1.
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
2.
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
3.
88 modern constellations by area
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The table below ranks the 88 modern constellations by the solid angle that they subtend in the sky, measured in square degrees and millisteradians. Before Delportes work, there was no standard list of the boundaries of each constellation and this skew will increase over the years and centuries to come. However, this does not change the angle of any constellation
4.
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
5.
Bayer designation
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A Bayer designation is a stellar designation in which a specific star is identified by a Greek letter, followed by the genitive form of its parent constellations Latin name. The original list of Bayer designations contained 1,564 stars, most of the brighter stars were assigned their first systematic names by the German astronomer Johann Bayer in 1603, in his star atlas Uranometria. Bayer assigned a lower-case Greek letter, such as alpha, beta, gamma, for example, Aldebaran is designated α Tauri, which means Alpha of the constellation Taurus. A single constellation may contain fifty or more stars, but the Greek alphabet has only twenty-four letters, when these ran out, Bayer began using Latin letters, upper case A, followed by lower case b through z, for a total of another 24 letters. Bayer never went beyond z, but later added more designations using both upper and lower case Latin letters, the upper case letters following the lower case ones in general. Examples include s Carinae, d Centauri, G Scorpii, and N Velorum, the last upper-case letter used in this way was Q. Bayer catalogued only a few stars too far south to be seen from Germany, in most constellations, Bayer assigned Greek and Latin letters to stars within a constellation in rough order of apparent brightness, from brightest to dimmest. Since the brightest star in a majority of constellations is designated Alpha, in Bayers day, however, stellar brightness could not be measured precisely. Within each magnitude class, Bayer made no attempt to arrange stars by relative brightness, as a result, the brightest star in each class did not always get listed first in Bayers order. Occasionally the order looks quite arbitrary, of the 88 modern constellations, there are at least 30 in which Alpha is not the brightest star, and four of those lack an alpha star altogether. Orion provides an example of Bayers method. Bayer first designated Betelgeuse and Rigel, the two 1st-magnitude stars, as Alpha and Beta from north to south, with Betelgeuse coming ahead of Rigel, Bayer then repeated the procedure for the stars of the 2nd magnitude, labeling them from gamma through zeta in top-down order. The First to Rise in the East order is used in a number of instances, Castor and Pollux of Gemini may be an example of this, Pollux is brighter than Castor, but the latter rises earlier and was assigned alpha. In this case, Bayer may also have influenced by the traditional order of the mythological names Castor and Pollux. Although the brightest star in Draco is Eltanin, Thuban was assigned alpha by Bayer because, due to precession, sometimes there is no apparent order, as exemplified by the stars in Sagittarius, where Bayers designations appear almost random to the modern eye. Alpha and Beta Sagittarii are perhaps the most anomalously designated stars in the sky, the order of the letters assigned in Sagittarius does correspond to the magnitudes as illustrated on Bayers chart, but the latter do not agree with modern determinations of the magnitudes. Bayer designations added by later astronomers generally were ordered by magnitude, in Libra, for example, the new designations sigma, tau, and upsilon were chosen to avoid conflict with Bayers earlier designations, even though several stars with earlier letters are not as bright. In Cygnus, for example, Bayers fixed stars run through g, Bayer did not intend such labels as catalog designations, but some have survived to refer to astronomical objects, P Cygni for example is still used as a designation for Nova Cyg 1600
6.
Exoplanet
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An exoplanet or extrasolar planet is a planet that orbits a star other than the Sun. The first scientific detection of an exoplanet was in 1988, HARPS has discovered about a hundred exoplanets while the Kepler space telescope has found more than two thousand. Kepler has also detected a few thousand candidate planets, of which about 11% may be false positives, on average, there is at least one planet per star, with a percentage having multiple planets. About 1 in 5 Sun-like stars have an Earth-sized planet in the habitable zone, the least massive planet known is Draugr, which is about twice the mass of the Moon. There are planets that are so near to their star that they take only a few hours to orbit, some are so far out that it is difficult to tell whether they are gravitationally bound to the star. Almost all of the planets detected so far are within the Milky Way, the nearest exoplanet is Proxima Centauri b, located 4.2 light-years from Earth and orbiting Proxima Centauri, the closest star to the Sun. The discovery of exoplanets has intensified interest in the search for extraterrestrial life, there is special interest in planets that orbit in a stars habitable zone, where it is possible for liquid water, a prerequisite for life on Earth, to exist on the surface. The study of planetary habitability also considers a range of other factors in determining the suitability of a planet for hosting life. The rogue planets in the Milky Way possibly number in the billions, the convention for designating exoplanets is an extension of the system used for designating multiple-star systems as adopted by the International Astronomical Union. For exoplanets orbiting a star, the designation is normally formed by taking the name or, more commonly, designation of its parent star. The first planet discovered in a system is given the designation b, if several planets in the same system are discovered at the same time, the closest one to the star gets the next letter, followed by the other planets in order of orbital size. A provisional IAU-sanctioned standard exists to accommodate the designation of circumbinary planets, a limited number of exoplanets have IAU-sanctioned proper names. Various detection claims made in the century were rejected by astronomers. The first scientific detection of an exoplanet began in 1988, However, the first confirmed detection came in 1992, with the discovery of several terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a star was made in 1995. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method, in the eighteenth century the same possibility was mentioned by Isaac Newton in the General Scholium that concludes his Principia. Claims of exoplanet detections have been made since the nineteenth century, some of the earliest involve the binary star 70 Ophiuchi. In 1855 William Stephen Jacob at the East India Companys Madras Observatory reported that orbital anomalies made it highly probable that there was a body in this system
7.
Alpha Andromedae
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Alpha Andromedae, also named Alpheratz, is located 97 light-years from the Sun and is the brightest star in the constellation of Andromeda. Located immediately northeast of the constellation of Pegasus, it is the star of the Great Square of Pegasus. Although it appears to the eye as a single star, with overall apparent visual magnitude +2.06. It is the brightest mercury-manganese star known, α Andromedae is the stars Bayer designation. Ptolemy considered Alpha Andromedae to be shared by Pegasus, and Johann Bayer assigned it a designation in both constellations, Alpha Andromedae and Delta Pegasi, when the modern constellation boundaries were fixed in 1930, the latter designation dropped from use. The star bore the traditional names Alpheratz or Alpherat and Sirrah deriving from the Arabic name, the word horse reflects the stars historical placement in Pegasus. In 2016, the International Astronomical Union organized a Working Group on Star Names to catalog, the WGSNs first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN, which included Alpheratz for this star. Another term for this used by medieval astronomers writing in Arabic was راس المراة المسلسلة rās al-mara al-musalsala the head of the woman in chains. Other Arabic names include al-kaff al-khaḍīb and kaff al-naṣīr, in the Hindu lunar zodiac, this star, together with the other stars in the Great Square of Pegasus, makes up the nakshatras of Pūrva Bhādrapadā and Uttara Bhādrapadā. In Chinese, 壁宿, meaning wall, refers to an asterism consisting of α Andromedae and γ Pegasi. Consequently, α Andromedae itself is known as 壁宿二 It is also known as one of the Three Guides that mark the meridian of the heavens. It was believed to bless those born under its influence with honour, the radial velocity of a star away from or towards the observer can be determined by measuring the red shift or blue shift of its spectrum. The American astronomer Vesto Slipher made a series of measurements from 1902 to 1904. He concluded that it was in orbit in a binary star system with a period of about 100 days. A preliminary orbit was published by Hans Ludendorff in 1907, and this work was published in 1992. The two stars are now known to each other with a period of 96.7 days. It is an early-type A star whose spectral type has been estimated as A3V, in 1906, Norman Lockyer and F. E. Baxandall reported that α Andromedae had a number of unusual lines in its spectrum. In 1914, Baxandall pointed out that most of the lines came from manganese
8.
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
9.
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
10.
Meteor shower
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A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of debris called meteoroids entering Earths atmosphere at extremely high speeds on parallel trajectories. Most meteors are smaller than a grain of sand, so almost all of them disintegrate, intense or unusual meteor showers are known as meteor outbursts and meteor storms, which may produce greater than 1000 meteors an hour. The Meteor Data Centre lists about 600 suspected meteor showers of which about 100 are well established, the first great storm in modern times was the Leonids of November 1833. American Denison Olmsted explained the event most accurately, after spending the last weeks of 1833 collecting information he presented his findings in January 1834 to the American Journal of Science and Arts, published in January–April 1834, and January 1836. Work continued, however, coming to understand the nature of showers though the occurrences of storms perplexed researchers. In the 1890s, Irish astronomer George Johnstone Stoney and British astronomer Arthur Matthew Weld Downing, were the first to attempt to calculate the position of the dust at Earths orbit. They studied the dust ejected in 1866 by comet 55P/Tempel-Tuttle in advance of the anticipated Leonid shower return of 1898 and 1899, Meteor storms were anticipated, but the final calculations showed that most of the dust would be far inside of Earths orbit. The same results were independently arrived at by Adolf Berberich of the Königliches Astronomisches Rechen Institut in Berlin, although the absence of meteor storms that season confirmed the calculations, the advance of much better computing tools was needed to arrive at reliable predictions. In 1981 Donald K. Yeomans of the Jet Propulsion Laboratory reviewed the history of showers for the Leonids. A graph from it was adapted and re-published in Sky and Telescope and it showed relative positions of the Earth and Tempel-Tuttle and marks where Earth encountered dense dust. In 1985, E. D. Kondrateva and E. A. Reznikov of Kazan State University first correctly identified the years when dust was released which was responsible for several past Leonid meteor storms, in 1995, Peter Jenniskens predicted the 1995 Alpha Monocerotids outburst from dust trails. In anticipation of the 1999 Leonid storm, Robert H. McNaught, David Asher, in 2006 Jenniskens has published predictions for future dust trail encounters covering the next 50 years. Jérémie Vaubaillon continues to update predictions based on each year for the Institut de Mécanique Céleste et de Calcul des Éphémérides. Because meteor shower particles are all traveling in parallel paths, and at the same velocity and this radiant point is caused by the effect of perspective, similar to parallel railroad tracks converging at a single vanishing point on the horizon when viewed from the middle of the tracks. Meteor showers are almost always named after the constellation from which the appear to originate. This fixed point slowly moves across the sky during the due to the Earth turning on its axis. The radiant also moves slightly from night to night against the stars due to the Earth moving in its orbit around the sun
11.
Andromedids
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The Andromedids meteor shower is associated with Bielas Comet, the showers occurring as Earth passes through old streams left by the comets tail. The comet was observed to have broken up by 1846, further drift of the pieces by 1852 suggested the moment of breakup was in either 1842 or early 1843, the breakup led to particularly spectacular showers in subsequent cycles. In the early 19th century, before the break-up of comet 3D/Biela, the first known sighting of the Andromedids was December 6,1741, over St Petersburg, Russia. Further strong showers were witnessed in 1798,1825,1830,1838 and 1847, the Andromedids produced spectacular displays of several thousand meteors per hour in 1872 and 1885, as a result of Earth crossing the comets debris stream. Schmidt, observing from Athens, said that the 1872 shower consisted mainly of faint meteors with broad and smoke-like trains, in Burma, the 1885 shower was perceived as a fateful omen and was indeed followed swiftly by the collapse of the Konbaung dynasty and the conquest by Britain. In recent years, peak activity had been less than three meteors per hour, around November 9 to 14, Andromedid activity of November comes from the newest streams, while that of early December comes from the oldest. On December 4,2011, six Canadian radar stations detected 50 meteors in an hour, the activity was likely from the 1649 stream. On December 8,2013, Meteor specialist Peter Brown reported that the Canadian Meteor Orbit Radar had recorded an outburst from the Andromedid meteors in the past 24 hours. Scientists postulate a somewhat weaker return in 2018, but a yield of up to 200 meteors an hour in 2023, Canadian Meteor Orbit Radar data also detected a spike of 30 meteors per hour on November 27,2008. During the 2012 shower an inconspicuous maximum occurred on November 9, history of the Andromedids and of the Biela Comet The Mother of All Meteor Storms
12.
Perseus (constellation)
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Perseus is a constellation in the northern sky, being named after the Greek mythological hero Perseus. It is one of the 48 listed by the 2nd-century astronomer Ptolemy and it is located near several other constellations named after ancient Greek legends surrounding Perseus, including Andromeda to the west and Cassiopeia to the north. Perseus is also bordered by Aries and Taurus to the south, Auriga to the east, Camelopardalis to the north, the galactic plane of the Milky Way passes through Perseus, whose brightest star is the yellow-white supergiant Alpha Persei, which shines at magnitude 1.79. It and many of the stars are members of an open cluster known as the Alpha Persei Cluster. The best-known star, however, is Algol, linked with ominous legends because of its variability, rather than being an intrinsically variable star, it is an eclipsing binary. Other notable star systems in Perseus include X Persei, a system containing a neutron star, and GK Persei. The Double Cluster, comprising two open clusters quite near each other in the sky, was known to the ancient Chinese, the constellation gives its name to the Perseus cluster, a massive galaxy cluster located 250 million light-years from Earth. It hosts the radiant of the annual Perseids meteor shower—one of the most prominent meteor showers in the sky, the constellation of Perseus may be derived from the Babylonian Old Man constellation, then associated with East in the MUL. APIN—an astronomical compilation dating to around 1000 BCE. In Greek mythology, Perseus was the son of Danaë, who was sent by King Polydectes to bring the head of Medusa the Gorgon—whose visage caused all who gazed upon her to turn to stone—as a wedding gift. Perseus slew Medusa in her sleep, and Pegasus and Chrysaor appeared from her body, Perseus continued to the realm of Cepheus whose daughter Andromeda was to be sacrificed to Cetus the sea monster. Perseus rescued Andromeda from the monster by killing it with his diamond sword and he turned Polydectes and his followers to stone with Medusas head and appointed Dictys the fisherman king. Perseus and Andromeda married and had six children, in the sky, Perseus lies near the constellations Andromeda, Cepheus, Cassiopeia, Cetus, and Pegasus. Four Chinese constellations are contained in the area of the sky identified with Perseus in the West, incorporating stars from the northern part of the constellation, it contained Mu, Delta, Psi, Alpha, Gamma and Eta Persei. Lambda and possibly Mu Persei lay within it, dàlíng, the Great Trench, was the fifth paranatellon of that house, representing the trenches where criminals executed en masse in August were interred. It was formed by Kappa, Omega, Rho,24,17 and 15 Persei, the pile of corpses prior to their interment was represented by Jīshī, the sixth paranatellon of the house. The Double Cluster, h and Chi Persei, had special significance in Chinese astronomy, known as Hsi and Ho, the two clusters represented two astronomers who failed to predict a total solar eclipse and were subsequently beheaded. In Polynesia, Perseus was not commonly recognized as a constellation, the only people that named it were those of the Society Islands. Algol may have been named Matohi by the Māori people, Matohi occasionally came into conflict with Tangaroa-whakapau over which of them should appear in the sky, the outcome affecting the tides
13.
Cassiopeia (constellation)
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Cassiopeia is a constellation in the northern sky, named after the vain queen Cassiopeia in Greek mythology, who boasted about her unrivalled beauty. Cassiopeia was one of the 48 constellations listed by the 2nd-century Greek astronomer Ptolemy and it is easily recognizable due to its distinctive W shape, formed by five bright stars. It is opposite the Big Dipper, in northern locations above 34ºN latitude it is visible year-round and in the tropics it can be seen at its clearest from September to early November. Even in low southern latitudes below 25ºS it can be low in the North. At magnitude 2.2, Alpha Cassiopeiae, or Schedar, is generally the brightest star in Cassiopeia, though is often shaded by Gamma Cassiopeiae, which has brightened to magnitude 1.6 on occasion. The constellation hosts some of the most luminous stars known, including the yellow hypergiants Rho Cassiopeiae and V509 Cassiopeiae, the semiregular variable PZ Cassiopeiae is one of the largest known stars. In 1572, Tycho Brahes supernova flared brightly in Cassiopeia, fourteen star systems have been found to have exoplanets, one of which—HR 8832—is thought to host seven planets. The constellation is named after Cassiopeia, the queen of Aethiopia, Cassiopeia was the wife of King Cepheus of Aethiopia and mother of Princess Andromeda. Cepheus and Cassiopeia were placed next to each other among the stars, Andromeda was then rescued by the hero Perseus, whom she later married. Cassiopeia has been variously portrayed throughout her history as a constellation, in Persia, she was drawn by al-Sufi as a queen holding a staff with a crescent moon in her right hand, wearing a crown, as well as a two-humped camel. In France, she was portrayed as having a marble throne and this depiction is from Augustin Royers 1679 atlas. In the ancient Celtic world Anu was the goddess and considered to be the mother of all the gods. Other references say that she is the earth goddess or the Goddess of fertility. Anu was known, in the Celtic World, by similar names. She still looks down on us from the sky where she appears as Llys Don. In Chinese astronomy, the forming the constellation Cassiopeia are found among three areas, the Purple Forbidden enclosure, the Black Tortoise of the North, and the White Tiger of the West. The Chinese astronomers saw several figures in what is modern-day Cassiopeia, Kappa, Eta, and Mu Cassopeiae formed a constellation called the Bridge of the Kings, when seen along with Alpha and Beta Cassiopeiae, they formed the great chariot Wang-Liang. The charioteers whip was represented by Gamma Cassiopeiae, sometimes called Tsih, in the 1600s, various Biblical figures were depicted in the stars of Cassiopeia
14.
Lacerta
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Lacerta is one of the 88 modern constellations defined by the International Astronomical Union. Its name is Latin for lizard, a small, faint constellation, it was created in 1687 by the astronomer Johannes Hevelius. Its brightest stars form a W shape similar to that of Cassiopeia and it is located between Cygnus, Cassiopeia and Andromeda on the northern celestial sphere. The northern part lies on the Milky Way and it also contains the prototypic blazar BL Lacertae. Alpha Lacertae is a blue-white hued main-sequence star of magnitude 3.8,102 light-years from Earth and it has a spectral type of A1 V and is an optical double star. Beta Lacertae is far dimmer, a giant of magnitude 4.4,170 light-years from Earth. Roe 47 is a star consisting of five components. ADS16402 is a star system in Lacerta, around which a planet orbits with some unusual properties. The Jupiter-sized planet exhibits a low density, about the same as cork. This planet is dubbed HAT P-1, EV Lacertae is a rapidly spinning magnitude 10 red dwarf with a strong magnetic field. It is a star that can emit powerful flares potentially visible to the naked eye. NGC7243 is an open cluster 2500 light-years from Earth, visible in amateur telescopes. It has a few dozen scattered stars, the brightest of which are of the 8th magnitude, BL Lacertae is the prototype of the BL Lacertae objects, which appear to be dim variable stars but are actually the variable nuclei of elliptical galaxies, they are similar to quasars. It lent its name to a type of celestial objects. The object varies irregularly between magnitudes 14 and 17 over a few days, centred on a region of the sky without apparently bright stars, Lacerta was apparently not regarded as a constellation by ancient Western astronomers. Johannes Hevelius created the constellation in 1687 and initially christened it Stellio, both Sceptrum and Frederici Honores are now obsolete, while Lacerta still survives. Similarly, the Chumash people of California call this part of the sky Lizard, USS Lacerta was an attack cargo ship in the United States navy named after the constellation. Ridpath, Ian, Tirion, Wil, Stars and Planets Guide, Princeton University Press, ISBN 0-691-08913-2 Ian Ridpath, Stars and Planets Guide, Collins, London
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Pegasus (constellation)
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Pegasus is a constellation in the northern sky, named after the winged horse Pegasus in Greek mythology. It was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, with an apparent magnitude varying between 2.37 and 2.45, the brightest star in Pegasus is the orange supergiant Epsilon Pegasi, also known as Enif, which marks the horses muzzle. Alpha, Beta, and Gamma, together with Alpha Andromedae form the asterism known as the Square of Pegasus. Twelve star systems have found to have exoplanets. 51 Pegasi was the first Sun-like star discovered to have an exoplanet companion, the Babylonian constellation IKU had four stars of which three were later part of the Greek constellation Hippos. Pegasus, in Greek mythology, was a horse with magical powers. One myth regarding his powers says that his hooves dug out a spring, Hippocrene, Pegasus was the one who delivered Medusas head to Polydectes, after which he travelled to Mount Olympus in order to be the bearer of thunder and lightning for Zeus. Eventually, he became the horse to Bellerophon, who was asked to kill the Chimera and succeeded with the help of Athena, despite this success, after the death of his children, Bellerophon asked Pegasus to take him to Mount Olympus. Though Pegasus agreed, he plummeted back to Earth after Zeus either threw a thunderbolt at him or made Pegasus buck him off. In ancient Persia, Pegasus was depicted by al-Sufi as a horse facing east, unlike most other uranographers. In al-Sufis depiction, Pegasuss head is made up of the stars of Lacerta the lizard and its right foreleg is represented by β Peg and its left foreleg is represented by η Peg, μ Peg, and λ Peg, its hind legs are marked by 9 Peg. The back is represented by π Peg and μ Cyg, in Chinese astronomy, the modern constellation of Pegasus lies in The Black Tortoise of the north, where the stars were classified in several separate asterisms of stars. Epsilon and Theta Pegasi are joined with Alpha Aquarii to form Wei 危 rooftop, in Hindu astronomy, the Great Square of Pegasus contained the 26th and 27th lunar mansions. More specifically, it represented a bedstead that was a place for the Moon. Covering 1121 square degrees, Pegasus is the seventh-largest of the 88 constellations, the three-letter abbreviation for the constellation, as adopted by the IAU in 1922, is Peg. The official constellation boundaries, as set by Eugène Delporte in 1930, are defined as a polygon of 35 segments. In the equatorial system the right ascension coordinates of these borders lie between 21h 12. 6m and 00h 14. 6m, while the declination coordinates are between 2. 33° and 36. 61°. Its position in the Northern Celestial Hemisphere means that the constellation is visible to observers north of 53°S
16.
Pisces (constellation)
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Pisces is a constellation of the zodiac. Its name is the Latin plural for fish and it lies between Aquarius to the west and Aries to the east. The ecliptic and the equator intersect within this constellation and in Virgo. The vernal equinox is currently located in Pisces, due south of ω Psc, van Maanens Star, at 12.36 magnitude, is located in this constellation, along with others, such as HD222410, at 7.45 magnitude. It has many clusters of stars and the associated nebulae. It was discovered by Pierre Méchain, a French astronomer, in 1780, NGC488 is an isolated face-on prototypical spiral galaxy. NGC520 is a pair of colliding galaxies located 90 million lightyears away, CL 0024+1654 is a massive galaxy cluster that lenses the galaxy behind it, creating arc-shaped images of the background galaxy. 3C31 is a galaxy and radio source in Perseus located at a distance of 237 million light-years from Earth. Its jets, caused by the black hole at its center. Pisces originates from some composition of the Babylonian constellations Šinunutu4 the great swallow in current western Pisces, in the first-millennium BC texts known as the Astronomical Diaries, part of the constellation was also called DU. NU. NU. Pisces is associated with Aphrodite and Eros, who escaped from the monster Typhon by leaping into the sea, in order not to lose each other, they tied themselves together with rope. The Romans adopted the Greek legend, with Venus and Cupid acting as the counterparts for Aphrodite, the knot of the rope is marked by Alpha Piscium, also called Al-Rischa. Linum Boreum, χ – ρ,94 – VX – η – π – ο – α Psc, linum Austrinum, α – ξ – ν – μ – ζ – ε – δ –41 –35 – ω Psc. Piscis Austrinus, ω – ι – θ –7 – β –5 – κ,9 – λ – TX Psc. However the proposal was largely neglected by other astronomers with the exception of Admiral Smyth, who mentioned it in his book The Bedford Catalogue, and it is now obsolete. The Fishes are also associated with the German legend of Antenteh, who owned just a tub and they offered him a wish, which he refused. However, his wife begged him to return to the fish and this wish was granted, but her desires were not satisfied. She then asked to be a queen and have a palace, but when she asked to become a goddess, the tub in the story is sometimes recognized as the Great Square of Pegasus
17.
Triangulum
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Triangulum is a small constellation in the northern sky. Its name is Latin for triangle, derived from its three brightest stars, which form a long and narrow triangle, known to the ancient Babylonians and Greeks, Triangulum was one of the 48 constellations listed by the 2nd century astronomer Ptolemy. The celestial cartographers Johann Bayer and John Flamsteed catalogued the constellations stars, giving six of them Bayer designations. The white stars Beta and Gamma Trianguli, of apparent magnitudes 3.00 and 4.00, respectively, form the base of the triangle and the yellow-white Alpha Trianguli, of magnitude 3.41, the apex. Iota Trianguli is a double star system, and there are three star systems with known planets located in Triangulum. The constellation contains several galaxies, the brightest and nearest of which is the Triangulum Galaxy or Messier 33—a member of the Local Group, the first quasar ever observed, 3C48, also lies within Triangulums boundaries. In the Babylonian star catalogues, Triangulum, together with Gamma Andromedae and it is notable as the first constellation presented on a pair of tablets containing canonical star lists that were compiled around 1000 BC, the MUL. APIN. The Plough was the first constellation of the Way of Enlil—that is, the northernmost quarter of the Suns path and its first appearance in the pre-dawn sky in February marked the time to begin spring ploughing in Mesopotamia. The Ancient Greeks called Triangulum Deltoton, as the constellation resembled an upper-case Greek letter delta and it was transliterated by Roman writers, then later Latinised as Deltotum. Eratosthenes linked it with the Nile Delta, while the Roman writer Hyginus associated it with the island of Sicily, formerly known as Trinacria due to its shape. It was also called Sicilia, because the Romans believed Ceres, patron goddess of Sicily, Greek astronomers such as Hipparchos and Ptolemy called it Trigonon, and later, it was Romanized as Trigonum. Other names referring to its shape include Tricuspis and Triquetrum, Alpha and Beta Trianguli were called Al Mīzān, which is Arabic for The Scale Beam. Later, the 17th-century German celestial cartographer Johann Bayer called the constellation Triplicitas and Orbis terrarum tripertitus, triangulus Septentrionalis was a name used to distinguish it from Triangulum Australe, the Southern Triangle. The smaller constellation was not recognised by the International Astronomical Union when the constellations were established in the 1920s. A small constellation, Triangulum is bordered by Andromeda to the north and west, Pisces to the west and south, Aries to the south, the centre of the constellation lies halfway between Gamma Andromedae and Alpha Arietis. The three-letter abbreviation for the constellation, as adopted by the IAU in 1922, is Tri, the official constellation boundaries, as set by Eugène Delporte in 1930, are defined as a polygon of 14 segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 01h 31. 3m and 02h 50. 4m, while the coordinates are between 25. 60° and 37. 35°. Covering 132 square degrees and 0. 320% of the night sky, Bayer catalogued five stars in the constellation, giving them the Bayer designations Alpha to Epsilon
18.
North Pole
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The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is defined as the point in the Northern Hemisphere where the Earths axis of rotation meets its surface. The North Pole is the northernmost point on the Earth, lying diametrically opposite the South Pole and it defines geodetic latitude 90° North, as well as the direction of true north. At the North Pole all directions point south, all lines of longitude converge there, along tight latitude circles, counterclockwise is east and clockwise is west. The North Pole is at the center of the Northern Hemisphere, while the South Pole lies on a continental land mass, the North Pole is located in the middle of the Arctic Ocean amid waters that are almost permanently covered with constantly shifting sea ice. This makes it impractical to construct a permanent station at the North Pole, however, the Soviet Union, and later Russia, constructed a number of manned drifting stations on a generally annual basis since 1937, some of which have passed over or very close to the Pole. Since 2002, the Russians have also established a base, Barneo. This operates for a few weeks during early spring, studies in the 2000s predicted that the North Pole may become seasonally ice-free because of Arctic ice shrinkage, with timescales varying from 2016 to the late 21st century or later. The sea depth at the North Pole has been measured at 4,261 m by the Russian Mir submersible in 2007 and at 4,087 m by USS Nautilus in 1958. The nearest land is said to be Kaffeklubben Island, off the northern coast of Greenland about 700 km away. The nearest permanently inhabited place is Alert in the Qikiqtaaluk Region, Nunavut, Canada, around the beginning of the 20th century astronomers noticed a small apparent variation of latitude, as determined for a fixed point on Earth from the observation of stars. Part of this variation could be attributed to a wandering of the Pole across the Earths surface, the wandering has several periodic components and an irregular component. The component with a period of about 435 days is identified with the eight-month wandering predicted by Euler and is now called the Chandler wobble after its discoverer and it is desirable to tie the system of Earth coordinates to fixed landforms. Of course, given plate tectonics and isostasy, there is no system in all geographic features are fixed. Yet the International Earth Rotation and Reference Systems Service and the International Astronomical Union have defined a framework called the International Terrestrial Reference System. As early as the 16th century, many eminent people correctly believed that the North Pole was in a sea and it was therefore hoped that passage could be found through ice floes at favorable times of the year. Several expeditions set out to find the way, generally with whaling ships, one of the earliest expeditions to set out with the explicit intention of reaching the North Pole was that of British naval officer William Edward Parry, who in 1827 reached latitude 82°45′ North. In 1871 the Polaris expedition, a US attempt on the Pole led by Charles Francis Hall, another British Royal Navy attempt on the pole, part of the British Arctic Expedition, by Commander Albert H. Markham reached a then-record 83°2026 North in May 1876 before turning back. An 1879–1881 expedition commanded by US naval officer George W. DeLong ended tragically when their ship, over half the crew, including DeLong, were lost
19.
Ancient Greek astronomy
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{{Refimprove|date=October 2011 Greek astronomy is written in the Greek language in classical antiquity. Greek astronomy is understood to include the ancient Greek, Hellenistic, Greco-Roman and it is not limited geographically to Greece or to ethnic Greeks, as the Greek language had become the language of scholarship throughout the Hellenistic world following the conquests of Alexander. This phase of Greek astronomy is known as Hellenistic astronomy. During the Hellenistic and Roman periods, much of the Greek and non-Greek astronomers working in the Greek tradition studied at the Musaeum, the development of astronomy by the Greek and Hellenistic astronomers is considered by historians to be a major phase in the history of astronomy. Greek astronomy is characterized from the start by seeking a rational, physical explanation for celestial phenomena, most of the constellations of the northern hemisphere derive from Greek astronomy, as are the names of many stars, asteroids, and planets. It was influenced by Egyptian and especially Babylonian astronomy, in turn, it influenced Indian, Arabic-Islamic, references to identifiable stars and constellations appear in the writings of Homer and Hesiod, the earliest surviving examples of Greek literature. Though neither Homer nor Hesiod set out to write a scientific work, some stars rise and set, others are ever-visible. At certain times of the year, certain stars will rise or set at sunrise or sunset, speculation about the cosmos was common in Pre-Socratic philosophy in the 6th and 5th centuries BC. Anaximander described a cylindrical earth suspended in the center of the cosmos, philolaus the Pythagorean described a cosmos with the stars, planets, Sun, Moon, Earth, and a counter-Earth —ten bodies in all—circling an unseen central fire. Such reports show that Greeks of the 6th and 5th centuries BC were aware of the planets and speculated about the structure of the cosmos. Also, a detailed description about the cosmos, Stars, Sun, Moon and the Earth can be found in the Orphism, which dates back to the end of the 5th century BC. The name planet comes from the Greek term πλανήτης, meaning wanderer, five planets can be seen with the naked eye, Mercury, Venus, Mars, Jupiter, and Saturn, the Greek names being Hermes, Aphrodite, Ares, Zeus and Cronus. Sometimes the luminaries, the Sun and Moon, are added to the list of naked eye planets to make a total of seven, since the planets disappear from time to time when they approach the Sun, careful attention is required to identify all five. Observations of Venus are not straightforward and they eventually came to recognize that both objects were the same planet. Pythagoras is given credit for this realization, in classical Greece, astronomy was a branch of mathematics, astronomers sought to create geometrical models that could imitate the appearances of celestial motions. This tradition began with the Pythagoreans, who placed astronomy among the four mathematical arts, the study of number comprising the four arts was later called the Quadrivium. Although he was not a mathematician, Plato included the quadrivium as the basis for philosophical education in the Republic. He encouraged a younger mathematician, Eudoxus of Cnidus, to develop a system of Greek astronomy, platos main books on cosmology are the Timaeus and the Republic
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Ptolemy
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Claudius Ptolemy was a Greek writer, known as a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in the city of Alexandria in the Roman province of Egypt, wrote in Koine Greek, beyond that, few reliable details of his life are known. His birthplace has been given as Ptolemais Hermiou in the Thebaid in a statement by the 14th-century astronomer Theodore Meliteniotes. This is a very late attestation, however, and there is no reason to suppose that he ever lived elsewhere than Alexandria. Ptolemy wrote several treatises, three of which were of importance to later Byzantine, Islamic and European science. The first is the astronomical treatise now known as the Almagest, although it was entitled the Mathematical Treatise. The second is the Geography, which is a discussion of the geographic knowledge of the Greco-Roman world. The third is the treatise in which he attempted to adapt horoscopic astrology to the Aristotelian natural philosophy of his day. This is sometimes known as the Apotelesmatika but more known as the Tetrabiblos from the Greek meaning Four Books or by the Latin Quadripartitum. The name Claudius is a Roman nomen, the fact that Ptolemy bore it indicates he lived under the Roman rule of Egypt with the privileges and political rights of Roman citizenship. It would have suited custom if the first of Ptolemys family to become a citizen took the nomen from a Roman called Claudius who was responsible for granting citizenship, if, as was common, this was the emperor, citizenship would have been granted between AD41 and 68. The astronomer would also have had a praenomen, which remains unknown and it occurs once in Greek mythology, and is of Homeric form. All the kings after him, until Egypt became a Roman province in 30 BC, were also Ptolemies, abu Mashar recorded a belief that a different member of this royal line composed the book on astrology and attributed it to Ptolemy. The correct answer is not known”, Ptolemy wrote in Greek and can be shown to have utilized Babylonian astronomical data. He was a Roman citizen, but most scholars conclude that Ptolemy was ethnically Greek and he was often known in later Arabic sources as the Upper Egyptian, suggesting he may have had origins in southern Egypt. Later Arabic astronomers, geographers and physicists referred to him by his name in Arabic, Ptolemys Almagest is the only surviving comprehensive ancient treatise on astronomy. Ptolemy presented his models in convenient tables, which could be used to compute the future or past position of the planets. The Almagest also contains a catalogue, which is a version of a catalogue created by Hipparchus
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88 modern constellations
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In modern astronomy, the sky is divided into 88 regions called constellations, generally based on the asterisms of Greek and Roman mythology. Those along the ecliptic are the constellations of the zodiac, the ancient Sumerians, and later the Greeks, established most of the northern constellations in international use today. Not all of these proposals caught on, but in 1922, after this, Eugène Joseph Delporte drew up precise boundaries for each constellation, so that every point in the sky belonged to exactly one constellation. Some constellations are no longer recognized by the International Astronomical Union, most notable is Argo Navis, which was one of Ptolemys original 48 constellations. The 88 constellations depict 42 animals,29 inanimate objects and 17 humans or mythological characters, each of the IAU constellations has an official 3 letter abbreviation. They are actually abbreviations of the form of the constellation names. The majority of the abbreviations are just the first three letters of the constellation, with the first character capitalised, Ori for Orion, Ara for Ara/Arae, Com for Coma Berenices. When letters are taken from the word of a two-word name. The abbreviations are unambiguous, with two exceptions, Leo for the constellation Leo could be mistaken for Leo Minor, and Tri for Triangulum could be mistaken for Triangulum Australe. For help with the literary English pronunciations, see the pronunciation key, there is considerable diversity in how Latinate names are pronounced in English. For traditions closer to the original, see Latin spelling and pronunciation, the Family column refers to the constellation families introduced by Donald Menzel in 1975. Various other unofficial patterns have existed alongside the constellations, examples include the Big Dipper/Plough and the Northern Cross. Some ancient asterisms, for example Coma Berenices, Serpens, http, //www. ianridpath. com/startales/contents. htm – Ian Ridpaths Star Tales. Http, //cdsarc. u-strasbg. fr/viz-bin/Cat. cat=VI/49 – CDSs archive of constellation boundaries, the text file constbnd. dat gives the 1875.0 coordinates of the vertices of the constellation regions, together with the constellations adjacent to each boundary segment
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Celestial equator
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The celestial equator is a great circle on the imaginary celestial sphere, in the same plane as the Earths equator. In other words, it is a projection of the terrestrial equator out into space, as a result of the Earths axial tilt, the celestial equator is inclined by 23. 4° with respect to the ecliptic plane. An observer standing on the Earths equator visualizes the celestial equator as a semicircle passing directly overhead through the zenith, as the observer moves north, the celestial equator tilts towards the opposite horizon. Celestial objects near the equator are visible worldwide, but they culminate the highest in the sky in the tropics. The celestial equator currently passes through these constellations, Celestial bodies other than Earth also have similarly defined celestial equators, Celestial pole Celestial sphere Declination Equatorial coordinate system
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Andromeda (mythology)
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In Greek mythology, Andromeda is the daughter of the Aethiopian king Cepheus and his wife Cassiopeia. When Cassiopeias hubris leads her to boast that Andromeda is more beautiful than the Nereids, Andromeda is stripped and chained naked to a rock as a sacrifice to sate the monster, but is saved from death by Perseus. Her name is the Latinized form of the Greek Ἀνδρομέδα or Ἀνδρομέδη, ruler of men, from ἀνήρ, ἀνδρός man, from the Renaissance, interest revived in the original story, typically as derived from Ovids account. In Greek mythology, Andromeda was the daughter of Cepheus and Cassiopeia, king and her mother Cassiopeia boasted that her daughter was more beautiful than the Nereids, the nymph-daughters of the sea god Nereus and often seen accompanying Poseidon. To punish the queen for her arrogance, Poseidon, brother to Zeus and god of the sea, the desperate king consulted the Oracle of Apollo, who announced that no respite would be found until the king sacrificed his daughter, Andromeda, to the monster. Stripped naked, she was chained to a rock on the coast, Perseus was returning from having slain the Gorgon, Medusa. After he happened upon the chained Andromeda, he approached Cetus while invisible and he set Andromeda free, and married her in spite of her having been previously promised to her uncle Phineus. At the wedding a quarrel took place between the rivals and Phineus was turned to stone by the sight of the Gorgons head, Andromeda followed her husband, first to his native island of Serifos, where he rescued his mother Danaë, and then to Tiryns in Argos. Together, they became the ancestors of the family of the Perseidae through the line of their son Perses, Perseus and Andromeda had seven sons, Perses, Alcaeus, Heleus, Mestor, Sthenelus, Electryon, and Cynurus as well as two daughters, Autochthe and Gorgophone. Their descendants ruled Mycenae from Electryon down to Eurystheus, after whom Atreus attained the kingdom, according to this mythology, Perseus is the ancestor of the Persians. Andromeda is represented in the sky by the constellation Andromeda. Four constellations are associated with the myth, jean-Baptiste Lullys opera, Persée, also dramatizes the myth. Andromeda has been the subject of ancient and modern works of art, which typically show the moment of rescue, with Andromeda usually still chained. Examples include, one of Titians poesies, and compositions by Joachim Wtewael, Veronese, many versions by Rubens, Ingres, from the Renaissance onward the chained nude figure of Andromeda typically was the centre of interest. Rembrandts Andromeda Chained to the Rocks is unusual in showing her alone, the Italian composer Salvatore Sciarrino composed an hour-long operatic drama called Perseo e Andromeda in 2000. In 1973, a film called Perseus was made in the Soviet Union as part of the Soviet animated film collection called Legends. The 1981 film Clash of the Titans retells the story of Perseus, Andromeda, and Cassiopeia, thetis was indeed a Nereid and also the future mother of Achilles. Andromeda is depicted as being strong-willed and independent, whereas in the stories she is only mentioned as being the princess whom Perseus saves from the sea monster
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Greek mythology
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It was a part of the religion in ancient Greece. Greek mythology is explicitly embodied in a collection of narratives. Greek myth attempts to explain the origins of the world, and details the lives and adventures of a variety of gods, goddesses, heroes, heroines. These accounts initially were disseminated in a tradition, today the Greek myths are known primarily from ancient Greek literature. The oldest known Greek literary sources, Homers epic poems Iliad and Odyssey, focus on the Trojan War, archaeological findings provide a principal source of detail about Greek mythology, with gods and heroes featured prominently in the decoration of many artifacts. Geometric designs on pottery of the eighth century BC depict scenes from the Trojan cycle as well as the adventures of Heracles, in the succeeding Archaic, Classical, and Hellenistic periods, Homeric and various other mythological scenes appear, supplementing the existing literary evidence. Greek mythology has had an influence on the culture, arts. Poets and artists from ancient times to the present have derived inspiration from Greek mythology and have discovered contemporary significance and relevance in the themes, Greek mythology is known today primarily from Greek literature and representations on visual media dating from the Geometric period from c. Mythical narration plays an important role in every genre of Greek literature. Nevertheless, the only general mythographical handbook to survive from Greek antiquity was the Library of Pseudo-Apollodorus and this work attempts to reconcile the contradictory tales of the poets and provides a grand summary of traditional Greek mythology and heroic legends. Apollodorus of Athens lived from c, 180–125 BC and wrote on many of these topics. His writings may have formed the basis for the collection, however the Library discusses events that occurred long after his death, among the earliest literary sources are Homers two epic poems, the Iliad and the Odyssey. Other poets completed the cycle, but these later and lesser poems now are lost almost entirely. Despite their traditional name, the Homeric Hymns have no connection with Homer. They are choral hymns from the part of the so-called Lyric age. Hesiods Works and Days, a poem about farming life, also includes the myths of Prometheus, Pandora. The poet gives advice on the best way to succeed in a dangerous world, lyrical poets often took their subjects from myth, but their treatment became gradually less narrative and more allusive. Greek lyric poets, including Pindar, Bacchylides and Simonides, and bucolic poets such as Theocritus and Bion, additionally, myth was central to classical Athenian drama
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Cetus (mythology)
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In Ancient Greek, the word kētos —Latinized as cetus —denotes a large fish, a whale, a shark, or a sea monster. The sea monsters slain by Perseus and Heracles were each referred to as a cetus by ancient sources, the term cetacean originates from cetus. In Greek art, cetea were depicted as serpentine fish, the name of the mythological figure Ceto is derived from ketos. The name of the constellation Cetus also derives from this word, when Queen Cassiopeia boasted that her daughter Andromeda was more beautiful than the Nereids, this invoked the wrath of Poseidon who sent the sea monster Cetus to attack Æthiopia. Upon consulting an oracle, King Cepheus and Queen Cassiopeia were told to sacrifice Andromeda to Cetus. They had Andromeda chained to a rock near the ocean so that Cetus could devour her, Perseus found Andromeda chained to the rock and learned of her plight. When Cetus emerged from the ocean to devour Andromeda, Perseus managed to slay it, in one version, Perseus drove his sword into Cetus back. In another version, Perseus used Medusas head to turn Cetus to stone, the Cetus is commonly depicted as fishlike, serpentine, with a long muzzle. Alternate depictions may include long ears, horns and legs instead of flippers and it is often depicted fighting Perseus or as the mount of a Nereid. In Jonah 2,1, the Hebrew text reads dag gadol, the Septuagint translates this phrase into Greek as mega ketos. The term ketos alone means huge fish, and in Greek mythology the term was associated with sea monsters. Jerome later translated this phrase as piscis grandis in his Latin Vulgate, Cetus is commonly used as a ships name or figurehead denoting either a ship unafraid of the sea or a ruthless pirate ship to be feared. Cetus are also viewed as misfortune or bad omen by sailors, superstitious sailors believed in a cetus as the bringer of a great storm or misfortune on the ship. They associated it with lost cargo, the presence of pirates, or being swept off course, some scholars theorize that images of the Ketos in Central Asia influenced depictions of the Chinese Dragon and Indian makara. They suggest that after contact with silk-road images of the Ketos, the Chinese dragon appeared more reptilian and shifted head-shape
26.
Northern Hemisphere
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The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined as being in the celestial hemisphere relative to the invariable plane of the solar system as Earths North pole. Due to the Earths axial tilt, winter in the Northern Hemisphere lasts from the December solstice to the March Equinox, the dates vary each year due to the difference between the calendar year and the astronomical year. Its surface is 60. 7% water, compared with 80. 9% water in the case of the Southern Hemisphere, the Arctic is the region north of the Arctic Circle. Its climate is characterized by cold winters and cool summers, precipitation mostly comes in the form of snow. The Arctic experiences some days in summer when the Sun never sets, the duration of these phases varies from one day for locations right on the Arctic Circle to several months near the North Pole, which is the middle of the Northern Hemisphere. Between the Arctic Circle and the Tropic of Cancer lies the Northern Temperate Zone, the changes in these regions between summer and winter are generally mild, rather than extreme hot or cold. However, a temperate climate can have very unpredictable weather, tropical regions are generally hot all year round and tend to experience a rainy season during the summer months, and a dry season during the winter months. In the Northern Hemisphere, objects moving across or above the surface of the Earth tend to turn to the right because of the coriolis effect, as a result, large-scale horizontal flows of air or water tend to form clockwise-turning gyres. These are best seen in circulation patterns in the North Atlantic. For the same reason, flows of air down toward the surface of the Earth tend to spread across the surface in a clockwise pattern. Thus, clockwise air circulation is characteristic of high pressure weather cells in the Northern Hemisphere, conversely, air rising from the northern surface of the Earth tends to draw air toward it in a counterclockwise pattern. Hurricanes and tropical storms spin counter-clockwise in the Northern Hemisphere, the shadow of a sundial moves clockwise in the Northern Hemisphere. When viewed from the Northern Hemisphere, the Moon appears inverted compared to a view from the Southern Hemisphere, the North Pole faces away from the galactic center of the Milky Way. The Northern Hemisphere is home to approximately 6.57 billion people which is around 90% of the total human population of 7.3 billion people
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Perseus
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Perseus beheaded the Gorgon Medusa and saved Andromeda from the sea monster Cetus. Perseus was the son of the mortal Danaë and the god Zeus and he was also the half-brother and great grandfather of Heracles. There is some prospect that it descended into Greek from the Proto-Indo-European language, in that regard Robert Graves has espoused the only Greek derivation available. Perseus might be from the Greek verb, πέρθειν, “to waste, ravage, sack, destroy”, according to Carl Darling Buck, the –eus suffix is typically used to form an agent noun, in this case from the aorist stem, pers-. Pers-eus therefore is a sacker of cities, that is, a soldier by occupation, the origin of perth- is more obscure. J. B. Hofmann lists the possible root as *bher-, from which Latin ferio and this corresponds to Julius Pokorny’s *bher-, “scrape, cut. ”Ordinarily *bh- descends to Greek as ph-. This difficulty can be overcome by presuming a dissimilation from the –th– in perthein, that is, Graves carries the meaning still further, to the perse- in Persephone, goddess of death. the classical Perse. daughter of Oceanus. Whether it may be identified with the first element of Persephone is only speculative. ”A Greek folk etymology connected the name of the Persian people. The native name, however, has always had an -a- in Persian, herodotus recounts this story, devising a foreign son, Perses, from whom the Persians took the name. Apparently the Persians themselves knew the story, as Xerxes tried to use it to suborn the Argives during his invasion of Greece, Perseus was the son of Zeus and Danaë, the daughter of Acrisius, King of Argos. Disappointed by his lack of luck in having a son, Acrisius consulted the oracle at Delphi, who warned him that he would one day be killed by his daughters son. In order to keep Danaë childless, Acrisius imprisoned her in a chamber, open to the sky, in the courtyard of his palace, This mytheme is also connected to Ares, Oenopion, Eurystheus. Zeus came to her in the form of a shower of gold, soon after, their child was born, Perseus—Perseus Eurymedon, for his mother gave him this name as well. Fearful for his future, but unwilling to provoke the wrath of the gods by killing the offspring of Zeus and his daughter, danaës fearful prayer, made while afloat in the darkness, has been expressed by the poet Simonides of Ceos. Mother and child washed ashore on the island of Serifos, where they were taken in by the fisherman Dictys, the brother of Dictys was Polydectes, the king of the island. When Perseus was grown, Polydectes came to fall in love with the beautiful Danaë, Perseus believed Polydectes was less than honourable, and protected his mother from him, then Polydectes plotted to send Perseus away in disgrace. He held a banquet where each guest was expected to bring a gift. Polydectes requested that the guests bring horses, under the pretense that he was collecting contributions for the hand of Hippodamia, Perseus had no horse to give, so he asked Polydectes to name the gift, he would not refuse it
28.
Full moon
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A full moon is the lunar phase that occurs when the Moon is completely illuminated as seen from Earth. This occurs when Earth is located directly between the Sun and the Moon and this means that the hemisphere of the Moon that is facing Earth is almost fully illuminated by the Sun and appears round. On some occasions at the time of full moon there is also a lunar eclipse so the face appears reddish due to the rayleigh scattering of blue light in Earths atmosphere. Lunar eclipses can occur only at full moon, where the Moons orbit allows it to pass through Earths shadow, Lunar eclipses do not occur every month because the Moon usually passes above or below Earths shadow. Lunar eclipses can only when the full moon occurs near the two nodes of the orbit, either the ascending or descending node. This causes eclipses to occur about every 6 months. The time interval between similar lunar phases—the synodic month—averages about 29.53 days, therefore, in those lunar calendars in which each month begins on the new moon, the full moon falls on either the 14th or 15th of the lunar month. Because calendar months have a number of days, lunar months may be either 29 or 30 days long. A full moon is thought of as an event of a full nights duration. This is somewhat misleading because the Moon seen from Earth is continuously becoming larger and/or smaller and its absolute maximum size occurs at the moment expansion has stopped. For any given location, about half of these absolute maximum full moons will be visible, as the other half occur during the day. Many almanacs list full moons not just by date, but by their time as well. Typical monthly calendars that include phases of the Moon may be offset by one day if intended for use in a different time zone, Full moons are generally a poor time to conduct astronomical observations, because the bright reflected sunlight from the Moon overwhelms the dimmer light from stars. On 12 December 2008, the moon occurred closer to the Earth than it had been at any time for the previous 15 years. On 19 March 2011, another full moon occurred, closer to the Earth than at any time for the previous ~18 years. On 14 November 2016, a full moon occurred closer to the Earth than at any time for the previous 68 years. The true time of a full moon may differ from this approximation by up to about 14.5 hours as a result of the non-circularity of the moons orbit, see New moon for an explanation of the formula and its parameters. The age and apparent size of the full moon vary in a cycle of just under 14 synodic months, Full moons are traditionally associated with temporal insomnia, insanity and various magical phenomena such as lycanthropy
29.
Hydra (constellation)
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Hydra is the largest of the 88 modern constellations, measuring 1303 square degrees. Also one of the longest at over 100 degrees, its southern end abuts Libra and Centaurus and it has a long history, having been included among the 48 constellations listed by the 2nd century astronomer Ptolemy. It is commonly represented as a water snake and it should not be confused with the similarly named constellation of Hydrus. The Greek constellation of Hydra is an adaptation of a Babylonian constellation and it is one of two Babylonian serpent constellations, a mythological hybrid of serpent, lion and bird. The shape of Hydra resembles a snake, and features as such in some Greek myths. One myth associates it with a snake that a crow served Apollo in a cup when it was sent to fetch water, Apollo saw through the fraud, and angrily cast the crow, cup. It is also associated with the monster Hydra, with its heads, killed by Hercules. According to legend, if one of the heads was cut off. However, Hercules burned out the roots of the heads he severed to prevent them from growing again, in Hindu Mythology the star that equivalents Hydra is Ashlesha. In Chinese astronomy, the stars that correspond to Hydra are located within the Vermilion Bird, in Japanese culture, the stars are known as Nuriko. Despite its size, Hydra contains only one reasonably bright star, Alphard and it is an orange giant of magnitude 2.0,177 light-years from Earth. Its traditional name means the solitary one, beta Hydrae is a blue-white star of magnitude 4.3,365 light-years from Earth. Gamma Hydrae is a giant of magnitude 3.0,132 light-years from Earth. Hydra has one bright binary star, Epsilon Hydrae, which is difficult to split in amateur telescopes, the primary is a yellow star of magnitude 3.4 and the secondary is a blue star of magnitude 6.7. However, there are several double stars and binary stars in Hydra. 27 Hydrae is a star with two components visible in binoculars and three visible in small amateur telescopes. The primary is a star of magnitude 4.8,244 light-years from Earth. The secondary, a star, appears in binoculars at magnitude 7.0 but is composed of a magnitude 7
30.
Crux
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Crux /ˈkrʌks/ is a constellation located in the southern sky in a bright portion of the Milky Way. Its name is Latin for cross, and it is dominated by a cross-shaped or kite-like asterism that is known as the Southern Cross. The constellation contains four Cepheid variables that are visible to the eye under optimum conditions. Crux also contains the bright and colourful open cluster known as the Jewel Box and, to the southwest, partly includes the dark nebula. Crux was known to the Ancient Greeks due to the fact that it can be seen from southern Egypt and it was entirely visible as far north as Britain in the fourth millennium BC. However, the precession of the equinoxes gradually lowered its stars below the European horizon, by AD400, most of the constellation never rose above the horizon for Athenians. The 15th-century Venetian navigator Alvise Cadamosto made note of what was probably the Southern Cross on exiting the Gambia River in 1455, however, Cadamostos accompanying diagram was inaccurate. Faras sketched and described the constellation in a letter written on the beaches of Brazil on May 1,1500, explorer Amerigo Vespucci seems to have observed not only the Southern Cross but also the neighboring Coalsack Nebula on his second voyage in 1501–02. Both authors, however, depended on unreliable sources and placed Crux in the wrong position, Crux was first shown in its correct position on the celestial globes of Petrus Plancius and Jodocus Hondius in 1598 and 1600. Its stars were first catalogued separately from Centaurus by Frederick de Houtman in 1603, later adopters of the constellation included Jakob Bartsch in 1624 and Augustin Royer in 1679. Royer is sometimes cited as initially distinguishing Crux. Crux is bordered by the constellations Centaurus on the east, north and west, covering 68 square degrees and 0. 165% of the night sky, it is the smallest of the 88 constellations. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is Cru, the official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of four segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 11h 56. 13m and 12h 57. 45m, while the coordinates are between −55. 68° and −64. 70°. The whole constellation is visible to observers south of latitude 25°N, in tropical regions Crux can be seen in the sky from April to June. Crux is exactly opposite to Cassiopeia on the sphere. For locations south of 34°S, Crux is circumpolar and thus visible in the night sky. Crux is sometimes confused with the nearby False Cross by stargazers, Crux is somewhat kite-shaped, and it has a fifth star
31.
Binary star
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A binary star is a star system consisting of two stars orbiting around their common barycenter. Systems of two or more stars are called multiple star systems and these systems, especially when more distant, often appear to the unaided eye as a single point of light, and are then revealed as multiple by other means. Research over the last two centuries suggests that half or more of visible stars are part of star systems. The term double star is used synonymously with binary star, however. Optical doubles are so called because the two stars close together in the sky as seen from the Earth, they are almost on the same line of sight. Nevertheless, their doubleness depends only on this effect, the stars themselves are distant from one another. A double star can be revealed as optical by means of differences in their measurements, proper motions. Most known double stars have not been studied closely to determine whether they are optical doubles or they are doubles physically bound through gravitation into a multiple star system. This also determines an empirical mass-luminosity relationship from which the masses of stars can be estimated. Binary stars are often detected optically, in case they are called visual binaries. Many visual binaries have long periods of several centuries or millennia. They may also be detected by indirect techniques, such as spectroscopy or astrometry, if components in binary star systems are close enough they can gravitationally distort their mutual outer stellar atmospheres. In some cases, these close binary systems can exchange mass, examples of binaries are Sirius, and Cygnus X-1. Binary stars are common as the nuclei of many planetary nebulae. This should be called a double star, and any two stars that are thus mutually connected, form the binary sidereal system which we are now to consider. By the modern definition, the binary star is generally restricted to pairs of stars which revolve around a common center of mass. Binary stars which can be resolved with a telescope or interferometric methods are known as visual binaries, for most of the known visual binary stars one whole revolution has not been observed yet, they are observed to have travelled along a curved path or a partial arc. The more general term double star is used for pairs of stars which are seen to be together in the sky
32.
Gamma Andromedae
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Gamma Andromedae is the third-brightest point of light in the constellation of Andromeda. In 1778, Johann Tobias Mayer discovered that γ Andromedae was a double star, when examined in a small telescope, it appears to be a bright, golden-yellow star next to a dimmer, indigo-blue star, separated by approximately 10 arcseconds. It is often considered by stargazers to be a double star with a striking contrast of color. It was later discovered that γ2 Andromedae is itself a triple star system, what appears as a single star to the naked eye is thus a quadruple star system, approximately 350 light-years from the Earth. Gamma Andromedae is the stars Bayer designation, in 2016, the International Astronomical Union organized a Working Group on Star Names to catalog and standardize proper names for stars. The WGSNs first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN, which included Almach for γ1 Andromedae, Almach was the traditional name, derived from the Arabic العناق الأرض al-‘anāq al-’arđ̧ the caracal. Consequently, γ Andromedae itself is known as 天大將軍一, in the Babylonian star catalogues, γ Andromedae together with Triangulum formed the constellation known as MULAPIN The Plough. Astrologically this star was considered honourable and eminent, γ1 Andromedae is a bright giant star with a spectral classification of K3IIb. It has an apparent visual magnitude of approximately 2.26, γ2 Andromedae, with an overall apparent visual magnitude of 4.84, is 9.6 arcseconds away from γ1 Andromedae at a position angle of 63 degrees. In October 1842, Wilhelm Struve found that γ2 Andromedae was itself a double star whose components were separated by less than an arcsecond. The components are an object of apparent visual magnitude 5.5, γ Andromedae B, and they have an orbital period of about 64 years. Spectrograms taken from 1957 to 1959 revealed that γ Andromedae B was itself a spectroscopic binary, the stars location is shown in the following chart of the Andromeda constellation, USS Almaack was the name of United States navy ship
33.
Beta Andromedae
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Beta Andromedae, also named Mirach, is a prominent star in the northern constellation of Andromeda. It is located northeast of the Great Square of Pegasus and is visible to all observers north of 54° S. It is commonly used by stargazers to find the Andromeda Galaxy, the galaxy NGC404, also known as Mirachs Ghost, is visible seven arc-minutes away. This star has an apparent visual magnitude of 2.05. However, the luminosity varies slightly from magnitude +2.01 to +2.10, based upon parallax measurements, it is located at a distance of roughly 197 light-years from the Sun. The apparent magnitude of this star is reduced by 0.06 from extinction caused by the gas, Beta Andromedae is a red giant with a stellar classification of M0 III. Since 1943, the spectrum of this star has served as one of the anchor points by which other stars are classified. It is suspected of being a variable star whose apparent visual magnitude varies from +2.01 to +2.10. At this stage of the evolution, the outer envelope has expanded to around 100 times the size of the Sun. It is radiating 1995 times the luminosity of the Sun at a temperature of 3842 K. Beta Andromedae is the stars Bayer designation and it had the traditional name of Mirach, and its variations, such as Mirac, Mirar, Mirath, Mirak, etc. which come from the stars description in the Alfonsine Tables of 1521 as super mizar. Here, mirat is a corruption of the Arabic ميزر mīzar girdle and this word refers to Mirachs position at the left hip of the princess Andromeda. In 2016, the International Astronomical Union organized a Working Group on Star Names to catalog, the WGSNs first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN, which included Mirach for this star. Medieval astronomers writing in Arabic called β Andromedae Janb al-Musalsalah, it was part of the 26th manzil Baṭn al-Ḥūt, the Belly of the Fish, or Qalb al-Ḥūt, the star has also been called Cingulum and Ventrale. This al-Ḥūt was an indigenous Arabic constellation, not the Western Northern Fish part of the constellation Pisces and these names are not from the Arabic marāqq, loins, because it was never called al-Marāqq in Arabian astronomy. Al Rishā, the Cord, on al-Sūfīs star map and it is origin of the proper name Alrescha for Alpha Piscium. Consequently, β Andromedae itself is known as 奎宿九 The people of Micronesia named this star as Kyyw The Porpoise, Mirach is listed in MUL. APIN as KA. MUSH. I. KU. E, meaning the Deleter. Davis Jr. G. A. Pronunciations, Derivations, and Meanings of a Selected List of Star Names, Cambridge, Kunitzsch, P. Arabische Sternnamen in Europa Kunitzsch
34.
Andromeda Galaxy
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The Andromeda Galaxy, also known as Messier 31, M31, or NGC224, is a spiral galaxy approximately 780 kiloparsecs from Earth. It is the nearest major galaxy to the Milky Way and was referred to as the Great Andromeda Nebula in older texts. It received its name from the area of the sky in which it appears, the constellation of Andromeda, which was named after the mythological princess Andromeda. Andromeda is approximately 220,000 light years across, and it is the largest galaxy of the Local Group, which contains the Milky Way, the Triangulum Galaxy. The mass of the Andromeda Galaxy is estimated to be 1. 5×1012 solar masses, the Milky Way and Andromeda galaxies are expected to collide in 4.5 billion years, eventually merging to form a giant elliptical galaxy or perhaps a large disc galaxy. Around the year 964, the Persian astronomer Abd al-Rahman al-Sufi described the Andromeda Galaxy, star charts of that period labeled it as the Little Cloud. In 1612, the German astronomer Simon Marius gave a description of the Andromeda Galaxy based on telescopic observations. In 1764, Charles Messier catalogued Andromeda as object M31 and incorrectly credited Marius as the discoverer despite it being visible to the naked eye, in 1785, the astronomer William Herschel noted a faint reddish hue in the core region of Andromeda. In 1850, William Parsons, 3rd Earl of Rosse, saw, in 1864, William Huggins noted that the spectrum of Andromeda differs from a gaseous nebula. The spectra of Andromeda displays a continuum of frequencies, superimposed with dark lines that help identify the chemical composition of an object. Andromedas spectrum is similar to the spectra of individual stars. In 1885, a supernova was seen in Andromeda, the first, at the time Andromeda was considered to be a nearby object, so the cause was thought to be a much less luminous and unrelated event called a nova, and was named accordingly, Nova 1885. In 1887, Isaac Roberts took the first photographs of Andromeda, Roberts actually mistook Andromeda and similar spiral nebulae as solar systems being formed. In 1912, Vesto Slipher used spectroscopy to measure the velocity of Andromeda with respect to our solar system—the largest velocity yet measured. In 1917, Heber Curtis observed a nova within Andromeda, searching the photographic record,11 more novae were discovered. Curtis noticed that these novae were, on average,10 magnitudes fainter than those that occurred elsewhere in the sky, as a result, he was able to come up with a distance estimate of 500,000 light-years. He became a proponent of the island universes hypothesis, which held that spiral nebulae were actually independent galaxies. In 1920, the Great Debate between Harlow Shapley and Curtis took place, concerning the nature of the Milky Way, spiral nebulae, in 1922 Ernst Öpik presented a method to estimate the distance of Andromeda using the measured velocities of its stars
35.
Messier 110
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Messier 110, also known as NGC205, is a dwarf elliptical galaxy that is a satellite of the Andromeda Galaxy. M110 contains some dust and hints of recent star formation, which is unusual for dwarf elliptical galaxies in general, the galaxy was independently discovered by Caroline Herschel on August 27,1783, her brother William Herschel described her discovery in 1785. The suggestion to assign the galaxy a Messier number was made by Kenneth Glyn Jones in 1967, a few novae have been detected in this galaxy, including one discovered in 1999 by Johnson and Modjaz, and another detected in 2002, by Nakano and Sumoto. The latter, designated EQ J004015. 8+414420, had also captured in images taken by the Sloan Digital Sky Survey in October,2002. Unlike M32, NGC205 does not show evidence for a black hole at its center
36.
Messier 32
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Messier 32 is a dwarf elliptical galaxy located about 2.65 million light-years from Earth, appearing in the constellation Andromeda. M32 is a galaxy of the Andromeda Galaxy and was discovered by Le Gentil in 1749. M32 measures 6.5 ±0.2 thousand light-years in diameter at the widest point, like most elliptical galaxies, M32 contains mostly older faint red and yellow stars with practically no dust or gas and consequently no current star formation. It does, however, show hints of star formation in the recent past. The structure and stellar content of M32 is difficult to explain by traditional galaxy formation models, some simulations suggest a scenario in which the strong tidal field of M31 can transform a spiral galaxy into a compact elliptical. As a small spiral galaxy falls into the parts of M31. The central bulge of the galaxy is less affected and retains its morphology. Tidal effects trigger a massive star burst in the core, resulting in the density of M32 observed today. There is also evidence that M32 has an outer disk, at least two techniques have been used to measure distances to M32. The infrared surface brightness fluctuations distance measurement technique estimates distances to galaxies based on the graininess of the appearance of their bulges. The distance measured to M32 using this technique is 2.46 ±0.09 million light-years, however, M32 is close enough that the tip of the red giant branch method may be used to estimate its distance. The estimated distance to M32 using this technique is 2.51 ±0.13 million light-years, M32 contains a supermassive black hole. Its mass has been estimated to lie between 1.5 and 5 million solar masses, andromedas satellite galaxies List of galaxies StarDate, M32 Fact Sheet SEDS, Elliptical Galaxy M32 Merrifield, Michael. Messier 32 on WikiSky, DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
37.
NGC 891
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NGC891 is an edge-on unbarred spiral galaxy about 30 million light-years away in the constellation Andromeda. It was discovered by William Herschel on October 6,1784, the galaxy is a member of the NGC1023 group of galaxies in the Local Supercluster. The object is visible in small to moderate size telescopes as a faint elongated smear of light with a dust lane visible in larger apertures, in 1999, the Hubble Space Telescope imaged NGC891 in infrared. In 2005, due to its attractiveness and scientific interest, NGC891 was selected to be the first light image of the Large Binocular Telescope, in 2012, it was again used as a first light image of the Discovery Channel Telescope with the Large Monolithic Imager. Supernova SN 1986J was discovered on August 21,1986 at apparent magnitude 14, despite this, recent high-resolution images of its dusty disk show unusual filamentary patterns. These patterns are extending into the halo of the galaxy, away from its galactic disk, scientists presume that supernova explosions caused this interstellar dust to be thrown out of the galactic disk toward the halo. It may also be possible that the pressure from surrounding stars causes this phenomenon. The galaxy is a member of a group of galaxies, sometimes called the NGC1023 Group. Other galaxies in this group are the NGCs 925,949,959,1003,1023, and 1058, and the UGCs 1807,1865,2014,2023,2034, and 2259. Its outskirts are populated by multiple low-surface brightness, coherent, and vast substructures, the bulge and the disk are surrounded by a flat and thick cocoon-like stellar structure. These have vertical and radial distances of up to 15 kpc and 40 kpc, respectively and are interpreted as the remmant of a satellite galaxy disrupted and in the process of being absorbed by NGC891. The soundtrack of the 1974 film Dark Star by John Carpenter features a muzak style instrumental piece called When Twilight Falls On NGC891, the first solo album by Edgar Froese, Aqua, contained a track called NGC891. Side 2 of the album, which included this track, was unusual in having been an example of a commercially issued piece of music recorded using the artificial head system
38.
NGC 7662
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NGC7662, also known as the Blue Snowball Nebula or Snowball Nebula, is a planetary nebula located in the constellation Andromeda. The distance to this nebula is not known with any real accuracy, according to the Skalnate Pleso Catalogue the distance of NGC7662 is about 1,800 light years, the actual diameter about 20,000 AU. In a more recent survey of the brighter planetaries, C. R. ODell derived a distance of 1,740 parsecs or about 5,600 light years, increasing the size to 0.8 light year. It has a faint central star that is variable, with a range of 12 to 16. The central star is a dwarf with a continuous spectrum. The nuclei of the planetary nebulae are among the hottest stars known, NGC7662 is a popular planetary nebula for casual observers. A small telescope will reveal a star-like object with slight nebulosity
39.
Planetary nebula
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A planetary nebula, often abbreviated as PN or plural PNe, is a kind of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from old red giant stars late in their lives. Herschels name for these objects was popularly adopted and has not been changed and they are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years. After most of the red giants atmosphere is dissipated, the radiation of the hot luminous core, called a planetary nebula nucleus. Absorbed ultraviolet light energises the shell of gas around the central star. Planetary nebulae likely play a role in the chemical evolution of the Milky Way by expelling elements to the interstellar medium from stars where those elements were created. Planetary nebulae are also observed in distant galaxies, yielding useful information about their chemical abundances. Starting from the 1990s, Hubble Space Telescope images have revealed many planetary nebulae to have extremely complex, about one-fifth are roughly spherical, but the majority are not spherically symmetric. The mechanisms that produce such a variety of shapes and features are not yet well understood. The first planetary nebula discovered was the Dumbbell Nebula in the constellation of Vulpecula and it was observed by Charles Messier in 1764 and listed as M27 in his catalogue of nebulous objects. To early observers with telescopes, M27 and subsequently discovered planetary nebulae resembled the giant planets like Uranus. William Herschel, discoverer of Uranus, eventually coined the term planetary nebula, the nature of planetary nebulae was unknown until the first spectroscopic observations were made in the mid-19th century. Using a prism to disperse their light, William Huggins was one of the earliest astronomers to study the spectra of astronomical objects. On August 29,1864, Huggins was the first to analyze the spectrum of a planetary nebula when he observed Cats Eye Nebula and his observations of stars showed that their spectra consisted of a continuum of radiation with many dark lines superimposed. He later found that many objects such as the Andromeda Nebula had spectra that were quite similar. Those nebulae were later shown to be collections of stars now called galaxies, however, when Huggins looked at the Cats Eye Nebula, he found a very different spectrum. Rather than a strong continuum with absorption lines superimposed, the Cats Eye Nebula, the brightest of these was at a wavelength of 500.7 nanometres, which did not correspond with a line of any known element. At first, it was hypothesized that the line might be due to an unknown element, a similar idea had led to the discovery of helium through analysis of the Suns spectrum in 1868. While helium was isolated on Earth soon after its discovery in the spectrum of the Sun, nebulium was not
40.
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
41.
Radiant (meteor shower)
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The radiant or apparent radiant of a meteor shower is the point in the sky, from which meteors appear to originate. The Perseids, for example, are meteors which appear to come from a point within the constellation of Perseus, an observer might see such a meteor anywhere in the sky but the direction of motion, when traced back, will point to the radiant. A meteor that does not point back to the radiant for a given shower is known as a sporadic and is not considered part of that shower. Many showers have a radiant point that changes position during the interval when it appears, for example, the radiant point for the Delta Aurigids drifts by more than a degree per night. Meteor showers are mostly caused by the trails of dust and debris left in the wake of a comet and this dust continues to move along the comets wake, and when the Earth moves through such debris, a meteor shower results. Because all of the debris is moving in roughly the same direction, as an exception, the Geminids are a shower caused by the object 3200 Phaethon, which is thought to be a Palladian asteroid. The radiant is an important factor in observation, if the radiant point is at or below the horizon, then few if any meteors will be observed. This is because the atmosphere shields the Earth from most of the debris, and only those meteors which happen to be travelling exactly tangential to the Earths surface will be viewable
42.
Johannes Hevelius
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Johannes Hevelius was a councillor and mayor of Danzig, then part of the Polish-Lithuanian Commonwealth. As an astronomer he gained a reputation as the founder of lunar topography and described ten new constellations, Hevelius father was Abraham Hewelke, his mother Kordula Hecker. They were German-speaking Lutherans, wealthy brewing merchants of Bohemian origin, as a young boy, Hevelius was sent to Gądecz where he studied the Polish language. Hevelius brewed the famous Jopen beer, which gave its name to the Jopengasse/Jopejska Street, after 1945 renamed as Piwna Street. In 1634 he settled in his town, and on 21 March 1635 married Katharine Rebeschke. The following year, Hevelius became a member of the beer-brewing guild, throughout his life, Hevelius took a leading part in municipal administration, becoming town councillor in 1651, but from 1639 on, his chief interest was astronomy. This may have been the longest tubed telescope before the advent of the tubeless aerial telescope, the observatory was known by the name Sternenburg or Star Castle This private observatory was visited by Polish Queen Marie Louise Gonzaga on 29 January 1660. While the noble status was not ratified by the Polish Sejm Heveliuss coat of arms includes the distinctive Polish royal crown, in May 1679 the young Englishman Edmond Halley visited him as emissary of the Royal Society, whose fellow Hevelius had been since 1664. The Royal Society considers him one of the first German fellows, małgorzata Czerniakowska writes that Jan Heweliusz was the first Pole to be inducted into the Royal Society in London. This important event took place on 19th March 1664 and he is thus considered the last astronomer to do major work without the use of a telescope. He discovered four comets, in 1652,1661,1672 and 1677 and these discoveries led to his thesis that such bodies revolve around the Sun in parabolic paths. A complex halo phenomenon was observed by many in the city on 20 February 1661, Katharine, his first wife, died in 1662, and a year later Hevelius married Elisabeth Hevelius née Koopmann, the young daughter of a merchant family. Elisabeth supported him, published two of his works after his death, and is considered the first female astronomer and his observatory, instruments and books were destroyed by fire on 26 September 1679. The catastrophe is described in the preface to his Annus climactericus and he promptly repaired the damage enough to enable him to observe the great comet of December 1680. He named the constellation Sextans in memory of these lost instruments and this constellation first occurred publicly in his star atlas Firmamentum Sobiescianum, that was printed in his own house at lavish expense, and he himself engraved many of the printing plates. His health had suffered from the shock of the 1679 fire, Hevelius was buried in St. Catherines Church in his hometown. Descendants of Hevelius live in Urzędów in Poland where they support local astronomy enthusiasts, Hevelius description of his naked eye observation method in the first part of this work led to a dispute with Robert Hooke who claimed observations without telescopic sights were of little value. Obsolete, Cerberus, Mons Maenalus, and Triangulum Minus
43.
Celestial cartography
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Measuring the position and light of charted objects requires a variety of instruments and techniques. Uranographers have historically produced planetary position tables, star tables and star maps for use by amateur and professional astronomers. More recently computerized star maps have been compiled, and automated positioning of telescopes is accomplished using databases of stars, the word uranography derived from the Greek ουρανογραφια through the Latin uranographia. In Renaissance times, Uranographia was used as the title of various celestial atlases. During the 19th century, uranography was defined as the description of the heavens, elijah H. Burritt re-defined it as the geography of the heavens. The German word for uranography is Uranographie, the French is uranographie, a determining fact source for drawing star charts is naturally a star table. C, AD150, Almagest – contains the last known star table from antiquity, C.964, Book of the Fixed Stars, Arabic version of the Almagest by al-Sufi. 1627, Rudolphine Tables – contains the first West Enlightenment star table,1690, Prodromus Astronomiae – by Johannes Hevelius for his Firmamentum Sobiescanum,1,564 stars. 1729, Britannic Catalogue – by John Flamsteed for his Atlas Coelestis,1903, Bonner Durchmusterung – by Friedrich Wilhelm Argelander and collaborators, circa 460,000 stars. 15th century BC – The ceiling of the tomb TT71 for the Egyptian architect and minister Senenmut, poeticon astronomicon, allegedly by Gaius Julius Hyginus 1092 – Xin Yi Xiang Fa Yao, by Su Song, a horological treatise which had the earliest existent star maps in printed form. True Visual Magnitude Photographic Star Atlas, pasachoff, Wil Tirion charts SkyGX – Christopher Watson The Great Atlas of the Sky – Piotr Brych. 100,000 Stars Cartes du Ciel Celestia 3D Galaxy Map CyberSky GoSkyWatch Planetarium Google Sky KStars Stellarium SKY-MAP. ORG SkyMap Online WorldWide Telescope XEphem, monthly star maps for every location on Earth Easy to use monthly star maps for northern and southern hemispheres. Helpful target lists for naked eye, binocular, or telescope viewing, collection of rare star atlases, charts, and maps available in full digital facsimile at Linda Hall Library. The Great Atlas of the Sky – worlds largest printed atlas of the sky, navigable online map of the stars, Stellarmap. com. The Digital Collections of the Linda Hall Library include, Astronomy, Star Atlases, Charts, and Maps, Astronomy, Selected Images, a collection of high-resolution star map images. History of Cosmology, Views of the Stars, high-resolution scans of prints relating to the study of the structure of the cosmos, EDSM, an external community supporting the recording of exploration data in Elite, Dangerous. GalNet, the community news source for Elite, Dangerous galactic activity, Community Goal, More Imperial Warships. Article citing the discovery of the lost Jaques station
44.
Celestial sphere
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In astronomy and navigation, the celestial sphere is an imaginary sphere of arbitrarily large radius, concentric with Earth. All objects in the sky can be thought of as projected upon the inside surface of the celestial sphere. The celestial sphere is a tool for spherical astronomy, allowing observers to plot positions of objects in the sky when their distances are unknown or unimportant. Because astronomical objects are at such distances, casual observation of the sky offers no information on the actual distances. All objects seem equally far away, as if fixed to the inside of a sphere of large but unknown radius, which rotates from east to west overhead while underfoot, the celestial sphere can be considered to be infinite in radius. This means any point within it, including that occupied by the observer, all parallel planes will seem to intersect the sphere in a coincident great circle. On an infinite-radius celestial sphere, all observers see the things in the same direction. For some objects, this is over-simplified, objects which are relatively near to the observer will seem to change position against the distant celestial sphere if the observer moves far enough, say, from one side of the Earth to the other. This effect, known as parallax, can be represented as an offset from a mean position. The celestial sphere can be considered to be centered at the Earths center, the Suns center, or any convenient location. Individual observers can work out their own small offsets from the mean positions, in many cases in astronomy, the offsets are insignificant. The celestial sphere can thus be thought of as a kind of astronomical shorthand, for many rough uses, this position, as seen from the Earths center, is adequate. This greatly abbreviates the amount of detail necessary in such almanacs and these concepts are important for understanding celestial coordinate systems – frameworks for measuring the positions of objects in the sky. Certain reference lines and planes on Earth, when projected onto the celestial sphere and these include the Earths equator, axis, and the Earths orbit. At their intersections with the sphere, these form the celestial equator, the north and south celestial poles. As the celestial sphere is considered infinite in radius, all observers see the celestial equator, celestial poles, from these bases, directions toward objects in the sky can be quantified by constructing celestial coordinate systems. Similar to terrestrial longitude and latitude, the coordinate system specifies positions relative to the celestial equator and celestial poles. The ecliptic coordinate system specifies positions relative to the Earths orbit, besides the equatorial and ecliptic systems, some other celestial coordinate systems, such as the galactic coordinate system, are more appropriate for particular purposes
45.
Urania's Mirror
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Uranias Mirror, or, a view of the Heavens is a set of 32 astronomical star chart cards, first published in November 1824. They had illustrations based on Alexander Jamiesons A Celestial Atlas, and they were engraved by Sidney Hall, and were said to be designed by a lady, but have since been identified as the work of the Reverend Richard Rouse Bloxam, an assistant master at Rugby School. The cover of the box-set showed a depiction of Urania, the muse of astronomy, P. D. Uranias Mirror illustrates 79 constellations, some of which are now obsolete, and various subconstellations, such as Caput Medusæ. Some cards focus on a constellation, others include several, with Card 32, centered on Hydra. Card 28 has six, and no other card has more than four, each card measures 8 inches by 5 1⁄2. A book by Jehoshaphat Aspin entitled A Familiar Treatise on Astronomy was written to accompany the cards. Both the book and cards were published by Samuel Leigh,18 Strand, London, although the publishing firm had moved to 421 Strand. The cards and books came within a box illustrated with a woman almost certainly intended to be Urania, hingley calls it One of the most charming and visually attractive of the many aids to astronomical self-instruction produced in the early nineteenth century. While he had several sons, he has no other known publications. The reasons for the disguise are unknown, hingley notes that many contemporary publications attempted to suggest women had played a role in their creation, perhaps to make them sound less threatening. Ian Ridpath, noting the plagiarism of the art from A Celestial Atlas, a December 1824 advertisement, which states the cards were just published, offered the cards plain at £1/8s or fully coloured for £1/14s. This first edition did not include any stars surrounding the named constellations and this was changed for the second edition, which added back stars around theose constellations. An American edition was published in 1832, modern reprints were produced in 1993, and Barnes & Noble reproduced the American edition in 2004. The accompanying book, A Familiar Treatise on Astronomy by Jehoshaphat Aspin went through at least four editions, the second edition featured a marked expansion in content, growing from 121 pages in the first edition to 200 pages in the second. A Second Part of Uranias Mirror, which was to have included illustrations of the planets and an orrery, was advertised. Includes a video presentation of the cards
. Bibcode:2006AJ....131.1405K. doi:10.1086/499534.
"Andromeda". Encyclopædia Britannica. 2 (9th ed.). 1878. p. 22.
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