1.
Supernova remnant
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A supernova remnant is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by a shock wave, and consists of ejected material expanding from the explosion. In either case, the supernova explosion expels much or all of the stellar material with velocities as much as 10% the speed of light. These ejecta are highly supersonic, assuming a typical temperature of the medium of 10,000 K. Therefore, a shock wave forms ahead of the ejecta. One of the best observed young supernova remnants was formed by SN 1987A, the youngest known remnant in our galaxy is G1. 9+0.3, discovered in the galactic center. An SNR passes through the stages as it expands, Free expansion of the ejecta. This can last tens to a few hundred years depending on the density of the surrounding gas, sweeping up of a shell of shocked circumstellar and interstellar gas. This begins the Sedov-Taylor phase, which can be modeled by a self-similar analytic solution. Strong X-ray emission traces the strong waves and hot shocked gas. Cooling of the shell, to form a thin, dense shell surrounding the hot interior and this is the pressure-driven snowplow phase. The shell can be seen in optical emission from recombining ionized hydrogen. The dense shell continues to expand from its own momentum and this stage is best seen in the radio emission from neutral hydrogen atoms. Merging with the interstellar medium. There are three types of supernova remnant, Shell-like, such as Cassiopeia A Composite, in which a shell contains a central pulsar wind nebula, mixed-morphology remnants, in which central thermal X-ray emission is seen, enclosed by a radio shell. The thermal X-rays are primarily from swept-up interstellar material, rather than supernova ejecta, examples of this class include the SNRs W28 and W44. Supernova remnants are considered the source of galactic cosmic rays. The connection between cosmic rays and supernovas was first suggested by Walter Baade and Fritz Zwicky in 1934 and this hypothesis is supported by a specific mechanism called shock wave acceleration based on Enrico Fermis ideas, which is still under development
2.
Hubble Space Telescope
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The Hubble Space Telescope is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. Although not the first space telescope, Hubble is one of the largest and most versatile, with a 2. 4-meter mirror, Hubbles four main instruments observe in the near ultraviolet, visible, and near infrared spectra. Hubbles orbit outside the distortion of Earths atmosphere allows it to take extremely high-resolution images, Hubble has recorded some of the most detailed visible light images ever, allowing a deep view into space and time. Many Hubble observations have led to breakthroughs in astrophysics, such as determining the rate of expansion of the universe. The HST was built by the United States space agency NASA, the Space Telescope Science Institute selects Hubbles targets and processes the resulting data, while the Goddard Space Flight Center controls the spacecraft. Space telescopes were proposed as early as 1923, Hubble was funded in the 1970s, with a proposed launch in 1983, but the project was beset by technical delays, budget problems, and the Challenger disaster. When finally launched in 1990, Hubbles main mirror was found to have been ground incorrectly, the optics were corrected to their intended quality by a servicing mission in 1993. Hubble is the telescope designed to be serviced in space by astronauts. After launch by Space Shuttle Discovery in 1990, five subsequent Space Shuttle missions repaired, upgraded, the fifth mission was canceled on safety grounds following the Columbia disaster. However, after spirited public discussion, NASA administrator Mike Griffin approved the fifth servicing mission, the telescope is operating as of 2017, and could last until 2030–2040. Its scientific successor, the James Webb Space Telescope, is scheduled for launch in 2018, the history of the Hubble Space Telescope can be traced back as far as 1946, to the astronomer Lyman Spitzers paper Astronomical advantages of an extraterrestrial observatory. In it, he discussed the two advantages that a space-based observatory would have over ground-based telescopes. First, the resolution would be limited only by diffraction, rather than by the turbulence in the atmosphere. Second, a telescope could observe infrared and ultraviolet light. Spitzer devoted much of his career to pushing for the development of a space telescope, space-based astronomy had begun on a very small scale following World War II, as scientists made use of developments that had taken place in rocket technology. An orbiting solar telescope was launched in 1962 by the United Kingdom as part of the Ariel space program, oAO-1s battery failed after three days, terminating the mission. It was followed by OAO-2, which carried out observations of stars and galaxies from its launch in 1968 until 1972. The continuing success of the OAO program encouraged increasingly strong consensus within the community that the LST should be a major goal
3.
Wide Field and Planetary Camera 2
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The Wide Field and Planetary Camera 2 is a camera formerly installed on the Hubble Space Telescope. The camera was built by the Jet Propulsion Laboratory and is roughly the size of a grand piano. It was installed by servicing mission 1 in 1993, replacing the telescopes original Wide Field, WFPC2 was used to image the Hubble Deep Field in 1995, the Hourglass Nebula and Egg Nebula in 1996, and the Hubble Deep Field South in 1998. During STS-125, WFPC2 was removed and replaced with the Wide Field Camera 3 as part of the missions first spacewalk on May 14,2009, WFPC2 was built by NASAs Jet Propulsion Laboratory, which also built the predecessor WF/PC camera launched with Hubble in 1990. WFPC2 contains internal corrective optics to fix the spherical aberration in the Hubble telescopes primary mirror, the charge-coupled devices in the WFPC2 detected electromagnetic radiation in a range from 120 nm to 1000 nm. This included the 380 nm to 780 nm of the spectrum, all of the near ultraviolet. The sensitivity distribution of these CCDs is roughly normal, with a peak around 700 nm, WFPC2 featured four identical CCD detectors, each 800x800 pixels. Three of these, arranged in an L-formation, comprise Hubbles Wide Field Camera, adjacent to them is the Planetary Camera, a fourth CCD with different optics. This afforded a more detailed view over a region of the visual field. WFC and PC images are combined, producing the WFPC2s characteristic stairstep image. To allow scientists to view parts of the electromagnetic spectrum the WFPC2 featured a rotating wheel which moves different optical filters into the lightpath. The 48 filter elements included, A set of standard wideband photometric filters, a graduated filter, featuring a wide range of very narrowband filters. By positioning the target object at a part of the field. A number of optical filters tuned to the wavelengths of various atomic emission lines. As predicted, over the course of its mission the WFPC2 experienced degradation of the CCDs, to avoid false positives caused by cosmic rays tripping a given pixel, the output of different calibration shots are compared. Pixels which are consistently hot are recorded, and astronomers who analyse raw WFPC2 images receive a list of these pixels, typically astronomers adjust their photo-processing software to ignore these bad pixels. WFPC2 was largely superseded for broad-band imaging by the Advanced Camera for Surveys, however, the early 2007 failure of ACS resulted in WFPC2 returning to its role as Hubbles primary visible light camera. WFPC2 was removed from HST during Servicing Mission 4 in May 2009, for return to Earth and eventual museum display
4.
Right ascension
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Right ascension is the angular distance measured eastward along the celestial equator from the vernal equinox to the hour circle of the point in question. When combined with declination, these astronomical coordinates specify the direction of a point on the sphere in the equatorial coordinate system. Right ascension is the equivalent of terrestrial longitude. Both right ascension and longitude measure an angle from a direction on an equator. Right ascension is measured continuously in a circle from that equinox towards the east. Any units of measure could have been chosen for right ascension, but it is customarily measured in hours, minutes. Astronomers have chosen this unit to measure right ascension because they measure a stars location by timing its passage through the highest point in the sky as the Earth rotates. The highest point in the sky, called meridian, is the projection of a line onto the celestial sphere. A full circle, measured in units, contains 24 × 60 × 60 = 86 400s, or 24 × 60 = 1 440m. Because right ascensions are measured in hours, they can be used to time the positions of objects in the sky. For example, if a star with RA = 01h 30m 00s is on the meridian, sidereal hour angle, used in celestial navigation, is similar to right ascension, but increases westward rather than eastward. Usually measured in degrees, it is the complement of right ascension with respect to 24h and it is important not to confuse sidereal hour angle with the astronomical concept of hour angle, which measures angular distance of an object westward from the local meridian. The Earths axis rotates slowly westward about the poles of the ecliptic and this effect, known as precession, causes the coordinates of stationary celestial objects to change continuously, if rather slowly. Therefore, equatorial coordinates are inherently relative to the year of their observation, coordinates from different epochs must be mathematically rotated to match each other, or to match a standard epoch. The right ascension of Polaris is increasing quickly, the North Ecliptic Pole in Draco and the South Ecliptic Pole in Dorado are always at right ascension 18h and 6h respectively. The currently used standard epoch is J2000.0, which is January 1,2000 at 12,00 TT, the prefix J indicates that it is a Julian epoch. Prior to J2000.0, astronomers used the successive Besselian Epochs B1875.0, B1900.0, the concept of right ascension has been known at least as far back as Hipparchus who measured stars in equatorial coordinates in the 2nd century BC. But Hipparchus and his successors made their star catalogs in ecliptic coordinates, the easiest way to do that is to use an equatorial mount, which allows the telescope to be aligned with one of its two pivots parallel to the Earths axis
5.
Declination
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In astronomy, declination is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declinations angle is measured north or south of the celestial equator, the root of the word declination means a bending away or a bending down. It comes from the root as the words incline and recline. Declination in astronomy is comparable to geographic latitude, projected onto the celestial sphere, points north of the celestial equator have positive declinations, while those south have negative declinations. Any units of measure can be used for declination, but it is customarily measured in the degrees, minutes. Declinations with magnitudes greater than 90° do not occur, because the poles are the northernmost and southernmost points of the celestial sphere, the Earths axis rotates slowly westward about the poles of the ecliptic, completing one circuit in about 26,000 years. This effect, known as precession, causes the coordinates of stationary celestial objects to change continuously, therefore, equatorial coordinates are inherently relative to the year of their observation, and astronomers specify them with reference to a particular year, known as an epoch. Coordinates from different epochs must be rotated to match each other. The currently used standard epoch is J2000.0, which is January 1,2000 at 12,00 TT, the prefix J indicates that it is a Julian epoch. Prior to J2000.0, astronomers used the successive Besselian Epochs B1875.0, B1900.0, the declinations of Solar System objects change very rapidly compared to those of stars, due to orbital motion and close proximity. This similarly occurs in the Southern Hemisphere for objects with less than −90° − φ. An extreme example is the star which has a declination near to +90°. Circumpolar stars never dip below the horizon, conversely, there are other stars that never rise above the horizon, as seen from any given point on the Earths surface. Generally, if a star whose declination is δ is circumpolar for some observer, then a star whose declination is −δ never rises above the horizon, as seen by the same observer. Likewise, if a star is circumpolar for an observer at latitude φ, neglecting atmospheric refraction, declination is always 0° at east and west points of the horizon. At the north point, it is 90° − |φ|, and at the south point, from the poles, declination is uniform around the entire horizon, approximately 0°. Non-circumpolar stars are visible only during certain days or seasons of the year, the Suns declination varies with the seasons. As seen from arctic or antarctic latitudes, the Sun is circumpolar near the summer solstice, leading to the phenomenon of it being above the horizon at midnight
6.
Parsec
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The parsec is a unit of length used to measure large distances to objects outside the Solar System. One parsec is the distance at which one astronomical unit subtends an angle of one arcsecond, a parsec is equal to about 3.26 light-years in length. The nearest star, Proxima Centauri, is about 1.3 parsecs from the Sun, most of the stars visible to the unaided eye in the nighttime sky are within 500 parsecs of the Sun. The parsec unit was likely first suggested in 1913 by the British astronomer Herbert Hall Turner, named from an abbreviation of the parallax of one arcsecond, it was defined so as to make calculations of astronomical distances quick and easy for astronomers from only their raw observational data. Partly for this reason, it is still the unit preferred in astronomy and astrophysics, though the light-year remains prominent in science texts. This corresponds to the definition of the parsec found in many contemporary astronomical references. Derivation, create a triangle with one leg being from the Earth to the Sun. As that point in space away, the angle between the Sun and Earth decreases. A parsec is the length of that leg when the angle between the Sun and Earth is one arc-second. One of the oldest methods used by astronomers to calculate the distance to a star is to record the difference in angle between two measurements of the position of the star in the sky. The first measurement is taken from the Earth on one side of the Sun, and the second is approximately half a year later. The distance between the two positions of the Earth when the two measurements were taken is twice the distance between the Earth and the Sun. The difference in angle between the two measurements is twice the angle, which is formed by lines from the Sun. Then the distance to the star could be calculated using trigonometry. 5-parsec distance of 61 Cygni, the parallax of a star is defined as half of the angular distance that a star appears to move relative to the celestial sphere as Earth orbits the Sun. Equivalently, it is the angle, from that stars perspective. The star, the Sun and the Earth form the corners of a right triangle in space, the right angle is the corner at the Sun. Therefore, given a measurement of the angle, along with the rules of trigonometry. A parsec is defined as the length of the adjacent to the vertex occupied by a star whose parallax angle is one arcsecond
7.
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
8.
Constellation
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A constellation is formally defined as a region of the celestial sphere, with boundaries laid down by the International Astronomical Union. The constellation areas mostly had their origins in Western-traditional patterns of stars from which the constellations take their names, in 1922, the International Astronomical Union officially recognized the 88 modern constellations, which cover the entire sky. They began as the 48 classical Greek constellations laid down by Ptolemy in the Almagest, Constellations in the far southern sky are late 16th- and mid 18th-century constructions. 12 of the 88 constellations compose the zodiac signs, though the positions of the constellations only loosely match the dates assigned to them in astrology. The term constellation can refer to the stars within the boundaries of that constellation. Notable groupings of stars that do not form a constellation are called asterisms, when astronomers say something is “in” a given constellation they mean it is within those official boundaries. Any given point in a coordinate system can unambiguously be assigned to a single constellation. Many astronomical naming systems give the constellation in which an object is found along with a designation in order to convey a rough idea in which part of the sky it is located. For example, the Flamsteed designation for bright stars consists of a number, the word constellation seems to come from the Late Latin term cōnstellātiō, which can be translated as set of stars, and came into use in English during the 14th century. It also denotes 88 named groups of stars in the shape of stellar-patterns, the Ancient Greek word for constellation was ἄστρον. Colloquial usage does not draw a distinction between constellation in the sense of an asterism and constellation in the sense of an area surrounding an asterism. The modern system of constellations used in astronomy employs the latter concept, the term circumpolar constellation is used for any constellation that, from a particular latitude on Earth, never sets below the horizon. From the North Pole or South Pole, all constellations south or north of the equator are circumpolar constellations. In the equatorial or temperate latitudes, the term equatorial constellation has sometimes been used for constellations that lie to the opposite the circumpolar constellations. They generally include all constellations that intersect the celestial equator or part of the zodiac, usually the only thing the stars in a constellation have in common is that they appear near each other in the sky when viewed from the Earth. In galactic space, the stars of a constellation usually lie at a variety of distances, since stars also travel on their own orbits through the Milky Way, the star patterns of the constellations change slowly over time. After tens to hundreds of thousands of years, their familiar outlines will become unrecognisable, the terms chosen for the constellation themselves, together with the appearance of a constellation, may reveal where and when its constellation makers lived. The earliest direct evidence for the constellations comes from inscribed stones and it seems that the bulk of the Mesopotamian constellations were created within a relatively short interval from around 1300 to 1000 BC
9.
Taurus (constellation)
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Taurus is one of the constellations of the zodiac, which means it is crossed by the plane of the ecliptic. Taurus is a large and prominent constellation in the northern hemispheres winter sky and it is one of the oldest constellations, dating back to at least the Early Bronze Age when it marked the location of the Sun during the spring equinox. Its importance to the agricultural calendar influenced various bull figures in the mythologies of Ancient Sumer, Akkad, Assyria, Babylon, Egypt, Greece, a number of features exist that are of interest to astronomers. Taurus hosts two of the nearest open clusters to Earth, the Pleiades and the Hyades, both of which are visible to the naked eye, at first magnitude, the red giant Aldebaran is the brightest star in the constellation. In the northwest part of Taurus is the supernova remnant Messier 1, one of the closest regions of active star formation, the Taurus-Auriga complex, crosses into the northern part of the constellation. The variable star T Tauri is the prototype of a class of pre-main-sequence stars, in September and October, Taurus is visible in the evening along the eastern horizon. The most favorable time to observe Taurus in the sky is during the months of December. By March and April, the constellation will appear to the west during the evening twilight and this constellation forms part of the zodiac, and hence is intersected by the ecliptic. This circle across the sphere forms the apparent path of the Sun as the Earth completes its annual orbit. As the orbital plane of the Moon and the planets lie near the ecliptic, the galactic plane of the Milky Way intersects the northeast corner of the constellation and the galactic anticenter is located near the border between Taurus and Auriga. Taurus is the only constellation crossed by all three of the equator, celestial equator, and ecliptic. A ring-like galactic structure known as the Goulds Belt passes through the Taurus constellation, the recommended three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is Tau. The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of 26 segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 03h 23. 4m and 05h 53. 3m, while the coordinates are between 31. 10° and −1. 35°. Because a small part of the lies to the south of the celestial equator. During November, the Taurid meteor shower appears to radiate from the direction of this constellation. The Beta Taurid meteor shower occurs during the months of June and July in the daytime, between 18 and 29 October, both the Northern Taurids and the Southern Taurids are active, though the latter stream is stronger. However, between November 1 and 10, the two streams equalize, the brightest member of this constellation is Aldebaran, an orange-hued, spectral class K5 III giant star
10.
Sharpless catalog
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The Sharpless catalog is a list of 313 HII regions, intended to be comprehensive north of declination -27°. The first edition was published in 1953 with 142 objects, Sharpless also includes some planetary nebulae and supernova remnants, in addition to HII regions. From this work Sharpless published his catalog of H II regions in two editions, the first in 1953 with 142 nebula, the second and final edition was published in 1959 with 312 nebulae. Sharpless coordinates are based on the star catalogs Bonner Durchmusterung and Cordoba Durchmusterung, in the second release, some coordinates for southern hemisphere regions have an uncertainty over 1 minute of arc. This can make difficult to find, so a revised catalog called BFS was released. BFS has 65 new regions and about 20 removals, most of the removed items were taken out because they were the aforementioned nebula or remnants. The 312 items in Sharpless sometimes overlap with the 110 Messier objects,7,840 objects in the New General Catalogue, the Caldwell catalogue, contemporary catalogs were Gum and RCW, but they mainly covered the southern hemisphere
11.
Messier object
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The Messier objects are a set of over 100 astronomical objects first listed by French astronomer Charles Messier in 1771. The number of objects in the lists he published reached 103, a similar list had been published in 1654 by Giovanni Hodierna, but attracted attention only recently and was probably not known to Messier. The first edition covered 45 objects numbered M1 to M45, the first such addition came from Nicolas Camille Flammarion in 1921, who added Messier 104 after finding a note Messier made in a copy of the 1781 edition of the catalogue. M105 to M107 were added by Helen Sawyer Hogg in 1947, M108 and M109 by Owen Gingerich in 1960, M102 was observed by Méchain, who communicated his notes to Messier. Méchain later concluded that this object was simply a re-observation of M101, though sources suggest that the object Méchain observed was the galaxy NGC5866. Messiers final catalogue was included in the Connaissance des Temps for 1784 and these objects are still known by their Messier number from this list. Messier lived and did his work at the Hôtel de Cluny. The list he compiled contains only objects found in the sky area he could observe and he did not observe or list objects visible only from farther south, such as the Large and Small Magellanic Clouds. A summary of the astrophysics of each Messier object can be found in the Concise Catalog of Deep-sky Objects, in early spring, astronomers sometimes gather for Messier marathons, when all of the objects can be viewed over a single night
12.
New General Catalogue
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The NGC contains 7,840 objects, known as the NGC objects. It is one of the largest comprehensive catalogues, as it includes all types of space objects and is not confined to, for example. Dreyer also published two supplements to the NGC in 1895 and 1908, known as the Index Catalogues, describing a further 5,386 astronomical objects. Objects in the sky of the southern hemisphere are catalogued somewhat less thoroughly, the Revised New General Catalogue and Index Catalogue was compiled in 2009 by Wolfgang Steinicke. The original New General Catalogue was compiled during the 1880s by John Louis Emil Dreyer using observations from William Herschel and his son John, Dreyer had already published a supplement to Herschels General Catalogue of Nebulae and Clusters, containing about 1,000 new objects. In 1886, he suggested building a second supplement to the General Catalogue and this led to the publication of the New General Catalogue in the Memoirs of the Royal Astronomical Society in 1888. Assembling the NGC was a challenge, as Dreyer had to deal with many contradicting and unclear reports, while he did check some himself, the sheer number of objects meant Dreyer had to accept them as published by others for the purpose of his compilation. Dreyer was a careful transcriber and made few errors himself, and he was very thorough in his referencing, which allowed future astronomers to review the original references and publish corrections to the original NGC. The first major update to the NGC is the Index Catalogue of Nebulae and Clusters of Stars and it serves as a supplement to the NGC, and contains an additional 5,386 objects, collectively known as the IC objects. It summarizes the discoveries of galaxies, clusters and nebulae between 1888 and 1907, most of them made possible by photography, a list of corrections to the IC was published in 1912. The Revised New Catalogue of Nonstellar Astronomical Objects was compiled by Jack W. Sulentic and William G. Tifft in the early 1970s, and was published in 1973, as an update to the NGC. However, because the update had to be completed in just three summers, it failed to incorporate several previously-published corrections to the NGC data, and even introduced new errors. NGC2000.0 is a 1988 compilation of the NGC and IC made by Roger W. Sinnott and it incorporates several corrections and errata made by astronomers over the years. However, it too ignored the original publications and favoured modern corrections, the NGC/IC Project is a collaboration formed in 1993. It aims to identify all NGC and IC objects, and collect images, the Revised New General Catalogue and Index Catalogue is a compilation made by Wolfgang Steinicke in 2009. It is considered one of the most comprehensive and authoritative treatments of the NGC, messier object Catalogue of Nebulae and Clusters of Stars The Interactive NGC Catalog Online Adventures in Deep Space, Challenging Observing Projects for Amateur Astronomers
13.
William Parsons, 3rd Earl of Rosse
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William Parsons, 3rd Earl of Rosse KP PRS was an Anglo-Irish astronomer who had several telescopes built. His 72-inch telescope, built in 1845 and colloquially known as the Leviathan of Parsonstown, was the worlds largest telescope, in terms of aperture size, from 1807 until 1841, he was styled as Baron Oxmantown. He was born in Yorkshire, England, in the city of York and he was educated, as Lord Oxmantown, at Trinity College, Dublin, and Oxford Universitys Magdalen College, graduating with first-class honours in mathematics in 1822. He inherited an earldom and an estate in Kings County in Ireland when his father, Lawrence, 2nd Earl of Rosse. Lord Rosse married Mary Field, daughter of John Wilmer Field and they had a total of thirteen children, but only four sons survived to adulthood, Lawrence, 4th Earl of Rosse. The Hon. Richard Clere Parsons, apparently known for developing railways in South America, sir Charles Algernon Parsons, known for inventing the steam turbine. During the 1840s, he had the Leviathan of Parsonstown built, the 72-inch telescope replaced a 36-inch telescope that he had built previously. Details of the metal, casting, grinding and polishing of the 3-ton speculum were presented in 1844 at the Belfast Natural History Society, Rosses telescope was considered a marvellous technical and architectural achievement, and images of it were circulated widely within the British commonwealth. Building of the Leviathan began in 1842 and it was first used in 1845 and it was the worlds largest telescope, in terms of aperture size, until the early 20th century. Using this telescope Rosse saw and catalogued a number of nebulae. Lord Rosse performed astronomical studies and discovered the nature of some nebulas. Rosses telescope Leviathan was the first to reveal the structure of M51, a galaxy nicknamed later as the Whirlpool Galaxy. Rosse named the Crab Nebula, based on a drawing made with his older 36-inch telescope in which it resembled a crab. A few years later, when the 72-inch telescope was in service, he produced a drawing of considerably different appearance. A main component of Rosses nebular research was his attempt to resolve the nebular hypothesis, Rosse himself did not believe that nebulas were truly gaseous, arguing rather that they were made of such an amount of fine stars that most telescopes could not resolve them individually. Rosses primary opponent in this was John Herschel, who used his own instruments to claim that the Orion nebula was a true nebula, eventually, neither man could establish sufficiently scientific results to resolve the question. But the genius displayed in all the contrivances for wielding this mighty monster even surpasses the design, the telescope weighs sixteen tons, and yet Lord Rosse raised it single-handed off its resting place, and two men with ease raised it to any height. Lord Rosse had a variety of optical reflecting telescopes built, Rosses telescopes used cast speculum metal ground parabolically and polished
14.
SN 1054
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SN1054 is a supernova that was first observed on 4 July 1054, and remained visible for around two years. The event was recorded in contemporary Chinese astronomy, and references to it are found in a later Japanese document. The remnant of SN1054, which consists of debris ejected during the explosion, is known as the Crab Nebula and it is located in the sky near the star Zeta Tauri. The core of the star formed a pulsar, called the Crab Pulsar. The nebula and the pulsar that it contains are some of the most studied astronomical objects outside the Solar System and it is one of the few Galactic supernovae where the date of the explosion is well known. The two objects are the most luminous in their respective categories, for these reasons, and because of the important role it has repeatedly played in the modern era, SN1054 is the best known supernova in the history of astronomy. When the French astronomer Charles Messier watched for the return of Halleys Comet in 1758, he confused the nebula for the comet, due to this error, he created his catalogue of non-cometary nebulous objects, the Messier Catalogue, to avoid such mistakes in the future. The nebula is catalogued as the first Messier object, or M1, the Crab Nebula was identified as the supernova remnant of SN1054 between 1921 and 1942, at first speculatively, with some plausibility by 1939, and beyond reasonable doubt by Jan Oort in 1942. In 1921, Carl Otto Lampland was the first to announce that he had changes in the structure of the Crab Nebula. This announcement occurred at a time when the nature of the nebulas in the sky was completely unknown and their nature, size and distance were subject to debate. Lamplands comments were confirmed some weeks later by John Charles Duncan, the points were moving away from the centre, and did so faster as they got further from it. Also in 1921, Knut Lundmark compiled the data for the guest stars mentioned in the Chinese chronicles known in the West. Lundmark gives a list of 60 suspected novae, then the term for a stellar explosion. The nova of 1054, already mentioned by the Biots in 1843, is part of the list. In 1928, Edwin Hubble was the first to note that the aspect of the Crab Nebula. Hubble therefore deduced, correctly, that this cloud was the remains of the explosion which was observed by Chinese astronomers, hubbles comment remained relatively unknown as the physical phenomenon of the explosion was not known at the time. This was under the assumption that the velocities of expansion along the line of sight, based on the reference to the brightness of the star which featured in the first documents discovered in 1934, he deduced that it was a supernova rather than a nova. This deduction was subsequently refined, which pushed Mayall and Jan Oort in 1942 to analyse historic accounts relating to the guest star more closely, other historical supernovae of which there are written accounts which precede the invention of the telescope are however established with certitude
15.
Chinese astronomy
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Astronomy in China has a very long history, with historians indicating that the Chinese were the most persistent and accurate observers of celestial phenomena anywhere in the world before the Arabs. Detailed records of observations began during the Warring States period. The telescope was introduced in the seventeenth century, in 1669, the Peking observatory was completely redesigned and refitted under the direction of Ferdinand Verbiest. Today, China continues to be active in astronomy, with many observatories, one of the main functions was for the purpose of timekeeping. The Chinese used a calendar, but, because the cycles of the sun. The Chinese calendar was considered to be a symbol of a dynasty, as dynasties would rise and fall, astronomers and astrologers of each period would often prepare a new calendar to be made, with observations for that purpose. Astrological divination was also an important part of astronomy, astronomers took careful note of guest stars, which suddenly appeared among the fixed stars. Ancient astronomical records of phenomena like comets and supernovae are used in modern astronomical studies. The Chinese developed three different cosmological models, the Gai Tian, or hemispherical dome, model conceived the heavens as a hemisphere lying over a dome-shaped earth. The second cosmological model, associated with the Hun Tian school, saw the heavens as a celestial sphere not unlike the spherical models developed in the Greek, the divisions of the sky began with the Northern Dipper and the 28 mansions. In 1977, a box was excavated from the tomb of Yi. Names of the 28 lunar mansions were found on the cover of the box, as lunar mansions have such an ancient origin, the meanings of most of their names have become obscure. Even worse, the name of each lunar mansion consists of only one Chinese word, the meanings of the names are still under discussion. Besides the 28 lunar mansions, most constellations are based on the works of Shi Shen-fu and Gan De, in the fourth century BC, the two Chinese astronomers responsible for the earliest information going into the star catalogues were Shi Shen and Gan De of the Warring States period. These books appeared to have lasted until the sixth century, but were lost after that, a number of books share similar names, often quoted and named after them. These texts should not be confused with the original written by them. Notable works that helped preserve the contents include, Wu Xian has been one of the astronomers in debate and he is often represented as one of the Three Schools Astronomical tradition along with Gan and Shi. Moreover, it was customary in the past for the Chinese to forge works of notable scholars, Wu Xian is generally mentioned as the astronomer who lived many years before Gan and Shi
16.
Nebula
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A nebula is an interstellar cloud of dust, hydrogen, helium and other ionized gases. Originally, nebula was a name for any diffuse astronomical object, the Andromeda Galaxy, for instance, was once referred to as the Andromeda Nebula before the true nature of galaxies was confirmed in the early 20th century by Vesto Slipher, Edwin Hubble and others. Most nebulae are of vast size, even millions of years in diameter. The Orion Nebula, the brightest nebula in the sky that occupies a region twice the diameter of the full Moon, can be viewed with the naked eye but was missed by early astronomers. Many nebulae are visible due to their fluorescence caused by the hot stars, while others are so diffuse they can only be detected with long exposures. Some nebulae are variably illuminated by T Tauri variable stars, Nebulae are often star-forming regions, such as in the Pillars of Creation in the Eagle Nebula. In these regions the formations of gas, dust, and other materials together to form denser regions, which attract further matter. The remaining material is believed to form planets and other planetary system objects. Around 150 AD, Claudius Ptolemaeus recorded, in books VII–VIII of his Almagest and he also noted a region of nebulosity between the constellations Ursa Major and Leo that was not associated with any star. The first true nebula, as distinct from a cluster, was mentioned by the Persian astronomer Abd al-Rahman al-Sufi. He noted a little cloud where the Andromeda Galaxy is located and he also cataloged the Omicron Velorum star cluster as a nebulous star and other nebulous objects, such as Brocchis Cluster. The supernova that created the Crab Nebula, the SN1054, was observed by Arabic, in 1610, Nicolas-Claude Fabri de Peiresc discovered the Orion Nebula using a telescope. This nebula was observed by Johann Baptist Cysat in 1618. However, the first detailed study of the Orion Nebula was not performed until 1659 by Christiaan Huygens, in 1715, Edmund Halley published a list of six nebulae. This number steadily increased during the century, with Jean-Philippe de Cheseaux compiling a list of 20 in 1746, from 1751 to 1753, Nicolas Louis de Lacaille cataloged 42 nebulae from the Cape of Good Hope, most of which were previously unknown. Charles Messier then compiled a catalog of 103 nebulae by 1781, his interest was detecting comets, the number of nebulae was then greatly expanded by the efforts of William Herschel and his sister Caroline Herschel. Their Catalogue of One Thousand New Nebulae and Clusters of Stars was published in 1786, a second catalog of a thousand was published in 1789 and the third and final catalog of 510 appeared in 1802. During much of their work, William Herschel believed that these nebulae were merely unresolved clusters of stars, in 1790, however, he discovered a star surrounded by nebulosity and concluded that this was a true nebulosity, rather than a more distant cluster
17.
Titan (moon)
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Titan is the largest moon of Saturn. It is the only known to have a dense atmosphere. Titan is the sixth ellipsoidal moon from Saturn, frequently described as a planet-like moon, Titan is 50% larger than Earths Moon, and it is 80% more massive. It is the second-largest moon in the Solar System, after Jupiters moon Ganymede, and is larger than the smallest planet, Mercury, discovered in 1655 by the Dutch astronomer Christiaan Huygens, Titan was the first known moon of Saturn, and the sixth known planetary satellite. Titan orbits Saturn at 20 Saturn radii, from Titans surface, Saturn subtends an arc of 5.09 degrees and would appear 11.4 times larger in the sky than the Moon from Earth. Titan is primarily composed of ice and rocky material. The geologically young surface is smooth, with few impact craters, although mountains. The atmosphere of Titan is largely nitrogen, minor components lead to the formation of methane and ethane clouds and nitrogen-rich organic smog. The climate—including wind and rain—creates surface features similar to those of Earth, such as dunes, rivers, lakes, seas, and deltas, Huygens was inspired by Galileos discovery of Jupiters four largest moons in 1610 and his improvements in telescope technology. Christiaan, with the help of his brother Constantijn Huygens, Jr. began building telescopes around 1650 and it was the sixth moon to be discovered. He named it Saturni Luna, publishing in the 1655 tract De Saturni Luna Observatio Nova, after Giovanni Domenico Cassini published his discoveries of four more moons of Saturn between 1673 and 1686, astronomers fell into the habit of referring to these and Titan as Saturn I through V. Other early epithets for Titan include Saturns ordinary satellite, Titan is officially numbered Saturn VI because after the 1789 discoveries the numbering scheme was frozen to avoid causing any more confusion. Numerous small moons have been discovered closer to Saturn since then and he suggested the names of the mythological Titans, brothers and sisters of Cronus, the Greek Saturn. In Greek mythology, the Titans were a race of powerful deities, descendants of Gaia and Uranus, Titan orbits Saturn once every 15 days and 22 hours. Because of this, there is a point on its surface. Longitudes on Titan are measured westward, starting from the passing through this point. Its orbital eccentricity is 0.0288, and the plane is inclined 0.348 degrees relative to the Saturnian equator. Viewed from Earth, Titan reaches a distance of about 20 Saturn radii from Saturn
18.
Binoculars
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Binoculars or field glasses are two telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes when viewing distant objects. Most are sized to be held using both hands, although sizes vary widely from opera glasses to large pedestal mounted military models. Almost from the invention of the telescope in the 17th century the advantages of mounting two of them side by side for binocular vision seems to have been explored, most early binoculars used Galilean optics, that is, they used a convex objective and a concave eyepiece lens. The Galilean design has the advantage of presenting an image but has a narrow field of view and is not capable of very high magnification. This type of construction is used in very cheap models. They also have large exit pupils making centering less critical and the field of view works well in those applications. These are typically mounted on a frame or custom-fit onto eyeglasses. An improved image and higher magnification is achieved in binoculars employing Keplerian optics, since the Keplerian configuration produces an inverted image, different methods were used to turn the image right way up. In aprismatic binoculars with Keplerian optics each tube has one or two additional lenses between the objective and the ocular and these lenses are used to erect the image. The binoculars with erecting lenses have a disadvantage, their length is too long. Such binoculars were popular in the 1800s, but became obsolete shortly after the Karl Zeiss company introduced improved prism binoculars in the 1890s, Optical prisms added to the design are another way to turn the image right way up, usually in a Porro prism or roof-prisms design. Porro prism binoculars are named after Italian optician Ignazio Porro who patented this image erecting system in 1854, Binoculars of this type use a Porro prism in a double prism Z-shaped configuration to erect the image. This feature results in binoculars that are wide, with lenses that are well separated. Thus, the size of binoculars is reduced, Binoculars using roof prisms may have appeared as early as the 1870s in a design by Achille Victor Emile Daubresse. Most roof prism binoculars use either the Abbe-Koenig prism or the Schmidt-Pechan prism designs to erect the image and they have objective lenses that are approximately in line with the eyepieces. Roof-prisms designs create an instrument that is narrower and more compact than Porro prisms, there is also a difference in image brightness. Roof-prisms designs also require tighter tolerances for alignment of their optical elements and this adds to their expense since the design requires them to use fixed elements that need to be set at a high degree of collimation at the factory. Porro prisms binoculars occasionally need their prism sets to be re-aligned to bring them into collimation, the fixed alignment in roof-prism designs means the binoculars normally will not need re-collimation
19.
Perseus Arm
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The Perseus arm is one of two major spiral arms of the Milky Way galaxy. The second major arm is called Scutum–Centaurus Arm, Perseus Arm begins from the distal end of the long Milky Way. Previously thought to be 13,000 light-years away, it is now thought to lie 6,400 light years from the Solar System, the Milky Way is a barred spiral galaxy with two major arms and a number of minor arms or spurs. The Perseus Spiral Arm, with a radius of approximately 10.7 kiloparsecs, is located between the minor Cygnus and Carina–Sagittarius Arms and it is named after the Perseus constellation in the direction of which it is seen from Earth. There is speculation that the spur known as the Orion–Cygnus Arm, which includes the Solar System and Earth and is located inside of Perseus Arm, is a branch of it. The Perseus Spiral arm contains a number of Messier objects, The Crab Nebula Open Cluster M36 Open Cluster M37 Open Cluster M38 Open Cluster M52 Open Cluster M103, list of Messier objects Messier Objects in the Milky Way Galaxy
20.
Milky Way
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The Milky Way is the galaxy that contains our Solar System. The descriptive milky is derived from the appearance from Earth of the galaxy – a band of light seen in the night sky formed from stars that cannot be distinguished by the naked eye. The term Milky Way is a translation of the Latin via lactea, from Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610, until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies, the Milky Way is a barred spiral galaxy with a diameter between 100,000 light-years and 180,000 light-years. The Milky Way is estimated to contain 100–400 billion stars, there are probably at least 100 billion planets in the Milky Way. The Solar System is located within the disk, about 26,000 light-years from the Galactic Center, on the edge of one of the spiral-shaped concentrations of gas. The stars in the inner ≈10,000 light-years form a bulge, the very center is marked by an intense radio source, named Sagittarius A*, which is likely to be a supermassive black hole. Stars and gases at a range of distances from the Galactic Center orbit at approximately 220 kilometers per second. The constant rotation speed contradicts the laws of Keplerian dynamics and suggests much of the mass of the Milky Way does not emit or absorb electromagnetic radiation. This mass has been termed dark matter, the rotational period is about 240 million years at the position of the Sun. The Milky Way as a whole is moving at a velocity of approximately 600 km per second with respect to frames of reference. The oldest stars in the Milky Way are nearly as old as the Universe itself, the Milky Way has several satellite galaxies and is part of the Local Group of galaxies, which is a component of the Virgo Supercluster, which is itself a component of the Laniakea Supercluster. The Milky Way can be seen as a band of white light some 30 degrees wide arcing across the sky. Dark regions within the band, such as the Great Rift, the area of the sky obscured by the Milky Way is called the Zone of Avoidance. The Milky Way has a low surface brightness. Its visibility can be reduced by background light such as light pollution or stray light from the Moon. The sky needs to be darker than about 20.2 magnitude per square arcsecond in order for the Milky Way to be seen and it should be visible when the limiting magnitude is approximately +5.1 or better and shows a great deal of detail at +6.1
21.
Minute and second of arc
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A minute of arc, arcminute, arc minute, or minute arc is a unit of angular measurement equal to 1/60 of one degree. Since one degree is 1/360 of a turn, one minute of arc is 1/21600 of a turn, a second of arc, arcsecond, or arc second is 1/60 of an arcminute, 1/3600 of a degree, 1/1296000 of a turn, and π/648000 of a radian. To express even smaller angles, standard SI prefixes can be employed, the number of square arcminutes in a complete sphere is 4 π2 =466560000 π ≈148510660 square arcminutes. The standard symbol for marking the arcminute is the prime, though a single quote is used where only ASCII characters are permitted. One arcminute is thus written 1′ and it is also abbreviated as arcmin or amin or, less commonly, the prime with a circumflex over it. The standard symbol for the arcsecond is the prime, though a double quote is commonly used where only ASCII characters are permitted. One arcsecond is thus written 1″ and it is also abbreviated as arcsec or asec. In celestial navigation, seconds of arc are used in calculations. This notation has been carried over into marine GPS receivers, which normally display latitude and longitude in the format by default. An arcsecond is approximately the angle subtended by a U. S. dime coin at a distance of 4 kilometres, a milliarcsecond is about the size of a dime atop the Eiffel Tower as seen from New York City. A microarcsecond is about the size of a period at the end of a sentence in the Apollo mission manuals left on the Moon as seen from Earth, since antiquity the arcminute and arcsecond have been used in astronomy. The principal exception is Right ascension in equatorial coordinates, which is measured in units of hours, minutes. These small angles may also be written in milliarcseconds, or thousandths of an arcsecond, the unit of distance, the parsec, named from the parallax of one arcsecond, was developed for such parallax measurements. It is the distance at which the radius of the Earths orbit would subtend an angle of one arcsecond. The ESA astrometric space probe Gaia is hoped to measure star positions to 20 microarcseconds when it begins producing catalog positions sometime after 2016, there are about 1.3 trillion µas in a turn. Currently the best catalog positions of stars actually measured are in terms of milliarcseconds, apart from the Sun, the star with the largest angular diameter from Earth is R Doradus, a red supergiant with a diameter of 0.05 arcsecond. The dwarf planet Pluto has proven difficult to resolve because its angular diameter is about 0.1 arcsecond, space telescopes are not affected by the Earths atmosphere but are diffraction limited. For example, the Hubble space telescope can reach a size of stars down to about 0. 1″
22.
Speed of light
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The speed of light in vacuum, commonly denoted c, is a universal physical constant important in many areas of physics. Its exact value is 299792458 metres per second, it is exact because the unit of length, the metre, is defined from this constant, according to special relativity, c is the maximum speed at which all matter and hence information in the universe can travel. It is the speed at which all particles and changes of the associated fields travel in vacuum. Such particles and waves travel at c regardless of the motion of the source or the reference frame of the observer. In the theory of relativity, c interrelates space and time, the speed at which light propagates through transparent materials, such as glass or air, is less than c, similarly, the speed of radio waves in wire cables is slower than c. The ratio between c and the speed v at which light travels in a material is called the index n of the material. In communicating with distant space probes, it can take minutes to hours for a message to get from Earth to the spacecraft, the light seen from stars left them many years ago, allowing the study of the history of the universe by looking at distant objects. The finite speed of light limits the theoretical maximum speed of computers. The speed of light can be used time of flight measurements to measure large distances to high precision. Ole Rømer first demonstrated in 1676 that light travels at a speed by studying the apparent motion of Jupiters moon Io. In 1865, James Clerk Maxwell proposed that light was an electromagnetic wave, in 1905, Albert Einstein postulated that the speed of light c with respect to any inertial frame is a constant and is independent of the motion of the light source. He explored the consequences of that postulate by deriving the theory of relativity and in doing so showed that the parameter c had relevance outside of the context of light and electromagnetism. After centuries of increasingly precise measurements, in 1975 the speed of light was known to be 299792458 m/s with a measurement uncertainty of 4 parts per billion. In 1983, the metre was redefined in the International System of Units as the distance travelled by light in vacuum in 1/299792458 of a second, as a result, the numerical value of c in metres per second is now fixed exactly by the definition of the metre. The speed of light in vacuum is usually denoted by a lowercase c, historically, the symbol V was used as an alternative symbol for the speed of light, introduced by James Clerk Maxwell in 1865. In 1856, Wilhelm Eduard Weber and Rudolf Kohlrausch had used c for a different constant later shown to equal √2 times the speed of light in vacuum, in 1894, Paul Drude redefined c with its modern meaning. Einstein used V in his original German-language papers on special relativity in 1905, but in 1907 he switched to c, sometimes c is used for the speed of waves in any material medium, and c0 for the speed of light in vacuum. This article uses c exclusively for the speed of light in vacuum, since 1983, the metre has been defined in the International System of Units as the distance light travels in vacuum in 1⁄299792458 of a second
23.
Crab Pulsar
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The Crab Pulsar is a relatively young neutron star. The star is the star in the Crab Nebula, a remnant of the supernova SN1054. Discovered in 1968, the pulsar was the first to be connected with a supernova remnant, the Crab Pulsar is one of very few pulsars to be identified optically. The optical pulsar is roughly 20 km in diameter and the pulsar beams rotate once every 33 milliseconds, the outflowing relativistic wind from the neutron star generates synchrotron emission, which produces the bulk of the emission from the nebula, seen from radio waves through to gamma rays. The most dynamic feature in the part of the nebula is the point where the pulsars equatorial wind slams into the surrounding nebula. The period of the rotation is slowing by 38 nanoseconds per day due to the large amounts of energy carried away in the pulsar wind. The Crab Nebula is often used as a source in X-ray astronomy. It is very bright in X-rays and the density and spectrum are known to be constant. The pulsar provides a periodic signal that is used to check the timing of the X-ray detectors. In X-ray astronomy, crab and millicrab are sometimes used as units of flux density, very few X-ray sources ever exceed one crab in brightness. The Crab Nebula was identified as the remnant of SN1054 by 1939, astronomers then searched for the nebulas central star. There were two candidates, referred to in the literature as the following and south preceding stars. In September 1942, Walter Baade ruled out the north following star, in late 1968, David H. Staelin and Edward C. Reifenstein III reported the discovery of two pulsating radio sources near the nebula that could be coincident with it using the 300-foot Green Bank radio antenna. They were given the designations NP0527 and NP0532, the period and location of the Crab Nebula pulsar NP0532 was discovered by Richard Lovelace and collaborators November 10,1968 at the Arecibo radio observatory. A subsequent study by them including William D. Brundage also found that the NP0532 source is located at the Crab Nebula, a radio source was also reported coincident with the crab nebula in late 1968 by L. I. Optical pulsations were first reported by Cocke, Disney, and Taylor using the 36-inch telescope on Kitt Peak of the Steward Observatory of the University of Arizona and their discovery was confirmed by Nather, Warner, and Macfarlane. The astronomer she spoke to, Elliot Moore, disregarded the effect as scintillation, despite the womans protestation that as a pilot she understood scintillation
24.
Pulsar
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A pulsar is a highly magnetized, rotating neutron star or white dwarf, that emits a beam of electromagnetic radiation. This radiation can be observed only when the beam of emission is pointing toward Earth, neutron stars are very dense, and have short, regular rotational periods. This produces a very precise interval between pulses that range from milliseconds to seconds for an individual pulsar, Pulsars are believed to be one of the candidates of high and ultra-high energy astroparticles. The precise periods of pulsars make them very useful tools, observations of a pulsar in a binary neutron star system were used to indirectly confirm the existence of gravitational radiation. The first extrasolar planets were discovered around a pulsar, PSR B1257+12, certain types of pulsars rival atomic clocks in their accuracy in keeping time. The first pulsar was observed on November 28,1967, by Jocelyn Bell Burnell and they observed pulses separated by 1.33 seconds that originated from the same location on the sky, and kept to sidereal time. When observations with another telescope confirmed the emission, it eliminated any sort of instrumental effects and it is an interesting problem—if one thinks one may have detected life elsewhere in the universe, how does one announce the results responsibly. Even so, they nicknamed the signal LGM-1, for little green men and it was not until a second pulsating source was discovered in a different part of the sky that the LGM hypothesis was entirely abandoned. Their pulsar was later dubbed CP1919, and is now known by a number of designators including PSR 1919+21, PSR B1919+21, although CP1919 emits in radio wavelengths, pulsars have, subsequently, been found to emit in visible light, X-ray, and/or gamma ray wavelengths. The word pulsar is a portmanteau of pulsating star, and first appeared in print in 1968, An entirely novel kind of came to light on Aug.6 last year and was referred to, by astronomers. Now it is thought to be a novel type between a white dwarf and a neutron, the name Pulsar is likely to be given to it. Dr. A. Hewish told me yesterday, … I am sure that today every radio telescope is looking at the Pulsars. The existence of stars was first proposed by Walter Baade and Fritz Zwicky in 1934. The discovery of the Crab pulsar later in 1968 seemed to provide confirmation of the neutron star model of pulsars. The Crab pulsar has a 33-millisecond pulse period, which was too short to be consistent with other proposed models for pulsar emission. Moreover, the Crab pulsar is so named because it is located at the center of the Crab Nebula, consistent with the 1933 prediction of Baade and Zwicky. Considerable controversy is associated with the fact that Professor Hewish was awarded the prize while Bell, Bell claims no bitterness upon this point, supporting the decision of the Nobel prize committee. In 1974, Joseph Hooton Taylor, Jr. and Russell Hulse discovered for the first time a pulsar in a binary system and this pulsar orbits another neutron star with an orbital period of just eight hours
25.
Radiation
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In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. Radiation is often categorized as either ionizing or non-ionizing depending on the energy of the radiated particles, Ionizing radiation carries more than 10 eV, which is enough to ionize atoms and molecules, and break chemical bonds. This is an important distinction due to the difference in harmfulness to living organisms. A common source of ionizing radiation is radioactive materials that emit α, β, or γ radiation, consisting of helium nuclei, electrons or positrons, gamma rays, X-rays and the higher energy range of ultraviolet light constitute the ionizing part of the electromagnetic spectrum. The lower-energy, longer-wavelength part of the spectrum including visible light, infrared light, microwaves and this type of radiation only damages cells if the intensity is high enough to cause excessive heating. Ultraviolet radiation has some features of both ionizing and non-ionizing radiation and these properties derive from ultraviolets power to alter chemical bonds, even without having quite enough energy to ionize atoms. The word radiation arises from the phenomenon of waves radiating from a source and this aspect leads to a system of measurements and physical units that are applicable to all types of radiation. This law does not apply close to a source of radiation or for focused beams. Radiation with sufficiently high energy can ionize atoms, that is to say it can knock electrons off atoms, ionization occurs when an electron is stripped from an electron shell of the atom, which leaves the atom with a net positive charge. Because living cells and, more importantly, the DNA in those cells can be damaged by this ionization, thus ionizing radiation is somewhat artificially separated from particle radiation and electromagnetic radiation, simply due to its great potential for biological damage. While an individual cell is made of trillions of atoms, only a fraction of those will be ionized at low to moderate radiation powers. If the source of the radiation is a radioactive material or a nuclear process such as fission or fusion. Particle radiation is subatomic particles accelerated to relativistic speeds by nuclear reactions, because of their momenta they are quite capable of knocking out electrons and ionizing materials, but since most have an electrical charge, they dont have the penetrating power of ionizing radiation. The exception is neutron particles, see below, there are several different kinds of these particles, but the majority are alpha particles, beta particles, neutrons, and protons. Roughly speaking, photons and particles with energies above about 10 electron volts are ionizing, particle radiation from radioactive material or cosmic rays almost invariably carries enough energy to be ionizing. The radiation is invisible and not directly detectable by human senses, as a result, in some cases, it may lead to secondary emission of visible light upon its interaction with matter, as in the case of Cherenkov radiation and radio-luminescence. Ionizing radiation has many uses in medicine, research and construction. Ultraviolet, of wavelengths from 10 nm to 125 nm, ionizes air molecules, causing it to be absorbed by air
26.
Gamma ray
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Gamma ray, denoted by the lower-case Greek letter gamma, is penetrating electromagnetic radiation of a kind arising from the radioactive decay of atomic nuclei. It consists of photons in the highest observed range of photon energy, paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays, Rutherford had previously discovered two other types of radioactive decay, which he named alpha and beta rays. Gamma rays are able to ionize atoms, and are thus biologically hazardous. The decay of a nucleus from a high energy state to a lower energy state. Natural sources of gamma rays on Earth are observed in the decay of radionuclides. There are rare terrestrial natural sources, such as lightning strikes and terrestrial gamma-ray flashes, However, a large fraction of such astronomical gamma rays are screened by Earths atmosphere and can only be detected by spacecraft. Gamma rays typically have frequencies above 10 exahertz, and therefore have energies above 100 keV and wavelengths less than 10 picometers, However, this is not a strict definition, but rather only a rule-of-thumb description for natural processes. Electromagnetic radiation from radioactive decay of nuclei is referred to as gamma rays no matter its energy. This radiation commonly has energy of a few hundred keV, in astronomy, gamma rays are defined by their energy, and no production process needs to be specified. The energies of gamma rays from astronomical sources range to over 10 TeV, a notable example is the extremely powerful bursts of high-energy radiation referred to as long duration gamma-ray bursts, of energies higher than can be produced by radioactive decay. These bursts of gamma rays are thought to be due to the collapse of stars called hypernovae, the first gamma ray source to be discovered historically was the radioactive decay process called gamma decay. In this type of decay, a nucleus emits a gamma ray almost immediately upon formation. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, However, Villard did not consider naming them as a different fundamental type. Rutherford also noted that gamma rays were not deflected by a field, another property making them unlike alpha. Gamma rays were first thought to be particles with mass, like alpha, Rutherford initially believed that they might be extremely fast beta particles, but their failure to be deflected by a magnetic field indicated that they had no charge. In 1914, gamma rays were observed to be reflected from crystal surfaces, Rutherford and his coworker Edward Andrade measured the wavelengths of gamma rays from radium, and found that they were similar to X-rays, but with shorter wavelengths and higher frequency. This was eventually recognized as giving them more energy per photon
27.
Radio wave
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Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies as high as 300 GHz to as low as 3 kHz, though some definitions describe waves above 1 or 3 GHz as microwaves, at 300 GHz, the corresponding wavelength is 1 mm, and at 3 kHz is 100 km. Like all other electromagnetic waves, they travel at the speed of light, naturally occurring radio waves are generated by lightning, or by astronomical objects. Radio waves are generated by radio transmitters and received by radio receivers, the radio spectrum is divided into a number of radio bands on the basis of frequency, allocated to different uses. Radio waves were first predicted by mathematical work done in 1867 by Scottish mathematical physicist James Clerk Maxwell, Maxwell noticed wavelike properties of light and similarities in electrical and magnetic observations. Radio waves were first used for communication in the mid 1890s by Guglielmo Marconi, different frequencies experience different combinations of these phenomena in the Earths atmosphere, making certain radio bands more useful for specific purposes than others. It does not necessarily require a cleared sight path, at lower frequencies radio waves can pass through buildings, foliage and this is the only method of propagation possible at microwave frequencies and above. On the surface of the Earth, line of propagation is limited by the visual horizon to about 40 miles. This is the used by cell phones, cordless phones, walkie-talkies, wireless networks, FM and television broadcasting. Indirect propagation, Radio waves can reach points beyond the line-of-sight by diffraction, diffraction allows a radio wave to bend around obstructions such as a building edge, a vehicle, or a turn in a hall. Radio waves also reflect from surfaces such as walls, floors, ceilings, vehicles and these effects are used in short range radio communication systems. Ground waves allow mediumwave and longwave broadcasting stations to have coverage areas beyond the horizon, the nonzero resistance of the earth absorbs energy from ground waves, so as they propagate the waves lose power and the wavefronts bend over at an angle to the surface. As frequency decreases, the decrease and the achievable range increases. Military very low frequency and extremely low frequency communication systems can communicate over most of the Earth, and with submarines hundreds of feet underwater. Tropospheric propagation, In the VHF and UHF bands, radio waves can travel somewhat beyond the horizon due to refraction in the troposphere. This is due to changes in the index of air with temperature and pressure. At times, radio waves can travel up to 500 -1000 km due to tropospheric ducting and these effects are variable and not as reliable as ionospheric propagation, below. So radio waves directed at an angle into the sky can return to Earth beyond the horizon, by using multiple skips communication at intercontinental distances can be achieved
28.
X-ray
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X-radiation is a form of electromagnetic radiation. Most X-rays have a wavelength ranging from 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz, X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays. Spelling of X-ray in the English language includes the variants x-ray, xray, X-rays with high photon energies are called hard X-rays, while those with lower energy are called soft X-rays. Due to their ability, hard X-rays are widely used to image the inside of objects, e. g. in medical radiography. The term X-ray is metonymically used to refer to an image produced using this method. Since the wavelengths of hard X-rays are similar to the size of atoms they are useful for determining crystal structures by X-ray crystallography. By contrast, soft X-rays are easily absorbed in air, the length of 600 eV X-rays in water is less than 1 micrometer. There is no consensus for a definition distinguishing between X-rays and gamma rays, one common practice is to distinguish between the two types of radiation based on their source, X-rays are emitted by electrons, while gamma rays are emitted by the atomic nucleus. This definition has problems, other processes also can generate these high-energy photons. One common alternative is to distinguish X- and gamma radiation on the basis of wavelength, with radiation shorter than some arbitrary wavelength, such as 10−11 m and this criterion assigns a photon to an unambiguous category, but is only possible if wavelength is known. Occasionally, one term or the other is used in specific contexts due to precedent, based on measurement technique. Thus, gamma-rays generated for medical and industrial uses, for radiotherapy, in the ranges of 6–20 MeV. X-ray photons carry enough energy to ionize atoms and disrupt molecular bonds and this makes it a type of ionizing radiation, and therefore harmful to living tissue. A very high radiation dose over a period of time causes radiation sickness. In medical imaging this increased risk is generally greatly outweighed by the benefits of the examination. The ionizing capability of X-rays can be utilized in treatment to kill malignant cells using radiation therapy. It is also used for material characterization using X-ray spectroscopy, hard X-rays can traverse relatively thick objects without being much absorbed or scattered. For this reason, X-rays are widely used to image the inside of visually opaque objects, the most often seen applications are in medical radiography and airport security scanners, but similar techniques are also important in industry and research
29.
Electronvolt
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In physics, the electronvolt is a unit of energy equal to approximately 1. 6×10−19 joules. By definition, it is the amount of energy gained by the charge of an electron moving across an electric potential difference of one volt. Thus it is 1 volt multiplied by the elementary charge, therefore, one electronvolt is equal to 6981160217662079999♠1. 6021766208×10−19 J. The electronvolt is not a SI unit, and its definition is empirical, like the elementary charge on which it is based, it is not an independent quantity but is equal to 1 J/C √2hα / μ0c0. It is a unit of energy within physics, widely used in solid state, atomic, nuclear. It is commonly used with the metric prefixes milli-, kilo-, in some older documents, and in the name Bevatron, the symbol BeV is used, which stands for billion electronvolts, it is equivalent to the GeV. By mass–energy equivalence, the electronvolt is also a unit of mass and it is common in particle physics, where units of mass and energy are often interchanged, to express mass in units of eV/c2, where c is the speed of light in vacuum. It is common to express mass in terms of eV as a unit of mass. The mass equivalent of 1 eV/c2 is 1 eV / c 2 = ⋅1 V2 =1.783 ×10 −36 kg. For example, an electron and a positron, each with a mass of 0.511 MeV/c2, the proton has a mass of 0.938 GeV/c2. In general, the masses of all hadrons are of the order of 1 GeV/c2, the unified atomic mass unit,1 gram divided by Avogadros number, is almost the mass of a hydrogen atom, which is mostly the mass of the proton. To convert to megaelectronvolts, use the formula,1 u =931.4941 MeV/c2 =0.9314941 GeV/c2, in high-energy physics, the electronvolt is often used as a unit of momentum. A potential difference of 1 volt causes an electron to gain an amount of energy and this gives rise to usage of eV as units of momentum, for the energy supplied results in acceleration of the particle. The dimensions of units are LMT−1. The dimensions of units are L2MT−2. Then, dividing the units of energy by a constant that has units of velocity. In the field of particle physics, the fundamental velocity unit is the speed of light in vacuum c. Thus, dividing energy in eV by the speed of light, the fundamental velocity constant c is often dropped from the units of momentum by way of defining units of length such that the value of c is unity
30.
Occultation
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An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy and it can also refer to any situation wherein an object in the foreground blocks from view an object in the background. In this general sense, occultation applies to the visual scene observed from low-flying aircraft wherein foreground objects obscure distant objects dynamically, as the scene changes over time. The term occultation is most frequently used to describe those relatively frequent occasions when the Moon passes in front of a star during the course of its orbital motion around the Earth. Events that take place on the Moons dark limb are of particular interest to observers, the Moons orbit is inclined to the ecliptic, and any stars with an ecliptic latitude of less than about 6.5 degrees may be occulted by it. There are three first magnitude stars that are close to the ecliptic that they may be occulted by the Moon and by planets – Regulus, Spica. Occultations of Aldebaran are presently only possible by the Moon, because the planets pass Aldebaran to the north, neither planetary nor lunar occultations of Pollux are currently possible. However, in the far future, occultations of Pollux will be possible, some deep-sky objects, such as the Pleiades, can also be occulted by the Moon. From an observational and scientific standpoint, these grazes are the most dynamic, the accurate timing of lunar occultations is performed regularly by astronomers. Lunar occultations timed to an accuracy of a few tenths of a second have various scientific uses, photoelectric analysis of lunar occultations have also discovered some stars to be very close visual or spectroscopic binaries. Some angular diameters of stars have been measured by timing of lunar occultations, several times during the year, someone on Earth can usually observe the Moon occulting a planet. Since planets, unlike stars, have significant angular sizes, lunar occultations of planets will create a zone on Earth from which a partial occultation of the planet will occur. An observer located within that narrow zone could observe the planets disk partly blocked by the moving moon. The same mechanic can be seen with the Sun, where observers on Earth will view it as a Solar Eclipse, therefore, a Total Solar Eclipse is effectively the same event as the Moon occulting the Sun. Stars may also be occulted by planets, uranuss rings were first discovered when that planet occulted a star in 1977. On 3 July 1989, Saturn passed in front of the 5th magnitude star 28 Sagittarii, pluto occulted stars in 1988,2002, and 2006, allowing its tenuous atmosphere to be studied via atmospheric limb sounding. In rare cases, one planet can pass in front of another, if the nearer planet appears larger than the more distant one, the event is called a mutual planetary occultation. An asteroid occultation occurs when an asteroid passes in front of a star, several events occur nearly every day over the world
31.
Corona
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A corona is an aura of plasma that surrounds the sun and other stars. The Suns corona extends millions of kilometres into space and is most easily seen during a solar eclipse. The word corona is a Latin word meaning crown, from the Ancient Greek κορώνη, the high temperature of the Suns corona gives it unusual spectral features, which led some in the 19th century to suggest that it contained a previously unknown element, coronium. Instead, these features have since been explained by highly ionized iron. Bengt Edlén, following the work of Grotrian, first identified the coronal spectral lines in 1940 as transitions from low-lying metastable levels of the configuration of highly ionised metals. These high stages of ionisation indicate a temperature in excess of 1,000,000 kelvins. Light from the corona comes from three sources, from the same volume of space. The suns corona is much hotter than the surface of the Sun. The corona is 10−12 times as dense as the photosphere, the corona is separated from the photosphere by the relatively shallow chromosphere. The exact mechanism by which the corona is heated is still the subject of some debate, the outer edges of the Suns corona are constantly being transported away due to open magnetic flux and hence generating the solar wind. The corona is not always evenly distributed across the surface of the sun, during periods of quiet, the corona is more or less confined to the equatorial regions, with coronal holes covering the polar regions. However, during the Suns active periods, the corona is evenly distributed over the equatorial and polar regions, the solar cycle spans approximately 11 years, from solar minimum to the following minimum. Associated with sunspots are coronal loops, loops of magnetic flux, the magnetic flux pushes the hotter photosphere aside, exposing the cooler plasma below, thus creating the relatively dark sun spots. The astronomers usually distinguish several regions, as described below, active regions are ensembles of loop structures connecting points of opposite magnetic polarity in the photosphere, the so-called coronal loops. They generally distribute in two zones of activity, which are parallel to the solar equator, the average temperature is between two and four million kelvins, while the density goes from 109 to 1010 particle per cm3. If flares are very violent, they can also perturb the photosphere, on the contrary, quiescent prominences are large, cool dense structures which are observed as dark, snake-like Hα ribbons on the solar disc. Their temperature is about 5000–8000 K, and so they are considered as chromospheric features. In 2013, images from the High Resolution Coronal Imager revealed never-before-seen magnetic braids of plasma within the layers of these active regions
32.
Pulsar wind nebula
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A pulsar wind nebula, sometimes called a plerion, is a type of nebula found inside the shells of supernova remnants that is powered by pulsar winds generated by its central pulsar. These nebulae were discovered in 1976 as small depressions at radio wavelengths near the centre of supernova remnants and they have since been found to be X-ray emitters and are possibly γ-ray sources. As the plerion ages, the nebulosity of the supernova remnant dissipates, over time, pulsar wind nebulae may change in behaviour and become relic nebulae surrounding millisecond radio pulsars or even older and slower rotating pulsars. Plerions are estimated to last around 15,000 years, after which the shell dissipates as the energies from the pulsar decreases, importantly, this depends on the rate of energy lost by the pulsar as its spin rate slows, which varies among the known pulsars. Pulsar winds are composed of charged particles accelerated to relativistic speeds by the rapidly rotating, the pulsar wind often streams into the surrounding interstellar medium, creating a standing shock wave called the wind termination shock, where matter is decelerated to sub-relativistic speed. Beyond this radius, synchrotron emission increases in the magnetized flow and these processes can switch on and off with many reversals, and this creates the numerous visible shells centred on the pulsar. Pulsar wind nebulae often show the properties, An increasing brightness towards the center. A highly polarized flux and a spectral index in the radio band. The index steepens at X-ray energies due to radiation losses. An X-ray size that is smaller than their radio and optical size. A photon index at TeV gamma-ray energies of ~2.3, Pulsar wind nebulae can be powerful probes of a pulsar/neutron stars interaction with its surroundings. Their unique properties can be used to infer the geometry, energetics, and composition of the wind, the space velocity of the pulsar itself. G292. 0+01.8 The Pulsar Wind Nebula Catalog
33.
H-alpha
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H-alpha is a specific deep-red visible spectral line in the Balmer series with a wavelength of 656.28 nm, it occurs when a hydrogen electron falls from its third to second lowest energy level. H-alpha light is important to astronomers as it is emitted by many emission nebulae and can be used to observe features in the Suns atmosphere, according to the Bohr model of the atom, electrons exist in quantized energy levels surrounding the atoms nucleus. These energy levels are described by the quantum number n =1,2,3. Electrons may only exist in these states, and may only transit between these states, for the Lyman series the naming convention is, n =2 to n =1 is called Lyman-alpha, n =3 to n =1 is called Lyman-beta, etc. H-alpha has a wavelength of 656.281 nm, is visible in the red part of the electromagnetic spectrum, instead, after being ionized, the electron and proton recombine to form a new hydrogen atom. In the new atom, the electron may begin in any energy level, approximately half the time, this cascade will include the n =3 to n =2 transition and the atom will emit H-alpha light. Therefore, the H-alpha line occurs where hydrogen is being ionized, instead, molecules such as carbon dioxide, carbon monoxide, formaldehyde, ammonia, or acetonitrile are typically used to determine the mass of a cloud. A hydrogen-alpha filter is a filter designed to transmit a narrow bandwidth of light generally centred on the H-alpha wavelength. They are characterized by a width that measures the width of the wavelength band that is transmitted. These filters can be dichroic filters manufactured by multiple vacuum-deposited layers and these layers are selected to produce interference effects that filter out any wavelengths except at the requisite band. Taken in isolation, H-alpha dichroic filters are useful in astrophotography and they do not have narrow enough bandwidth for observing the suns atmosphere. This combination will pass only a range of wavelengths of light centred on the H-alpha emission line. The physics of the etalon and the dichroic interference filters are essentially the same, due to the high velocities sometimes associated with features visible in H-alpha light, solar H-alpha etalons can often be tuned to cope with the associated Doppler effect. Commercially available H-alpha filters for amateur solar observing usually state bandwidths in Angstrom units and are typically 0. 7Å, by using a second etalon, this can be reduced to 0. 5Å leading to improved contrast in details observed on the suns disc. An even more narrow band filter can be using a Lyot filter. Hydrogen spectral series Rydberg formula Spectrohelioscope Description of etalon filter by Colin Kaminski
34.
Liverpool Telescope
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The Liverpool Telescope is a 2-metre fully robotic Ritchey–Chrétien telescope that observes autonomously, i. e. it operates without human intervention. Professional astronomers and other registered users submit observation specifications to be considered by the robotic control system at any time of the day or night using an online GUI. Each night the RCS decides for itself what to observe next based on target visibility, the RCS additionally has a rapid-response capability where it can automatically interrupt regular observations to slew to observe transient phenomena with higher priority, such as gamma-ray bursts. The LT is one of the largest robotic telescopes in the world and was built by Telescope Technologies Ltd, the telescope is owned by Liverpool John Moores University, and operated by the Astrophysics Research Institute with operational funding partly from STFC. It is sited at the Roque de los Muchachos Observatory on La Palma, along with the Faulkes Telescope North and the Faulkes Telescope South, the Liverpool Telescope is also available for use by school children around the world over the internet. The registration and time allocation for the LT is organised by the National Schools Observatory, plans for an improved version of the telescope, the Liverpool Telescope 2, are underway
35.
Carl Otto Lampland
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Carl Otto Lampland was an American astronomer. He was born into a family of ten children, both his father Ole Helliksen Lampland and his mother Berit Gulliksdatter Skartum were born in Norway. He was educated first at Valparaiso Normal school in Valparaiso, Indiana and he then studied at Indiana University, where he received a B. A. degree in astronomy in 1902, an M. A. in 1906, and an honorary LL. D in 1930. He first went to Lowell Observatory in 1902 when invited by Percival Lowell and he designed cameras used for astronomy and also designed and maintained telescopes, including resilvering the mirror of the 40-inch telescope. He also constructed thermocouples and used them to temperatures of planets. He won the Royal Photographic Society Medal in 1905 for the camera which he designed for the 24-inch Clark telescope, together with William Coblentz, he measured large differences between the day and night temperatures on Mars which implied a thin Martian atmosphere. He discovered the asteroid 1604 Tombaugh, in 1907 Lampland and Lowell won a Royal Photographic Society exhibition medal for their photographs of Mars. His date of birth is the point for the Mars Sol Date calendar. The lunar crater Lampland as well as the Martian crater Lampland were named after him, the main-belt asteroid 1767 Lampland is also named after him. Lampland Collection in maintained at the Lowell Observatory Archives in Flagstaff
36.
Fujiwara no Teika
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Fujiwara Sadaie, better-known as Fujiwara no Teika, was a Japanese poet, critic, calligrapher, novelist, anthologist, scribe, and scholar of the late Heian and early Kamakura periods. Teikas critical ideas on composing poetry were influential and studied until as late as the Meiji era. A member of a clan, Teika was born to the noted poet Fujiwara no Shunzei. After coming to the attention of the Retired Emperor Go-Toba, Teika began his long and distinguished career and his relationship with Go-Toba was at first cordial and led to commissions to compile anthologies, but later resulted in his banishment from the retired emperors court. His descendants and ideas would dominate classical Japanese poetry for centuries afterwards and his branch of the clan sought prestige and power in the court by aligning itself with the Mikohidari family, and by specializing in artistic endeavors, principally poetry. Teikas grandfather was the venerable poet Fujiwara no Toshitada and his father was Fujiwara no Shunzei, a well known and greatly respected poet, who had compiled the seventh Imperial anthology of waka. His sister would become a well-respected poet of waka and renga, known as Kengozen or Shunzeis Daughter. His elder brother, Fujiwara no Nariee, would be successful in court. Teikas foster-brother, the priest Jakuren or Sadanaga c, 1139–1202 would be successful as a poet although his career was cut tragically short, he had been adopted by Shunzei when Shunzeis younger brother retired from the world. Teikas goals as the male of his branch were to inherit and cement his fathers position in poetry. The Retired Emperor Go-Toba announced, in the year of his abdication that he would be conducting a poetry contest. Go-Toba regarded all these pursuits as hobbies, taking one up, one of these was his support of poetry, especially the waka. The first contest was considered a crucial political nexus, if a clans poet did well and impressed the powerful Go-Toba, Teikas diary records that he looked forward to this chance to improve himself. He was 38, and had reached middle age, while he was recognized as a talented poet, his career was stagnant, he had been in the Palace Guards of the Left for twenty years, and had not been promoted for nearly 10. He was Lesser Commander of the Palace Guards of the Left with little prospect of further advancement and he had wider political problems, The influence of his patrons, the Kujōs, over the Emperors had declined drastically. His revenge was well-done, Teika was furious, writing in his Meigetsuki, I can just see Suetsune at the bottom of this, contriving by some bribe that I be left out. It has to be Suetsune, Tsuneie, that whole family, well, I have no regrets, for there is no possible hope for me now. But I did write in confidence to Kintsune so this may all come out eventually and he has replied that there is still room for hope
37.
Ibn Butlan
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Ibn Butlan was an Arab Nestorian Christian physician who was active in Baghdad during the Islamic Golden Age. The work treated matters of hygiene, dietetics, and exercise and it emphasized the benefits of regular attention to the personal physical and mental well-being. One of his Greek sources was Dioscorides
38.
Nestorianism
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Nestorianism is a Christological doctrine that emphasizes a distinction between the human and divine persons of Jesus. It was advanced by Nestorius, Patriarch of Constantinople from 428 to 431, following that, many of Nestoriuss supporters relocated to the Sasanian Empire, where they affiliated with the local Christian community, known as the Church of the East. Over the next decades the Church of the East became increasingly Nestorian in doctrine, Nestorianism is a form of dyophysitism. It can be seen as the antithesis to monophysitism, which emerged in reaction to Nestorianism, where Nestorianism holds that Christ had two loosely united natures, divine and human, monophysitism holds that he had but a single nature, his human nature being absorbed into his divinity. Both Nestorianism and monophysitism were condemned as heretical at the Council of Chalcedon, monophysitism survived and developed into the Miaphysitism of the Oriental Orthodoxy. Nestorianism never again became prominent in the Roman Empire or later Europe, though the diffusion of the Church of the East in and after the seventh century, despite this initial Eastern expansion, the Nestorians missionary success was eventually deterred. Isolated pockets of Christianity survived only in India, Nestorius took his Antiochene leanings with him when he was appointed Patriarch of Constantinople by Byzantine emperor Theodosius II in 428. Nestoriuss teachings became the root of controversy when he challenged the long-used title Theotokos for Mary. He suggested that the title denied Christs full humanity, arguing instead that Jesus had two persons, the divine Logos and the human Jesus, as a result of this duality, he proposed Christotokos as a more suitable title for Mary. Nestorius opponents found his teaching too close to the heresy of adoptionism – the idea that Christ had been born a man who had later been adopted as Gods son. Nestorius was especially criticized by Cyril of Alexandria, Patriarch of Alexandria, a more elaborate Nestorian theology developed from there, which came to see Christ as having two natures united, or hypostases, the divine Logos and the human Christ. However, this formulation was never adopted by all churches termed Nestorian, indeed, the modern Assyrian Church of the East, which reveres Nestorius, does not fully subscribe to Nestorian doctrine, though it does not employ the title Theotokos. Nestorianism became a distinct sect following the Nestorian Schism, beginning in the 430s, Nestorius had come under fire from Western theologians, most notably Cyril of Alexandria. Cyril and Nestorius asked Pope Celestine I to weigh in on the matter, Celestine found that the title Theotokos was orthodox, and authorized Cyril to ask Nestorius to recant. Cyril, however, used the opportunity to further attack Nestorius, in 431 Theodosius called the Council of Ephesus. However, the council sided with Cyril, who, being a monophysite. The council accused Nestorius of heresy, and deposed him as patriarch, Nestorianism was officially anathematized, a ruling reiterated at the Council of Chalcedon in 451. However, a number of churches, particularly associated with the School of Edessa, supported Nestorius – though not necessarily his doctrine –
39.
Charles Messier
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Charles Messier was a French astronomer most notable for publishing an astronomical catalogue consisting of nebulae and star clusters that came to be known as the 110 Messier objects. The purpose of the catalogue was to help astronomical observers, in particular comet hunters such as himself, Messier was born in Badonviller in the Lorraine region of France, being the tenth of twelve children of Françoise B. Grandblaise and Nicolas Messier, a Court usher, six of his brothers and sisters died while young and in 1741, his father died. Charles interest in astronomy was stimulated by the appearance of the spectacular, great six-tailed comet in 1744, in 1751 he entered the employ of Joseph Nicolas Delisle, the astronomer of the French Navy, who instructed him to keep careful records of his observations. Messiers first documented observation was that of the Mercury transit of 6 May 1753, according to Meyer, Messier is buried in Père Lachaise Cemetery, Paris, in Section 11. Messiers occupation as a comet hunter led him to come across fixed diffuse objects in the night sky which could be mistaken for comets. He compiled a list of them, in collaboration with his friend and assistant Pierre Méchain, the entries are now known to be galaxies, planetary nebulae, other types of nebulae, and star clusters. Messier did his observing with a 100 mm refracting telescope from Hôtel de Cluny, in downtown Paris, the list he compiled contains only objects found in the area of the sky he could observe, from the north celestial pole to a declination of about −35. 7°. They are not organized scientifically by object type, or even by location, the first version of Messiers catalogue contained 45 objects and was published in 1774 in the journal of the French Academy of Sciences in Paris. In addition to his own discoveries, this version included objects previously observed by other astronomers, by 1780 the catalog had increased to 80 objects. The final version of the catalogue was published in 1781, in the 1784 issue of Connaissance des Temps, the final list of Messier objects had grown to 103. These seven objects, M104 through M110, are accepted by astronomers as official Messier objects, the crater Messier on the Moon and the asteroid 7359 Messier were named in his honor. Deep sky object List of Messier objects Messier object Messier marathon Caldwell catalogue OMeara, deep Sky Companions, The Messier Objects. Charles Messier Biography at Students for the Exploration and Development of Space, retrieved July 2007 Short biography of Charles Messier and history of the Messier Object Catalog by Jon Zander at OurDarkSkies. com. Retrieved July 2007 Life of a Comet Hunter, Messier and Astrobiology Professor Mark Brake and Martin Griffiths, Astrobiology Magazine European Edition, retrieved July 2007 Interactive Messier Catalog Greenhawk Observatory Amateur Photos of Charles Messier Objects Biography - Messier website. Messier Marathon Attempts to find as many Messier objects as possible in one night, retrieved July 2007 Clickable table of Messier objects Charles Messier explains his catalog on YouTube
40.
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
41.
Alexis Clairaut
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Alexis Claude Clairaut was a French mathematician, astronomer, and geophysicist. He was a prominent Newtonian whose work helped to establish the validity of the principles, Clairaut was one of the key figures in the expedition to Lapland that helped to confirm Newtons theory for the figure of the Earth. In that context, Clairaut worked out a mathematical result now known as Clairauts theorem and he also tackled the gravitational three-body problem, being the first to obtain a satisfactory result for the apsidal precession of the Moons orbit. In mathematics he is credited with Clairauts equation and Clairauts relation. Clairaut was born in Paris, France, to Jean-Babtiste and Catherine Petit Clairaut, the couple had 20 children, however only a few of them survived childbirth. Alexis was a prodigy — at the age of ten he began studying calculus, Clairaut was unmarried, and known for leading an active social life. Though he led a social life, he was very prominent in the advancement of learning in young mathematicians. He was elected a Fellow of the Royal Society of London in November,1737, Clairaut died in Paris in 1765. In 1736, together with Pierre Louis Maupertuis, he took part in the expedition to Lapland, the goal of the excursion was to geometrically calculate the shape of the Earth, which Sir Issac Newton theorized in his book Principia was an ellipsoid shape. They sought to prove if Newtons theory and calculations were correct or not, before the expedition team returned to Paris, Clairaut sent his calculations to the Royal Society of London. The writing was published by the society in the 1736-37 volume of Philosophical Transactions. Initially, Clairaut disagrees with Newtons theory on the shape of the Earth, in the article, he outlines several key problems that effectively disprove Newtons calculations, and provides some solutions to the complications. The issues addressed include calculating gravitational attraction, the rotation of an ellipsoid on its axis, and this conclusion suggests not only that the Earth is of an oblate ellipsoid shape, but it is flattened more at the poles and is wider at the center. His article in Philosophical Transactions created much controversy, as he addressed the problems of Newtons theory, after his return, he published his treatise Théorie de la figure de la terre. This proved Sir Issac Newtons theory that the shape of the Earth was an oblate ellipsoid, in 1849 Stokes showed that Clairauts result was true whatever the interior constitution or density of the Earth, provided the surface was a spheroid of equilibrium of small ellipticity. In 1741, Alexis Clairaut wrote a book called Èléments de Géométrie, the book outlines the basic concepts of geometry. Geometry in the 1700s was complex to the average learner and it was considered to be a dry subject. Clairaut saw this trend, and wrote the book in an attempt to make the more interesting for the average learner
. Bibcode:2008ApJ...677.1201K. doi:10.1086/529026.
