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158-411: Betelgeuse is a red supergiant star in the constellation of Orion . It is usually the tenth-brightest star in the night sky and, after Rigel , the second-brightest in its constellation. It is a distinctly reddish, semiregular variable star whose apparent magnitude , varying between +0.0 and +1.6, has the widest range displayed by any first-magnitude star . Betelgeuse is the brightest star in

316-416: A B–V color index of 1.85 – a figure which points to its pronounced "redness". The photosphere has an extended atmosphere , which displays strong lines of emission rather than absorption , a phenomenon that occurs when a star is surrounded by a thick gaseous envelope (rather than ionized). This extended gaseous atmosphere has been observed moving toward and away from Betelgeuse, depending on fluctuations in

474-575: A collection of related dialects that constitute the precursor of Arabic, first emerged during the Iron Age . Previously, the earliest attestation of Old Arabic was thought to be a single 1st century CE inscription in Sabaic script at Qaryat al-Faw , in southern present-day Saudi Arabia. However, this inscription does not participate in several of the key innovations of the Arabic language group, such as

632-435: A corpus of poetic texts, in addition to Qur'an usage and Bedouin informants whom he considered to be reliable speakers of the ʿarabiyya . Arabic spread with the spread of Islam . Following the early Muslim conquests , Arabic gained vocabulary from Middle Persian and Turkish . In the early Abbasid period , many Classical Greek terms entered Arabic through translations carried out at Baghdad's House of Wisdom . By

790-550: A degenerate helium core and without undergoing a helium flash. They will universally go on to burn heavier elements and undergo core-collapse resulting in a supernova . Less massive stars may develop a supergiant spectral luminosity class at relatively low luminosity, around 1,000  L ☉ when they are on the asymptotic giant branch (AGB) undergoing helium shell burning. Researchers now prefer to categorize these as AGB stars distinct from supergiants because they are less massive, have different chemical compositions at

948-1081: A dialect of Arabic and written in the Latin alphabet . The Balkan languages, including Albanian, Greek , Serbo-Croatian, and Bulgarian , have also acquired many words of Arabic origin, mainly through direct contact with Ottoman Turkish . Arabic has influenced languages across the globe throughout its history, especially languages where Islam is the predominant religion and in countries that were conquered by Muslims. The most markedly influenced languages are Persian , Turkish , Hindustani ( Hindi and Urdu ), Kashmiri , Kurdish , Bosnian , Kazakh , Bengali , Malay ( Indonesian and Malaysian ), Maldivian , Pashto , Punjabi , Albanian , Armenian , Azerbaijani , Sicilian, Spanish, Greek, Bulgarian, Tagalog , Sindhi , Odia , Hebrew and African languages such as Hausa , Amharic , Tigrinya , Somali , Tamazight , and Swahili . Conversely, Arabic has borrowed some words (mostly nouns) from other languages, including its sister-language Aramaic, Persian, Greek, and Latin and to

1106-431: A diameter of 0.047″ , although the stellar disk was likely 17% larger due to the limb darkening , resulting in an estimate for its angular diameter of about 0.055". Since then, other studies have produced angular diameters that range from 0.042 to 0.069″ . Combining these data with historical distance estimates of 180 to 815 ly yields a projected radius of the stellar disk of anywhere from 1.2 to 8.9 AU . Using

1264-528: A diameter of 3.84 × 10 km ( 2.58  AU ) based on the parallax value of 0.018 ″ . But limb darkening and measurement errors resulted in uncertainty about the accuracy of these measurements. The 1950s and 1960s saw two developments that affected stellar convection theory in red supergiants: the Stratoscope projects and the 1958 publication of Structure and Evolution of the Stars , principally

1422-460: A distance of 197 ± 45 pc or 643 ± 146 ly . As the researcher, Harper, points out: "The revised Hipparcos parallax leads to a larger distance ( 152 ± 20 pc ) than the original; however, the astrometric solution still requires a significant cosmic noise of 2.4 mas. Given these results it is clear that the Hipparcos data still contain systematic errors of unknown origin." Although

1580-485: A dozen M class stars M v −7 and brighter, around a quarter of a million times more luminous than the Sun, and from about 1,000 times the radius of the Sun upwards. Arabic language Arabic (endonym: اَلْعَرَبِيَّةُ , romanized :  al-ʿarabiyyah , pronounced [al ʕaraˈbijːa] , or عَرَبِيّ , ʿarabīy , pronounced [ˈʕarabiː] or [ʕaraˈbij] )

1738-544: A dust cloud that blocked the starlight coming from about a quarter of Betelgeuse's surface. Hubble captured signs of dense, heated material moving through the star's atmosphere in September, October and November before several telescopes observed the more marked dimming in December and the first few months of 2020. By January 2020, Betelgeuse had dimmed by a factor of approximately 2.5 from magnitude 0.5 to 1.5 and

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1896-516: A few hundred days are typically due to fundamental and first overtone pulsation. Lines in the spectrum of Betelgeuse show doppler shifts indicating radial velocity changes corresponding, very roughly, to the brightness changes. This demonstrates the nature of the pulsations in size, although corresponding temperature and spectral variations are not clearly seen. Variations in the diameter of Betelgeuse have also been measured directly. First overtone pulsations of 185 days have been observed, and

2054-546: A good match for slightly higher mass red supergiants with high mass-loss rates. There are no known supernova progenitors corresponding to the most luminous red supergiants, and it is expected that these evolve to Wolf Rayet stars before exploding. Red supergiants are necessarily no more than about 25 million years old and such massive stars are expected to form only in relatively large clusters of stars , so they are expected to be found mostly near prominent clusters. However they are fairly short-lived compared to other phases in

2212-481: A helium flash before fusing helium on the horizontal branch , evolve along the AGB while burning helium in a shell around a degenerate carbon-oxygen core, then rapidly lose their outer layers to become a white dwarf with a planetary nebula. AGB stars may develop spectra with a supergiant luminosity class as they expand to extreme dimensions relative to their small mass, and they may reach luminosities tens of thousands times

2370-487: A lesser extent and more recently from Turkish, English, French, and Italian. Arabic is spoken by as many as 380 million speakers, both native and non-native, in the Arab world, making it the fifth most spoken language in the world, and the fourth most used language on the internet in terms of users. It also serves as the liturgical language of more than 2 billion Muslims . In 2011, Bloomberg Businessweek ranked Arabic

2528-533: A little over twenty times that of the Sun . For various reasons , its distance has been quite difficult to measure; current best estimates are of the order of 400–600  light-years from the Sun ;– a comparatively wide uncertainty for a relatively nearby star. Its absolute magnitude is about −6. With an age of less than 10 million years, Betelgeuse has evolved rapidly because of its large mass, and

2686-690: A millennium before the modern period . Early lexicographers ( لُغَوِيُّون lughawiyyūn ) sought to explain words in the Quran that were unfamiliar or had a particular contextual meaning, and to identify words of non-Arabic origin that appear in the Quran. They gathered shawāhid ( شَوَاهِد 'instances of attested usage') from poetry and the speech of the Arabs—particularly the Bedouin ʾaʿrāb  [ ar ] ( أَعْراب ) who were perceived to speak

2844-562: A more normal brightness range, reaching a peak of 0.0 visual and 0.1 V-band magnitude in April 2023. Infrared observations found no significant change in luminosity over the last 50 years, suggesting that the dimming was due to a change in extinction around the star rather than a more fundamental change. A study using the Hubble Space Telescope suggests that occluding dust was created by a surface mass ejection; this material

3002-535: A number of likely causes for variation: just a few stars show large amplitudes and strong noise indicating variability at many frequencies, thought to indicate powerful stellar winds that occur towards the end of the life of a red supergiant; more common are simultaneous radial mode variations over a few hundred days and probably non-radial mode variations over a few thousand days; only a few stars appear to be truly irregular, with small amplitudes, likely due to photospheric granulation . Red supergiant photospheres contain

3160-435: A number of well-known naked-eye examples: Mira was historically thought to be a red supergiant star, but is now widely accepted to be an asymptotic giant branch star. Some red supergiants are larger and more luminous, with radii exceeding over a thousand times that of the Sun. These are hence also referred to as red hypergiants : A survey expected to capture virtually all Magellanic Cloud red supergiants detected around

3318-522: A particular temperature. The Yerkes or Morgan-Keenan (MK) classification system is almost universal. It groups stars into five main luminosity groups designated by roman numerals : Specific to supergiants, the luminosity class is further divided into normal supergiants of class Ib and brightest supergiants of class Ia. The intermediate class Iab is also used. Exceptionally bright, low surface gravity, stars with strong indications of mass loss may be designated by luminosity class 0 (zero) although this

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3476-547: A portrait of high resolution. It was this methodology that identified the hotspots on Betelgeuse in the 1990s. Other technological breakthroughs include adaptive optics , space observatories like Hipparcos, Hubble and Spitzer , and the Astronomical Multi-BEam Recombiner (AMBER) , which combines the beams of three telescopes simultaneously, allowing researchers to achieve milliarcsecond spatial resolution . Observations in different regions of

3634-483: A refined parallax of 5.95 +0.58 −0.85 mas, a radius of 764 +116 −62 R ☉ , and a distance of 168.1 +27.5 −14.4 pc or 548 +90 −49 ly, which, if accurate, would mean Betelgeuse is nearly 25% smaller and 25% closer to Earth than previously thought. Although the European Space Agency 's current Gaia mission was not expected to produce good results for stars brighter than

3792-476: A relatively small number of very large convection cells compared to stars like the Sun . This causes variations in surface brightness that can lead to visible brightness variations as the star rotates. The spectra of red supergiants are similar to other cool stars, dominated by a forest of absorption lines of metals and molecular bands. Some of these features are used to determine the luminosity class, for example certain near-infrared cyanogen band strengths and

3950-508: A resolution superior to that obtained by ground-based interferometers—the first conventional-telescope image (or "direct-image" in NASA terminology) of the disk of another star. Because ultraviolet light is absorbed by the Earth's atmosphere , observations at these wavelengths are best performed by space telescopes . This image, like earlier pictures, contained a bright patch indicating a region in

4108-594: A result, many European languages have borrowed words from it. Arabic influence, mainly in vocabulary, is seen in European languages (mainly Spanish and to a lesser extent Portuguese , Catalan , and Sicilian ) owing to the proximity of Europe and the long-lasting Arabic cultural and linguistic presence, mainly in Southern Iberia, during the Al-Andalus era. Maltese is a Semitic language developed from

4266-462: A script derived from ASA attest to a language known as Hasaitic . On the northwestern frontier of Arabia, various languages known to scholars as Thamudic B , Thamudic D, Safaitic , and Hismaic are attested. The last two share important isoglosses with later forms of Arabic, leading scholars to theorize that Safaitic and Hismaic are early forms of Arabic and that they should be considered Old Arabic . Linguists generally believe that "Old Arabic",

4424-451: A semi-major axis of 8.60 ± 0.33 AU . Parallax is the apparent change of the position of an object, measured in seconds of arc, caused by the change of position of the observer of that object. As the Earth orbits the Sun, every star is seen to shift by a fraction of an arc second, which measure, combined with the baseline provided by the Earth's orbit gives the distance to that star. Since

4582-683: A similar mass of the order of 10  M ☉ by the time their cores collapse. The exact value depends on the initial chemical makeup of the star and its rotation rate. Most red supergiants show some degree of visual variability , but only rarely with a well-defined period or amplitude. Therefore, they are usually classified as irregular or semiregular variables. They even have their own sub-classes, SRC and LC for slow semi-regular and slow irregular supergiant variables respectively. Variations are typically slow and of small amplitude, but amplitudes up to four magnitudes are known. Statistical analysis of many known variable red supergiants shows

4740-470: A single language, despite mutual incomprehensibility among differing spoken versions. From a linguistic standpoint, it is often said that the various spoken varieties of Arabic differ among each other collectively about as much as the Romance languages . This is an apt comparison in a number of ways. The period of divergence from a single spoken form is similar—perhaps 1500 years for Arabic, 2000 years for

4898-453: A small area of the sky in the direction of these clusters. These four clusters appear to be part of a massive burst of star formation 10–20 million years ago at the near end of the bar at the centre of the galaxy. Similar massive clusters have been found near the far end of the galactic bar, but not such large numbers of red supergiants. Red supergiants are rare stars, but they are visible at great distance and are often variable so there are

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5056-405: A star, hence determining its size relative to its mass. Larger stars are more luminous at a given temperature and can now be grouped into bands of differing luminosity. The luminosity differences between stars are most apparent at low temperatures, where giant stars are much brighter than main-sequence stars. Supergiants have the lowest surface gravities and hence are the largest and brightest at

5214-466: A third estimate in the near-infrared corroborating the 2009 numbers, this time showing a limb-darkened disk diameter of 42.49 ± 0.06 mas . The near-infrared photospheric diameter of 43.33 mas at the Hipparcos distance of 152 ± 20 pc equates to about 3.4 AU or 730  R ☉ . A 2014 paper derives an angular diameter of 42.28 mas (equivalent to a 41.01 mas uniform disc) using H and K band observations made with

5372-443: A thousand times the radius of the Sun , although size is not the primary factor in a star being designated as a supergiant. A bright cool giant star can easily be larger than a hotter supergiant. For example, Alpha Herculis is classified as a giant star with a radius of between 264 to 303  R ☉ while Epsilon Pegasi is a K2 supergiant of only 185  R ☉ . Although red supergiants are much cooler than

5530-507: A type of Arabic. Cypriot Arabic is recognized as a minority language in Cyprus. The sociolinguistic situation of Arabic in modern times provides a prime example of the linguistic phenomenon of diglossia , which is the normal use of two separate varieties of the same language, usually in different social situations. Tawleed is the process of giving a new shade of meaning to an old classical word. For example, al-hatif lexicographically means

5688-507: A variety of regional vernacular Arabic dialects , which are not necessarily mutually intelligible. Classical Arabic is the language found in the Quran , used from the period of Pre-Islamic Arabia to that of the Abbasid Caliphate . Classical Arabic is prescriptive, according to the syntactic and grammatical norms laid down by classical grammarians (such as Sibawayh ) and the vocabulary defined in classical dictionaries (such as

5846-402: A wide range of distance estimates, leading to significant variances in the calculation of the star's attributes. The results from the Hipparcos mission were released in 1997. The measured parallax of Betelgeuse was 7.63 ± 1.64 mas , which equated to a distance of roughly 131 pc or 427 ly , and had a smaller reported error than previous measurements. However, later evaluation of

6004-476: A wider audience." In the wake of the industrial revolution and European hegemony and colonialism , pioneering Arabic presses, such as the Amiri Press established by Muhammad Ali (1819), dramatically changed the diffusion and consumption of Arabic literature and publications. Rifa'a al-Tahtawi proposed the establishment of Madrasat al-Alsun in 1836 and led a translation campaign that highlighted

6162-737: Is a Central Semitic language of the Afroasiatic language family spoken primarily in the Arab world . The ISO assigns language codes to 32 varieties of Arabic , including its standard form of Literary Arabic, known as Modern Standard Arabic , which is derived from Classical Arabic . This distinction exists primarily among Western linguists; Arabic speakers themselves generally do not distinguish between Modern Standard Arabic and Classical Arabic, but rather refer to both as al-ʿarabiyyatu l-fuṣḥā ( اَلعَرَبِيَّةُ ٱلْفُصْحَىٰ "the eloquent Arabic") or simply al-fuṣḥā ( اَلْفُصْحَىٰ ). Arabic

6320-590: Is a minimum level of comprehension between all Arabic dialects, this level can increase or decrease based on geographic proximity: for example, Levantine and Gulf speakers understand each other much better than they do speakers from the Maghreb. The issue of diglossia between spoken and written language is a complicating factor: A single written form, differing sharply from any of the spoken varieties learned natively, unites several sometimes divergent spoken forms. For political reasons, Arabs mostly assert that they all speak

6478-559: Is a sister language rather than their direct ancestor. Arabia had a wide variety of Semitic languages in antiquity. The term "Arab" was initially used to describe those living in the Arabian Peninsula , as perceived by geographers from ancient Greece . In the southwest, various Central Semitic languages both belonging to and outside the Ancient South Arabian family (e.g. Southern Thamudic) were spoken. It

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6636-402: Is already a red supergiant, but this produces little immediate change at the surface. Red supergiants develop deep convection zones reaching from the surface over halfway to the core and these cause strong enrichment of nitrogen at the surface, with some enrichment of heavier elements. Some red supergiants undergo blue loops where they temporarily increase in temperature before returning to

6794-498: Is also surrounded by a complex, asymmetric envelope , roughly 250 times the size of the star, caused by mass loss from the star itself. The Earth-observed angular diameter of Betelgeuse is exceeded only by those of R Doradus and the Sun. Starting in October 2019, Betelgeuse began to dim noticeably, and by mid-February 2020 its brightness had dropped by a factor of approximately 3, from magnitude 0.5 to 1.7. It then returned to

6952-478: Is believed that the ancestors of the Modern South Arabian languages (non-Central Semitic languages) were spoken in southern Arabia at this time. To the north, in the oases of northern Hejaz , Dadanitic and Taymanitic held some prestige as inscriptional languages. In Najd and parts of western Arabia, a language known to scholars as Thamudic C is attested. In eastern Arabia, inscriptions in

7110-408: Is credited with establishing the rules of Arabic prosody . Al-Jahiz (776–868) proposed to Al-Akhfash al-Akbar an overhaul of the grammar of Arabic, but it would not come to pass for two centuries. The standardization of Arabic reached completion around the end of the 8th century. The first comprehensive description of the ʿarabiyya "Arabic", Sībawayhi's al - Kitāb , is based first of all upon

7268-472: Is credited with standardizing Arabic grammar , or an-naḥw ( النَّحو "the way" ), and pioneering a system of diacritics to differentiate consonants ( نقط الإعجام nuqaṭu‿l-i'jām "pointing for non-Arabs") and indicate vocalization ( التشكيل at-tashkīl ). Al-Khalil ibn Ahmad al-Farahidi (718–786) compiled the first Arabic dictionary, Kitāb al-'Ayn ( كتاب العين "The Book of the Letter ع "), and

7426-677: Is easy to find with the naked eye. It is one of three stars that make up the Winter Triangle asterism , and it marks the center of the Winter Hexagon . It can be seen rising in the east at the beginning of January of each year, just after sunset. Between mid-September and mid-March (best in mid-December), it is visible to virtually every inhabited region of the globe, except in Antarctica at latitudes south of 82°. In May (moderate northern latitudes) or June (southern latitudes),

7584-544: Is expected to end its evolution with a supernova explosion, most likely within 100,000 years. When Betelgeuse explodes, it will shine as bright as the half-Moon for more than three months; life on Earth will be unharmed. Having been ejected from its birthplace in the Orion OB1 association  – which includes the stars in Orion's Belt  – this runaway star has been observed to be moving through

7742-402: Is generally believed to be a variation in just a portion of the extended atmosphere around Betelgeuse, and observations at other wavelengths have shown an increase in diameter over a similar period. Red supergiant Stars are classified as supergiants on the basis of their spectral luminosity class . This system uses certain diagnostic spectral lines to estimate the surface gravity of

7900-410: Is generally considered to be a single isolated star and a runaway star , not currently associated with any cluster or star-forming region, although its birthplace is unclear. Two spectroscopic companions to Betelgeuse have been proposed. Analysis of polarization data from 1968 through 1983 indicated a close companion with a periodic orbit of about 2.1 years, and by using speckle interferometry ,

8058-550: Is less abundant than either, reflecting abundances from the formation of the star. Carbon and oxygen are quickly depleted and nitrogen enhanced as a result of the dredge-up of CNO-processed material from the fusion layers. Red supergiants are observed to rotate slowly or very slowly. Models indicate that even rapidly rotating main-sequence stars should be braked by their mass loss so that red supergiants hardly rotate at all. Those red supergiants such as Betelgeuse that do have modest rates of rotation may have acquired it after reaching

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8216-526: Is listed in the General Catalogue of Variable Stars with a possible period of 2,335 days. More detailed analyses have shown a main period near 400 days, a short period of 185 days, and a longer secondary period around 2,100 days. The lowest reliably-recorded V-band magnitude of +1.614 was reported in February 2020. Radial pulsations of red supergiants are well-modelled and show that periods of

8374-535: Is negligible, so the classical photosphere can be directly seen; in the mid-infrared the scattering increases once more, causing the thermal emission of the warm atmosphere to increase the apparent diameter. Studies with the IOTA and VLTI published in 2009 brought strong support to the idea of dust shells and a molecular shell (MOLsphere) around Betelgeuse, and yielded diameters ranging from 42.57 to 44.28 mas with comparatively insignificant margins of error. In 2011,

8532-574: Is not present in the spoken varieties, but deletes Classical words that sound obsolete in MSA. In addition, MSA has borrowed or coined many terms for concepts that did not exist in Quranic times, and MSA continues to evolve. Some words have been borrowed from other languages—notice that transliteration mainly indicates spelling and not real pronunciation (e.g., فِلْم film 'film' or ديمقراطية dīmuqrāṭiyyah 'democracy'). The current preference

8690-456: Is now up to 40% but there is little enrichment of heavier elements. The supergiants continue to cool and most will rapidly pass through the Cepheid instability strip , although the most massive will spend a brief period as yellow hypergiants . They will reach late K or M class and become a red supergiant. Helium fusion in the core begins smoothly either while the star is expanding or once it

8848-855: Is official in Mali and recognized as a minority language in Morocco, while the Senegalese government adopted the Latin script to write it. Maltese is official in (predominantly Catholic ) Malta and written with the Latin script . Linguists agree that it is a variety of spoken Arabic, descended from Siculo-Arabic , though it has experienced extensive changes as a result of sustained and intensive contact with Italo-Romance varieties, and more recently also with English. Due to "a mix of social, cultural, historical, political, and indeed linguistic factors", many Maltese people today consider their language Semitic but not

9006-467: Is proposed that this is due to granulation , similar to the same effect on the sun but on a much larger scale. On 13 December 1920, Betelgeuse became the first star outside the Solar System to have the angular size of its photosphere measured. Although interferometry was still in its infancy, the experiment proved a success. The researchers, using a uniform disk model, determined that Betelgeuse had

9164-417: Is rarely seen. More often the designation Ia-0 will be used, and more commonly still Ia . These hypergiant spectral classifications are very rarely applied to red supergiants, although the term red hypergiant is sometimes used for the most extended and unstable red supergiants like VY Canis Majoris and NML Cygni . The "red" part of "red supergiant" refers to the cool temperature. Red supergiants are

9322-400: Is subject to multiple cycles of increasing and decreasing brightness due to changes in its size and temperature. The astronomers who first noted the dimming of Betelgeuse, Villanova University astronomers Richard Wasatonic and Edward Guinan , and amateur Thomas Calderwood, theorize that a coincidence of a normal 5.9 year light-cycle minimum and a deeper-than-normal 425 day period are

9480-572: Is the third most widespread official language after English and French, one of six official languages of the United Nations , and the liturgical language of Islam . Arabic is widely taught in schools and universities around the world and is used to varying degrees in workplaces, governments and the media. During the Middle Ages , Arabic was a major vehicle of culture and learning, especially in science, mathematics and philosophy. As

9638-590: Is the variety used in most current, printed Arabic publications, spoken by some of the Arabic media across North Africa and the Middle East, and understood by most educated Arabic speakers. "Literary Arabic" and "Standard Arabic" ( فُصْحَى fuṣḥá ) are less strictly defined terms that may refer to Modern Standard Arabic or Classical Arabic. Some of the differences between Classical Arabic (CA) and Modern Standard Arabic (MSA) are as follows: MSA uses much Classical vocabulary (e.g., dhahaba 'to go') that

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9796-413: Is to avoid direct borrowings, preferring to either use loan translations (e.g., فرع farʻ 'branch', also used for the branch of a company or organization; جناح janāḥ 'wing', is also used for the wing of an airplane, building, air force, etc.), or to coin new words using forms within existing roots ( استماتة istimātah ' apoptosis ', using the root موت m/w/t 'death' put into

9954-524: Is used to denote concepts that have arisen in the industrial and post-industrial era , especially in modern times. Due to its grounding in Classical Arabic, Modern Standard Arabic is removed over a millennium from everyday speech, which is construed as a multitude of dialects of this language. These dialects and Modern Standard Arabic are described by some scholars as not mutually comprehensible. The former are usually acquired in families, while

10112-445: The Lisān al-ʻArab ). Modern Standard Arabic (MSA) largely follows the grammatical standards of Classical Arabic and uses much of the same vocabulary. However, it has discarded some grammatical constructions and vocabulary that no longer have any counterpart in the spoken varieties and has adopted certain new constructions and vocabulary from the spoken varieties. Much of the new vocabulary

10270-509: The American Association of Variable Star Observers (AAVSO) show a maximum brightness of 0.2 in 1933 and 1942, and a minimum of 1.2, observed in 1927 and 1941. This variability in brightness may explain why Johann Bayer , with the publication of his Uranometria in 1603, designated the star alpha , as it probably rivaled the usually brighter Rigel ( beta ). From Arctic latitudes, Betelgeuse's red colour and higher location in

10428-746: The Ca II triplet . Maser emission is common from the circumstellar material around red supergiants. Most commonly this arises from H 2 O and SiO, but hydroxyl (OH) emission also occurs from narrow regions. In addition to high resolution mapping of the circumstellar material around red supergiants, VLBI or VLBA observations of masers can be used to derive accurate parallaxes and distances to their sources. Currently this has been applied mainly to individual objects, but it may become useful for analysis of galactic structure and discovery of otherwise obscured red supergiant stars. Surface abundances of red supergiants are dominated by hydrogen even though hydrogen at

10586-483: The Cavendish Astrophysics Group , the new technique employed a small mask with several holes in the telescope pupil plane, converting the aperture into an ad hoc interferometric array. The technique contributed some of the most accurate measurements of Betelgeuse while revealing bright spots on the star's photosphere. These were the first optical and infrared images of a stellar disk other than

10744-634: The Orion OB1 association and Antares in the Scorpius–Centaurus association . Since 2006, a series of massive clusters have been identified near the base of the Crux-Scutum Arm of the galaxy, each containing multiple red supergiants. RSGC1 contains at least 12 red supergiants, RSGC2 (also known as Stephenson 2 ) contains at least 26, RSGC3 contains at least 8, and RSGC4 (also known as Alicante 8 ) also contains at least 8. A total of 80 confirmed red supergiants have been identified within

10902-479: The RV Tauri variables , AGB or post-AGB stars lying on the instability strip and showing distinctive semi-regular variations. Red supergiants develop from main-sequence stars with masses between about 8  M ☉ and 30 or 40  M ☉ . Higher-mass stars never cool sufficiently to become red supergiants. Lower-mass stars develop a degenerate helium core during a red giant phase, undergo

11060-485: The Sun , taken first from ground-based interferometers and later from higher-resolution observations of the COAST telescope . The "bright patches" or "hotspots" observed with these instruments appeared to corroborate a theory put forth by Schwarzschild decades earlier of massive convection cells dominating the stellar surface. In 1995, the Hubble Space Telescope 's Faint Object Camera captured an ultraviolet image with

11218-568: The Xth form , or جامعة jāmiʻah 'university', based on جمع jamaʻa 'to gather, unite'; جمهورية jumhūriyyah 'republic', based on جمهور jumhūr 'multitude'). An earlier tendency was to redefine an older word although this has fallen into disuse (e.g., هاتف hātif 'telephone' < 'invisible caller (in Sufism)'; جريدة jarīdah 'newspaper' < 'palm-leaf stalk'). Colloquial or dialectal Arabic refers to

11376-477: The interstellar medium at a speed of 30 km/s , creating a bow shock over four light-years wide. Betelgeuse became the first extrasolar star whose photosphere 's angular size was measured in 1920, and subsequent studies have reported an angular diameter (i.e., apparent size) ranging from 0.042 to 0.056 arcseconds ; that range of determinations is ascribed to non-sphericity, limb darkening , pulsations and varying appearance at different wavelengths . It

11534-494: The northern Hejaz . These features are evidence of common descent from a hypothetical ancestor , Proto-Arabic . The following features of Proto-Arabic can be reconstructed with confidence: On the other hand, several Arabic varieties are closer to other Semitic languages and maintain features not found in Classical Arabic, indicating that these varieties cannot have developed from Classical Arabic. Thus, Arabic vernaculars do not descend from Classical Arabic: Classical Arabic

11692-484: The stellar age and mass . When the first interferometric studies were performed on the star's diameter in 1920, the assumed parallax was 0.0180 ″ . This equated to a distance of 56  pc or roughly 180  ly , producing not only an inaccurate radius for the star but every other stellar characteristic. Since then, there has been ongoing work to measure the distance of Betelgeuse, with proposed distances as high as 400 pc or about 1,300 ly . Before

11850-419: The "learned" tradition (Classical Arabic). This variety and both its classicizing and "lay" iterations have been termed Middle Arabic in the past, but they are thought to continue an Old Higazi register. It is clear that the orthography of the Quran was not developed for the standardized form of Classical Arabic; rather, it shows the attempt on the part of writers to record an archaic form of Old Higazi. In

12008-454: The 11th and 12th centuries in al-Andalus , the zajal and muwashah poetry forms developed in the dialectical Arabic of Cordoba and the Maghreb. The Nahda was a cultural and especially literary renaissance of the 19th century in which writers sought "to fuse Arabic and European forms of expression." According to James L. Gelvin , " Nahda writers attempted to simplify the Arabic language and script so that it might be accessible to

12166-615: The 19th century, before modern systems of stellar classification , Angelo Secchi included Betelgeuse as one of the prototypes for his Class III (orange to red) stars. Three centuries before Ptolemy, in contrast, Chinese astronomers observed Betelgeuse as yellow ; Such an observation, if accurate, could suggest the star was in a yellow supergiant phase around this time, a credible possibility, given current research into these stars' complex circumstellar environment. Aboriginal groups in South Australia have shared oral tales of

12324-571: The 4th to the 6th centuries, the Nabataean script evolved into the Arabic script recognizable from the early Islamic era. There are inscriptions in an undotted, 17-letter Arabic script dating to the 6th century CE, found at four locations in Syria ( Zabad , Jebel Usays , Harran , Umm el-Jimal ). The oldest surviving papyrus in Arabic dates to 643 CE, and it uses dots to produce the modern 28-letter Arabic alphabet. The language of that papyrus and of

12482-834: The 8th century, knowledge of Classical Arabic had become an essential prerequisite for rising into the higher classes throughout the Islamic world, both for Muslims and non-Muslims. For example, Maimonides , the Andalusi Jewish philosopher, authored works in Judeo-Arabic —Arabic written in Hebrew script . Ibn Jinni of Mosul , a pioneer in phonology , wrote prolifically in the 10th century on Arabic morphology and phonology in works such as Kitāb Al-Munṣif , Kitāb Al-Muḥtasab , and Kitāb Al-Khaṣāʾiṣ    [ ar ] . Ibn Mada' of Cordoba (1116–1196) realized

12640-552: The European name. In English, there are four common pronunciations of this name, depending on whether the first e is pronounced short or long and whether the s is pronounced /s/ or /z/ : In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin, issued July 2016, included a table of

12798-503: The Hipparcos parallax measurements for variable stars like Betelgeuse found that the uncertainty of these measurements had been underestimated. In 2007, an improved figure of 6.55 ± 0.83 was calculated, hence a much tighter error factor yielding a distance of roughly 152 ± 20 pc or 500 ± 65 ly . In 2008, measurements using the Very Large Array (VLA) produced a radio solution of 5.07 ± 1.10 mas , equaling

12956-412: The Middle East and North Africa have become a badge of sophistication and modernity and ... feigning, or asserting, weakness or lack of facility in Arabic is sometimes paraded as a sign of status, class, and perversely, even education through a mélange of code-switching practises." Arabic has been taught worldwide in many elementary and secondary schools, especially Muslim schools. Universities around

13114-690: The Qur'an is referred to by linguists as "Quranic Arabic", as distinct from its codification soon thereafter into " Classical Arabic ". In late pre-Islamic times, a transdialectal and transcommunal variety of Arabic emerged in the Hejaz , which continued living its parallel life after literary Arabic had been institutionally standardized in the 2nd and 3rd century of the Hijra , most strongly in Judeo-Christian texts, keeping alive ancient features eliminated from

13272-576: The Romance languages. Also, while it is comprehensible to people from the Maghreb , a linguistically innovative variety such as Moroccan Arabic is essentially incomprehensible to Arabs from the Mashriq , much as French is incomprehensible to Spanish or Italian speakers but relatively easily learned by them. This suggests that the spoken varieties may linguistically be considered separate languages. With

13430-508: The Solar System for comparison, the orbit of Mars is about 1.5 AU , Ceres in the asteroid belt 2.7 AU , Jupiter 5.5 AU —so, assuming Betelgeuse occupying the place of the Sun, its photosphere might extend beyond the Jovian orbit, not quite reaching Saturn at 9.5 AU . The precise diameter has been hard to define for several reasons: The generally reported radii of large cool stars are Rosseland radii , defined as

13588-429: The Sun is below the horizon). Betelgeuse is a variable star whose visual magnitude ranges between 0.0 and +1.6 . There are periods during which it surpasses Rigel to become the sixth brightest star, and occasionally it will become even brighter than Capella . At its faintest, Betelgeuse can fall behind Deneb and Beta Crucis , themselves both slightly variable, to be the twentieth-brightest star. Betelgeuse has

13746-422: The Sun, the outer layers of these hot main-sequence stars are not convective. These pre-red supergiant main-sequence stars exhaust the hydrogen in their cores after 5–20 million years. They then start to burn a shell of hydrogen around the now-predominantly helium core, and this causes them to expand and cool into supergiants. Their luminosity increases by a factor of about three. The surface abundance of helium

13904-633: The Sun, they are so much larger that they are highly luminous, typically tens or hundreds of thousands  L ☉ . There is a theoretical upper limit to the radius of a red supergiant at around 1,500  R ☉ . In the Hayashi limit , stars above this radius would be too unstable and simply do not form. Red supergiants have masses between about 10  M ☉ and 30 or 40  M ☉ . Main-sequence stars more massive than about 40  M ☉ do not expand and cool to become red supergiants. Red supergiants at

14062-637: The VLTI AMBER instrument. In 2009 it was announced that the radius of Betelgeuse had shrunk from 1993 to 2009 by 15%, with the 2008 angular measurement equal to 47.0 mas . Unlike most earlier papers, this study used measurements at one specific wavelength over 15 years. The diminution in Betelgeuse's apparent size equates to a range of values between 56.0 ± 0.1 mas seen in 1993 to 47.0 ± 0.1 mas seen in 2008—a contraction of almost 0.9 AU in 15 years . The observed contraction

14220-489: The approximately V=6 saturation limit of the mission's instruments, actual operation has shown good performance on objects to about magnitude +3. Forced observations of brighter stars mean that final results should be available for all bright stars and a parallax for Betelgeuse will be published an order of magnitude more accurate than currently available. There is no data on Betelgeuse in Gaia Data Release 2 , which

14378-401: The complex circumstellar shells surrounding the supergiant, causing them to suspect the presence of huge gas bubbles resulting from convection. However, it was not until the late 1980s and early 1990s, when Betelgeuse became a regular target for aperture masking interferometry , that breakthroughs occurred in visible-light and infrared imaging . Pioneered by J.E. Baldwin and colleagues of

14536-574: The conversion of Semitic mimation to nunation in the singular. It is best reassessed as a separate language on the Central Semitic dialect continuum. It was also thought that Old Arabic coexisted alongside—and then gradually displaced— epigraphic Ancient North Arabian (ANA), which was theorized to have been the regional tongue for many centuries. ANA, despite its name, was considered a very distinct language, and mutually unintelligible, from "Arabic". Scholars named its variant dialects after

14694-573: The coolest supergiants, M-type, and at least some K-type stars although there is no precise cutoff. K-type supergiants are uncommon compared to M-type because they are a short-lived transition stage and somewhat unstable. The K-type stars, especially early or hotter K types, are sometimes described as orange supergiants (e.g. Zeta Cephei ), or even as yellow (e.g. yellow hypergiant HR 5171 Aa). Red supergiants are cool and large. They have spectral types of K and M, hence surface temperatures below 4,100  K . They are typically several hundred to over

14852-424: The core has been completely consumed. In the latest stages of mass loss, before a star explodes, surface helium may become enriched to levels comparable with hydrogen. In theoretical extreme mass loss models, sufficient hydrogen may be lost that helium becomes the most abundant element at the surface. When pre-red supergiant stars leave the main sequence, oxygen is more abundant than carbon at the surface, and nitrogen

15010-477: The dimming could have come from a short-term minimum coinciding with a long-term minimum producing a grand minimum, a 416-day cycle and 2010 day cycle respectively, a mechanism first suggested by astronomer L. Goldberg . In April 2023, astronomers reported the star reached a peak of 0.0 visual and 0.1 V-band magnitude. As a result of its distinctive orange-red color and position within Orion, Betelgeuse

15168-451: The driving factors. Other possible causes hypothesized by late 2019 were an eruption of gas or dust or fluctuations in the star's surface brightness. By August 2020, long-term and extensive studies of Betelgeuse, primarily using ultraviolet observations by the Hubble Space Telescope , had suggested that the unexpected dimming was probably caused by an immense amount of superhot material ejected into space. The material cooled and formed

15326-418: The electromagnetic spectrum—the visible, near-infrared ( NIR ), mid-infrared (MIR), or radio—produce very different angular measurements. In 1996, Betelgeuse was shown to have a uniform disk of 56.6 ± 1.0 mas . In 2000, a Space Sciences Laboratory team measured a diameter of 54.7 ± 0.3 mas , ignoring any possible contribution from hotspots, which are less noticeable in the mid-infrared. Also included

15484-587: The emergence of Central Semitic languages, particularly in grammar. Innovations of the Central Semitic languages—all maintained in Arabic—include: There are several features which Classical Arabic, the modern Arabic varieties, as well as the Safaitic and Hismaic inscriptions share which are unattested in any other Central Semitic language variety, including the Dadanitic and Taymanitic languages of

15642-728: The eve of the conquests: Northern and Central (Al-Jallad 2009). The modern dialects emerged from a new contact situation produced following the conquests. Instead of the emergence of a single or multiple koines, the dialects contain several sedimentary layers of borrowed and areal features, which they absorbed at different points in their linguistic histories. According to Veersteegh and Bickerton, colloquial Arabic dialects arose from pidginized Arabic formed from contact between Arabs and conquered peoples. Pidginization and subsequent creolization among Arabs and arabized peoples could explain relative morphological and phonological simplicity of vernacular Arabic compared to Classical and MSA. In around

15800-455: The existence of surrounding dust and gas shells would give a diameter of 41.9 mas . To overcome these challenges, researchers have employed various solutions. Astronomical interferometry, first conceived by Hippolyte Fizeau in 1868, was the seminal concept that has enabled major improvements in modern telescopy and led to the creation of the Michelson interferometer in the 1880s, and

15958-607: The fact that they participate in the innovations common to all forms of Arabic. The earliest attestation of continuous Arabic text in an ancestor of the modern Arabic script are three lines of poetry by a man named Garm(')allāhe found in En Avdat, Israel , and dated to around 125 CE. This is followed by the Namara inscription , an epitaph of the Lakhmid king Imru' al-Qays bar 'Amro, dating to 328 CE, found at Namaraa, Syria. From

16116-430: The first successful parallax measurement by Friedrich Bessel in 1838, astronomers have been puzzled by Betelgeuse's apparent distance. Knowledge of the star's distance improves the accuracy of other stellar parameters, such as luminosity that, when combined with an angular diameter, can be used to calculate the physical radius and effective temperature ; luminosity and isotopic abundances can also be used to estimate

16274-489: The first successful measurement of Betelgeuse. Just as human depth perception increases when two eyes instead of one perceive an object, Fizeau proposed the observation of stars through two apertures instead of one to obtain interferences that would furnish information on the star's spatial intensity distribution. The science evolved quickly and multiple-aperture interferometers are now used to capture speckled images , which are synthesized using Fourier analysis to produce

16432-564: The first two batches of names approved by the WGSN, which included Betelgeuse for this star. It is now so entered in the IAU Catalog of Star Names . Betelgeuse and its red coloration have been noted since antiquity ; the classical astronomer Ptolemy described its color as ὑπόκιρρος ( hypókirrhos = more or less orange-tawny), a term later described by a translator of Ulugh Beg 's Zij-i Sultani as rubedo , Latin for "ruddiness". In

16590-510: The fourth most useful language for business, after English, Mandarin Chinese , and French. Arabic is written with the Arabic alphabet , an abjad script that is written from right to left . Arabic is usually classified as a Central Semitic language . Linguists still differ as to the best classification of Semitic language sub-groups. The Semitic languages changed between Proto-Semitic and

16748-531: The ground between May and August because it is too close to the Sun. Before entering its 2020 conjunction with the Sun, Betelgeuse had reached a brightness of +0.4 . Observations with the STEREO-A spacecraft made in June and July 2020 showed that the star had dimmed by 0.5 since the last ground-based observation in April. This is surprising, because a maximum was expected for August/September 2020, and

16906-597: The inclusion of new words into their published standard dictionaries. They also publish old and historical Arabic manuscripts. In 1997, a bureau of Arabization standardization was added to the Educational, Cultural, and Scientific Organization of the Arab League . These academies and organizations have worked toward the Arabization of the sciences, creating terms in Arabic to describe new concepts, toward

17064-613: The language. Software and books with tapes are an important part of Arabic learning, as many of Arabic learners may live in places where there are no academic or Arabic language school classes available. Radio series of Arabic language classes are also provided from some radio stations. A number of websites on the Internet provide online classes for all levels as a means of distance education; most teach Modern Standard Arabic, but some teach regional varieties from numerous countries. The tradition of Arabic lexicography extended for about

17222-604: The late 6th century AD, a relatively uniform intertribal "poetic koine" distinct from the spoken vernaculars developed based on the Bedouin dialects of Najd , probably in connection with the court of al-Ḥīra . During the first Islamic century, the majority of Arabic poets and Arabic-writing persons spoke Arabic as their mother tongue. Their texts, although mainly preserved in far later manuscripts, contain traces of non-standardized Classical Arabic elements in morphology and syntax. Abu al-Aswad al-Du'ali ( c.  603 –689)

17380-420: The latter is taught in formal education settings. However, there have been studies reporting some degree of comprehension of stories told in the standard variety among preschool-aged children. The relation between Modern Standard Arabic and these dialects is sometimes compared to that of Classical Latin and Vulgar Latin vernaculars (which became Romance languages ) in medieval and early modern Europe. MSA

17538-540: The life of a star and only form from relatively uncommon massive stars, so there will generally only be small numbers of red supergiants in each cluster at any one time. The massive Hodge 301 cluster in the Tarantula Nebula contains three. Until the 21st century the largest number of red supergiants known in a single cluster was five in NGC 7419 . Most red supergiants are found singly, for example Betelgeuse in

17696-883: The many national or regional varieties which constitute the everyday spoken language. Colloquial Arabic has many regional variants; geographically distant varieties usually differ enough to be mutually unintelligible , and some linguists consider them distinct languages. However, research indicates a high degree of mutual intelligibility between closely related Arabic variants for native speakers listening to words, sentences, and texts; and between more distantly related dialects in interactional situations. The varieties are typically unwritten. They are often used in informal spoken media, such as soap operas and talk shows , as well as occasionally in certain forms of written media such as poetry and printed advertising. Hassaniya Arabic , Maltese , and Cypriot Arabic are only varieties of modern Arabic to have acquired official recognition. Hassaniya

17854-482: The most likely explanation for the dimming of the star. A study that uses observations at submillimetre wavelengths rules out significant contributions from dust absorption. Instead, large starspots appear to be the cause for the dimming. Followup studies, reported on 31 March 2020 in The Astronomer's Telegram , found a rapid rise in the brightness of Betelgeuse. Betelgeuse is almost unobservable from

18012-782: The need for a lexical injection in Arabic, to suit concepts of the industrial and post-industrial age (such as sayyārah سَيَّارَة 'automobile' or bākhirah باخِرة 'steamship'). In response, a number of Arabic academies modeled after the Académie française were established with the aim of developing standardized additions to the Arabic lexicon to suit these transformations, first in Damascus (1919), then in Cairo (1932), Baghdad (1948), Rabat (1960), Amman (1977), Khartum  [ ar ] (1993), and Tunis (1993). They review language development, monitor new words and approve

18170-448: The next minimum should occur around April 2021. However Betelgeuse's brightness is known to vary irregularly, making predictions difficult. The fading could indicate that another dimming event might occur much earlier than expected. On 30 August 2020, astronomers reported the detection of a second dust cloud emitted from Betelgeuse, and associated with recent substantial dimming (a secondary minimum on 3 August) in luminosity of

18328-471: The night sky at near-infrared wavelengths. Its Bayer designation is α Orionis , Latinised to Alpha Orionis and abbreviated Alpha Ori or α Ori . With a radius between 640 and 764 times that of the Sun, if it were at the center of our Solar System , its surface would lie beyond the asteroid belt and it would engulf the orbits of Mercury , Venus , Earth , and Mars . Calculations of Betelgeuse's mass range from slightly under ten to

18486-424: The one whose sound is heard but whose person remains unseen. Now the term al-hatif is used for a telephone. Therefore, the process of tawleed can express the needs of modern civilization in a manner that would appear to be originally Arabic. In the case of Arabic, educated Arabs of any nationality can be assumed to speak both their school-taught Standard Arabic as well as their native dialects, which depending on

18644-423: The outer layers. All red supergiants will exhaust the helium in their cores within one or two million years and then start to burn carbon. This continues with fusion of heavier elements until an iron core builds up, which then inevitably collapses to produce a supernova. The time from the onset of carbon fusion until the core collapse is no more than a few thousand years. In most cases, core-collapse occurs while

18802-549: The overhaul of Arabic grammar first proposed by Al-Jahiz 200 years prior. The Maghrebi lexicographer Ibn Manzur compiled Lisān al-ʿArab ( لسان العرب , "Tongue of Arabs"), a major reference dictionary of Arabic, in 1290. Charles Ferguson 's koine theory claims that the modern Arabic dialects collectively descend from a single military koine that sprang up during the Islamic conquests; this view has been challenged in recent times. Ahmad al-Jallad proposes that there were at least two considerably distinct types of Arabic on

18960-502: The photosphere. Betelgeuse is the brightest near-infrared source in the sky with a J band magnitude of −2.99; only about 13% of the star's radiant energy is emitted as visible light. If human eyes were sensitive to radiation at all wavelengths, Betelgeuse would appear as the brightest star in the night sky. Catalogues list up to nine faint visual companions to Betelgeuse. They are at distances of about one to four arc-minutes and all are fainter than 10th magnitude. Betelgeuse

19118-596: The possibility of a close companion contributing to the overall flux has never been fully ruled out. High-resolution interferometry of Betelgeuse and its vicinity, far beyond the technology of the 1980s and 1990s, has not detected any companions. A more recent study found that a not yet directly-observed, dust-modulating stellar-mass companion of 1.17 ± 0.7   M ☉ would be the most likely solution for Betelgeuse's 2170-day secondary periodicity, fluctuating radial velocity, moderate radius and low variation in effective temperature. The candidate companion would have

19276-545: The process by which mass is lost remains a mystery. With advances in interferometric methodologies, astronomers may be close to resolving this conundrum. Images released by the European Southern Observatory in July 2009, taken by the ground-based Very Large Telescope Interferometer (VLTI), showed a vast plume of gas extending 30 AU from the star into the surrounding atmosphere. This mass ejection

19434-601: The publication of the Hipparcos Catalogue (1997), there were two slightly conflicting parallax measurements for Betelgeuse. The first, in 1991, gave a parallax of 9.8 ± 4.7  mas , yielding a distance of roughly 102 pc or 330 ly . The second was the Hipparcos Input Catalogue (1993) with a trigonometric parallax of 5 ± 4 mas , a distance of 200 pc or 650 ly . Given this uncertainty, researchers were adopting

19592-571: The radio data also have systematic errors, the Harper solution combines the datasets in the hope of mitigating such errors. An updated result from further observations with ALMA and e-Merlin gives a parallax of 4.51 ± 0.8 mas and a distance of 222 +34 −48 pc or 724 +111 −156 ly. In 2020, new observational data from the space-based Solar Mass Ejection Imager aboard the Coriolis satellite and three different modeling techniques produced

19750-443: The radius of the photosphere at a specific optical depth of two-thirds. This corresponds to the radius calculated from the effective temperature and bolometric luminosity. The Rosseland radius differs from directly measured radii, with corrections for limb darkening and the observation wavelength. For example, a measured angular diameter of 55.6 mas would correspond to a Rosseland mean diameter of 56.2 mas, while further corrections for

19908-402: The ratio of the fundamental to overtone periods gives valuable information about the internal structure of the star and its age. The source of the long secondary periods is unknown, but they cannot be explained by radial pulsations . Interferometric observations of Betelgeuse have shown hotspots that are thought to be created by massive convection cells, a significant fraction of the diameter of

20066-493: The red supergiant can be seen briefly on the western horizon after sunset, reappearing again a few months later on the eastern horizon before sunrise. In the intermediate period (June–July, centered around mid June), it is invisible to the naked eye (visible only with a telescope in daylight), except around midday low in the north in Antarctic regions between 70° and 80° south latitude (during midday twilight in polar night , when

20224-463: The red supergiant stage, perhaps through binary interaction. The cores of red supergiants are still rotating and the differential rotation rate can be very large. Supergiant luminosity classes are easy to determine and apply to large numbers of stars, but they group several very different types of stars into a single category. An evolutionary definition restricts the term supergiant to those massive stars which start core helium fusion without developing

20382-445: The red supergiant state. This depends on the mass, rate of rotation, and chemical makeup of the star. While many red supergiants will not experience a blue loop, some can have several. Temperatures can reach 10,000K at the peak of the blue loop. The exact reasons for blue loops vary in different stars, but they are always related to the helium core increasing as a proportion of the mass of the star and forcing higher mass-loss rates from

20540-410: The region may be mutually unintelligible. Some of these dialects can be considered to constitute separate languages which may have "sub-dialects" of their own. When educated Arabs of different dialects engage in conversation (for example, a Moroccan speaking with a Lebanese), many speakers code-switch back and forth between the dialectal and standard varieties of the language, sometimes even within

20698-458: The same sentence. The issue of whether Arabic is one language or many languages is politically charged, in the same way it is for the varieties of Chinese , Hindi and Urdu , Serbian and Croatian , Scots and English, etc. In contrast to speakers of Hindi and Urdu who claim they cannot understand each other even when they can, speakers of the varieties of Arabic will claim they can all understand each other even when they cannot. While there

20856-456: The sky than Rigel meant the Inuit regarded it as brighter, and one local name was Ulluriajjuaq ("large star"). In 1920, Albert A. Michelson and Francis G. Pease mounted a six-meter interferometer on the front of the 2.5-meter telescope at Mount Wilson Observatory , helped by John August Anderson . The trio measured the angular diameter of Betelgeuse at 0.047 ″ , a figure that resulted in

21014-602: The solar atmosphere. Astronomers saw some major advances in astronomical imaging technology in the 1970s, beginning with Antoine Labeyrie 's invention of speckle interferometry , a process that significantly reduced the blurring effect caused by astronomical seeing . It increased the optical resolution of ground-based telescopes , allowing for more precise measurements of Betelgeuse's photosphere. With improvements in infrared telescopy atop Mount Wilson , Mount Locke , and Mauna Kea in Hawaii, astrophysicists began peering into

21172-458: The sole example of Medieval linguist Abu Hayyan al-Gharnati – who, while a scholar of the Arabic language, was not ethnically Arab – Medieval scholars of the Arabic language made no efforts at studying comparative linguistics, considering all other languages inferior. In modern times, the educated upper classes in the Arab world have taken a nearly opposite view. Yasir Suleiman wrote in 2011 that "studying and knowing English or French in most of

21330-515: The southwestern quadrant 2,000  K hotter than the stellar surface. Subsequent ultraviolet spectra taken with the Goddard High Resolution Spectrograph suggested that the hot spot was one of Betelgeuse's poles of rotation. This would give the rotational axis an inclination of about 20° to the direction of Earth, and a position angle from celestial North of about 55°. In a study published in December 2000,

21488-563: The standardization of these new terms throughout the Arabic-speaking world, and toward the development of Arabic as a world language . This gave rise to what Western scholars call Modern Standard Arabic. From the 1950s, Arabization became a postcolonial nationalist policy in countries such as Tunisia, Algeria, Morocco, and Sudan. Arabic usually refers to Standard Arabic, which Western linguists divide into Classical Arabic and Modern Standard Arabic. It could also refer to any of

21646-456: The star and each emitting 5–10% of the total light of the star. One theory to explain long secondary periods is that they are caused by the evolution of such cells combined with the rotation of the star. Other theories include close binary interactions, chromospheric magnetic activity influencing mass loss, or non-radial pulsations such as g-modes . In addition to the discrete dominant periods, small-amplitude stochastic variations are seen. It

21804-485: The star had shrunk by 15% since 1993 at an increasing rate without a significant diminution in magnitude. Subsequent observations suggest that the apparent contraction may be due to shell activity in the star's extended atmosphere. In addition to the star's diameter, questions have arisen about the complex dynamics of Betelgeuse's extended atmosphere. The mass that makes up galaxies is recycled as stars are formed and destroyed , and red supergiants are major contributors, yet

21962-797: The star is still a red supergiant, the large remaining hydrogen-rich atmosphere is ejected, and this produces a type II supernova spectrum. The opacity of this ejected hydrogen decreases as it cools and this causes an extended delay to the drop in brightness after the initial supernova peak, the characteristic of a Type II-P supernova. The most luminous red supergiants, at near solar metallicity , are expected to lose most of their outer layers before their cores collapse, hence they evolve back to yellow hypergiants and luminous blue variables. Such stars can explode as type II-L supernovae, still with hydrogen in their spectra but not with sufficient hydrogen to cause an extended brightness plateau in their light curves. Stars with even less hydrogen remaining may produce

22120-477: The star showed signs of rebrightening. On 22 February 2020, Betelgeuse may have stopped dimming altogether, all but ending the dimming episode. On 24 February 2020, no significant change in the infrared over the last 50 years was detected; this seemed unrelated to the recent visual fading and suggested that an impending core collapse may be unlikely. Also on 24 February 2020, further studies suggested that occluding "large-grain circumstellar dust " may be

22278-642: The star's diameter was measured with the Infrared Spatial Interferometer (ISI) at mid-infrared wavelengths producing a limb-darkened estimate of 55.2 ± 0.5  mas – a figure entirely consistent with Michelson's findings eighty years earlier. At the time of its publication, the estimated parallax from the Hipparcos mission was 7.63 ± 1.64 mas , yielding an estimated radius for Betelgeuse of 3.6 AU . However, an infrared interferometric study published in 2009 announced that

22436-492: The star. In June 2021, the dust was explained as possibly caused by a cool patch on its photosphere and in August a second independent group confirmed these results. The dust is thought to have resulted from the cooling of gas ejected from the star. An August 2022 study using the Hubble Space Telescope confirmed previous research and suggested the dust could have been created by a surface mass ejection. It conjectured as well that

22594-602: The sun's. Intermediate "super-AGB" stars, around 9  M ☉ , can undergo carbon fusion and may produce an electron capture supernova through the collapse of an oxygen - neon core. Main-sequence stars, burning hydrogen in their cores, with masses between 10 and 30 or 40  M ☉ will have temperatures between about 25,000K and 32,000K and spectral types of early B, possibly very late O. They are already very luminous stars of 10,000–100,000  L ☉ due to rapid CNO cycle fusion of hydrogen and they have fully convective cores. In contrast to

22752-457: The surface, undergo different types of pulsation and variability, and will evolve differently, usually producing a planetary nebula and white dwarf. Most AGB stars will not become supernovae although there is interest in a class of super-AGB stars , those almost massive enough to undergo full carbon fusion, which may produce peculiar supernovae although without ever developing an iron core. One notable group of low mass high luminosity stars are

22910-426: The team concluded that the closer of the two companions was located at 0.06″ ± 0.01″ (≈9 AU) from the main star with a position angle of 273°, an orbit that would potentially place it within the star's chromosphere . The more distant companion was at 0.51″ ± 0.01″ (≈77 AU) with a position angle of 278°. Further studies have found no evidence for these companions or have actively refuted their existence, but

23068-475: The top 10 brightest stars in the sky to outside the top 20, noticeably dimmer than its near neighbor Aldebaran . Mainstream media reports discussed speculation that Betelgeuse might be about to explode as a supernova, but astronomers note that the supernova is expected to occur within approximately the next 100,000 years and is thus unlikely to be imminent. By 17 February 2020, Betelgeuse's brightness had remained constant for about 10 days, and

23226-501: The towns where the inscriptions were discovered (Dadanitic, Taymanitic, Hismaic, Safaitic). However, most arguments for a single ANA language or language family were based on the shape of the definite article, a prefixed h-. It has been argued that the h- is an archaism and not a shared innovation, and thus unsuitable for language classification, rendering the hypothesis of an ANA language family untenable. Safaitic and Hismaic, previously considered ANA, should be considered Old Arabic due to

23384-647: The uncommon type IIb supernova, where there is so little hydrogen remaining that the hydrogen lines in the initial type II spectrum fade to the appearance of a Type Ib supernova. The observed progenitors of type II-P supernovae all have temperatures between 3,500K and 4,400K and luminosities between 10,000  L ☉ and 300,000  L ☉ . This matches the expected parameters of lower mass red supergiants. A small number of progenitors of type II-L and type IIb supernovae have been observed, all having luminosities around 100,000  L ☉ and somewhat higher temperatures up to 6,000K. These are

23542-443: The upper end of the possible mass and luminosity range are the largest known. Their low surface gravities and high luminosities cause extreme mass loss, millions of times higher than the Sun, producing observable nebulae surrounding the star. By the end of their lives red supergiants may have lost a substantial fraction of their initial mass. The more massive supergiants lose mass much more rapidly and all red supergiants appear to reach

23700-690: The variable brightness of Betelgeuse for at least 1,000 years. The variation in Betelgeuse's brightness was described in 1836 by Sir John Herschel in Outlines of Astronomy . From 1836 to 1840, he noticed significant changes in magnitude when Betelgeuse outshone Rigel in October 1837 and again in November 1839. A 10-year quiescent period followed; then in 1849, Herschel noted another short cycle of variability, which peaked in 1852. Later observers recorded unusually high maxima with an interval of years, but only small variations from 1957 to 1967. The records of

23858-536: The work of Martin Schwarzschild and his colleague at Princeton University , Richard Härm. This book disseminated ideas on how to apply computer technologies to create stellar models, while the Stratoscope projects, by taking balloon-borne telescopes above the Earth's turbulence , produced some of the finest images of solar granules and sunspots ever seen, thus confirming the existence of convection in

24016-451: The world have classes that teach Arabic as part of their foreign languages , Middle Eastern studies , and religious studies courses. Arabic language schools exist to assist students to learn Arabic outside the academic world. There are many Arabic language schools in the Arab world and other Muslim countries. Because the Quran is written in Arabic and all Islamic terms are in Arabic, millions of Muslims (both Arab and non-Arab) study

24174-406: Was 43.33 ± 0.04 mas . The study also put forth an explanation as to why varying wavelengths from the visible to mid-infrared produce different diameters: the star is seen through a thick, warm extended atmosphere. At short wavelengths (the visible spectrum) the atmosphere scatters light, thus slightly increasing the star's diameter. At near-infrared wavelengths ( K and L bands ), the scattering

24332-435: Was a theoretical allowance for limb darkening, yielding a diameter of 55.2 ± 0.5 mas . The earlier estimate equates to a radius of roughly 5.6 AU or 1,200  R ☉ , assuming the 2008 Harper distance of 197.0 ± 45 pc , a figure roughly the size of the Jovian orbit of 5.5 AU . In 2004, a team of astronomers working in the near-infrared announced that the more accurate photospheric measurement

24490-481: Was cast millions of miles from the star, and then cooled to form the dust that caused the dimming. The star's designation is α Orionis (Latinised to Alpha Orionis ), given by Johann Bayer in 1603. The traditional name Betelgeuse was derived from the Arabic يد الجوزاء Yad al-Jawzā’ "the hand of al-Jawzā’ [i.e. Orion]". An error in the 13th-century reading of the Arabic initial yā’ ( يـ ) as bā’ ( بـ —a difference in i‘jām ) led to

24648-423: Was equal to the distance between the Sun and Neptune and is one of multiple events occurring in Betelgeuse's surrounding atmosphere. Astronomers have identified at least six shells surrounding Betelgeuse. Solving the mystery of mass loss in the late stages of a star's evolution may reveal those factors that precipitate the explosive deaths of these stellar giants. A pulsating semiregular variable star , Betelgeuse

24806-610: Was released in 2018. Betelgeuse is classified as a semiregular variable star , indicating that some periodicity is noticeable in the brightness changes, but amplitudes may vary, cycles may have different lengths, and there may be standstills or periods of irregularity. It is placed in subgroup SRc; these are pulsating red supergiants with amplitudes around one magnitude and periods from tens to hundreds of days. Betelgeuse typically shows only small brightness changes near to magnitude +0.5, although at its extremes it can become as bright as magnitude 0.0 or as faint as magnitude +1.6. Betelgeuse

24964-491: Was reported still fainter in February in The Astronomer's Telegram at a record minimum of +1.614, noting that the star is currently the "least luminous and coolest" in the 25 years of their studies and also calculating a decrease in radius. Astronomy magazine described it as a "bizarre dimming", and popular speculation inferred that this might indicate an imminent supernova . This dropped Betelgeuse from one of

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