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136-446: Polaris, the brightest star in the constellation, is a yellow-white supergiant and the brightest Cepheid variable star in the night sky, ranging in apparent magnitude from 1.97 to 2.00. Beta Ursae Minoris , also known as Kochab, is an aging star that has swollen and cooled to become an orange giant with an apparent magnitude of 2.08, only slightly fainter than Polaris. Kochab and 3rd-magnitude Gamma Ursae Minoris have been called

272-456: 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

408-467: 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

544-483: A Seyfert 2 active galactic nucleus , and is one of the most extreme examples of a Seyfert galaxy . This galaxy may be associated with gamma-ray source 3EG J1621+8203, which has high-energy gamma-ray emission. It is also noted for its one-sided radio jet —one of the brightest known—discovered in 1977. The Ursids , a prominent meteor shower that occurs in Ursa Minor, peaks between December 18 and 25. Its parent body

680-487: 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

816-444: A broad labial (for example, lebor /ˈLʲev u r/ "book"; domun /ˈdoṽ u n/ "world"). The phoneme /ə/ occurred in other circumstances. The occurrence of the two phonemes was generally unrelated to the nature of the corresponding Proto-Celtic vowel, which could be any monophthong: long or short. Long vowels also occur in unstressed syllables. However, they rarely reflect Proto-Celtic long vowels, which were shortened prior to

952-496: 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

1088-423: A complex sound system involving grammatically significant consonant mutations to the initial consonant of a word. Apparently, neither characteristic was present in the preceding Primitive Irish period, though initial mutations likely existed in a non-grammaticalised form in the prehistoric era. Contemporary Old Irish scholarship is still greatly influenced by the works of a small number of scholars active in

1224-429: A consonant ensures its unmutated sound. While the letter ⟨c⟩ may be voiced / ɡ / at the end of some words, but when it is written double ⟨cc⟩ it is always voiceless / k / in regularised texts; however, even final /ɡ/ was often written "cc", as in bec / becc "small, little" (Modern Irish and Scottish beag , Manx beg ). In later Irish manuscripts, lenited f and s are denoted with

1360-410: 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

1496-440: 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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1632-470: A member of this class is Zeta Ursae Minoris , a white star of spectral type A3V, which has begun cooling, expanding and brightening. It is likely to have been a B3 main-sequence star and is now slightly variable. At magnitude 4.95 the dimmest of the seven stars of the Little Dipper is Eta Ursae Minoris . A yellow-white main-sequence star of spectral type F5V, it is 97 light-years distant. It is double

1768-518: 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"

1904-546: 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

2040-463: 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

2176-614: 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,

2312-459: A sound / h / and a letter h , there is no consistent relationship between the two. Vowel-initial words are sometimes written with an unpronounced h , especially if they are very short (the Old Irish preposition i "in" was sometimes written hi ) or if they need to be emphasised (the name of Ireland, Ériu , was sometimes written Hériu ). On the other hand, words that begin with

2448-499: 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

2584-434: 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

2720-407: 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

2856-433: A white dwarf. Its atmosphere, composed of roughly half carbon, half oxygen and 2% neon, is devoid of hydrogen and helium—its composition unexplainable by current models of stellar evolution. WD 1337+705 is a cooler white dwarf that has magnesium and silicon in its spectrum, suggesting a companion or circumstellar disk, though no evidence for either has come to light. WISE 1506+7027 is a brown dwarf of spectral type T6 that

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2992-469: A word containing it being variably spelled with ⟨au, ai, e, i, u⟩ across attestations. Tulach "hill, mound" is the most commonly cited example of this vowel, with the spelling of its inflections including tulach itself, telaig , telocho , tilchaib , taulich and tailaig . This special vowel also ran rampant in many words starting with the stressed prefix air- (from Proto-Celtic *ɸare ). Archaic Old Irish (before about 750) had

3128-426: Is septentrio , from septem (seven) and triones ( oxen ), from seven oxen driving a plough, which the seven stars also resemble. This name has also been attached to the main stars of Ursa Major. In Inuit astronomy , the three brightest stars — Polaris, Kochab, and Pherkad — were known as Nuutuittut ("never moving"), though the term is more frequently used in the singular to refer to Polaris alone. The Pole Star

3264-613: Is 6.8 AU distant from its star. Ursa Minor is rather devoid of deep-sky objects. The Ursa Minor Dwarf , a dwarf spheroidal galaxy , was discovered by Albert George Wilson of the Lowell Observatory in the Palomar Sky Survey in 1955. Its centre is around 225 000 light-years distant from Earth. In 1999, Kenneth Mighell and Christopher Burke used the Hubble Space Telescope to confirm that

3400-482: Is a barred spiral galaxy located some 67 million light-years away, which can be located with a 10 cm (4 in) or larger telescope as an 11th-magnitude object about 2.5° east-northeast of Zeta Ursae Minoris. It has been characterized as a starburst galaxy , which means it is undergoing a high rate of star formation compared with a typical galaxy. NGC 6251 is an active supergiant elliptical radio galaxy more than 340 million light-years away from Earth. It has

3536-439: Is a faint variable star that suddenly dropped 6 magnitudes in 1992 and was identified as one of a rare class of stars— R Coronae Borealis variables . Eclipsing variables are star systems that vary in brightness because of one star passing in front of the other rather than from any intrinsic change in luminosity. W Ursae Minoris is one such system, its magnitude ranging from 8.51 to 9.59 over 1.7 days. The combined spectrum of

3672-571: Is a mere 11.1 +2.3 −1.3 light-years away from Earth. A faint object of magnitude 14, it was discovered by the Wide-field Infrared Survey Explorer (WISE) in 2011. Kochab aside, three more stellar systems have been discovered to contain planets. 11 Ursae Minoris is an orange giant of spectral type K4III around 1.8 times as massive as the Sun. Around 1.5 billion years old, it has cooled and expanded since it

3808-422: Is a semiregular variable varying from magnitude 8.5 to 11.5 over 328 days, while S Ursae Minoris is a long-period variable that ranges between magnitudes 8.0 and 11 over 331 days. Located south of Kochab and Pherkad towards Draco is RR Ursae Minoris , a red giant of spectral type M5III that is also a semiregular variable ranging from magnitude 4.44 to 4.85 over a period of 43.3 days. T Ursae Minoris

3944-447: Is a spectroscopic binary, with a companion 0.36 AU distant, and a third star—an orange main-sequence star of spectral type K0—8100 AU distant. Located close to Polaris is Lambda Ursae Minoris , a red giant of spectral type M1III. It is a semiregular variable varying between magnitudes 6.35 and 6.45. The northerly nature of the constellation means that the variable stars can be observed all year: The red giant R Ursae Minoris

4080-584: Is a yellow-white supergiant that varies between spectral types F7Ib and F8Ib, and has around 6 times the Sun's mass, 2,500 times its luminosity, and 45 times its radius. Polaris is the brightest Cepheid variable star visible from Earth. It is a triple star system, the supergiant primary star having two yellow-white main-sequence star companions that are 17 and 2,400  astronomical units (AU) distant and take 29.6 and 42,000 years respectively to complete one orbit. Traditionally called Kochab, Beta Ursae Minoris, at apparent magnitude 2.08,

4216-430: Is another red-giant variable star that has undergone a dramatic change in status—from being a long-period (Mira) variable ranging from magnitude 7.8 to 15 over 310–315 days, to being a semiregular variable. The star is thought to have undergone a shell helium flash —a point where the shell of helium around the star's core reaches a critical mass and ignites—marked by its abrupt change in variability in 1979. Z Ursae Minoris

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4352-420: 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

4488-453: Is known). Instead, the mythographic tradition of Catasterismi makes Cynosura the name of an Oread nymph described as a nurse of Zeus , honoured by the god with a place in the sky. There are various proposed explanations for the name Cynosura . One suggestion connects it to the myth of Callisto , with her son Arcas replaced by her dog being placed in the sky by Zeus. Others have suggested that an archaic interpretation of Ursa Major

4624-409: 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,

4760-508: Is shown in the chart below. The complexity of Old Irish phonology is from a four-way split of phonemes inherited from Primitive Irish, with both a fortis–lenis and a "broad–slender" ( velarised vs. palatalised ) distinction arising from historical changes. The sounds /f v θ ð x ɣ h ṽ n l r/ are the broad lenis equivalents of broad fortis /p b t d k ɡ s m N L R/ ; likewise for the slender (palatalised) equivalents. (However, most /f fʲ/ sounds actually derive historically from /w/ , since /p/

4896-426: Is slightly less bright than Polaris. Located around 131 light-years away from Earth, it is an orange giant —an evolved star that has used up the hydrogen in its core and moved off the main sequence —of spectral type K4III. Slightly variable over a period of 4.6 days, Kochab has had its mass estimated at 1.3 times that of the Sun via measurement of these oscillations. Kochab is 450 times more luminous than

5032-431: Is subject to u -affection, becoming ⟨éu⟩ or ⟨íu⟩ , while /e₁ː/ is not. A similar distinction may have existed between /o₁ː/ and /o₂ː/ , both written ⟨ó⟩ , and stemming respectively from former diphthongs (*eu, *au, *ou) and from compensatory lengthening. However, in later Old Irish both sounds appear usually as ⟨úa⟩ , sometimes as ⟨ó⟩ , and it

5168-575: 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

5304-491: 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

5440-461: Is the ancestor of all modern Goidelic languages: Modern Irish , Scottish Gaelic and Manx . A still older form of Irish is known as Primitive Irish . Fragments of Primitive Irish, mainly personal names, are known from inscriptions on stone written in the Ogham alphabet. The inscriptions date from about the 4th to the 6th centuries. Primitive Irish appears to have been very close to Common Celtic ,

5576-460: Is the comet 8P/Tuttle . Star 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

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5712-520: Is the nickname given to an X-ray source known as 1RXS J141256.0+792204 in the ROSAT All-Sky Survey Bright Source Catalog (RASS/BSC). It has been identified as an isolated neutron star , one of the closest of its kind to Earth. Ursa Minor has two enigmatic white dwarfs . Documented on January 27, 2011, H1504+65 is a faint (magnitude 15.9) star with the hottest surface temperature—200,000 K—yet discovered for

5848-401: Is too high in the sky at far northern latitudes to be of use in navigation. In Chinese astronomy , the main stars of Ursa Minor are divided between two asterisms : 勾陳 Gòuchén (Curved Array) (including α UMi, δ UMi , ε UMi , ζ UMi , η UMi , θ UMi , λ UMi ) and 北極 Běijí (Northern Pole) (including β UMi and γ UMi ). Ursa Minor is bordered by Camelopardalis to the west, Draco to

5984-594: Is unclear whether /o₂ː/ existed as a separate sound any time in the Old Irish period. /ou/ existed only in early archaic Old Irish ( c. 700 or earlier); afterwards it merged into /au/ . Neither sound occurred before another consonant, and both sounds became ⟨ó⟩ in later Old Irish (often ⟨ú⟩ or ⟨u⟩ before another vowel). The late ⟨ó⟩ does not develop into ⟨úa⟩ , suggesting that ⟨áu⟩ > ⟨ó⟩ postdated ⟨ó⟩ > ⟨úa⟩ . Later Old Irish had

6120-406: Is within 1° of the north celestial pole and remains the current Pole star . Its Neo-Latin name of stella polaris was coined only in the early modern period. The ancient name of the constellation is Cynosura ( Greek Κυνοσούρα "dog's tail"). The origin of this name is unclear (Ursa Minor being a "dog's tail" would imply that another constellation nearby is "the dog", but no such constellation

6256-559: The eclipsis consonants also denoted with a superdot: Old Irish digraphs include the lenition consonants: the eclipsis consonants: the geminatives : and the diphthongs : The following table indicates the broad pronunciation of various consonant letters in various environments: When the consonants b, d, g are eclipsed by the preceding word (always from a word-initial position), their spelling and pronunciation change to: ⟨mb⟩ / m / , ⟨nd⟩ /N/ , ⟨ng⟩ / ŋ / Generally, geminating

6392-537: The Algol paradox , where the most-evolved star in a system is the least massive. Old Irish Old Irish , also called Old Gaelic ( Old Irish : Goídelc , Ogham script : ᚌᚑᚔᚇᚓᚂᚉ; Irish : Sean-Ghaeilge ; Scottish Gaelic : Seann-Ghàidhlig ; Manx : Shenn Yernish or Shenn Ghaelg ), is the oldest form of the Goidelic/Gaelic language for which there are extensive written texts. It

6528-479: The Book of Leinster , contain texts which are thought to derive from written exemplars in Old Irish now lost and retain enough of their original form to merit classification as Old Irish. The preservation of certain linguistic forms current in the Old Irish period may provide reason to assume that an Old Irish original directly or indirectly underlies the transmitted text or texts. The consonant inventory of Old Irish

6664-701: 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

6800-526: 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

6936-618: The abbey of Reichenau , now in St. Paul in Carinthia (Austria), contains a spell and four Old Irish poems. The Liber Hymnorum and the Stowe Missal date from about 900 to 1050. In addition to contemporary witnesses, the vast majority of Old Irish texts are attested in manuscripts of a variety of later dates. Manuscripts of the later Middle Irish period, such as the Lebor na hUidre and

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7072-461: 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

7208-460: The celestial pole was somewhat closer to Beta Ursae Minoris than to Alpha Ursae Minoris , and the entire constellation was taken to indicate the northern direction. Since the medieval period, it has become convenient to use Alpha Ursae Minoris (or "Polaris") as the North Star . (Even though, in the medieval period, Polaris was still several degrees away from the celestial pole. ) Now, Polaris

7344-632: 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

7480-468: The orthography of Old Irish is not fixed, so the following statements are to be taken as generalisations only. Individual manuscripts may vary greatly from these guidelines. The Old Irish alphabet consists of the following eighteen letters of the Latin alphabet : in addition to the five long vowels , shown by an acute accent (´): the lenited consonants denoted with a superdot (◌̇): and

7616-453: 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

7752-555: 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

7888-438: The "guardians of the pole star" or "Guardians of The Pole". Planets have been detected orbiting four of the stars, including Kochab. The constellation also contains an isolated neutron star— Calvera —and H1504+65 , the hottest white dwarf yet discovered, with a surface temperature of 200,000 K . In the Babylonian star catalogues , Ursa Minor was known as the "Wagon of Heaven " ( MAR.GÍD.DA.AN.NA , also associated with

8024-449: The "guardians of the pole star". A white bright giant of spectral type A3II-III, with around 4.8 times the Sun's mass, 1,050 times its luminosity and 15 times its radius, it is 487±8 light-years distant from Earth. Pherkad belongs to a class of stars known as Delta Scuti variables —short period (six hours at most) pulsating stars that have been used as standard candles and as subjects to study asteroseismology . Also possibly

8160-591: 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

8296-476: 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,

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8432-413: 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

8568-413: 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,

8704-577: The Modern Irish and Scottish dialects that still possess a four-way distinction in the coronal nasals and laterals . /Nʲ/ and /Lʲ/ may have been pronounced [ɲ] and [ʎ] respectively. The difference between /R(ʲ)/ and /r(ʲ)/ may have been that the former were trills while the latter were flaps . /m(ʲ)/ and /ṽ(ʲ)/ were derived from an original fortis–lenis pair. Old Irish had distinctive vowel length in both monophthongs and diphthongs . Short diphthongs were monomoraic , taking up

8840-469: The Old Irish period, but merged with /u/ later on and in many instances was replaced with /o/ due to paradigmatic levelling. It is attested once in the phrase i r ou th by the prima manus of the Würzburg Glosses . /æ ~ œ/ arose from the u-infection of stressed /a/ by a /u/ that preceded a palatalized consonant. This vowel faced much inconsistency in spelling, often detectable by

8976-540: The Pointers—that form the end of the "bowl" of the Big Dipper, for 30 degrees (three upright fists at arms' length) across the night sky. The four stars constituting the bowl of the Little Dipper are of second, third, fourth, and fifth magnitudes, respectively, and provide an easy guide to determining what magnitude stars are visible, useful for city dwellers or testing one's eyesight. The three-letter abbreviation for

9112-497: 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

9248-475: The Sun and has 42 times its diameter, with a surface temperature of approximately 4,130 K. Estimated to be around 2.95 billion years old, ±1 billion years, Kochab was announced to have a planetary companion around 6.1 times as massive as Jupiter with an orbit of 522 days. Traditionally known as Pherkad, Gamma Ursae Minoris has an apparent magnitude that varies between 3.04 and 3.09 roughly every 3.4 hours. It and Kochab have been termed

9384-439: 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

9520-495: The Sun's diameter, 1.4 times as massive, and shines with 7.4 times its luminosity. Nearby Zeta lies 5.00-magnitude Theta Ursae Minoris . Located 860 ± 80 light-years distant, it is an orange giant of spectral type K5III that has expanded and cooled off the main sequence, and has an estimated diameter around 4.8 times that of the Sun. Making up the handle of the Little Dipper are Delta Ursae Minoris , or Yildun, and Epsilon Ursae Minoris . Just over 3.5 degrees from

9656-449: 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

9792-611: The ancestor of all Celtic languages , and it had a lot of the characteristics of other archaic Indo-European languages. Relatively little survives in the way of strictly contemporary sources. They are represented mainly by shorter or longer glosses on the margins or between the lines of religious Latin manuscripts , most of them preserved in monasteries in Germany, Italy, Switzerland, France and Austria, having been taken there by early Irish missionaries . Whereas in Ireland, many of

9928-502: 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

10064-616: The brightest stars have proper names . Astronomers have assembled star catalogues that identify 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

10200-502: 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

10336-408: 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

10472-612: 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

10608-610: The complexities of PIE verbal conjugation are also maintained, and there are new complexities introduced by various sound changes (see below ). Old Irish was the only known member of the Goidelic branch of the Celtic languages , which is, in turn, a subfamily of the wider Indo-European language family that also includes the Slavonic , Italic / Romance , Indo-Aryan and Germanic subfamilies, along with several others. Old Irish

10744-435: The constellation, as adopted by the IAU ( International Astronomical Union ) in 1922, is "UMi". The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of 22 segments ( illustrated in infobox ). In the equatorial coordinate system , the right ascension coordinates of these borders lie between 08 41.4 and 22 54.0 , while the declination coordinates range from

10880-400: 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

11016-468: The deletion (syncope) of inner syllables. Rather, they originate in one of the following ways: Stress is generally on the first syllable of a word. However, in verbs it occurs on the second syllable when the first syllable is a clitic (the verbal prefix as- in as·beir /asˈberʲ/ "he says"). In such cases, the unstressed prefix is indicated in grammatical works with a following centre dot ( ⟨·⟩ ). As with most medieval languages ,

11152-417: 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

11288-721: The early 9th century. Important Continental collections of glosses from the 8th and 9th century include the Würzburg Glosses (mainly) on the Pauline Epistles , the Milan Glosses on a commentary to the Psalms and the St Gall Glosses on Priscian 's Grammar. Further examples are found at Karlsruhe (Germany), Paris (France), Milan, Florence and Turin (Italy). A late 9th-century manuscript from

11424-405: 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

11560-526: 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

11696-433: The following consonant (in certain clusters) or a directly following vowel in hiatus . It is generally thought that /e₁ː/ was higher than /e₂ː/ . Perhaps /e₁ː/ was [eː] while /e₂ː/ was [ɛː] . They are clearly distinguished in later Old Irish, in which /e₁ː/ becomes ⟨ía⟩ (but ⟨é⟩ before a palatal consonant). /e₂ː/ becomes ⟨é⟩ in all circumstances. Furthermore, /e₂ː/

11832-409: The following inventory of long vowels: Both /e₁ː/ and /e₂ː/ were normally written ⟨é⟩ but must have been pronounced differently because they have different origins and distinct outcomes in later Old Irish. /e₁ː/ stems from Proto-Celtic *ē (< PIE *ei), or from ē in words borrowed from Latin. /e₂ː/ generally stems from compensatory lengthening of short *e because of loss of

11968-470: The following inventory of long vowels: Early Old Irish /ai/ and /oi/ merged in later Old Irish. It is unclear what the resulting sound was, as scribes continued to use both ⟨aí⟩ and ⟨oí⟩ to indicate the merged sound. The choice of /oi/ in the table above is somewhat arbitrary. The distribution of short vowels in unstressed syllables is a little complicated. All short vowels may appear in absolutely final position (at

12104-426: The galaxy had had a single burst of star formation that took place around 14 billion years ago and lasted around 2 billion years, and that the galaxy was probably as old as the Milky Way itself. NGC 3172 (also known as Polarissima Borealis) is a faint, magnitude-14.9 galaxy that happens to be the closest NGC object to the north celestial pole . It was discovered by John Herschel in 1831. NGC 6217

12240-697: The goddess Damkina ). It is listed in the MUL.APIN catalogue, compiled around 1000 BC, among the "Stars of Enlil "—that is, the northern sky. According to Diogenes Laërtius , citing Callimachus , Thales of Miletus "measured the stars of the Wagon by which the Phoenicians sail". Diogenes identifies these as the constellation of Ursa Minor, which for its reported use by the Phoenicians for navigation at sea were also named Phoinikē . The tradition of naming

12376-643: The late 19th and early 20th centuries, such as Rudolf Thurneysen (1857–1940) and Osborn Bergin (1873–1950). Notable characteristics of Old Irish compared with other old Indo-European languages , are: Old Irish also preserves most aspects of the complicated Proto-Indo-European (PIE) system of morphology. Nouns and adjectives are declined in three genders (masculine, feminine, neuter); three numbers (singular, dual, plural); and five cases (nominative, vocative, accusative, dative and genitive). Most PIE noun stem classes are maintained ( o -, yo -, ā -, yā -, i -, u -, r -, n -, s -, and consonant stems). Most of

12512-422: The letter h ⟨fh⟩ , ⟨sh⟩ , instead of using a superdot ⟨ḟ⟩ , ⟨ṡ⟩ . When initial s stemmed from Primitive Irish *sw- , its lenited version is ⟨f⟩ [ ɸ ] . The slender ( palatalised ) variants of the 13 consonants are denoted with / ʲ / marking the letter. They occur in the following environments: Although Old Irish has both

12648-437: 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

12784-677: 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;

12920-412: 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

13056-456: 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

13192-445: 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

13328-404: The name (a loan from an Assyrian An‑nas-sur‑ra "high-rising"). An alternative myth tells of two bears that saved Zeus from his murderous father Cronus by hiding him on Mount Ida . Later Zeus set them in the sky, but their tails grew long from their being swung up into the sky by the god. Because Ursa Minor consists of seven stars, the Latin word for "north" ( i.e. , where Polaris points)

13464-484: 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

13600-540: The north celestial pole to 65.40° in the south. Its position in the far northern celestial hemisphere means that the whole constellation is visible only to observers in the northern hemisphere. The German cartographer Johann Bayer used the Greek letters alpha to theta to label the most prominent stars in the constellation, while his countryman Johann Elert Bode subsequently added iota through phi . Only lambda and pi remain in use, likely because of their proximity to

13736-434: The north celestial pole, Delta is a white main-sequence star of spectral type A1V with an apparent magnitude of 4.35, located 172±1 light-years from Earth. It has around 2.8 times the diameter and 47 times the luminosity of the Sun. A triple star system, Epsilon Ursae Minoris shines with a combined average light of magnitude 4.22. A yellow giant of spectral type G5III, the primary is a RS Canum Venaticorum variable star. It

13872-583: The north celestial pole. Within the constellation's borders, there are 39 stars brighter than or equal to apparent magnitude 6.5. The traditional names of the main seven in Johann Bayer 's ordering are: Marking the Little Bear's tail, Polaris , or Alpha Ursae Minoris, is the brightest star in the constellation, varying between apparent magnitudes 1.97 and 2.00 over a period of 3.97 days. Located around 432  light-years away from Earth, it

14008-512: The northern constellations "bears" appears to be genuinely Greek, although Homer refers to just a single "bear". The original "bear" is thus Ursa Major , and Ursa Minor was admitted as the second, or "Phoenician Bear" (Ursa Phoenicia, hence Φοινίκη, Phoenice) only later, according to Strabo (I.1.6, C3) due to a suggestion by Thales , who suggested it as a navigation aid to the Greeks, who had been navigating by Ursa Major. In classical antiquity ,

14144-403: 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

14280-530: The older manuscripts appear to have been worn out through extended and heavy use, their counterparts on the Continent were much less prone to the same risk because once they ceased to be understood, they were rarely consulted. The earliest Old Irish passages may be the transcripts found in the Cambrai Homily , which is thought to belong to the early 8th century. The Book of Armagh contains texts from

14416-417: 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

14552-404: 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

14688-664: 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

14824-513: The primary. RW Ursae Minoris is a cataclysmic variable star system that flared up as a nova in 1956, reaching magnitude 6. In 2003, it was still two magnitudes brighter than its baseline, and dimming at a rate of 0.02 magnitude a year. Its distance has been calculated as 5,000±800 parsecs (16,300 light-years), which puts its location in the galactic halo . Taken from the villain in The Magnificent Seven , Calvera

14960-403: 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

15096-497: 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

15232-410: The radial velocity of the star in 2013. HD 150706 is a sunlike star of spectral type G0V some 89 light-years distant from the Solar System. It was thought to have a planet as massive as Jupiter at a distance of 0.6 AU, but this was discounted in 2007. A further study published in 2012 showed that it has a companion around 2.7 times as massive as Jupiter that takes around 16 years to complete an orbit and

15368-569: The same amount of time as short vowels, while long diphthongs were bimoraic, the same as long vowels. (This is much like the situation in Old English but different from Ancient Greek whose shorter and longer diphthongs were bimoraic and trimoraic, respectively: /ai/ vs. /aːi/ .) The inventory of Old Irish long vowels changed significantly over the Old Irish period, but the short vowels changed much less. The following short vowels existed: The short diphthong ŏu likely existed very early in

15504-461: The same mass. For example, when any star expands to become 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

15640-455: 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

15776-408: The sound /h/ are usually written without it: a ór /a hoːr/ "her gold". If the sound and the spelling co-occur , it is by coincidence, as ní hed /Nʲiː heð/ "it is not". The voiceless stops of Old Irish are c, p, t . They contrast with the voiced stops g, b, d . Additionally, the letter m can behave similarly to a stop following vowels. These seven consonants often mutate when not in

15912-506: 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

16048-400: 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

16184-485: The supply of hydrogen at their core, they start to fuse hydrogen in 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

16320-468: 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

16456-444: The system is A2V, but the masses of the two component stars are unknown. A slight change in the orbital period in 1973 suggests there is a third component of the multiple star system—most likely a red dwarf —with an orbital period of 62.2±3.9 years. RU Ursae Minoris is another example, ranging from 10 to 10.66 over 0.52 days. It is a semidetached system, as the secondary star is filling its Roche lobe and transferring matter to

16592-458: 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

16728-400: 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

16864-431: The very end of a word) after both broad and slender consonants. The front vowels /e/ and /i/ are often spelled ⟨ae⟩ and ⟨ai⟩ after broad consonants, which might indicate a retracted pronunciation here, perhaps something like [ɘ] and [ɨ] . All ten possibilities are shown in the following examples: The distribution of short vowels in unstressed syllables, other than when absolutely final,

17000-491: The west, and Cepheus to the east. Covering 256  square degrees , it ranks 56th of the 88 constellations in size. Ursa Minor is colloquially known in the US as the Little Dipper because its seven brightest stars seem to form the shape of a dipper ( ladle or scoop). The star at the end of the dipper handle is Polaris. Polaris can also be found by following a line through the two stars— Alpha and Beta Ursae Majoris , popularly called

17136-567: The word-initial position. In non-initial positions, the single-letter voiceless stops c, p, and t become the voiced stops / ɡ / , / b / , and / d / respectively unless they are written double. Ambiguity in these letters' pronunciations arises when a single consonant follows an l, n, or r . The lenited stops ch, ph, and th become / x / , / f / , and / θ / respectively. The voiced stops b, d, and g become fricative / v / , / ð / , and / ɣ / , respectively—identical sounds to their word-initial lenitions. In non-initial positions,

17272-479: Was an A-type main-sequence star. Around 390 light-years distant, it shines with an apparent magnitude of 5.04. A planet around 11 times the mass of Jupiter was discovered in 2009 orbiting the star with a period of 516 days. HD 120084 is another evolved star, a yellow giant of spectral type G7III, around 2.4 times the mass of the Sun. It has a planet 4.5 times the mass of Jupiter, with one of the most eccentric planetary orbits (e = 0.66), discovered by precisely measuring

17408-435: 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

17544-419: 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

17680-488: Was quite restricted. It is usually thought that there were only two allowed phonemes: /ə/ (written ⟨a, ai, e, i⟩ depending on the quality of surrounding consonants) and /u/ (written ⟨u⟩ or ⟨o⟩ ). The phoneme /u/ tended to occur when the following syllable contained an *ū in Proto-Celtic (for example, dligud /ˈdʲlʲiɣ u ð/ "law" (dat.) < PC * dligedū ), or after

17816-519: Was relatively rare in Old Irish, being a recent import from other languages such as Latin.) Some details of Old Irish phonetics are not known. /sʲ/ may have been pronounced [ɕ] or [ʃ] , as in Modern Irish. /hʲ/ may have been the same sound as /h/ or /xʲ/ . The precise articulation of the fortis sonorants /N/, /Nʲ/, /L/, /Lʲ/, /R/, /Rʲ/ is unknown, but they were probably longer, tenser and generally more strongly articulated than their lenis counterparts /n/, /nʲ/, /l/, /lʲ/, /r/, /rʲ/ , as in

17952-476: Was that of a cow, forming a group with Boötes as herdsman, and Ursa Minor as a dog. George William Cox explained it as a variant of Λυκόσουρα , understood as "wolf's tail" but by him etymologized as "trail, or train, of light" (i.e. λύκος "wolf" vs. λύκ- "light"). Allen points to the Old Irish name of the constellation, drag-blod "fire trail", for comparison. Brown (1899) suggested a non-Greek origin of

18088-600: 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

18224-614: 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

18360-570: Was used from c. 600 to c. 900. The main contemporary texts are dated c. 700–850; by 900 the language had already transitioned into early Middle Irish . Some Old Irish texts date from the 10th century, although these are presumably copies of texts written at an earlier time. Old Irish is forebear to Modern Irish , Manx and Scottish Gaelic . Old Irish is known for having a particularly complex system of morphology and especially of allomorphy (more or less unpredictable variations in stems and suffixes in differing circumstances), as well as

18496-480: 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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