129-506: A star is a luminous spheroid of plasma held together by self-gravity . The nearest star to Earth is the Sun . Many other stars are visible to the naked eye at night ; their immense distances from Earth make them appear as fixed points of light. The most prominent stars have been categorised into constellations and asterisms , and many of the brightest stars have proper names . Astronomers have assembled star catalogues that identify
258-622: A moral , fable , allegory or a parable , or collection of traditional stories, understood to be false. It came eventually to be applied to similar bodies of traditional stories among other polytheistic cultures around the world. Thus "mythology" entered the English language before "myth". Johnson 's Dictionary , for example, has an entry for mythology, but not for myth. Indeed, the Greek loanword mythos ( pl. mythoi ) and Latinate mythus (pl. mythi ) both appeared in English before
387-455: A protoplanetary disk and powered mainly by the conversion of gravitational energy. The period of gravitational contraction lasts about 10 million years for a star like the sun, up to 100 million years for a red dwarf. Early stars of less than 2 M ☉ are called T Tauri stars , while those with greater mass are Herbig Ae/Be stars . These newly formed stars emit jets of gas along their axis of rotation, which may reduce
516-462: A stellar wind of particles that causes a continual outflow of gas into space. For most stars, the mass lost is negligible. The Sun loses 10 M ☉ every year, or about 0.01% of its total mass over its entire lifespan. However, very massive stars can lose 10 to 10 M ☉ each year, significantly affecting their evolution. Stars that begin with more than 50 M ☉ can lose over half their total mass while on
645-449: A "disease of language". He speculated that myths arose due to the lack of abstract nouns and neuter gender in ancient languages. Anthropomorphic figures of speech , necessary in such languages, were eventually taken literally, leading to the idea that natural phenomena were in actuality conscious or divine. Not all scholars, not even all 19th-century scholars, accepted this view. Lucien Lévy-Bruhl claimed that "the primitive mentality
774-478: A ; therefore, e may again be identified as the eccentricity . (See ellipse .) These formulas are identical in the sense that the formula for S oblate can be used to calculate the surface area of a prolate spheroid and vice versa. However, e then becomes imaginary and can no longer directly be identified with the eccentricity. Both of these results may be cast into many other forms using standard mathematical identities and relations between parameters of
903-449: A book on the comparative study of mythology and religion—argued that humans started out with a belief in magical rituals; later, they began to lose faith in magic and invented myths about gods, reinterpreting their rituals as religious rituals intended to appease the gods. Historically, important approaches to the study of mythology have included those of Vico , Schelling , Schiller , Jung , Freud , Lévy-Bruhl , Lévi-Strauss , Frye ,
1032-487: A brief period of carbon fusion before the core becomes degenerate. During the AGB phase, stars undergo thermal pulses due to instabilities in the core of the star. In these thermal pulses, the luminosity of the star varies and matter is ejected from the star's atmosphere, ultimately forming a planetary nebula. As much as 50 to 70% of a star's mass can be ejected in this mass loss process. Because energy transport in an AGB star
1161-495: A burst of electron capture and inverse beta decay . The shockwave formed by this sudden collapse causes the rest of the star to explode in a supernova. Supernovae become so bright that they may briefly outshine the star's entire home galaxy. When they occur within the Milky Way, supernovae have historically been observed by naked-eye observers as "new stars" where none seemingly existed before. A supernova explosion blows away
1290-409: A continuous image due to the effect of refraction from sublunary material, citing his observation of the conjunction of Jupiter and Mars on 500 AH (1106/1107 AD) as evidence. Early European astronomers such as Tycho Brahe identified new stars in the night sky (later termed novae ), suggesting that the heavens were not immutable. In 1584, Giordano Bruno suggested that the stars were like
1419-439: A difference between " fixed stars ", whose position on the celestial sphere does not change, and "wandering stars" ( planets ), which move noticeably relative to the fixed stars over days or weeks. Many ancient astronomers believed that the stars were permanently affixed to a heavenly sphere and that they were immutable. By convention, astronomers grouped prominent stars into asterisms and constellations and used them to track
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#17327652824481548-477: A failed or obsolete mode of thought, often by interpreting myth as the primitive counterpart of modern science within a unilineal framework that imagined that human cultures are travelling, at different speeds, along a linear path of cultural development. One of the dominant mythological theories of the latter 19th century was nature mythology , the foremost exponents of which included Max Müller and Edward Burnett Tylor . This theory posited that "primitive man"
1677-404: A massive body in a close orbit. The most extreme example is Jupiter's moon Io , which becomes slightly more or less prolate in its orbit due to a slight eccentricity, causing intense volcanism . The major axis of the prolate spheroid does not run through the satellite's poles in this case, but through the two points on its equator directly facing toward and away from the primary. This combines with
1806-446: A methodology that allows us to understand the complexity of the myth and its manifestations in contemporary times, is justified. Because "myth" is sometimes used in a pejorative sense, some scholars have opted for "mythos" instead. "Mythos" now more commonly refers to its Aristotelian sense as a "plot point" or to a body of interconnected myths or stories, especially those belonging to a particular religious or cultural tradition. It
1935-517: A much larger gravitationally bound structure, such as a star cluster or a galaxy. The word "star" ultimately derives from the Proto-Indo-European root "h₂stḗr" also meaning star, but further analyzable as h₂eh₁s- ("to burn", also the source of the word "ash") + -tēr (agentive suffix). Compare Latin stella , Greek aster , German Stern . Some scholars believe the word is a borrowing from Akkadian " istar " ( Venus ). "Star"
2064-535: A myth can be highly controversial. Many religious adherents believe that the narratives told in their respective religious traditions are historical without question, and so object to their identification as myths while labelling traditional narratives from other religions as such. Hence, some scholars may label all religious narratives as "myths" for practical reasons, such as to avoid depreciating any one tradition because cultures interpret each other differently relative to one another. Other scholars may abstain from using
2193-545: A net release of energy. Some massive stars, particularly luminous blue variables , are very unstable to the extent that they violently shed their mass into space in events supernova impostors , becoming significantly brighter in the process. Eta Carinae is known for having underwent a supernova impostor event, the Great Eruption, in the 19th century. As a star's core shrinks, the intensity of radiation from that surface increases, creating such radiation pressure on
2322-486: A pattern of behavior to be imitated, testifies to the efficacy of ritual with its practical ends and establishes the sanctity of cult . Another definition of myth comes from myth criticism theorist and professor José Manuel Losada . According to Cultural Myth Criticism, the studies of myth must explain and understand "myth from inside", that is, only "as a myth". Losada defines myth as "a functional, symbolic and thematic narrative of one or several extraordinary events with
2451-536: A poetic description of the sea as "raging" was eventually taken literally and the sea was then thought of as a raging god. Some thinkers claimed that myths result from the personification of objects and forces. According to these thinkers, the ancients worshiped natural phenomena, such as fire and air, gradually deifying them. For example, according to this theory, ancients tended to view things as gods, not as mere objects. Thus, they described natural events as acts of personal gods, giving rise to myths. According to
2580-600: A primordial age when the world had not achieved its later form. Origin myths explain how a society's customs , institutions , and taboos were established and sanctified. National myths are narratives about a nation's past that symbolize the nation's values. There is a complex relationship between recital of myths and the enactment of rituals . The word "myth" comes from Ancient Greek μῦθος ( mȳthos ), meaning 'speech, narrative, fiction, myth, plot'. In turn, Ancient Greek μυθολογία ( mythología , 'story', 'lore', 'legends', or 'the telling of stories') combines
2709-400: A red giant, it may overflow its Roche lobe , the surrounding region where material is gravitationally bound to it; if stars in a binary system are close enough, some of that material may overflow to the other star, yielding phenomena including contact binaries , common-envelope binaries, cataclysmic variables , blue stragglers , and type Ia supernovae . Mass transfer leads to cases such as
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#17327652824482838-621: A scholarly term for "[a] traditional story, especially one concerning the early history of a people or explaining a natural or social phenomenon, and typically involving supernatural beings or events." The Greek term mythología was then borrowed into Late Latin , occurring in the title of Latin author Fulgentius ' 5th-century Mythologiæ to denote what is now referred to as classical mythology —i.e., Greco-Roman etiological stories involving their gods. Fulgentius' Mythologiæ explicitly treated its subject matter as allegories requiring interpretation and not as true events. The Latin term
2967-461: A series of star maps and applied Greek letters as designations to the stars in each constellation. Later a numbering system based on the star's right ascension was invented and added to John Flamsteed 's star catalogue in his book "Historia coelestis Britannica" (the 1712 edition), whereby this numbering system came to be called Flamsteed designation or Flamsteed numbering . The internationally recognized authority for naming celestial bodies
3096-613: A set of nominal solar values (defined as SI constants, without uncertainties) which can be used for quoting stellar parameters: The solar mass M ☉ was not explicitly defined by the IAU due to the large relative uncertainty ( 10 ) of the Newtonian constant of gravitation G . Since the product of the Newtonian constant of gravitation and solar mass together ( G M ☉ ) has been determined to much greater precision,
3225-415: A shell surrounding the helium core. The outer layers of the star expand and cool greatly as they transition into a red giant . In some cases, they will fuse heavier elements at the core or in shells around the core. As the stars expand, they throw part of their mass, enriched with those heavier elements, into the interstellar environment, to be recycled later as new stars. In about 5 billion years, when
3354-505: A society. For scholars, this is very different from the vernacular usage of the term "myth" that refers to a belief that is not true. Instead, the veracity of a myth is not a defining criterion. Myths are often endorsed by secular and religious authorities and are closely linked to religion or spirituality . Many societies group their myths, legends, and history together, considering myths and legends to be factual accounts of their remote past. In particular, creation myths take place in
3483-456: A sphere. An oblate spheroid with c < a has surface area The oblate spheroid is generated by rotation about the z -axis of an ellipse with semi-major axis a and semi-minor axis c , therefore e may be identified as the eccentricity . (See ellipse .) A prolate spheroid with c > a has surface area The prolate spheroid is generated by rotation about the z -axis of an ellipse with semi-major axis c and semi-minor axis
3612-415: A spheroid as having a major axis c , and minor axes a = b , the moments of inertia along these principal axes are C , A , and B . However, in a spheroid the minor axes are symmetrical. Therefore, our inertial terms along the major axes are: where M is the mass of the body defined as Myth Myth is a genre of folklore consisting primarily of narratives that play a fundamental role in
3741-496: A star begins with gravitational instability within a molecular cloud, caused by regions of higher density—often triggered by compression of clouds by radiation from massive stars, expanding bubbles in the interstellar medium, the collision of different molecular clouds, or the collision of galaxies (as in a starburst galaxy ). When a region reaches a sufficient density of matter to satisfy the criteria for Jeans instability , it begins to collapse under its own gravitational force. As
3870-432: A star of more than 9 solar masses expands to form first a blue supergiant and then a red supergiant . Particularly massive stars (exceeding 40 solar masses, like Alnilam , the central blue supergiant of Orion's Belt ) do not become red supergiants due to high mass loss. These may instead evolve to a Wolf–Rayet star , characterised by spectra dominated by emission lines of elements heavier than hydrogen, which have reached
3999-565: A step further, incorporating the study of the transcendent dimension (its function, its disappearance) to evaluate the role of myth as a mirror of contemporary culture. Cultural myth criticism Cultural myth criticism, without abandoning the analysis of the symbolic , invades all cultural manifestations and delves into the difficulties in understanding myth today. This cultural myth criticism studies mythical manifestations in fields as wide as literature , film and television , theater , sculpture , painting , video games , music , dancing ,
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4128-436: A transcendent, sacred and supernatural referent; that lacks, in principle, historical testimony; and that refers to an individual or collective, but always absolute, cosmogony or eschatology". According to the hylistic myth research by assyriologist Annette Zgoll and classic philologist Christian Zgoll , "A myth can be defined as an Erzählstoff [narrative material] which is polymorphic through its variants and – depending on
4257-404: A tri-axial ellipsoid centred at the origin with semi-axes a , b and c aligned along the coordinate axes is The equation of a spheroid with z as the symmetry axis is given by setting a = b : The semi-axis a is the equatorial radius of the spheroid, and c is the distance from centre to pole along the symmetry axis. There are two possible cases: The case of a = c reduces to
4386-406: A white dwarf is no longer a plasma. Eventually, white dwarfs fade into black dwarfs over a very long period of time. In massive stars, fusion continues until the iron core has grown so large (more than 1.4 M ☉ ) that it can no longer support its own mass. This core will suddenly collapse as its electrons are driven into its protons, forming neutrons, neutrinos , and gamma rays in
4515-576: A world of the remote past, very different from that of the present. Definitions of "myth" vary to some extent among scholars, though Finnish folklorist Lauri Honko offers a widely-cited definition: Myth, a story of the gods, a religious account of the beginning of the world , the creation , fundamental events, the exemplary deeds of the gods as a result of which the world, nature and culture were created together with all parts thereof and given their order, which still obtains. A myth expresses and confirms society's religious values and norms, it provides
4644-421: Is a condition of the human mind and not a stage in its historical development." Recent scholarship, noting the fundamental lack of evidence for "nature mythology" interpretations among people who actually circulated myths, has likewise abandoned the key ideas of "nature mythology". Frazer saw myths as a misinterpretation of magical rituals, which were themselves based on a mistaken idea of natural law. This idea
4773-465: Is a form of understanding and telling stories that are connected to power, political structures, and political and economic interests. These approaches contrast with approaches, such as those of Joseph Campbell and Eliade , which hold that myth has some type of essential connection to ultimate sacred meanings that transcend cultural specifics. In particular, myth was studied in relation to history from diverse social sciences. Most of these studies share
4902-419: Is cognate (shares the same root) with the following words: asterisk , asteroid , astral , constellation , Esther . Historically, stars have been important to civilizations throughout the world. They have been part of religious practices, divination rituals, mythology , used for celestial navigation and orientation, to mark the passage of seasons, and to define calendars. Early astronomers recognized
5031-423: Is nobody's truth. Myths are somebody's truth." One theory claims that myths are distorted accounts of historical events. According to this theory, storytellers repeatedly elaborate upon historical accounts until the figures in those accounts gain the status of gods. For example, the myth of the wind-god Aeolus may have evolved from a historical account of a king who taught his people to use sails and interpret
5160-472: Is often thought to differ from genres such as legend and folktale in that neither are considered to be sacred narratives. Some kinds of folktales, such as fairy stories , are not considered true by anyone, and may be seen as distinct from myths for this reason. Main characters in myths are usually gods , demigods or supernatural humans, while legends generally feature humans as their main characters. Many exceptions and combinations exist, as in
5289-407: Is primarily by convection , this ejected material is enriched with the fusion products dredged up from the core. Therefore, the planetary nebula is enriched with elements like carbon and oxygen. Ultimately, the planetary nebula disperses, enriching the general interstellar medium. Therefore, future generations of stars are made of the "star stuff" from past stars. During their helium-burning phase,
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5418-495: Is rotated about its major axis , the result is a prolate spheroid , elongated like a rugby ball . The American football is similar but has a pointier end than a spheroid could. If the ellipse is rotated about its minor axis , the result is an oblate spheroid , flattened like a lentil or a plain M&;M . If the generating ellipse is a circle, the result is a sphere . Due to the combined effects of gravity and rotation ,
5547-636: Is sometimes known as "mythography", a term also used for a scholarly anthology of myths or of the study of myths generally. Key mythographers in the Classical tradition include: Other prominent mythographies include the thirteenth-century Prose Edda attributed to the Icelander Snorri Sturluson , which is the main surviving survey of Norse Mythology from the Middle Ages. Jeffrey G. Snodgrass (professor of anthropology at
5676-510: Is sometimes used specifically for modern, fictional mythologies, such as the world building of H. P. Lovecraft . Mythopoeia ( mytho- + -poeia , 'I make myth') was termed by J. R. R. Tolkien , amongst others, to refer to the "conscious generation" of mythology. It was notoriously also suggested, separately, by Nazi ideologist Alfred Rosenberg . Comparative mythology is a systematic comparison of myths from different cultures. It seeks to discover underlying themes that are common to
5805-569: Is the International Astronomical Union (IAU). The International Astronomical Union maintains the Working Group on Star Names (WGSN) which catalogs and standardizes proper names for stars. A number of private companies sell names of stars which are not recognized by the IAU, professional astronomers, or the amateur astronomy community. The British Library calls this an unregulated commercial enterprise , and
5934-488: Is the Orion Nebula . Most stars form in groups of dozens to hundreds of thousands of stars. Massive stars in these groups may powerfully illuminate those clouds, ionizing the hydrogen, and creating H II regions . Such feedback effects, from star formation, may ultimately disrupt the cloud and prevent further star formation. All stars spend the majority of their existence as main sequence stars , fueled primarily by
6063-544: Is the approximate shape of the ball in several sports, such as in the rugby ball . Several moons of the Solar System approximate prolate spheroids in shape, though they are actually triaxial ellipsoids . Examples are Saturn 's satellites Mimas , Enceladus , and Tethys and Uranus ' satellite Miranda . In contrast to being distorted into oblate spheroids via rapid rotation, celestial objects distort slightly into prolate spheroids via tidal forces when they orbit
6192-579: The Iliad , Odyssey and Aeneid . Moreover, as stories spread between cultures or as faiths change, myths can come to be considered folktales, their divine characters recast as either as humans or demihumans such as giants , elves and faeries . Conversely, historical and literary material may acquire mythological qualities over time. For example, the Matter of Britain (the legendary history of Great Britain, especially those focused on King Arthur and
6321-457: The Republic . His critique was primarily on the grounds that the uneducated might take the stories of gods and heroes literally. Nevertheless, he constantly referred to myths throughout his writings. As Platonism developed in the phases commonly called Middle Platonism and neoplatonism , writers such as Plutarch , Porphyry , Proclus , Olympiodorus , and Damascius wrote explicitly about
6450-860: The Theologia Mythologica (1532). The first modern, Western scholarly theories of myth appeared during the second half of the 19th century —at the same time as "myth" was adopted as a scholarly term in European languages. They were driven partly by a new interest in Europe's ancient past and vernacular culture, associated with Romantic Nationalism and epitomised by the research of Jacob Grimm (1785–1863). This movement drew European scholars' attention not only to Classical myths, but also material now associated with Norse mythology , Finnish mythology , and so forth. Western theories were also partly driven by Europeans' efforts to comprehend and control
6579-450: The Algol paradox , where the most-evolved star in a system is the least massive. Spheroid A spheroid , also known as an ellipsoid of revolution or rotational ellipsoid , is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters . A spheroid has circular symmetry . If the ellipse
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#17327652824486708-622: The Colorado State University ) has termed India's Bhats as mythographers. Myth criticism is a system of anthropological interpretation of culture created by French philosopher Gilbert Durand . Scholars have used myth criticism to explain the mythical roots of contemporary fiction, which means that modern myth criticism needs to be interdisciplinary . Professor Losada offers his own methodologic, hermeneutic and epistemological approach to myth. While assuming mythopoetical perspectives, Losada's Cultural Myth Criticism takes
6837-522: The Equator and 6,356.752 km (3,949.903 mi) at the poles . The word spheroid originally meant "an approximately spherical body", admitting irregularities even beyond the bi- or tri-axial ellipsoidal shape; that is how the term is used in some older papers on geodesy (for example, referring to truncated spherical harmonic expansions of the Earth's gravity geopotential model ). The equation of
6966-696: The M87 and M100 galaxies of the Virgo Cluster , as well as luminous stars in some other relatively nearby galaxies. With the aid of gravitational lensing , a single star (named Icarus ) has been observed at 9 billion light-years away. The concept of a constellation was known to exist during the Babylonian period. Ancient sky watchers imagined that prominent arrangements of stars formed patterns, and they associated these with particular aspects of nature or their myths. Twelve of these formations lay along
7095-989: The Maclaurin spheroid and the Jacobi ellipsoid . Spheroid is also a shape of archaeological artifacts. The oblate spheroid is the approximate shape of rotating planets and other celestial bodies , including Earth, Saturn , Jupiter , and the quickly spinning star Altair . Saturn is the most oblate planet in the Solar System , with a flattening of 0.09796. See planetary flattening and equatorial bulge for details. Enlightenment scientist Isaac Newton , working from Jean Richer 's pendulum experiments and Christiaan Huygens 's theories for their interpretation, reasoned that Jupiter and Earth are oblate spheroids owing to their centrifugal force . Earth's diverse cartographic and geodetic systems are based on reference ellipsoids , all of which are oblate. The prolate spheroid
7224-573: The New York City Department of Consumer and Worker Protection issued a violation against one such star-naming company for engaging in a deceptive trade practice. Although stellar parameters can be expressed in SI units or Gaussian units , it is often most convenient to express mass , luminosity , and radii in solar units, based on the characteristics of the Sun. In 2015, the IAU defined
7353-400: The actinide and lanthanide elements are shaped like prolate spheroids. In anatomy, near-spheroid organs such as testis may be measured by their long and short axes . Many submarines have a shape which can be described as prolate spheroid. For a spheroid having uniform density, the moment of inertia is that of an ellipsoid with an additional axis of symmetry. Given a description of
7482-458: The angular momentum of the collapsing star and result in small patches of nebulosity known as Herbig–Haro objects . These jets, in combination with radiation from nearby massive stars, may help to drive away the surrounding cloud from which the star was formed. Early in their development, T Tauri stars follow the Hayashi track —they contract and decrease in luminosity while remaining at roughly
7611-476: The figure of the Earth (and of all planets ) is not quite a sphere, but instead is slightly flattened in the direction of its axis of rotation. For that reason, in cartography and geodesy the Earth is often approximated by an oblate spheroid, known as the reference ellipsoid , instead of a sphere. The current World Geodetic System model uses a spheroid whose radius is 6,378.137 km (3,963.191 mi) at
7740-632: The interstellar medium . These elements are then recycled into new stars. Astronomers can determine stellar properties—including mass, age, metallicity (chemical composition), variability , distance , and motion through space —by carrying out observations of a star's apparent brightness , spectrum , and changes in its position in the sky over time. Stars can form orbital systems with other astronomical objects, as in planetary systems and star systems with two or more stars. When two such stars orbit closely, their gravitational interaction can significantly impact their evolution. Stars can form part of
7869-452: The photographic magnitude . The development of the photoelectric photometer allowed precise measurements of magnitude at multiple wavelength intervals. In 1921 Albert A. Michelson made the first measurements of a stellar diameter using an interferometer on the Hooker telescope at Mount Wilson Observatory . Important theoretical work on the physical structure of stars occurred during
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#17327652824487998-555: The thermonuclear fusion of hydrogen into helium in its core. This process releases energy that traverses the star's interior and radiates into outer space . At the end of a star's lifetime as a fusor , its core becomes a stellar remnant : a white dwarf , a neutron star , or—if it is sufficiently massive—a black hole . Stellar nucleosynthesis in stars or their remnants creates almost all naturally occurring chemical elements heavier than lithium . Stellar mass loss or supernova explosions return chemically enriched material to
8127-590: The 11th century, the Persian polymath scholar Abu Rayhan Biruni described the Milky Way galaxy as a multitude of fragments having the properties of nebulous stars, and gave the latitudes of various stars during a lunar eclipse in 1019. According to Josep Puig, the Andalusian astronomer Ibn Bajjah proposed that the Milky Way was made up of many stars that almost touched one another and appeared to be
8256-424: The 2015 IAU nominal constants will remain the same SI values as they remain useful measures for quoting stellar parameters. Large lengths, such as the radius of a giant star or the semi-major axis of a binary star system, are often expressed in terms of the astronomical unit —approximately equal to the mean distance between the Earth and the Sun (150 million km or approximately 93 million miles). In 2012,
8385-412: The IAU defined the astronomical constant to be an exact length in meters: 149,597,870,700 m. Stars condense from regions of space of higher matter density, yet those regions are less dense than within a vacuum chamber . These regions—known as molecular clouds —consist mostly of hydrogen, with about 23 to 28 percent helium and a few percent heavier elements. One example of such a star-forming region
8514-412: The IAU defined the nominal solar mass parameter to be: The nominal solar mass parameter can be combined with the most recent (2014) CODATA estimate of the Newtonian constant of gravitation G to derive the solar mass to be approximately 1.9885 × 10 kg . Although the exact values for the luminosity, radius, mass parameter, and mass may vary slightly in the future due to observational uncertainties,
8643-584: The Internet and other artistic fields . Myth criticism, a discipline that studies myths (mythology contains them, like a pantheon its statues), is by nature interdisciplinary: it combines the contributions of literary theory, the history of literature, the fine arts and the new ways of dissemination in the age of communication. Likewise, it undertakes its object of study from its interrelation with other human and social sciences, in particular sociology , anthropology and economics . The need for an approach, for
8772-435: The Solar System, Isaac Newton suggested that the stars were equally distributed in every direction, an idea prompted by the theologian Richard Bentley . The Italian astronomer Geminiano Montanari recorded observing variations in luminosity of the star Algol in 1667. Edmond Halley published the first measurements of the proper motion of a pair of nearby "fixed" stars, demonstrating that they had changed positions since
8901-567: The Soviet school, and the Myth and Ritual School . The critical interpretation of myth began with the Presocratics . Euhemerus was one of the most important pre-modern mythologists. He interpreted myths as accounts of actual historical events, though distorted over many retellings. Sallustius divided myths into five categories: Plato condemned poetic myth when discussing education in
9030-437: The Sun enters the helium burning phase, it will expand to a maximum radius of roughly 1 astronomical unit (150 million kilometres), 250 times its present size, and lose 30% of its current mass. As the hydrogen-burning shell produces more helium, the core increases in mass and temperature. In a red giant of up to 2.25 M ☉ , the mass of the helium core becomes degenerate prior to helium fusion . Finally, when
9159-445: The Sun, and may have other planets , possibly even Earth-like, in orbit around them, an idea that had been suggested earlier by the ancient Greek philosophers , Democritus and Epicurus , and by medieval Islamic cosmologists such as Fakhr al-Din al-Razi . By the following century, the idea of the stars being the same as the Sun was reaching a consensus among astronomers. To explain why these stars exerted no net gravitational pull on
9288-500: The band of the ecliptic and these became the basis of astrology . Many of the more prominent individual stars were given names, particularly with Arabic or Latin designations. As well as certain constellations and the Sun itself, individual stars have their own myths . To the Ancient Greeks , some "stars", known as planets (Greek πλανήτης (planētēs), meaning "wanderer"), represented various important deities, from which
9417-499: The chemical composition of the stellar atmosphere to be determined. With the exception of rare events such as supernovae and supernova impostors , individual stars have primarily been observed in the Local Group , and especially in the visible part of the Milky Way (as demonstrated by the detailed star catalogues available for the Milky Way galaxy) and its satellites. Individual stars such as Cepheid variables have been observed in
9546-407: The cloud collapses, individual conglomerations of dense dust and gas form " Bok globules ". As a globule collapses and the density increases, the gravitational energy converts into heat and the temperature rises. When the protostellar cloud has approximately reached the stable condition of hydrostatic equilibrium , a protostar forms at the core. These pre-main-sequence stars are often surrounded by
9675-611: The cloud into multiple stars distributes some of that angular momentum. The primordial binaries transfer some angular momentum by gravitational interactions during close encounters with other stars in young stellar clusters. These interactions tend to split apart more widely separated (soft) binaries while causing hard binaries to become more tightly bound. This produces the separation of binaries into their two observed populations distributions. Stars spend about 90% of their lifetimes fusing hydrogen into helium in high-temperature-and-pressure reactions in their cores. Such stars are said to be on
9804-470: The concept of the Oedipus complex in his 1899 The Interpretation of Dreams . Jung likewise tried to understand the psychology behind world myths. Jung asserted that all humans share certain innate unconscious psychological forces, which he called archetypes . He believed similarities between the myths of different cultures reveals the existence of these universal archetypes. The mid-20th century saw
9933-458: The core. The blown-off outer layers of dying stars include heavy elements, which may be recycled during the formation of new stars. These heavy elements allow the formation of rocky planets. The outflow from supernovae and the stellar wind of large stars play an important part in shaping the interstellar medium. Binary stars ' evolution may significantly differ from that of single stars of the same mass. For example, when any star expands to become
10062-597: The cultures, stories and religions they were encountering through colonialism . These encounters included both extremely old texts such as the Sanskrit Rigveda and the Sumerian Epic of Gilgamesh , and current oral narratives such as mythologies of the indigenous peoples of the Americas or stories told in traditional African religions . The intellectual context for nineteenth-century scholars
10191-415: The direction of the Milky Way core . His son John Herschel repeated this study in the southern hemisphere and found a corresponding increase in the same direction. In addition to his other accomplishments, William Herschel is noted for his discovery that some stars do not merely lie along the same line of sight, but are physical companions that form binary star systems. The science of stellar spectroscopy
10320-399: The ellipse. The volume inside a spheroid (of any kind) is If A = 2 a is the equatorial diameter, and C = 2 c is the polar diameter, the volume is Let a spheroid be parameterized as where β is the reduced latitude or parametric latitude , λ is the longitude , and − π / 2 < β < + π / 2 and −π < λ < +π . Then,
10449-404: The end of the star's life, fusion continues along a series of onion-layer shells within a massive star. Each shell fuses a different element, with the outermost shell fusing hydrogen; the next shell fusing helium, and so forth. The final stage occurs when a massive star begins producing iron. Since iron nuclei are more tightly bound than any heavier nuclei, any fusion beyond iron does not produce
10578-570: The equatorial length: The first eccentricity (usually simply eccentricity, as above) is often used instead of flattening. It is defined by: The relations between eccentricity and flattening are: All modern geodetic ellipsoids are defined by the semi-major axis plus either the semi-minor axis (giving the aspect ratio), the flattening, or the first eccentricity. While these definitions are mathematically interchangeable, real-world calculations must lose some precision. To avoid confusion, an ellipsoidal definition considers its own values to be exact in
10707-525: The first decades of the twentieth century. In 1913, the Hertzsprung-Russell diagram was developed, propelling the astrophysical study of stars. Successful models were developed to explain the interiors of stars and stellar evolution. Cecilia Payne-Gaposchkin first proposed that stars were made primarily of hydrogen and helium in her 1925 PhD thesis. The spectra of stars were further understood through advances in quantum physics . This allowed
10836-493: The first example of "myth" in 1830. The main characters in myths are usually non-humans, such as gods , demigods , and other supernatural figures. Others include humans, animals, or combinations in their classification of myth. Stories of everyday humans, although often of leaders of some type, are usually contained in legends , as opposed to myths. Myths are sometimes distinguished from legends in that myths deal with gods, usually have no historical basis, and are set in
10965-402: The foremost functions of myth is to establish models for behavior and that myths may provide a religious experience. By telling or reenacting myths, members of traditional societies detach themselves from the present, returning to the mythical age, thereby coming closer to the divine. Honko asserted that, in some cases, a society reenacts a myth in an attempt to reproduce the conditions of
11094-522: The form it gives. The most common shapes for the density distribution of protons and neutrons in an atomic nucleus are spherical , prolate, and oblate spheroidal, where the polar axis is assumed to be the spin axis (or direction of the spin angular momentum vector). Deformed nuclear shapes occur as a result of the competition between electromagnetic repulsion between protons, surface tension and quantum shell effects . Spheroids are common in 3D cell cultures . Rotating equilibrium spheroids include
11223-423: The influential development of a structuralist theory of mythology , led by Lévi-Strauss . Strauss argued that myths reflect patterns in the mind and interpreted those patterns more as fixed mental structures, specifically pairs of opposites (good/evil, compassionate/callous), rather than unconscious feelings or urges. Meanwhile, Bronislaw Malinowski developed analyses of myths focusing on their social functions in
11352-711: The knights of the Round Table ) and the Matter of France , seem distantly to originate in historical events of the 5th and 8th centuries, respectively, and became mythologised over the following centuries. In colloquial use, "myth" can also be used of a collectively held belief that has no basis in fact, or any false story. This usage, which is often pejorative , arose from labelling the religious myths and beliefs of other cultures as incorrect, but it has spread to cover non-religious beliefs as well. As commonly used by folklorists and academics in other relevant fields, such as anthropology , "myth" has no implication whether
11481-511: The known stars and provide standardized stellar designations . The observable universe contains an estimated 10 to 10 stars. Only about 4,000 of these stars are visible to the naked eye—all within the Milky Way galaxy . A star's life begins with the gravitational collapse of a gaseous nebula of material largely comprising hydrogen , helium, and trace heavier elements. Its total mass mainly determines its evolution and eventual fate. A star shines for most of its active life due to
11610-434: The main sequence and are called dwarf stars. Starting at zero-age main sequence, the proportion of helium in a star's core will steadily increase, the rate of nuclear fusion at the core will slowly increase, as will the star's temperature and luminosity. The Sun, for example, is estimated to have increased in luminosity by about 40% since it reached the main sequence 4.6 billion ( 4.6 × 10 ) years ago. Every star generates
11739-411: The main sequence. Besides mass, the elements heavier than helium can play a significant role in the evolution of stars. Astronomers label all elements heavier than helium "metals", and call the chemical concentration of these elements in a star, its metallicity . A star's metallicity can influence the time the star takes to burn its fuel, and controls the formation of its magnetic fields, which affects
11868-674: The main sequence. The time a star spends on the main sequence depends primarily on the amount of fuel it has and the rate at which it fuses it. The Sun is expected to live 10 billion ( 10 ) years. Massive stars consume their fuel very rapidly and are short-lived. Low mass stars consume their fuel very slowly. Stars less massive than 0.25 M ☉ , called red dwarfs , are able to fuse nearly all of their mass while stars of about 1 M ☉ can only fuse about 10% of their mass. The combination of their slow fuel-consumption and relatively large usable fuel supply allows low mass stars to last about one trillion ( 10 × 10 ) years;
11997-454: The most extreme of 0.08 M ☉ will last for about 12 trillion years. Red dwarfs become hotter and more luminous as they accumulate helium. When they eventually run out of hydrogen, they contract into a white dwarf and decline in temperature. Since the lifespan of such stars is greater than the current age of the universe (13.8 billion years), no stars under about 0.85 M ☉ are expected to have moved off
12126-443: The motions of the planets and the inferred position of the Sun. The motion of the Sun against the background stars (and the horizon) was used to create calendars , which could be used to regulate agricultural practices. The Gregorian calendar , currently used nearly everywhere in the world, is a solar calendar based on the angle of the Earth's rotational axis relative to its local star, the Sun. The oldest accurately dated star chart
12255-465: The myth-ritual theory, myth is tied to ritual. In its most extreme form, this theory claims myths arose to explain rituals. This claim was first put forward by Smith , who argued that people begin performing rituals for reasons not related to myth. Forgetting the original reason for a ritual, they account for it by inventing a myth and claiming the ritual commemorates the events described in that myth. James George Frazer —author of The Golden Bough ,
12384-583: The mythical age. For example, it might reenact the healing performed by a god at the beginning of time in order to heal someone in the present. Similarly, Barthes argued that modern culture explores religious experience. Since it is not the job of science to define human morality, a religious experience is an attempt to connect with a perceived moral past, which is in contrast with the technological present. Pattanaik defines mythology as "the subjective truth of people communicated through stories, symbols and rituals." He says, "Facts are everybody's truth. Fiction
12513-430: The myths of multiple cultures. In some cases, comparative mythologists use the similarities between separate mythologies to argue that those mythologies have a common source. This source may inspire myths or provide a common "protomythology" that diverged into the mythologies of each culture. A number of commentators have argued that myths function to form and shape society and social behaviour. Eliade argued that one of
12642-483: The names of the planets Mercury , Venus , Mars , Jupiter and Saturn were taken. ( Uranus and Neptune were Greek and Roman gods , but neither planet was known in Antiquity because of their low brightness. Their names were assigned by later astronomers.) Circa 1600, the names of the constellations were used to name the stars in the corresponding regions of the sky. The German astronomer Johann Bayer created
12771-565: The narrative may be understood as true or otherwise. Among biblical scholars of both the Old and New Testament, the word "myth" has a technical meaning, in that it usually refers to "describe the actions of the other‐worldly in terms of this world" such as the Creation and the Fall. Since "myth" is popularly used to describe stories that are not objectively true , the identification of a narrative as
12900-402: The nuclear fusion of hydrogen into helium within their cores. However, stars of different masses have markedly different properties at various stages of their development. The ultimate fate of more massive stars differs from that of less massive stars, as do their luminosities and the impact they have on their environment. Accordingly, astronomers often group stars by their mass: The formation of
13029-416: The outer convective envelope collapses and the star then moves to the horizontal branch. After a star has fused the helium of its core, it begins fusing helium along a shell surrounding the hot carbon core. The star then follows an evolutionary path called the asymptotic giant branch (AGB) that parallels the other described red-giant phase, but with a higher luminosity. The more massive AGB stars may undergo
13158-403: The outer shell of gas that it will push those layers away, forming a planetary nebula. If what remains after the outer atmosphere has been shed is less than roughly 1.4 M ☉ , it shrinks to a relatively tiny object about the size of Earth, known as a white dwarf . White dwarfs lack the mass for further gravitational compression to take place. The electron-degenerate matter inside
13287-662: The positions of the stars. They built the first large observatory research institutes, mainly to produce Zij star catalogues. Among these, the Book of Fixed Stars (964) was written by the Persian astronomer Abd al-Rahman al-Sufi , who observed a number of stars, star clusters (including the Omicron Velorum and Brocchi's Clusters ) and galaxies (including the Andromeda Galaxy ). According to A. Zahoor, in
13416-402: The problem of deriving an orbit of binary stars from telescope observations was made by Felix Savary in 1827. The twentieth century saw increasingly rapid advances in the scientific study of stars. The photograph became a valuable astronomical tool. Karl Schwarzschild discovered that the color of a star and, hence, its temperature, could be determined by comparing the visual magnitude against
13545-497: The proper motion of the star Sirius and inferred a hidden companion. Edward Pickering discovered the first spectroscopic binary in 1899 when he observed the periodic splitting of the spectral lines of the star Mizar in a 104-day period. Detailed observations of many binary star systems were collected by astronomers such as Friedrich Georg Wilhelm von Struve and S. W. Burnham , allowing the masses of stars to be determined from computation of orbital elements . The first solution to
13674-484: The rationalization of myths, putting themes formerly imbued with mythological qualities into pragmatic contexts. An example of this would be following a cultural or religious paradigm shift (notably the re-interpretation of pagan mythology following Christianization ). Interest in polytheistic mythology revived during the Renaissance , with early works of mythography appearing in the sixteenth century, among them
13803-543: The real world. He is associated with the idea that myths such as origin stories might provide a "mythic charter"—a legitimisation—for cultural norms and social institutions . Thus, following the Structuralist Era ( c. 1960s –1980s), the predominant anthropological and sociological approaches to myth increasingly treated myth as a form of narrative that can be studied, interpreted, and analyzed like ideology, history, and culture. In other words, myth
13932-453: The same temperature. Less massive T Tauri stars follow this track to the main sequence, while more massive stars turn onto the Henyey track . Most stars are observed to be members of binary star systems, and the properties of those binaries are the result of the conditions in which they formed. A gas cloud must lose its angular momentum in order to collapse and form a star. The fragmentation of
14061-492: The smaller oblate distortion from the synchronous rotation to cause the body to become triaxial. The term is also used to describe the shape of some nebulae such as the Crab Nebula . Fresnel zones , used to analyze wave propagation and interference in space, are a series of concentric prolate spheroids with principal axes aligned along the direct line-of-sight between a transmitter and a receiver. The atomic nuclei of
14190-399: The spheroid's Gaussian curvature is and its mean curvature is Both of these curvatures are always positive, so that every point on a spheroid is elliptic. The aspect ratio of an oblate spheroid/ellipse, c : a , is the ratio of the polar to equatorial lengths, while the flattening (also called oblateness ) f , is the ratio of the equatorial-polar length difference to
14319-504: The star's outer layers, leaving a remnant such as the Crab Nebula. The core is compressed into a neutron star , which sometimes manifests itself as a pulsar or X-ray burster . In the case of the largest stars, the remnant is a black hole greater than 4 M ☉ . In a neutron star the matter is in a state known as neutron-degenerate matter , with a more exotic form of degenerate matter, QCD matter , possibly present in
14448-466: The strength of its stellar wind. Older, population II stars have substantially less metallicity than the younger, population I stars due to the composition of the molecular clouds from which they formed. Over time, such clouds become increasingly enriched in heavier elements as older stars die and shed portions of their atmospheres . As stars of at least 0.4 M ☉ exhaust the supply of hydrogen at their core, they start to fuse hydrogen in
14577-467: The surface due to strong convection and intense mass loss, or from stripping of the outer layers. When helium is exhausted at the core of a massive star, the core contracts and the temperature and pressure rises enough to fuse carbon (see Carbon-burning process ). This process continues, with the successive stages being fueled by neon (see neon-burning process ), oxygen (see oxygen-burning process ), and silicon (see silicon-burning process ). Near
14706-421: The symbolic interpretation of traditional and Orphic myths. Mythological themes were consciously employed in literature, beginning with Homer . The resulting work may expressly refer to a mythological background without itself becoming part of a body of myths ( Cupid and Psyche ). Medieval romance in particular plays with this process of turning myth into literature. Euhemerism , as stated earlier, refers to
14835-458: The temperature increases sufficiently, core helium fusion begins explosively in what is called a helium flash , and the star rapidly shrinks in radius, increases its surface temperature, and moves to the horizontal branch of the HR diagram. For more massive stars, helium core fusion starts before the core becomes degenerate, and the star spends some time in the red clump , slowly burning helium, before
14964-464: The term "myth" altogether for purposes of avoiding placing pejorative overtones on sacred narratives. In present use, "mythology" usually refers to the collection of myths of a group of people. For example, Greek mythology , Roman mythology , Celtic mythology and Hittite mythology all describe the body of myths retold among those cultures. "Mythology" can also refer to the study of myths and mythologies. The compilation or description of myths
15093-399: The time of the ancient Greek astronomers Ptolemy and Hipparchus. William Herschel was the first astronomer to attempt to determine the distribution of stars in the sky. During the 1780s, he established a series of gauges in 600 directions and counted the stars observed along each line of sight. From this, he deduced that the number of stars steadily increased toward one side of the sky, in
15222-483: The variant – polystratic; an Erzählstoff in which transcending interpretations of what can be experienced are combined into a hyleme sequence with an implicit claim to relevance for the interpretation and mastering of the human condition." Scholars in other fields use the term "myth" in varied ways. In a broad sense, the word can refer to any traditional story , popular misconception or imaginary entity. Though myth and other folklore genres may overlap, myth
15351-739: The winds. Herodotus (fifth-century BCE) and Prodicus made claims of this kind. This theory is named euhemerism after mythologist Euhemerus ( c. 320 BCE ), who suggested that Greek gods developed from legends about humans. Some theories propose that myths began as allegories for natural phenomena: Apollo represents the sun, Poseidon represents water, and so on. According to another theory, myths began as allegories for philosophical or spiritual concepts: Athena represents wise judgment, Aphrodite romantic desire, and so on. Müller supported an allegorical theory of myth. He believed myths began as allegorical descriptions of nature and gradually came to be interpreted literally. For example,
15480-405: The word mȳthos with the suffix - λογία ( -logia , 'study') in order to mean 'romance, fiction, story-telling.' Accordingly, Plato used mythología as a general term for 'fiction' or 'story-telling' of any kind. In Anglicised form, this Greek word began to be used in English (and was likewise adapted into other European languages) in the early 19th century, in a much narrower sense, as
15609-1029: Was central to the " myth and ritual " school of thought. According to Frazer, humans begin with an unfounded belief in impersonal magical laws. When they realize applications of these laws do not work, they give up their belief in natural law in favor of a belief in personal gods controlling nature, thus giving rise to religious myths. Meanwhile, humans continue practicing formerly magical rituals through force of habit, reinterpreting them as reenactments of mythical events. Finally, humans come to realize nature follows natural laws, and they discover their true nature through science. Here again, science makes myth obsolete as humans progress "from magic through religion to science." Segal asserted that by pitting mythical thought against modern scientific thought, such theories imply modern humans must abandon myth. The earlier 20th century saw major work developing psychoanalytical approaches to interpreting myth, led by Sigmund Freud , who, drawing inspiration from Classical myth, began developing
15738-433: Was developed by Annie J. Cannon during the early 1900s. The first direct measurement of the distance to a star ( 61 Cygni at 11.4 light-years ) was made in 1838 by Friedrich Bessel using the parallax technique. Parallax measurements demonstrated the vast separation of the stars in the heavens. Observation of double stars gained increasing importance during the 19th century. In 1834, Friedrich Bessel observed changes in
15867-418: Was pioneered by Joseph von Fraunhofer and Angelo Secchi . By comparing the spectra of stars such as Sirius to the Sun, they found differences in the strength and number of their absorption lines —the dark lines in stellar spectra caused by the atmosphere's absorption of specific frequencies. In 1865, Secchi began classifying stars into spectral types . The modern version of the stellar classification scheme
15996-618: Was primarily concerned with the natural world. It tended to interpret myths that seemed distasteful to European Victorians —such as tales about sex, incest, or cannibalism—as metaphors for natural phenomena like agricultural fertility . Unable to conceive impersonal natural laws, early humans tried to explain natural phenomena by attributing souls to inanimate objects, thus giving rise to animism . According to Tylor, human thought evolved through stages, starting with mythological ideas and gradually progressing to scientific ideas. Müller also saw myth as originating from language, even calling myth
16125-530: Was profoundly shaped by emerging ideas about evolution . These ideas included the recognition that many Eurasian languages—and therefore, conceivably, stories—were all descended from a lost common ancestor (the Indo-European language ) which could rationally be reconstructed through the comparison of its descendant languages. They also included the idea that cultures might evolve in ways comparable to species. In general, 19th-century theories framed myth as
16254-537: Was the SN 1006 supernova, which was observed in 1006 and written about by the Egyptian astronomer Ali ibn Ridwan and several Chinese astronomers. The SN 1054 supernova, which gave birth to the Crab Nebula , was also observed by Chinese and Islamic astronomers. Medieval Islamic astronomers gave Arabic names to many stars that are still used today and they invented numerous astronomical instruments that could compute
16383-611: Was the result of ancient Egyptian astronomy in 1534 BC. The earliest known star catalogues were compiled by the ancient Babylonian astronomers of Mesopotamia in the late 2nd millennium BC, during the Kassite Period ( c. 1531 BC – c. 1155 BC ). The first star catalogue in Greek astronomy was created by Aristillus in approximately 300 BC, with the help of Timocharis . The star catalog of Hipparchus (2nd century BC) included 1,020 stars, and
16512-545: Was then adopted in Middle French as mythologie . Whether from French or Latin usage, English adopted the word "mythology" in the 15th century, initially meaning 'the exposition of a myth or myths', 'the interpretation of fables', or 'a book of such expositions'. The word is first attested in John Lydgate 's Troy Book ( c. 1425 ). From Lydgate until the 17th or 18th century, "mythology" meant
16641-476: Was used to assemble Ptolemy 's star catalogue. Hipparchus is known for the discovery of the first recorded nova (new star). Many of the constellations and star names in use today derive from Greek astronomy. Despite the apparent immutability of the heavens, Chinese astronomers were aware that new stars could appear. In 185 AD, they were the first to observe and write about a supernova , now known as SN 185 . The brightest stellar event in recorded history
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