1.
Biela's Comet
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Bielas Comet or Comet Biela was a periodic Jupiter-family comet first recorded in 1772 by Montaigne and Messier and finally identified as periodic in 1826 by Wilhelm von Biela. It was subsequently observed to split in two and has not been seen since 1852, as a result it is currently considered to have been destroyed, although remnants appeared to have survived for some time as a meteor shower, the Andromedids. The comet was first recorded on 8 March 1772 by Jacques Leibax Montaigne and it was also recorded in 1805 by Jean-Louis Pons, but was not recognized as the same object.6 years. At the time it was only the third comet known to be periodic, after comets Halley, a third claim was made by Thomas Clausen, who had independently linked the comets. The comet appeared as predicted during its 1832 apparition, when it was first recovered by John Herschel on 24 September. Despite this, the fact that Bielas Comet was the comet known to intersect the Earths orbit was to make it of particular interest. The 1839 apparition was extremely unfavourable and no observations were made, the comet was recovered on November 26,1845, by Francesco de Vico. Initially a small, faint nebulosity, subsequent observations showed that something remarkable had happened to it, matthew Fontaine Maury, observing on 14 January 1846, noted that an apparent companion was located 1 arc minute north of the comet. After this announcement many astronomers began observing the comet, and noted that the two alternated in brightness, developing parallel tails as they approached perihelion. In 1852 the comet was recovered more or less as predicted, with Comet A being recovered first. Comet B was finally relocated on September 16, and once again both nuclei alternated in brightness during the period of observation, a was last detected on this apparition on September 26 and B on September 29, in both cases by Otto Wilhelm Struve. Neither part could be found on their periodic returns in 1859,1865. However, on November 27,1872, a brilliant meteor shower was observed radiating from the part of the sky where the comet had been predicted to cross in September 1872 and this was the date when Earth intersected the comets trajectory. These meteors became known as the Andromedids or Bielids and it seems apparent that they were produced by the breakup of the comet. The meteors were seen again on subsequent occasions for the rest of the 19th century, there were, however, inconclusive observations during the 1865 and 1872 returns. Charles Talmage, using ephemerides provided by John Russell Hind, claimed to have observed a nebulous object in approximately the right position in November 1865. Despite the apparent destruction of the comet, there were a number of searches for it during the later 20th century and it has been calculated that the mass of the debris left in the Andromedid meteor stream is still much less than the total mass of the comet. Given that it is likely that the main mass loss occurred near aphelion before the 1845 apparition
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.
Perihelion and aphelion
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The perihelion is the point in the orbit of a celestial body where it is nearest to its orbital focus, generally a star. It is the opposite of aphelion, which is the point in the orbit where the body is farthest from its focus. The word perihelion stems from the Ancient Greek words peri, meaning around or surrounding, aphelion derives from the preposition apo, meaning away, off, apart. According to Keplers first law of motion, all planets, comets. Hence, a body has a closest and a farthest point from its parent object, that is, a perihelion. Each extreme is known as an apsis, orbital eccentricity measures the flatness of the orbit. Because of the distance at aphelion, only 93. 55% of the solar radiation from the Sun falls on a given area of land as does at perihelion. However, this fluctuation does not account for the seasons, as it is summer in the northern hemisphere when it is winter in the southern hemisphere and vice versa. Instead, seasons result from the tilt of Earths axis, which is 23.4 degrees away from perpendicular to the plane of Earths orbit around the sun. Winter falls on the hemisphere where sunlight strikes least directly, and summer falls where sunlight strikes most directly, in the northern hemisphere, summer occurs at the same time as aphelion. Despite this, there are larger land masses in the northern hemisphere, consequently, summers are 2.3 °C warmer in the northern hemisphere than in the southern hemisphere under similar conditions. Apsis Ellipse Solstice Dates and times of Earths perihelion and aphelion, 2000–2025 from the United States Naval Observatory
4.
Lost minor planet
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Lost minor planets are minor planets that observers lose track of due to too short an observation arc to accurately predict the future location of the minor planet. Many of the asteroids that were discovered early were lost and rediscovered in the 1980s and 1990s, some minor planets and comets discovered in previous decades were lost because the observational data obtained was insufficient to determine a reliable orbit. Without this information, astronomers would not know where to look for the object at future dates, occasionally, a newly discovered object turns out to be a rediscovery of a previously lost object. This can be determined by calculating the new objects orbit backwards and this may greatly extend the observation arc, thus fixing the orbit much more precisely. For lost comets the back orbit calculations are especially tricky because of forces that can affect their orbits. However, Brian G. Marsden has specialized in calculating such nongravitational forces, notably, he successfully predicted the 1992 return of the once-lost periodic comet Swift–Tuttle. This is a selection of some early lost or notable asteroids with their discovery and rediscovery dates. The true number of lost asteroids may be over 150,000, there are also about 30,000 unnumbered bodies with a condition code of U = 9, indicating the highest possible uncertainty of their orbit determination. Many of these bodies have been observed if not decades ago. There are also more than a thousand objects with an observation arc of one or two days only. There are earlier examples also, such as 132 Aethra, which was lost between 1873 and 1922, leif Kahl Kristensen at the University of Aarhus rediscovered 452 Hamiltonia and 1537 Transylvania, along with numerous other small objects, in 1981. He named it China, or 中華 Zhōnghuá, however, this asteroid was not observed beyond its initial appearance and a precise orbit could not be calculated. However, in 1986, the newly discovered object 1986 QK1 was confirmed to be a rediscovery of the original 1928 UF, and this object was named 3789 Zhongguo, the near-Earth asteroid 1950 DA was discovered on 23 February 1950 by Carl Wirtanen at Lick Observatory. It was observed for 17 days and then lost, since not enough observations were made to allow its orbit to be plotted and it was then rediscovered on 31 December 2000. The chance it will impact Earth on 16 March 2880 is about 1 in 4,000,7796 Járacimrman was discovered at the Czech Kleť Observatory on 16 January 1996 by Zdeněk Moravec and was designated 1996 BG. It was observed until April 1996 and then in June and July 1997, recently lost minor planets 2007 WD5 is a 50 m Apollo-class NEO and a Mars-crosser discovered on 20 November 2007, by Andrea Boattini of the Catalina Sky Survey. Early observations of 2007 WD5 caused excitement amongst the community when it was estimated as having as high as a 1 in 25 chance of colliding with Mars on 30 January 2008. However, by 9 January 2008 additional observations allowed NASAs Near Earth Object Program to reduce the uncertainty region resulting in only a 1-in-10,000 chance of impact,2007 WD5 most likely passed Mars at a distance of 6.5 Mars radii
5.
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
6.
5D/Brorsen
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5D/Brorsen was a periodic Jupiter-family comet discovered February 26,1846, by the Danish astronomer Theodor Brorsen. The perihelion of 5D/Brorsen was February 25, just a day before its discovery, as a result of this close encounter to Earth the comets coma diameter increased. Johann Friedrich Julius Schmidt estimating it as 3 to 4 arcmin across on March 9, last seen on April 22, it was stationed about 20 degrees from the north celestial pole. By the end of this first apparition the orbital period was identified as 5.5 years and it was discovered that a close approach to Jupiter in 1842 put in its discovery orbit. The comets 5.5 year period would mean that apparitions would alternate between good and poor, as expected, the comet was missed in its 1851 apparition, when the comet only came as close as 1.5 AU to Earth. The comets orbit was still uncertain, made worse by the fact it had approached Jupiter in 1854. In 1857, Karl Christian Bruhns found a comet on 18 March 1857, soon an orbit was computed and it was found to be 5D/Brorsen, although predictions were three months off. The comet was followed until June 1857, and the orbit was now well known, the comet was missed in 1862, and the next recovery was in 1868. A close approach to Jupiter shortened the period enough to make the visible in 1873. A very favorable apparition followed in 1879, allowing the comet to be observed for the longest time to date – four months, the comet was missed in 1884, due to observing circumstances, but was also missed in 1890, a favorable apparition. The next favorable apparition occurred in 1901, but searches did not locate the comet, the next serious search was started by Brian G. Marsden, who believed the comet had faded out of existence, but computed the orbit for a very favorable 1973 apparition. Japanese observers made intensive searches for the comet, but nothing turned up, the comet is currently considered lost. ^ Orbital data taken from this preprint, Neslusan, Lubos, The identification of asteroid 1996 SK with the nucleus of comet 5D/Brorsen, Memorie della Società Astronomica Italiana. Conf. held at Palermo, Italy, June 11–16,2001 5D at Gary W. Kronks Cometography
7.
Perturbation (astronomy)
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In astronomy, perturbation is the complex motion of a massive body subject to forces other than the gravitational attraction of a single other massive body. The other forces can include a body, resistance, as from an atmosphere. The study of perturbations began with the first attempts to predict planetary motions in the sky, in ancient times the causes were a mystery. Newton, at the time he formulated his laws of motion and of gravitation, applied them to the first analysis of perturbations, the complex motions of gravitational perturbations can be broken down. The hypothetical motion that the body follows under the effect of one other body only is typically a conic section. This is called a problem, or an unperturbed Keplerian orbit. The differences between that and the motion of the body are perturbations due to the additional gravitational effects of the remaining body or bodies. If there is one other significant body then the perturbed motion is a three-body problem. A general analytical solution exists for the problem, when more than two bodies are considered analytic solutions exist only for special cases. Even the two-body problem becomes insoluble if one of the bodies is irregular in shape, most systems that involve multiple gravitational attractions present one primary body which is dominant in its effects. The gravitational effects of the bodies can be treated as perturbations of the hypothetical unperturbed motion of the planet or satellite around its primary body. In methods of general perturbations, general differential equations, either of motion or of change in the elements, are solved analytically, usually by series expansions. The result is expressed in terms of algebraic and trigonometric functions of the orbital elements of the body in question. This can be applied generally to many different sets of conditions, historically, general perturbations were investigated first. The classical methods are known as variation of the elements, variation of parameters or variation of the constants of integration, in these methods, it is considered that the body is always moving in a conic section, however the conic section is constantly changing due to the perturbations. General perturbations is applicable if the perturbing forces are about one order of magnitude smaller, or less. In the Solar System, this is usually the case, Jupiter, general perturbation methods are preferred for some types of problems, as the source of certain observed motions are readily found. In effect, the positions and velocities are perturbed directly, special perturbations can be applied to any problem in celestial mechanics, as it is not limited to cases where the perturbing forces are small
8.
Jupiter
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Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a giant planet with a mass one-thousandth that of the Sun, Jupiter and Saturn are gas giants, the other two giant planets, Uranus and Neptune are ice giants. Jupiter has been known to astronomers since antiquity, the Romans named it after their god Jupiter. Jupiter is primarily composed of hydrogen with a quarter of its mass being helium and it may also have a rocky core of heavier elements, but like the other giant planets, Jupiter lacks a well-defined solid surface. Because of its rotation, the planets shape is that of an oblate spheroid. The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence, a prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope. Surrounding Jupiter is a faint planetary ring system and a powerful magnetosphere, Jupiter has at least 67 moons, including the four large Galilean moons discovered by Galileo Galilei in 1610. Ganymede, the largest of these, has a greater than that of the planet Mercury. Jupiter has been explored on several occasions by robotic spacecraft, most notably during the early Pioneer and Voyager flyby missions and later by the Galileo orbiter. In late February 2007, Jupiter was visited by the New Horizons probe, the latest probe to visit the planet is Juno, which entered into orbit around Jupiter on July 4,2016. Future targets for exploration in the Jupiter system include the probable ice-covered liquid ocean of its moon Europa, Earth and its neighbor planets may have formed from fragments of planets after collisions with Jupiter destroyed those super-Earths near the Sun. Astronomers have discovered nearly 500 planetary systems with multiple planets, Jupiter moving out of the inner Solar System would have allowed the formation of inner planets, including Earth. Jupiter is composed primarily of gaseous and liquid matter and it is the largest of the four giant planets in the Solar System and hence its largest planet. It has a diameter of 142,984 km at its equator, the average density of Jupiter,1.326 g/cm3, is the second highest of the giant planets, but lower than those of the four terrestrial planets. Jupiters upper atmosphere is about 88–92% hydrogen and 8–12% helium by percent volume of gas molecules, a helium atom has about four times as much mass as a hydrogen atom, so the composition changes when described as the proportion of mass contributed by different atoms. Thus, Jupiters atmosphere is approximately 75% hydrogen and 24% helium by mass, the atmosphere contains trace amounts of methane, water vapor, ammonia, and silicon-based compounds. There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, the outermost layer of the atmosphere contains crystals of frozen ammonia. The interior contains denser materials - by mass it is roughly 71% hydrogen, 24% helium, through infrared and ultraviolet measurements, trace amounts of benzene and other hydrocarbons have also been found
