximate to Mars and are composed of mostly stone and iron. V class asteroids They are a nappy group of asteroids that follow a path between the orbits of Jupiter and Uranus, and are made of igneous, eruptive materials. A near-Earth asteroid collided with the Earth about 65 one million million years ago, which triggered environmental changes, leading to the extinction of the dinosaurs. This asteroid created a huge ci rcular depression called the Chicxulub Basin and is bear on in Mexicos Yucatan Peninsula, a major holidaymaker attraction. Though the chances of asteroid collision with the Earth is very rare, they do come very close to our planet due to collisions and gravitational tugs on the extremely pissmelon-shaped Suns orbit. Most asteroids burn up in the atmosphere and never reach the Earth. NASA projects, such as the Lincoln skilful-Earth Asteroid enquiry (LINEAR) and the Near Earth Asteroid Tracking (NEAT) main objectives are to detect and intercept asteroids or other ethe original bodies coming close to the Earth earlier they cause untold damage to our planet.Asteroids are small celestial bodies composed of rock and metal, that revolve around the Sun. Their size can vary some asteroids are large and roughly spherical in shape, due to which they appear like miniature planets while the others are small and irregularly shaped. The matter of these celestial bodies also differs. The as teroid Vesta, is believed to have a nickel-iron core, olivine mantle and basaltic crust, while the asteroid 10 Hygiea is composed of carbonaceous chondrite. Most of the small asteroids are piles of rubble held together by gravity. Some asteroids supposedly have traces of amino-acids and other organic compounds, and it is take for granted that the impact of asteroids on the Earth could have seatd life on the planet by seeding it with the necessary chemical substances. Although, it is believed that the asteroids may have planted life on the Earth, they are capable of having catastrophic effect on the planet as well.Asteroids with a diameter of 5 to 10 meters, and energy rival to 15 kilotons of TNT, enter into the Earths atmosphere approximately once every year while, those with a diameter of over 50 meters enter the Earths atmosphere approximately once in a thousand years. Their impact can be devastating if they hit the Earth, but they disintegrate in the upper atmosphere and most of the particles are vaporized, therefrom rendering them harmless. In the distant past, our planet has experience a massive climate change and large-scale extinction of animal and plant species, ascribed to the impact of some large asteroids on the planet. The exogenesis possibleness suggests that origin of life on the Earth must have been triggered by the impact of some asteroid, carrying organic chemicals needed to initiate life form. The Cretaceous-Tertiary extinction event, which led to the end of dinosaurs and the Permian-Triassic extinction event that led to the end of the Permian flow complete off 90% of the species on the planet, are believed to be the result of an asteroid impact on the Earth.The craters on the solid bodies in the solar system, which were attributed to volcanic activities till 1960s, were actually formed due to the impact of celestial bodies. Researchers have determined that in the last 600 million years, 60 objects with a diameter of five km or more, have struck the Earth. Even the smallest of these object possessed energy of ten million megatons of TNT, and would have formed a crater, approximately 95 km in diameter, on the surface of our planet. The Rio Cuarto craters in genus Argentina are believed to have formed due to the impact of asteroids that struck this area around 10,000 years ago. In 1490, ten thousand people reportedly disjointed their lives due to a hail of stones from the sky. This hail of stones is assumed to be result of the disintegration of a large asteroid, after it entered the Earths atmosphere. In 1908, a mid-air explosion of an asteroid destroyed 80 million trees, deep down an area of 830 miles, near the Podkamennaya Tunguska River, in Siberia.In many cases, the sighting of a foreign frame, such as an asteroid or a meteoroids is reported as a fireball in the sky. Millions of asteroids go out pass by the Earth in the years to come. Though, they are outlander now, they are detectable as they come closer to the planet. The Lincoln Near-Earth Asteroid Research (LINEAR) and the Near Earth Asteroid Tracking (NEAT) are projects initiated by NASA to detect asteroids or other such foreign bodies coming close to the Earth.The need of the hour is to develop an intercept system in space, to destroy or deflect foreign objects heading towards our planet, before they prove catastrophic. Asteroids are celestial bodies consisting of rocks and metals. They are principally concentrated in the region known as the asteroid belt which lies between the orbits of Mars and Jupiter. Asteroids can be as big as Ceres, which is close to 1000 kilometers in diameter, or can be just a few feet in diameter. some(prenominal) the size, asteroids are neither big enough to be called planets nor are they as small as comets. They are classified as minor planets that include the Kuiper Belt Objects.DiscoveryOn January 1, 1801, Giuseppe Piazzi discovered the first asteroid which he initially thought to be a comet. He named this asteroid Ceres, after the Sicilian Goddess of grain. Ceres is also the largest asteroid to have been discovered so far. Soon, other large asteroids like Pallas, Juno and Vista were discovered. By the end of the 19th century, several hundred asteroids were discovered. governing body of AsteroidsIt was once believed that asteroids were formed by the explosion of a planet orbiting between Mars and Jupiter. However, according to present day astronomers, asteroids are debris left behind by the Big Bang that could not come together to form a tenth planet because of the effect of Jupiters gravitational pull.Asteroid HitsAsteroids have been hitting the Earth since millions of years. However, due to the friction with Earths atmosphere most of the asteroids get burnt. The asteroids that enter the Earth s atmosphere are called meteors while the ones that get burnt and appear as shooting stars are called meteorites. According to the Giant Impact Theory, the Moon was created when The ia, an asteroid of the size of Mars, collided with the Earth in the early days of the solar system. However, some consider Theia to be more of a planetoid than an asteroid. The largest crater caused by an asteroid hit is the Chicxulub Crater in Mexico that is 180 km in diameter. The asteroid that formed the crater had a diameter of 10 km. This collision is supposed to be accountable for the extinction of a large number of flora and fauna including the dinosaur. However, the evidence of the largest asteroid hit is in the Vredefort crater in South Africa that is 300 km in diameter.Impacts of Asteroid HitsThe damage that an asteroids impact can cause depends mainly upon its mass and velocity, as these are the two factors that determine the energy that is released when an asteroid hits the Earth. magical spell some asteroids are capable of sending thermal waves that can incinerate most flora and fauna within a few hundred kilometers, some larger asteroids can create huge impacts causi ng magma to cover areas as big as continents. The worst effect of an asteroid hit is the blocking out of sunniness for months together due to formation of dust corrupts and lampblack in the upper atmosphere. This would hamper the discolor plants might to prepare intellectual nourishment through the process of photosynthesis and the food chain would be disrupted.Near-Earth AsteroidsNear-Earth asteroids are those that have moved closer to the Earths orbit as they have been knocked out of the asteroid belt due to collision with other asteroids or comets, or due to the gravitational forces of Jupiter. They are classified into the following three groups The Amors These are near-Earth asteroids that cross the orbit of Mars but do not go out of the Earths orbit. The Apollos The orbits of these near-Earth asteroids cross the Earths orbit but have an orbital period of greater than one year.The Atens These near-Earth asteroids have orbits that cross the Earths orbit but have an orbital period of less than one year. Asteroids are currently beingness monitored for their probability of colliding with the Earth. such(prenominal) studies have predicted that asteroids may hit the Earth on February 1, 2019 and March 16, 2880. The probability of the 2880 collision is as high as 1 in 300. A number of projects in the field of astronomy, like Spacewatch, Near-Earth Asteroid Tracking and Catalina Sky Survey are being carried out to detect any panic of such catastrophes.CometsA comet is a small body in space. It was matter of great interest to astronomers like Sir Edmond Halley. Many decades later, comets still remain a challenge mystery for the field of astronomy. Space research institutes around the world have reported the existence of 3628 comets that are known and examine. Annually, an average of one comet is spy by the naked eye from the surface of the Earth. According to the definitions attached by the various space research organizations, a comet can be defined as a space body that travels in an ovate orbit around the sun. Most of the comets travel in elliptical orbits. When the comet comes in the vicinity of the star it is orbiting around, its comma-like tail gets lighten. A majority of comets are visible only through telescopes and other aids. There are however, some comets which are also visible to the naked eye.What is a Comet make Up of?A comet is principally made up of ice, dust and different forms of gases. The nature of the components differs from comet to comet. The central part of a comet that looks like a ball is termed as the nucleus. The nucleus is principally made up of ice and frozen gases. The frozen components also include many other compounds like ammonia, methane and carbon dioxide. Rocks are other component of the nucleus. Due to such composition, the nucleus of the comet often resembles a huge ball of dirt and snow. It is also believed by some astronomers, that the nucleus of a comet is quite a fragile because several comets have split into part without any explainable reason except large velocity.The huge elliptical orbit takes the comet in the range of heat of the star around which it is orbiting. When the comet enters the inner parts of the solar system, the frozen content of the nucleus starts melting. The gases and water within the nucleus vaporize as a result of radiation from the star and the solar wind. The massive velocity of the comet and the solar wind, push the vaporized matter away from the nucleus. This gives the comet its distinct tail and the comma-like appearance. The high amount of heat and the ions (charged particles that are formed due to the heat of the sun) cause the tail of the comet to glow.How are Comets make?According to their formation or birth, the comets can be classified into two types. The first type is short comets which originate in the Kuiper belt as space bodies beyond the orbit of Pluto. The gravitational pull of the planets in the solar system, causes th e origin of short term comets. These comets enter the solar system and take the form of alive(p) and glowing comets. Long term comets originate as traveling bodies in the Oort cloud (located around 50,000 light years away from the sun). The gravitational attraction of the planets in the solar system and other gravitational forces cause these comets to form elliptical orbits.Death of a CometThe account of comets has revealed that they have a fragile structure. Sometimes, comets split into parts due to sheer velocity. The entry and exit of comets in the solar system in course of its orbit, reduces the amount of matter (ice and frozen gases) in it. Due to this simplification in matter, the comets break-up and disperse into clouds. A dead comet is slide fastener but an asteroid or a similar form of a space body. Sometimes the comets also crash in other planets when their orbits cross each other. The most famous example of such a comet is the Shoemaker Levy 9, that crashed into Jupit er. For astronomers who have spent their lives take in comets, it a very heart-breaking moment to gaze at a dying comet. The Halleys Comet is said to be one of the most beautiful comets.Another very beautiful comet is the Hale-Bopp, that was discovered in the year 1995, on 23rd July. It was predicted by astronomers that the Halleys Comet would be sighted in the November of 1835. Mark couplet, the famous writer, was born just two weeks after the sighting. He developed a very special liking towards the Halleys Comet. In his biography he comments,I came in with the Halleys Comet, and expect to go with it. The Almighty has said no doubt, Now here are two inexplicable freaks they came in together they must go out together. Halleys Comet was side by side(p) sighted on twentieth April, 1910. Twain ended the journey of his life the very next day. The journey of any comet is indeed like that of Mark Twain. It is remarkably long, fast, adventurous as it streaks crosswise the dark sky.Hale ys cometHistorical SpottingsBritish scientist, Edmond Halley who observed the comet in 1682, was the first person to establish its episodic reappearance after every 75-76 years. He studied the comet and quite accurately predicted that it had earlier appeared in 1531 and in 1607. It was named Halley in his honor and was observed again in 1758 as stated by him. It was last seen in February 1986. However, this was not the first time the comet was in focus. The first sighting recorded, was way back in 240 BC, by the Chinese and was mentioned in a chronicle, Records of the Great historiographer. The comet also finds a mention in a Babylonian clay inscription of 164 BC. It has always been a subject of great interest, since it was believed to have an influence on the contemporary events. Armenian king Tigranes II, had its image printed on the coins issued in his regime after it was sighted in 87 BC. Therefore, even though the recurrence of the comet was an unknown fact, people were fasci nated by its appearance.The bright star that appeared in the night sky in 12 BC, coinciding with the birth of Jesus, is widely believed to be the Halleys comet. Giotto Di Bondone, the famous Italian painter, who lived before the renaissance era, mixed it in his work The Star of Bethlehem in the Nativity, in 1305. He had seen the comet appear in 1301 and was impressed by the spectacle. In the middle ages, the appearance of a comet was considered to be a warning sign of a extraverted danger.The most famous incident of spotting a comet during this period, was in 1066, before the Battle of Hastings. King Harold who had scattered the employment, was believed to have seen the comet due to which he was cursed. In fact, the Bayeux tapis in Normandy, France, signifies the Norman victory in this battle with an image of King Harold looking at the comet in the sky. In 1456, Pope Calixtus III had condemned its appearance considering it to be an evil omen. Three years antecedent to this, Eur ope was defeated by the Ottoman Empire. Human beings have always blamed celestial phenomena, whenever they have not been able to explain the causes of certain un affirmatory events.Historically, the heraldic bearing of a comet in the night sky was usually cited as the reason behind difficult situations that were beyond the reasoning of common man. A French physician, Ambroise, had exposit the pitiful conditions of middle ages, when a comet was seen just before the spread of a big epidemic. According to him, some people were scared to death while others fell sick on seeing the comet. It was believed to be some evil form leaving behind a trail of blood, believed to be a sign of misery. new SpottingsIn the 16th and the 17th century, scientists learned to calculate the speed and outstrip at which comets travel around the Sun. Once, Edmond Halley had established the year of its reappearance, Halleys comet became a matter of great interest. Although, he didnt live to see his predictio n coming true, his observation had a evidentiary impact on the way society comprehend comets. The sighting of a comet, especially Halleys comet became less of a concern and more of a peculiarity among people. Once people realized that comets are orbiting bodies just like planets, they became less apprehensive on the reaching of a comet in the Earths visibleness zone. The change in the attitude of the people was seen in the depiction of the comet in the contemporary pictures. Halleys comet was a subject of scientific study and was depicted as a beautiful heavenly body in the sky. Famous American writer Mark Twain was born in 1835, the year when Halleys comet had appeared.He predicted in 1909 that since he had come with the comet he will go out with it. Sure enough, he passed away a year after the comet reappeared in 1910. In the 1900s, it had appeared twice once in 1910 and then in 1986. Further studies gave us a deep discernment into the structure, composition and orbital journ ey of many different comets. Halleys comet has one of the shortest orbital paths. It is classified as a short period comet, i.e. comets having an orbit period of 200 years or less.Once upon a time, it belonged to the long period class, but due to the gravitational force of planets, its orbit shortened over a period of time. Today, it is known that comets like Hale Bopp which appeared in 1997, will reappear after 4200 years Thus, Halleys comet is the most frequently spotted one. Recently, it was seen in February 1986. During this visit, it was subjected to its biggest test ever. Five ballistic capsules from The European Space Agency, Japan and the USSR were launched to study its surface. Structure and Composition of Halleys CometHalleys comet is a big mass of ice and dust, having an elliptical orbit and shaped like a peanut. It has a super elongated orbit, taking it very close to the Sun. It flings off far in the outer solar system, similar to a slingshot motion. The composition is mainly of water, atomic number 11 monoxide, methane, ammonia, hydrocarbons, iron and sodium. Its closest blank space from the Sun was found to be just 0.6 AU ( galactic unit) and the farthest distance was calculated to be 35 AU, roughly the same distance as that of Pluto. It orbits the Sun in a retrograde or in the direction opponent to that of the planets revolution. The speed with respect to the Earth is quite high, since it is exceedingly eccentric and inclined.The day time is relatively more on its surface and its maximum temperature rises up to 77 degrees celsius. Due to its large size and a absolved and regular orbit, it was easy for the probe missions photograph it well and study its surface. The mass of the comet is 1.71015 kilograms and the size of the nucleus has been estimated to be 15 km 7 km 7 km. Winds blowing near its surface are so well-set that 1 gram particle of dust which hit the Giotto space probe, briefly destabilized it. Halleys comet will next appear in 2062. Comets have always been a fascination for human beings and will continue to charm generations to come, as we discover more interesting facts about these spectacular fireballs, the comets.Comet lullinComet Lulin was discovered on July 11, 2007, by the duette of Ye Quanzhi and Lin Chi-Sheng. A non-periodic comet, Lulin appears to be greenish in color. This green color is attributed to the presence of gases such as cyanogen and diatomic carbon, which produce a green glow when illuminated by sunlight in the nihility of the space. formally designated as C/2007 N3 (Lulin), it is also known as the Comet of Cooperation in China and Taiwan, as the two individuals refer in its uncovering, were from these two countries. This comet was first photographed by Taiwanese astronomer Lin Chi-Sheng on July 11, 2007, while he was working on the Lulin Sky Survey abide (LUSS) at the Lulin observatory in Nantou, Taiwan. The Lulin Sky Survey Project aims to identify the numerous small obje cts in the solar system, particularly those that pose possible hazards to our planet. Lin used a 16-inch telescope to photograph this comet, which was initially assumed to be an asteroid.A few days later, Ye Quanzhi, a 19-year old student of meteorology from Sun Yat-Sen University, China, recognized this comet while going through Lins photographs. Its status of being a comet was confirmed after the presence of coma, the turbid windbag around the nucleus of the comet, was noticed. Both, Lin and Quanzhi were accredited with the discovery of this new comet. As it was first noticed from the Lulin Observatory, it was named as Comet Lulin. Comet Lulin was seen in the Libra constellation from January to March 2009. In January, it was getting brighter and could be seen just before pass over while in February, the brightness reached its peak. Eventually, in March, it started to draw as it went farther away from the Earth. While it was near the Earth, it had a typical tail pointing away from the Sun, as well as an anti-tail which was directly pointing towards the sun. Although, it was assumed that this anti-tail was observed only in photographs, some observers reported that it was visible even from a telescope in February 2009.According to Brian Marsden, an astronomer at Smithsonian Astrophysical Observatory, Massachusetts, this comets closest shape up to the sun was on January 10, 2009 when it reached a distance of 113 million miles from the sun. He noticed that the comet was moving in a retrograde orbit that is near-parabolic. On February 24, Comet Lulin came the closest to the Earth, at a distance of 0.41 AU or 38 million miles to be precise. On February 4, 2009, a team of Italian astronomers, under the leadership of Ernesto Guido, witnessed a strange phenomenon taking place in comet Lulin. While photographing the comet with a remotely controlled telescope in sassy Mexico, they saw that its tail suddenly disconnected. Ernesto attributed this odd phenomenon to magnetic disturbance of the solar wind hitting the comet. Earlier, this had been observed with Comet Encke too, when coronal mass ejection occurred, due to such magnetic storms.Photographs taken by NASAs quick Gamma-ray Explorer satellite in ultra-violet and X-rays show that Lulin is cast 800 gallons of water every second. Observations by NASA also revealed that the surface material of the comet was burning away due to suns heat. This sighting of Comet Lulin was a once-in-a-lifetime opportunity for the whole world, as there is no possibility of this comet go to the inner solar system, at least not for the next thousand years. Human kind has always looked to the heavens in awe and wonder, and sometimes in fear. Perhaps no other astronomical phenomenon except a total solar eclipse has historically evoked as much fear as comets. When the specter of fear is removed, however, they emerge as strikingly beautiful objects in the sky. It was once believed that if earth passed through a ta il of a comet, its inhabitants would die this theory has been discredited. Comets are messengers from a time long past.Most are chunks of dirty ice, locked away in the Oort cloud for billions of years. (Oort cloud It is the source for long period comets, with orbital periods of greater than two hundred years.) Comets are well-known(prenominal) to nearly everyone as striking star like objects with long tails stretching across a wide band of the sky. The most famous comet, Halleys comet makes its drive home to the skies every seventy-five years. The word comet is derived from a Greek word meaning long haired Comets were greatly feared before the twentieth century as deleterious omens. Since then, they have been identified and cataloged as objects that come from deep space. Most of them occupy orbits that carry them far outside the solar system. Many of them make only a single approach to the sun and never return again, while others exist in stable, but highly elliptical orbits tha t allow them to return after an lengthened period of time, such as the Halleys comet. In 1986, the European space probe Giotto passed about 600 kilometers from the Comet Halley as it made its close approach to the sun.The probe verify existing theories that comets are made up of ices covered by black dust or soil. The ballistic capsule confirmed a theory that had been advanced prior to the reconnaissance that described comets as dirty snowballs. victimisation data taken by the spacecraft, scientists determined that the dust is composed of carbon, hydrogen, oxygen, and nitrogen. Other metals have also been discovered in comets, such as iron, calcium, nickel, potassium, copper and silicon. Halleys comet was one of the darkest objects ever seen in the solar system it was basically flat black. Comets are composed of a medley of ices and dust. As a comet approaches the sun, it absorbs the suns energy and warms up. The main body of the comet is called the nucleus. As the nucleus warms, the ice downstairs the comets soil melts. Because the comet has no atmosphere, the evaporated substance (also called a inconstant) escapes into the vacuum of space as a gaseous envelope that surrounds the comet called coma. As the coma grows, it forms a plume of vapor that carries away some of the comets surface as well.This mixture of evaporated volatile particles and dust is carried away from the comet by solar wind, is ionized by high-energy particles, and creates the spectacular tail of the comet. The comets tail, glowing in the solar wind, can stream behind the comet for millions of kilometers. The nucleus of the comet consists of mostly volatile ices and dust. The ice is nearly all water ice, but there is also evidence of ices composed of carbon dioxide and methane. More elementary compounds of nitrogen, oxygen, and carbon monoxide may exist as volatile ices. Comets are typically small bodies (comparatively). Halleys comet is a potato shaped object, 14 by 17 kilometers. The largest known comet is Chiron, which is estimated to be approximately 200 kilometers in diameter.Comets are thought to have formed as the solar system evolved. The material of which comets are composed was constructed by accretion at the outer edge of the disk of material that ultimately became the sun and planets. Because the comet material was fashioned at the outer edge of the solar system, the sun did not evaporate the volatiles in the cometary material. At the same time, the devil planets of the solar system formed at what would become the outer orbits of the solar system. These massive planets encountered the newly formed comets, and the ones that were not engulfed by the giant planets were, over the first billion years, catapulted into interstellar space by the planets massive gravitational fields. Not all comets met that fate, however. Some were quietly nudged into stable orbits closer to the sun. Others were flung into the inner solar system and impacted the inner planet s.Relevance The study of comets involves expatiate knowledge of its composition of the outer regions of the solar system and the space between the last planet and 100,000 astronomical units onwards. Cometary study also seeks to understand heterogeneous gravitational interactions between bodies separated by wide distances and even gravitational interactions between tiny comets, their behavior when approaching the sun, and something of the makeup and evolution of the early solar system. New comets approaching the sun for the first time have been held in deep freeze in the Oort cloud and are thought to be composed of primordial material of the newly forming solar system. They have been tied up in the Oort cloud for billions of years at temperatures slightly above absolute zero. As they approach the sun, their internal gases begin to steam away. A detailed study of an approaching comet may tell cosmologists about the composition of the early solar systems.Comets and their approach hav e also hinted at the existence of the tough brown shadow, thought to be one of the most common bodies of interstellar space. Because they are so dim, they are all but invisible from Earth. On the other hand, because brown dwarfs are thought to be so plentiful, the study of comets and their orbits may give the first real clues to the formers reality and abundance. In the early 1980s the existence of the galactic tidal action was merely speculation. Since then, careful study of cometary orbits and approaches has favorable supported the theory of galactic tides. In the close approach of Halleys comet by an unmanned spacecraft in 1986, a wealth of information was vulcanized on the shape, behavior, and composition of comets.The existence of the Oort cloud and the theory gravitational interactions by passing objects in space have led to the theory of periodic comet showers. Such comet showers, separated by periods of tens of millions of years, may be responsible for the mass extinction on Earth. There is a wide speculation that Earth was struck by one or more comets 70 million years ago, which wiped out the dinosaurs. Some scientists have speculated that this extinction was the result of a shower of comets from the Oort cloud, sent on their close approach to the sun by a passing star or brown dwarf through the Oort cloud.Comets have been used to judge vast distances, evaluate the composition of the solar system as it was being born, and even test the idea that the gravity of the entire galaxy can make a difference to the smallest objects in space. Comets have been used as yardsticks to evaluate what may be the most type of star in the galaxy-the brown dwarf-which ironically is one that may never be seen. They have also been called dirty snowballs. Halleys comet was so black that it was the darkest object ever seen in space. Yet, from these dirty specks of ice, cosmologists have witnessed some of the most spectacular light shows. Ultimately comets may also generat e clues to some of the most essential secrets about the solar system and planets. From these tiny messengers, cosmologists may unlock and examine pristine elements from creation itself.