155-539: The Dog Star is a nickname for Sirius , a star in the constellation Canis Major (Greater Dog). Dog Star or Dogstar may also refer to: Sirius Sirius is the brightest star in the night sky . Its name is derived from the Greek word Σείριος (Latin script: Seirios ), meaning lit. 'glowing' or 'scorching'. The star is designated α Canis Majoris , Latinized to Alpha Canis Majoris , and abbreviated α CMa or Alpha CMa . With
310-558: A harat , which in many cases had gates that could be closed off at night or during disturbances. When the traveller Ibn Battuta first came to Cairo in 1326, he described it as the principal district of Egypt. When he passed through the area again on his return journey in 1348, the Black Death was ravaging most major cities. He cited reports of thousands of deaths per day in Cairo. Although Cairo avoided Europe 's stagnation during
465-463: A province , with Cairo as its capital. For this reason, the history of Cairo during Ottoman times is often described as inconsequential, especially in comparison to other time periods. During the 16th and 17th centuries, Cairo still remained an important economic and cultural centre. Although no longer on the spice route, the city facilitated the transportation of Yemeni coffee and Indian textiles , primarily to Anatolia , North Africa , and
620-569: A bright giant). It is still around 25 times more luminous than the Sun. The closest large neighbouring star to Sirius is Procyon, 1.61 parsecs (5.24 ly) away. The Voyager 2 spacecraft, launched in 1977 to study the four giant planets in the Solar System, is expected to pass within 4.3 light-years (1.3 pc) of Sirius in approximately 296,000 years. Sirius is a binary star system consisting of two white stars orbiting each other with
775-618: A centre of the region's political and cultural life, and is titled "the city of a thousand minarets " for its preponderance of Islamic architecture . Cairo's historic center was awarded World Heritage Site status in 1979. Cairo is considered a World City with a "Beta +" classification according to GaWC . Cairo has the oldest and largest film and music industry in the Arab world , as well as Egypt's oldest institution of higher learning, Al-Azhar University . Many international media, businesses, and organizations have regional headquarters in
930-508: A commander of Turkic origin named Bakbak was sent to Egypt by the Abbasid caliph al-Mu'taz to restore order after a rebellion in the country. He was accompanied by his stepson, Ahmad ibn Tulun , who became effective governor of Egypt. Over time, Ibn Tulun gained an army and accumulated influence and wealth, allowing him to become the de facto independent ruler of both Egypt and Syria by 878. In 870, he used his growing wealth to found
1085-468: A distance of 2.6 parsecs (8.6 ly), the Sirius system contains two of the eight nearest stars to the Sun, and it is the fifth closest stellar system to the Sun. This proximity is the main reason for its brightness, as with other near stars such as Alpha Centauri , Procyon and Vega and in contrast to distant, highly luminous supergiants such as Canopus, Rigel or Betelgeuse (although Canopus may be
1240-576: A feature of the city's housing during the later Ottoman period. These apartments were often laid out as multi-story duplexes or triplexes. They were sometimes attached to caravanserais, where the two lower floors were for commercial and storage purposes and the multiple stories above them were rented out to tenants. The oldest partially-preserved example of this type of structure is the Wikala of Amir Qawsun , built before 1341. Residential buildings were in turn organized into close-knit neighbourhoods called
1395-411: A final summary in 1926. He cited not only Ptolemy but also the poet Aratus , the orator Cicero , and general Germanicus all calling the star red, though acknowledging that none of the latter three authors were astronomers, the last two merely translating Aratus's poem Phaenomena . Seneca had described Sirius as being of a deeper red than Mars . It is therefore possible that the description as red
1550-761: A major power in the region and was responsible for repelling the advance of the Mongols (most famously at the Battle of Ain Jalut in 1260) and for eliminating the last Crusader states in the Levant. Despite their military character, the Mamluks were also prolific builders and left a rich architectural legacy throughout Cairo. Continuing a practice started by the Ayyubids, much of the land occupied by former Fatimid palaces
1705-433: A much higher population density than formal housing. By 2009, over 63% of the population of Greater Cairo lived in informal neighbourhoods, even though these occupied only 17% of the total area of Greater Cairo. According to economist David Sims, informal housing has the benefits of providing affordable accommodation and vibrant communities to huge numbers of Cairo's working classes, but it also suffers from government neglect,
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#17327984842841860-447: A neighbourhood of urban villas with gardens and curved streets. The British occupation was intended to be temporary, but it lasted well into the 20th century. Nationalists staged large-scale demonstrations in Cairo in 1919, five years after Egypt had been declared a British protectorate . Nevertheless, this led to Egypt's independence in 1922 . The King Fuad I Edition of the Qur'an
2015-509: A new administrative capital, al-Qata'i ( Arabic : القطائـع , lit. 'the allotments'), to the northeast of Fustat and of al-Askar. The new city included a palace known as the Dar al-Imara , a parade ground known as al-Maydan , a bimaristan (hospital), and an aqueduct to supply water. Between 876 and 879 Ibn Tulun built a great mosque, now known as the Mosque of Ibn Tulun , at
2170-520: A paper and spoke at a meeting of the Royal Society in London in 1760. The existence of other stars changing in brightness gave credibility to the idea that some may change in colour too; Sir John Herschel noted this in 1839, possibly influenced by witnessing Eta Carinae two years earlier. Thomas J.J. See resurrected discussion on red Sirius with the publication of several papers in 1892, and
2325-404: A parallax of nearly 0.4 arcseconds . The Hipparcos parallax for Sirius is only accurate to about ± 0.04 light years , giving a distance of 8.6 light years . Sirius B is generally assumed to be at the same distance. Sirius B has a Gaia Data Release 3 parallax with a much smaller statistical margin of error, giving a distance of 8.709 ± 0.005 light years , but it
2480-571: A period of almost exactly 365.25 days holding it constant relative to the solar year . This rising occurs at Cairo on 19 July ( Julian ), placing it just before the onset of the annual flooding of the Nile during antiquity. Owing to the flood's own irregularity, the extreme precision of the star's return made it important to the ancient Egyptians , who worshipped it as the goddess Sopdet ( Ancient Egyptian : Spdt , "Triangle"; ‹See Tfd› Greek : Σῶθις }, Sō̂this ), guarantor of
2635-476: A political and economic hub for North Africa and the Arab world , with many multinational businesses and organisations, including the Arab League , operating out of the city. In 1979 the historic districts of Cairo were listed as a UNESCO World Heritage Site . In 1992, Cairo was hit by an earthquake causing 545 deaths, injuring 6,512 and leaving around 50,000 people homeless. Cairo's Tahrir Square
2790-410: A real change in the Sirius system over the past two millennia, of which the most widely discussed is the proposal that the white dwarf Sirius B was a red giant as recently as 2000 years ago. Extrinsic theories are concerned with the possibility of transient reddening in an intervening medium through which the star is observed, such as might be caused by dust in the interstellar medium , or by particles in
2945-542: A relative lack of services, and overcrowding. The "formal" city was also expanded. The most notable example was the creation of Madinat Nasr , a huge government-sponsored expansion of the city to the east which officially began in 1959 but was primarily developed in the mid-1970s. Starting in 1977 the Egyptian government established the New Urban Communities Authority to initiate and direct
3100-439: A separation of about 20 AU (roughly the distance between the Sun and Uranus ) and a period of 50.1 years. The brighter component, termed Sirius A, is a main-sequence star of spectral type early A , with an estimated surface temperature of 9,940 K . Its companion, Sirius B, is a star that has already evolved off the main sequence and become a white dwarf. Currently 10,000 times less luminous in
3255-564: A series of demonstrations, marches, acts of civil disobedience, and labour strikes. Millions of protesters from a variety of socio-economic and religious backgrounds demanded the overthrow of the regime of Egyptian President Hosni Mubarak. Despite being predominantly peaceful in nature, the revolution was not without violent clashes between security forces and protesters, with at least 846 people killed and 6,000 injured. The uprising took place in Cairo, Alexandria, and in other cities in Egypt, following
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#17327984842843410-552: A sizeable city existed. The city was important enough that its bishop , Cyrus, participated in the Second Council of Ephesus in 449. The Byzantine-Sassanian War between 602 and 628 caused great hardship and likely caused much of the urban population to leave for the countryside, leaving the settlement partly deserted. The site today remains at the nucleus of the Coptic Orthodox community, which separated from
3565-430: A third star or a planet. An apparent "third star" observed in the 1920s is now believed to be a background object. In 1915, Walter Sydney Adams , using a 60-inch (1.5 m) reflector at Mount Wilson Observatory , observed the spectrum of Sirius B and determined that it was a faint whitish star. This led astronomers to conclude that it was a white dwarf—the second to be discovered. The diameter of Sirius A
3720-401: A third star sufficiently luminous to affect the visible colour of the system in recent millennia is inconsistent with observational evidence. Intrinsic theories may therefore be disregarded. Extrinsic theories based on reddening by interstellar dust are similarly implausible. A transient dust cloud passing between the Sirius system and an observer on Earth would, indeed redden the appearance of
3875-516: A visual apparent magnitude of −1.46, Sirius is almost twice as bright as Canopus , the next brightest star. Sirius is a binary star consisting of a main-sequence star of spectral type A0 or A1 , termed Sirius A, and a faint white dwarf companion of spectral type DA2, termed Sirius B. The distance between the two varies between 8.2 and 31.5 astronomical units as they orbit every 50 years. Sirius appears bright because of its intrinsic luminosity and its proximity to
4030-457: Is 25,200 K. Because there is no internal heat source, Sirius B will steadily cool as the remaining heat is radiated into space over the next two billion years or so. A white dwarf forms after a star has evolved from the main sequence and then passed through a red giant stage. This occurred when Sirius B was less than half its current age, around 120 million years ago. The original star had an estimated 5 M ☉ and
4185-401: Is a poetic metaphor for ill fortune. In 1985, German astronomers Wolfhard Schlosser and Werner Bergmann published an account of an 8th-century Lombardic manuscript, which contains De cursu stellarum ratio by St. Gregory of Tours . The Latin text taught readers how to determine the times of nighttime prayers from positions of the stars, and a bright star described as rubeola ("reddish")
4340-482: Is a relatively low 16 km/s, which does not produce any significant flattening of its disk. This is at marked variance with the similar-sized Vega , which rotates at a much faster 274 km/s and bulges prominently around its equator. A weak magnetic field has been detected on the surface of Sirius A. Stellar models suggest that the star formed during the collapsing of a molecular cloud and that, after 10 million years, its internal energy generation
4495-461: Is another Coptic name for Cairo, although others think that it is rather a name for the Abbasid province capital al-Askar . Ⲕⲁϩⲓⲣⲏ ( Kahi•ree ) is a popular modern rendering of an Arabic name (others being Ⲕⲁⲓⲣⲟⲛ [Kairon] and Ⲕⲁϩⲓⲣⲁ [Kahira]) which is modern folk etymology meaning 'land of sun'. Some argue that it was the name of an Egyptian settlement upon which Cairo was built, but it
4650-521: Is attested in the modern Coptic text Ⲡⲓⲫⲓⲣⲓ ⲛ̀ⲧⲉ ϯⲁⲅⲓⲁ ⲙ̀ⲙⲏⲓ Ⲃⲉⲣⲏⲛⲁ (The Tale of Saint Verina ). Lioui ( Ⲗⲓⲟⲩⲓ Late Coptic: [lɪˈjuːj] ) or Elioui ( Ⲉⲗⲓⲟⲩⲓ Late Coptic: [ælˈjuːj] ) is another name which is descended from the Greek name of Heliopolis ( Ήλιούπολις ). Some argue that Mistram ( Ⲙⲓⲥⲧⲣⲁⲙ Late Coptic: [ˈmɪs.təɾɑm] ) or Nistram ( Ⲛⲓⲥⲧⲣⲁⲙ Late Coptic: [ˈnɪs.təɾɑm] )
4805-565: Is between 200 and 300 million years old. It was originally composed of two bright bluish stars. The initially more massive of these, Sirius B, consumed its hydrogen fuel and became a red giant before shedding its outer layers and collapsing into its current state as a white dwarf around 120 million years ago. Sirius is colloquially known as the " Dog Star ", reflecting its prominence in its constellation , Canis Major (the Greater Dog). The heliacal rising of Sirius marked
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4960-481: Is classed as a type Am star , because the spectrum shows deep metallic absorption lines , indicating an enhancement of its surface layers in elements heavier than helium, such as iron. The spectral type has been reported as A0mA1 Va, which indicates that it would be classified as A1 from hydrogen and helium lines, but A0 from the metallic lines that cause it to be grouped with the Am ;stars. When compared to
5115-515: Is depicted as a white horse. In Chinese astronomy Sirius is known as the star of the "celestial wolf" ( Chinese and Japanese : 天狼 Chinese romanization : Tiānláng; Japanese romanization : Tenrō; Korean and romanization: 천랑 /Cheonrang) in the Mansion of Jǐng (井宿). Many nations among the indigenous peoples of North America also associated Sirius with canines; the Seri and Tohono Oʼodham of
5270-854: Is derived from the Arabic al-Qāhirah ( القاهرة ), meaning 'the Vanquisher' or 'the Conqueror', given by the Fatimid Caliph al-Mu'izz following the establishment of the city as the capital of the Fatimid dynasty. Its full, formal name was al-Qāhirah al-Mu'izziyyah (القاهرة المعزيّة), meaning 'the Vanquisher of al-Mu'izz'. It is also supposedly due to the fact that the planet Mars , known in Arabic by names such as an-Najm al-Qāhir ( النجم القاهر , 'the Conquering Star'),
5425-437: Is dominated by wide boulevards, open spaces, and modern architecture of European influence, the eastern half, having grown haphazardly over the centuries, is dominated by small lanes, crowded tenements, and Islamic architecture . Northern and extreme eastern parts of Cairo, which include satellite towns , are among the most recent additions to the city, as they developed in the late-20th and early-21st centuries to accommodate
5580-568: Is either a calque meaning 'man breaker' ( Ϯ- , 'the', ⲕⲁϣ- , 'to break', and ⲣⲱⲙⲓ , 'man'), akin to Arabic al-Qāhirah , or a derivation from Arabic قَصْر الرُوم ( qaṣr ar-rūm , "the Roman castle"), another name of Babylon Fortress in Old Cairo . The Arabic name is also calqued as ⲧⲡⲟⲗⲓⲥ ϯⲣⲉϥϭⲣⲟ , "the victor city" in the Coptic antiphonary. The form Khairon ( Coptic : ⲭⲁⲓⲣⲟⲛ )
5735-454: Is flagged as having a very large value for astrometric excess noise, which indicates that the parallax value may be unreliable. In a letter dated 10 August 1844, the German astronomer Friedrich Wilhelm Bessel deduced from changes in the proper motion of Sirius that it had an unseen companion. On 31 January 1862, American telescope-maker and astronomer Alvan Graham Clark first observed
5890-548: Is informally referred to as Cairo by people from Alexandria ( IPA: [ˈkæjɾo] ; Egyptian Arabic : كايرو ). The area around present-day Cairo had long been a focal point of Ancient Egypt due to its strategic location at the junction of the Nile Valley and the Nile Delta regions (roughly Upper Egypt and Lower Egypt ), which also placed it at the crossing of major routes between North Africa and
6045-533: Is now so entered in the IAU Catalog of Star Names. Sirius has over 50 other designations and names attached to it. In Geoffrey Chaucer 's essay Treatise on the Astrolabe , it bears the name Alhabor and is depicted by a hound's head. This name is widely used on medieval astrolabes from Western Europe. In Sanskrit it is known as Mrgavyadha "deer hunter", or Lubdhaka "hunter". As Mrgavyadha,
6200-516: Is now sometimes known as Sirius A. Since 1894, some apparent orbital irregularities in the Sirius system have been observed, suggesting a third very small companion star, but this has never been confirmed. The best fit to the data indicates a six-year orbit around Sirius A and a mass of 0.06 M ☉ . This star would be five to ten magnitudes fainter than the white dwarf Sirius B, which would make it difficult to observe. Observations published in 2008 were unable to detect either
6355-470: Is rather doubtful as this name is not attested in any Hieroglyphic or Demotic source, although some researchers, like Paul Casanova, view it as a legitimate theory. Cairo is also referred to as Ⲭⲏⲙⲓ ( Late Coptic: [ˈkɪ.mi] ) or Ⲅⲩⲡⲧⲟⲥ ( Late Coptic: [ˈɡɪp.dos] ), which means Egypt in Coptic, the same way it is referred to in Egyptian Arabic. Sometimes the city
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6510-400: Is sparse and only happens in the colder months, but sudden showers can cause severe flooding. The summer months have high humidity due to its coastal location. Snowfall is extremely rare; a small amount of graupel , widely believed to be snow , fell on Cairo's easternmost suburbs on 13 December 2013, the first time Cairo's area received this kind of precipitation in many decades. Dew points in
6665-703: Is the capital and largest city of Egypt and the Cairo Governorate , being home to more than 10 million people. It is also part of the largest urban agglomeration in Africa , the Arab world and the Middle East . The Greater Cairo metropolitan area is the 12th-largest in the world by population with over 22.1 million people. Cairo is associated with ancient Egypt , as the Giza pyramid complex and
6820-695: Is the bright star, named Mirzam Al-Jawza' (Sirius), which a group of Arabs used to worship". The alternate name Aschere , used by Johann Bayer , is derived from this. In theosophy , it is believed the Seven Stars of the Pleiades transmit the spiritual energy of the Seven Rays from the Galactic Logos to the Seven Stars of the Great Bear , then to Sirius. From there is it sent via
6975-479: Is visible from almost everywhere on Earth, except latitudes north of 73° N , and it does not rise very high when viewed from some northern cities (reaching only 13° above the horizon from Saint Petersburg ). Because of its declination of roughly −17°, Sirius is a circumpolar star from latitudes south of 73° S . From the Southern Hemisphere in early July, Sirius can be seen in both
7130-517: The Balkans . Cairene merchants were instrumental in bringing goods to the barren Hejaz , especially during the annual hajj to Mecca . It was during this same period that al-Azhar University reached the predominance among Islamic schools that it continues to hold today; pilgrims on their way to hajj often attested to the superiority of the institution, which had become associated with Egypt's body of Islamic scholars . The first printing press of
7285-631: The Belgian industrialist Édouard Empain and his Egyptian counterpart Boghos Nubar , built a suburb called Heliopolis (city of the sun in Greek) ten kilometers from the center of Cairo. In 1905–1907 the northern part of the Gezira island was developed by the Baehler Company into Zamalek , which would later become Cairo's upscale "chic" neighbourhood. In 1906 construction began on Garden City,
7440-625: The Bering Strait called it "Moon Dog". Several cultures also associated the star with a bow and arrows. The ancient Chinese visualized a large bow and arrow across the southern sky, formed by the constellations of Puppis and Canis Major. In this, the arrow tip is pointed at the wolf Sirius. A similar association is depicted at the Temple of Hathor in Dendera , where the goddess Satet has drawn her arrow at Hathor (Sirius). Known as "Tir",
7595-545: The British invasion in 1882. The city's economic centre quickly moved west toward the Nile , away from the historic Islamic Cairo section and toward the contemporary, European-style areas built by Isma'il. Europeans accounted for five percent of Cairo's population at the end of the 19th century, by which point they held most top governmental positions. In 1906 the Heliopolis Oasis Company headed by
7750-514: The Cape of Good Hope (4 seconds); by Piazzi (the same amount); using Lacaille's observations made at Paris , more numerous and certain than those made at the Cape (no sensible parallax); by Bessel (no sensible parallax). Scottish astronomer Thomas Henderson used his observations made in 1832–1833 and South African astronomer Thomas Maclear 's observations made in 1836–1837, to determine that
7905-520: The Hyades and the Pleiades , and each of these clusters consists of hundreds of stars. In 2017, a massive star cluster was discovered only 10 arcminutes from Sirius, making the two appear to be visually close to one other when viewed from the point of view of the Earth . It was discovered during a statistical analysis of Gaia data. The cluster is over a thousand times further away from us than
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#17327984842848060-475: The Khalij , continued to be a major feature of Cairo's geography and of its water supply until the 19th century. In 861, on the orders of the Abbasid caliph al-Mutawakkil , a Nilometer was built on Roda Island near Fustat. Although it was repaired and given a new roof in later centuries, its basic structure is still preserved today, making it the oldest preserved Islamic-era structure in Cairo today. In 868
8215-551: The Late Middle Ages , it could not escape the Black Death, which struck the city more than fifty times between 1348 and 1517. During its initial, and most deadly waves, approximately 200,000 people were killed by the plague, and, by the 15th century, Cairo's population had been reduced to between 150,000 and 300,000. The population decline was accompanied by a period of political instability between 1348 and 1412. It
8370-724: The Levant . Memphis , the capital of Egypt during the Old Kingdom and a major city up until the Ptolemaic period , was located a short distance south west of present-day Cairo. Heliopolis , another important city and major religious center, was located in what are now the modern districts of Matariya and Ain Shams in northeastern Cairo. It was largely destroyed by the Persian invasions in 525 BC and 343 BC and partly abandoned by
8525-509: The Mamluks and Ottomans further contributed to expansion on the east bank of the river. Because of the Nile's movement, the newer parts of the city— Garden City , Downtown Cairo , and Zamalek—are located closest to the riverbank. The areas, which are home to most of Cairo's embassies , are surrounded on the north, east, and south by the older parts of the city. Old Cairo , located south of
8680-521: The Mamluks , partly with the help of al-Salih's wife, Shajar ad-Durr , who ruled for a brief period around this time. Mamluks were soldiers who were purchased as young slaves and raised to serve in the sultan's army. Between 1250 and 1517 the throne of the Mamluk Sultanate passed from one mamluk to another in a system of succession that was generally non-hereditary, but also frequently violent and chaotic. The Mamluk Empire nonetheless became
8835-824: The Marquesas Islands , Rehua in New Zealand, and Ta'urua-fau-papa "Festivity of original high chiefs" and Ta'urua-e-hiti-i-te-tara-te-feiai "Festivity who rises with prayers and religious ceremonies" in Tahiti. In 1717, Edmond Halley discovered the proper motion of the hitherto presumed fixed stars after comparing contemporary astrometric measurements with those from the second century AD given in Ptolemy's Almagest . The bright stars Aldebaran , Arcturus and Sirius were noted to have moved significantly; Sirius had progressed about 30 arcminutes (about
8990-464: The Shi'a Isma'ili Fatimid empire conquered Egypt after ruling from Ifriqiya. The Fatimid general Jawhar Al Saqili founded a new fortified city northeast of Fustat and of former al-Qata'i. It took four years to build the city, initially known as al-Manṣūriyyah, which was to serve as the new capital of the caliphate. During that time, the construction of the al-Azhar Mosque was commissioned by order of
9145-459: The Solar System . At a distance of 2.64 parsecs (8.6 ly ), the Sirius system is one of Earth's nearest neighbours . Sirius is gradually moving closer to the Solar System; it is expected to increase in brightness slightly over the next 60,000 years to reach a peak magnitude of −1.68. Coincidentally, at about the same time, Sirius will take its turn as the southern Pole Star, around
9300-549: The Tunisian revolution that resulted in the overthrow of the long-time Tunisian president Zine El Abidine Ben Ali . On 11 February, following weeks of determined popular protest and pressure, Hosni Mubarak resigned from office. Under the rule of President el-Sisi , in March 2015 plans were announced for another yet-unnamed planned city to be built further east of the existing satellite city of New Cairo , intended to serve as
9455-745: The flooding of the Nile in Ancient Egypt and the " dog days " of summer for the ancient Greeks , while to the Polynesians , mostly in the Southern Hemisphere, the star marked winter and was an important reference for their navigation around the Pacific Ocean. As the brightest star in the night sky, Sirius appears in some of the earliest astronomical records. Its displacement from the ecliptic causes its heliacal rising to be remarkably regular compared to other stars, with
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#17327984842849610-579: The new capital of Egypt . Cairo is located in northern Egypt , known as Lower Egypt , 165 km (100 mi) south of the Mediterranean Sea and 120 km (75 mi) west of the Gulf of Suez and Suez Canal . The city lies along the Nile River , immediately south of the point where the river leaves its desert-bound valley and branches into the low-lying Nile Delta region. Although
9765-612: The precession of the equinoxes . At the time of the introduction of the Gregorian calendar in the year 1582, its culmination occurred 17 minutes before midnight into the new year under the assumption of a constant motion. According to Richard Hinckley Allen its midnight culmination was celebrated at the Temple of Demeter at Eleusis . Cairo Cairo ( / ˈ k aɪ r oʊ / KY -roh ; Arabic : القاهرة , romanized : al-Qāhirah , Egyptian Arabic pronunciation: [el.qɑ(ː)ˈheɾɑ] )
9920-400: The sacred texts of the Avesta , the Avestan language Tishtrya followed by the version Tir in Middle and New Persian is also depicted in the Persian epic Shahnameh of Ferdowsi . Because of the concept of the yazatas , powers which are "worthy of worship", Tishtrya is a divinity of rain and fertility and an antagonist of apaosha , the demon of drought. In this struggle, Tishtrya
10075-401: The terrestrial atmosphere . The possibility that stellar evolution of either Sirius A or Sirius B could be responsible for the discrepancy has been rejected on the grounds that the timescale of thousands of years is orders of magnitude too short and that there is no sign of the nebulosity in the system that would be expected had such a change taken place. Similarly, the presence of
10230-467: The "Faruq edition" in honour of then ruler, King Faruq . British troops remained in the country until 1956. During this time, urban Cairo, spurred by new bridges and transport links, continued to expand to include the upscale neighbourhoods of Garden City, Zamalek, and Heliopolis. Between 1882 and 1937, the population of Cairo more than tripled—from 347,000 to 1.3 million —and its area increased from 10 to 163 km (4 to 63 sq mi). The city
10385-403: The "dog days", the hottest days of the summer. The Romans knew these days as dies caniculares , and the star Sirius was called Canicula, "little dog". The excessive panting of dogs in hot weather was thought to place them at risk of desiccation and disease. In extreme cases, a foaming dog might have rabies, which could infect and kill humans they had bitten. Homer , in the Iliad , describes
10540-405: The 20th century Cairo continue to grow enormously in both population and area. Between 1947 and 2006 the population of Greater Cairo went from 2,986,280 to 16,292,269. The population explosion also drove the rise of "informal" housing ( 'ashwa'iyyat ), meaning housing that was built without any official planning or control. The exact form of this type of housing varies considerably but usually has
10695-406: The 7th century BC in Hesiod 's poetic work Works and Days . 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 of July 2016 included a table of the first two batches of names approved by the WGSN, which included Sirius for the star α Canis Majoris A. It
10850-399: The Albanians, and the long-weakened Mamluks jostling for control of the country. Continued civil war allowed an Albanian named Muhammad Ali Pasha to ascend to the role of commander and eventually, with the approval of the religious establishment , viceroy of Egypt in 1805. Until his death in 1848, Muhammad Ali Pasha instituted a number of social and economic reforms that earned him
11005-401: The Cairo metropolis extends away from the Nile in all directions, the city of Cairo resides only on the east bank of the river and two islands within it on a total area of 453 km (175 sq mi). Geologically, Cairo lies on alluvium and sand dunes which date from the quaternary period. Until the mid-19th century, when the river was tamed by dams, levees, and other controls,
11160-607: The Citadel, Saladin also began the construction of a new 20-kilometre-long wall that would protect both Cairo and Fustat on their eastern side and connect them with the new Citadel. These construction projects continued beyond Saladin's lifetime and were completed under his Ayyubid successors. In 1250, during the Seventh Crusade , the Ayyubid dynasty had a crisis with the death of al-Salih and power transitioned instead to
11315-479: The Earth's atmosphere are better supported by available evidence. Scintillations caused by atmospheric turbulence result in rapid, transient changes in the apparent colour of the star, especially when observed near the horizon, although with no particular preference for red. However, systematic reddening of the star's light results from absorption and scattering by particles in the atmosphere, exactly analogous to
11470-531: The Earth's night sky for approximately the next 210,000 years, at which point Vega , another A-type star that is intrinsically more luminous than Sirius, becomes the brightest star. Sirius A is about twice as massive as the Sun ( M ☉ ) and has an absolute visual magnitude of +1.43. It is 25 times as luminous as the Sun , but has a significantly lower luminosity than other bright stars such as Canopus, Betelgeuse , or Rigel . The system
11625-637: The Hubble Space Telescope ruled out the existence of a stellar mass sized Sirius C, while still allowing a substellar mass candidate such as a lower mass Brown dwarf . The 1995 study predicted an astrometric movement of roughly 90 mas (0.09 arcsecond), but Hubble was unable to detect any location anomaly to an accuracy of 5 mas (0.005 arcsec). This ruled out any objects orbiting Sirius A with more than 0.033 solar mass (35 Jupiter masses) in 0.5 years, and 0.014 (15 Jupiter masses) in 2 years. The study
11780-690: The Middle East, printing in Hebrew , was established in Cairo c. 1557 by a scion of the Soncino family of printers, Italian Jews of Ashkenazi origin who operated a press in Constantinople. The existence of the press is known solely from two fragments discovered in the Cairo Geniza . Under the Ottomans, Cairo expanded south and west from its nucleus around the Citadel. The city
11935-525: The Nile Corniche , and improved the city's network of bridges and highways. Meanwhile, additional controls of the Nile fostered development within Gezira Island and along the city's waterfront. The metropolis began to encroach on the fertile Nile Delta , prompting the government to build desert satellite towns and devise incentives for city-dwellers to move to them. In the second half of
12090-472: The Nile in the vicinity of Cairo was highly susceptible to changes in course and surface level. Over the years, the Nile gradually shifted westward, providing the site between the eastern edge of the river and the Mokattam highlands on which the city now stands. The land on which Cairo was established in 969 (present-day Islamic Cairo ) was located underwater just over three hundred years earlier, when Fustat
12245-645: The Polynesian night sky into two hemispheres. Just as the appearance of Sirius in the morning sky marked summer in Greece, it marked the onset of winter for the Māori , whose name Takurua described both the star and the season. Its culmination at the winter solstice was marked by celebration in Hawaii , where it was known as Ka'ulua , "Queen of Heaven". Many other Polynesian names have been recorded, including Tau-ua in
12400-518: The Roman and Byzantine churches in the late 4th century. Cairo's oldest extant churches, such as the Church of Saint Barbara and the Church of Saints Sergius and Bacchus (from the late 7th or early 8th century), are located inside the fortress walls in what is now known as Old Cairo or Coptic Cairo . The Muslim conquest of Byzantine Egypt was led by Amr ibn al-As from 639 to 642. Babylon Fortress
12555-583: The Roman period, mapped the stars in Books ;VII and VIII of his Almagest , in which he used Sirius as the location for the globe's central meridian. He described Sirius as reddish, along with five other stars, Betelgeuse , Antares , Aldebaran , Arcturus , and Pollux , all of which are at present observed to be of orange or red hue. The discrepancy was first noted by amateur astronomer Thomas Barker , squire of Lyndon Hall in Rutland , who prepared
12710-589: The Sun to the god of Earth ( Sanat Kumara ), and finally through the seven Masters of the Seven Rays to the human race. The midnight culmination of Sirius in the northern hemisphere coincides with the beginning of the New Year of the Gregorian calendar during the decades around the year 2000. Over the years, its midnight culmination moves slowly, owing to the combination of the star's proper motion and
12865-415: The Sun's, has an age that is only half this, making it too young to belong to the group. Sirius may instead be a member of the proposed Sirius Supercluster, along with other scattered stars such as Beta Aurigae , Alpha Coronae Borealis , Beta Crateris , Beta Eridani and Beta Serpentis . This would be one of three large clusters located within 500 light-years (150 pc) of the Sun. The other two are
13020-419: The Sun, the proportion of iron in the atmosphere of Sirius A relative to hydrogen is given by [ Fe H ] = 0.5 , {\displaystyle \textstyle \ \left[{\frac {{\ce {Fe}}}{{\ce {H}}}}\right]=0.5\ ,} meaning iron is 316% as abundant as in the Sun's atmosphere. The high surface content of metallic elements is unlikely to be true of
13175-410: The ancient Polynesians for navigation of the Pacific Ocean. They also served as latitude markers; the declination of Sirius matches the latitude of the archipelago of Fiji at 17°S and thus passes directly over the islands each sidereal day . Sirius served as the body of a "Great Bird" constellation called Manu , with Canopus as the southern wingtip and Procyon the northern wingtip, which divided
13330-610: The ancient cities of Memphis and Heliopolis are located in its geographical area. Located near the Nile Delta , the city first developed as Fustat following the Muslim conquest of Egypt in 641 next to an existing ancient Roman fortress, Babylon . Cairo was founded by the Fatimid dynasty in 969. It later superseded Fustat as the main urban centre during the Ayyubid and Mamluk periods (12th–16th centuries). Cairo has long been
13485-476: The approach of Achilles toward Troy in these words: Sirius rises late in the dark, liquid sky On summer nights, star of stars, Orion's Dog they call it, brightest Of all, but an evil portent, bringing heat And fevers to suffering humanity. In a little-attested Greek myth, the star-god that personified Sirius fell in love with a fertility goddess named Opora , but he was unable to have her. Thus he began to burn hot, making humans suffer, who prayed to
13640-403: The area now composing Downtown Cairo , came to fruition. Isma'il also sought to modernize the city, which was merging with neighbouring settlements, by establishing a public works ministry, bringing gas and lighting to the city, and opening a theatre and opera house. The immense debt resulting from Isma'il's projects provided a pretext for increasing European control, which culminated with
13795-509: The caliph, which developed into the third-oldest university in the world. Cairo would eventually become a centre of learning, with the library of Cairo containing hundreds of thousands of books. When Caliph al-Mu'izz li Din Allah arrived from the old Fatimid capital of Mahdia in Tunisia in 973, he gave the city its present name, Qāhirat al-Mu'izz ("The Vanquisher of al-Mu'izz"), from which
13950-583: The capital of the caliphate in Arabia . Ibn al-As also founded a mosque for the city at the same time, now known as the Mosque of Amr Ibn al-As , the oldest mosque in Egypt and Africa (although the current structure dates from later expansions). In 750, following the overthrow of the Umayyad caliphate by the Abbasids , the new rulers created their own settlement to the northeast of Fustat which became
14105-522: The center of the city, next to the palace. After his death in 884, Ibn Tulun was succeeded by his son and his descendants who continued a short-lived dynasty, the Tulunids . In 905, the Abbasids sent general Muhammad Sulayman al-Katib to re-assert direct control over the country. Tulunid rule was ended and al-Qatta'i was razed to the ground, except for the mosque which remains standing today. In 969,
14260-417: The centre, holds the remnants of Fustat and the heart of Egypt's Coptic Christian community, Coptic Cairo . The Boulaq district, which lies in the northern part of the city, was born out of a major 16th-century port and is now a major industrial centre. The Citadel is located east of the city centre around Islamic Cairo , which dates back to the Fatimid era and the foundation of Cairo. While western Cairo
14415-642: The city walls in stone and constructed the city gates of Bab al-Futuh , Bab al-Nasr , and Bab Zuweila that still stand today. During the Fatimid period Fustat reached its apogee in size and prosperity, acting as a center of craftsmanship and international trade and as the area's main port on the Nile. Historical sources report that multi-story communal residences existed in the city, particularly in its center, which were typically inhabited by middle and lower-class residents. Some of these were as high as seven stories and could house some 200 to 350 people. They may have been similar to Roman insulae and may have been
14570-643: The city's infrastructure and cleanliness. Its economy and politics also became more deeply connected with the wider Mediterranean. Some Mamluk sultans in this period, such as Barbsay (r. 1422–1438) and Qaytbay (r. 1468–1496), had relatively long and successful reigns. After al-Nasir Muhammad, Qaytbay was one of the most prolific patrons of art and architecture of the Mamluk era. He built or restored numerous monuments in Cairo, in addition to commissioning projects beyond Egypt. The crisis of Mamluk power and of Cairo's economic role deepened after Qaytbay. The city's status
14725-597: The city's rapid growth. The western bank of the Nile is commonly included within the urban area of Cairo, but it composes the city of Giza and the Giza Governorate . Giza city has also undergone significant expansion over recent years, and today has a population of 2.7 million. The Cairo Governorate was just north of the Helwan Governorate from 2008 when some Cairo's southern districts, including Maadi and New Cairo , were split off and annexed into
14880-460: The city, from March to May and the air often becomes uncomfortably dry. Winters are mild to warm, while summers are long and hot. High temperatures in winter range from 14 to 22 °C (57 to 72 °F), while night-time lows drop to below 11 °C (52 °F), often to 5 °C (41 °F). In summer, the highs often exceed 31 °C (88 °F) but rarely surpass 40 °C (104 °F), and lows drop to about 20 °C (68 °F). Rainfall
15035-516: The city; the Arab League has had its headquarters in Cairo for most of its existence. Cairo, like many other megacities , suffers from high levels of pollution and traffic. The Cairo Metro , opened in 1987, is the oldest metro system in Africa, and ranks amongst the fifteen busiest in the world, with over 1 billion annual passenger rides. The economy of Cairo was ranked first in the Middle East in 2005, and 43rd globally on Foreign Policy 's 2010 Global Cities Index . The name of Cairo
15190-405: The colour of Sirius preferentially when it was situated low in the sky (and therefore apparently red). In several Mediterranean cultures, the local visibility of Sirius at heliacal rising and setting (whether it appeared bright and clear or dimmed) was thought to have astrological significance and was thus subject to systematic observation and intense interest. Thus Sirius, more than any other star,
15345-441: The development of new planned cities on the outskirts of Cairo, generally established on desert land. These new satellite cities were intended to provide housing, investment, and employment opportunities for the region's growing population as well as to pre-empt the further growth of informal neighbourhoods. As of 2014, about 10% of the population of Greater Cairo lived in the new cities. Concurrently, Cairo established itself as
15500-451: The diameter of the Moon) to the southwest. In 1868, Sirius became the first star to have its velocity measured, the beginning of the study of celestial radial velocities . Sir William Huggins examined the spectrum of the star and observed a red shift . He concluded that Sirius was receding from the Solar System at about 40 km/s. Compared to the modern value of −5.5 km/s, this
15655-457: The entire star; rather the iron-peak and heavy metals are radiatively levitated towards the surface. Sirius B, also known as the Pup Star, is one of the most massive white dwarfs known. With a mass of 1.02 M ☉ , it is almost double the 0.5–0.6 M ☉ average. This mass is packed into a volume roughly equal to the Earth's. The current surface temperature
15810-500: The entrance of a canal connecting the Nile to the Red Sea that was created earlier by emperor Trajan (r. 98–117). Further north of the fortress, near the present-day district of al-Azbakiya , was a port and fortified outpost known as Tendunyas ( Coptic : ϯⲁⲛⲧⲱⲛⲓⲁⲥ ) or Umm Dunayn. While no structures older than the 7th century have been preserved in the area aside from the Roman fortifications, historical evidence suggests that
15965-538: The evening where it sets after the Sun and in the morning where it rises before the Sun. Along with Procyon and Betelgeuse , Sirius forms one of the three vertices of the Winter Triangle to observers in the Northern Hemisphere . Sirius can be observed in daylight with the naked eye under the right conditions. Ideally, the sky should be very clear, with the observer at a high altitude,
16120-553: The faint companion, which is now called Sirius B, or affectionately "the Pup". This happened during testing of an 18.5-inch (470 mm) aperture great refractor telescope for Dearborn Observatory , which was one of the largest refracting telescope lenses in existence at the time, and the largest telescope in the United States. Sirius B's sighting was confirmed on 8 March with smaller telescopes. The visible star
16275-762: The family of the last Fatimid caliph, al-'Āḍid . As the first Sultan of Egypt , Saladin established the Ayyubid dynasty , based in Cairo, and aligned Egypt with the Sunni Abbasids, who were based in Baghdad . In 1176, Saladin began construction on the Cairo Citadel , which was to serve as the seat of the Egyptian government until the mid-19th century. The construction of the Citadel definitively ended Fatimid-built Cairo's status as an exclusive palace-city and opened it up to common Egyptians and to foreign merchants, spurring its commercial development. Along with
16430-472: The fertility of their land. The ancient Greeks observed that the appearance of Sirius as the morning star heralded the hot and dry summer and feared that the star caused plants to wilt, men to weaken, and women to become aroused. Owing to its brightness, Sirius would have been seen to twinkle more in the unsettled weather conditions of early summer. To Greek observers, this signified emanations that caused its malignant influence. Anyone suffering its effects
16585-505: The genesis of present-day Cairo to the foundation of Fustat. The choice of founding a new settlement at this inland location, instead of using the existing capital of Alexandria on the Mediterranean coast, may have been due to the new conquerors' strategic priorities. One of the first projects of the new Muslim administration was to clear and re-open Trajan's ancient canal in order to ship grain more directly from Egypt to Medina ,
16740-488: The gods. The god of the north wind, Boreas , solved the problem by ordering his sons to deliver Opora to Sirius, while he cooled down the earth with blasts of his own cold wind. In Iranian mythology, especially in Persian mythology and in Zoroastrianism , the ancient religion of Persia , Sirius appears as Tishtrya and is revered as the rain-maker divinity (Tishtar of New Persian poetry). Beside passages in
16895-461: The late first century BC. However, the origins of modern Cairo are generally traced back to a series of settlements in the first millennium AD. Around the turn of the fourth century, as Memphis was continuing to decline in importance, the Romans established a large fortress along the east bank of the Nile . The fortress, called Babylon , was built by the Roman emperor Diocletian (r. 285–305) at
17050-532: The mass of Jupiter at 1–2 AU distance, and down to around 4 times the mass of Jupiter at 10 AU distance. Similarly, Lucas and colleagues did not detect any companions around Sirius B. Sirius A, also known as the Dog Star, has a mass of 2.063 M ☉ . The radius of this star has been measured by an astronomical interferometer , giving an estimated angular diameter of 5.936±0.016 mas . The projected rotational velocity
17205-441: The name "Cairo" ( al-Qāhira ) originates. The caliphs lived in a vast and lavish palace complex that occupied the heart of the city. Cairo remained a relatively exclusive royal city for most of this era, but during the tenure of Badr al-Gamali as vizier (1073–1094) the restrictions were loosened for the first time and richer families from Fustat were allowed to move into the city. Between 1087 and 1092 Badr al-Gamali also rebuilt
17360-794: The new governorate, to 2011 when the Helwan Governorate was reincorporated into the Cairo Governorate. According to the World Health Organization , the level of air pollution in Cairo is nearly 12 times higher than the recommended safety level. In Cairo, and along the Nile River Valley, the climate is a hot desert climate ( BWh according to the Köppen climate classification system ). Wind storms can be frequent, bringing Saharan dust into
17515-415: The new provincial capital. This was known as al-Askar ( Arabic : العسكر , lit. 'the camp') as it was laid out like a military camp. A governor's residence and a new mosque were also added, with the latter completed in 786. The Red Sea canal re-excavated in the 7th century was closed by the Abbasid caliph al-Mansur in al-Mansur ( r. 754–775 ), but a part of the canal, known as
17670-480: The prototypes for the rental apartment complexes which became common in the later Mamluk and Ottoman periods. However, in 1168 the Fatimid vizier Shawar set fire to unfortified Fustat to prevent its potential capture by Amalric , the Crusader king of Jerusalem . While the fire did not destroy the city and it continued to exist afterward, it did mark the beginning of its decline. Over the following centuries it
17825-441: The redness of the Sun at sunrise and sunset . Because the particles that cause reddening in the Earth's atmosphere are different (typically much smaller) than those that cause reddening in the interstellar medium, there is far less dimming of the starlight, and in the case of Sirius the change in colour can be seen without the aid of a telescope. There may be cultural reasons to explain why some ancient observers might have reported
17980-408: The reign of the Mamluk sultan al-Nasir Muhammad (1293–1341, with interregnums ), Cairo reached its apogee in terms of population and wealth. By 1340, Cairo had a population of close to half a million, making it the largest city west of China . Multi-story buildings occupied by rental apartments, known as a rab' (plural ribā' or urbu ), became common in the Mamluk period and continued to be
18135-575: The southwest note the star as a dog that follows mountain sheep, while the Blackfoot called it "Dog-face". The Cherokee paired Sirius with Antares as a dog-star guardian of either end of the "Path of Souls". The Pawnee of Nebraska had several associations; the Wolf (Skidi) tribe knew it as the "Wolf Star", while other branches knew it as the "Coyote Star". Further north, the Alaskan Inuit of
18290-591: The standard for modern printings of the Quran for much of the Islamic world. The publication has been called a "terrific success", and the edition has been described as one "now widely seen as the official text of the Qur'an", so popular among both Sunni and Shi'a that the common belief among less well-informed Muslims is "that the Qur'an has a single, unambiguous reading". Minor amendments were made later in 1924 and in 1936 -
18445-415: The star passing overhead, and the Sun low on the horizon. These observing conditions are more easily met in the Southern Hemisphere, owing to the southerly declination of Sirius. The orbital motion of the Sirius binary system brings the two stars to a minimum angular separation of 3 arcseconds and a maximum of 11 arcseconds. At the closest approach, it is an observational challenge to distinguish
18600-538: The star represents Rudra ( Shiva ). The star is referred to as Makarajyoti in Malayalam and has religious significance to the pilgrim center Sabarimala . In Scandinavia , the star has been known as Lokabrenna ("burning done by Loki", or "Loki's torch"). In the astrology of the Middle Ages , Sirius was a Behenian fixed star , associated with beryl and juniper . Its astrological symbol [REDACTED]
18755-573: The star system, but given its size it still appears at magnitude 8.3. The proper name "Sirius" comes from the Latin Sīrius , from the Ancient Greek Σείριος ( Seirios , "glowing" or "scorcher"). The Greek word itself may have been imported from elsewhere before the Archaic period , one authority suggesting a link with the Egyptian god Osiris . The name's earliest recorded use dates from
18910-427: The star to some degree, but reddening sufficient to cause it to appear similar in colour to intrinsically red bright stars such as Betelgeuse and Arcturus would also dim the star by several magnitudes, inconsistent with historical accounts: indeed, the dimming would be sufficient to render the colour of the star imperceptible to the human eye without the aid of a telescope. Extrinsic theories based on optical effects in
19065-569: The star was portrayed as the arrow itself in later Persian culture. Sirius is mentioned in Surah , An-Najm ("The Star"), of the Qur'an , where it is given the name الشِّعْرَى (transliteration: aš-ši'rā or ash-shira ; the leader). The verse is: " وأنَّهُ هُوَ رَبُّ الشِّعْرَى ", "That He is the Lord of Sirius (the Mighty Star)." (An-Najm:49) Ibn Kathir said in his commentary "that it
19220-510: The system, which is considered somewhat unusual for a binary star. The Chandra X-ray Observatory image shows Sirius B outshining its partner as an X-ray source. In 2015, Vigan and colleagues used the VLT Survey Telescope to search for evidence of substellar companions, and were able to rule out the presence of giant planets 11 times more massive than Jupiter at 0.5 AU distance from Sirius A, 6–7 times
19375-465: The title of founder of modern Egypt. However, while Muhammad Ali initiated the construction of public buildings in the city, those reforms had minimal effect on Cairo's landscape. Bigger changes came to Cairo under Isma'il Pasha (r. 1863–1879), who continued the modernisation processes started by his grandfather. Drawing inspiration from Paris , Isma'il envisioned a city of maidans and wide avenues; due to financial constraints, only some of them, in
19530-579: The two stars are believed to be too far apart for it to occur, even if Sirius A swells into a red giant . Novas , however, may be possible. Since 1894, irregularities have been tentatively observed in the orbits of Sirius A and B with an apparent periodicity of 6–6.4 years. A 1995 study concluded that such a companion likely exists, with a mass of roughly 0.05 solar mass—a small red dwarf or large brown dwarf , with an apparent magnitude of more than 15, and less than 3 arcseconds from Sirius A. In 2017, more accurate astrometric observations by
19685-410: The value of the parallax was 0.23 arcsecond , and error of the parallax was estimated not to exceed a quarter of a second, or as Henderson wrote in 1839, "On the whole we may conclude that the parallax of Sirius is not greater than half a second in space; and that it is probably much less." Astronomers adopted a value of 0.25 arcsecond for much of the 19th century. It is now known to have
19840-433: The visual spectrum, Sirius B was once the more massive of the two. The age of the system has been estimated at 230 million years. Early in its life, it is thought to have been two bluish-white stars orbiting each other in an elliptical orbit every 9.1 years. The system emits a higher than expected level of infrared radiation , as measured by IRAS space-based observatory. This might be an indication of dust in
19995-432: The white dwarf from its more luminous companion, requiring a telescope with at least 300 mm (12 in) aperture and excellent seeing conditions. After a periastron occurred in 1994, the pair moved apart, making them easier to separate with a telescope. Apoastron occurred in 2019, but from the Earth's vantage point, the greatest observational separation occurred in 2023, with an angular separation of 11.333″. At
20150-448: The year 66,270 AD. In that year, Sirius will come to within 1.6 degrees of the south celestial pole. This is due to axial precession and proper motion of Sirius itself which moves slowly in the SSW direction, so it will be visible from the southern hemisphere only. After that time, its distance will begin to increase, and it will become fainter, but it will continue to be the brightest star in
20305-608: Was Cairo, the former palace-city, that became the new economic center and attracted migration from Fustat. While the Crusaders did not capture the city in 1168, a continuing power struggle between Shawar, King Amalric, and the Zengid general Shirkuh led to the downfall of the Fatimid establishment. In 1169, Shirkuh's nephew Saladin was appointed as the new vizier of Egypt by the Fatimids and two years later he seized power from
20460-412: Was a B-type star (most likely B5V for 5 M ☉ ) when it was still on the main sequence, potentially burning around 600–1200 times more luminous than the sun. While it passed through the red giant stage, Sirius B may have enriched the metallicity of its companion, explaining the very high metallicity of Sirius A. This star is primarily composed of a carbon–oxygen mixture that
20615-657: Was a member of the Ursa Major Moving Group , based on his observations of the system's movements across the sky. The Ursa Major Group is a set of 220 stars that share a common motion through space. It was once a member of an open cluster , but has since become gravitationally unbound from the cluster. Analyses in 2003 and 2005 found Sirius's membership in the group to be questionable: the Ursa Major Group has an estimated age of 500 ± 100 million years, whereas Sirius, with metallicity similar to
20770-414: Was also able to rule out any companions to Sirius B with more than 0.024 solar mass (25 Jupiter masses) orbiting in 0.5 year, and 0.0095 (10 Jupiter masses) orbiting in 1.8 years. Effectively, there are almost certainly no additional bodies in the Sirius system larger than a small brown dwarf or large exoplanet. In 1909, Ejnar Hertzsprung was the first to suggest that Sirius
20925-551: Was an overestimate and had the wrong sign; the minus sign (−) means that it is approaching the Sun. In his 1698 book, Cosmotheoros , Christiaan Huygens estimated the distance to Sirius at 27,664 times the distance from the Earth to the Sun (about 0.437 light-year, translating to a parallax of roughly 7.5 arcseconds). There were several unsuccessful attempts to measure the parallax of Sirius: by Jacques Cassini (6 seconds); by some astronomers (including Nevil Maskelyne ) using Lacaille 's observations made at
21080-460: Was at the height of Mamluk—and Cairene—influence in the mid-14th century. The French occupation was short-lived as British and Ottoman forces, including a sizeable Albanian contingent, recaptured the country in 1801. Cairo itself was besieged by a British and Ottoman force culminating with the French surrender on 22 June 1801. The British vacated Egypt two years later, leaving the Ottomans,
21235-574: Was besieged in September 640 and fell in April 641. In 641 or early 642, after the surrender of Alexandria (the Egyptian capital at the time), he founded a new settlement next to Babylon Fortress. The city, known as Fustat ( Arabic : الفسطاط , romanized : al-Fusṭāṭ , lit. 'the tent'), served as a garrison town and as the new administrative capital of Egypt. Historians such as Janet Abu-Lughod and André Raymond trace
21390-416: Was claimed to be Sirius. The authors proposed this as evidence that Sirius B had been a red giant at the time of observation. Other scholars replied that it was likely St. Gregory had been referring to Arcturus . It is notable that not all ancient observers saw Sirius as red. The 1st-century poet Marcus Manilius described it as "sea-blue", as did the 4th-century Avienius . Furthermore, Sirius
21545-491: Was consistently reported as a white star in ancient China: a detailed re-evaluation of Chinese texts from the 2nd century BC up to the 7th century AD concluded that all such reliable sources are consistent with Sirius being white. Nevertheless, historical accounts referring to Sirius as red are sufficiently extensive to lead researchers to seek possible physical explanations. Proposed theories fall into two categories: intrinsic and extrinsic. Intrinsic theories postulate
21700-469: Was derived entirely from nuclear reactions. The core became convective and used the CNO cycle for energy generation. It is calculated that Sirius A will have completely exhausted the store of hydrogen at its core within a billion (10 ) years of its formation, and will then evolve away from the main sequence. It will pass through a red giant stage and eventually become a white dwarf. Sirius A
21855-554: Was devastated during the 1952 riots known as the Cairo Fire or Black Saturday, which saw the destruction of nearly 700 shops, movie theatres, casinos and hotels in downtown Cairo. The British departed Cairo following the Egyptian Revolution of 1952 , but the city's rapid growth showed no signs of abating. Seeking to accommodate the increasing population, President Gamal Abdel Nasser redeveloped Tahrir Square and
22010-456: Was diminished after Vasco da Gama discovered a sea route around the Cape of Good Hope between 1497 and 1499, thereby allowing spice traders to avoid Cairo. Cairo's political influence diminished significantly after the Ottomans defeated Sultan al-Ghuri in the Battle of Marj Dabiq in 1516 and conquered Egypt in 1517. Ruling from Constantinople , Sultan Selim I relegated Egypt to
22165-494: Was first built. Low periods of the Nile during the 11th century continued to add to the landscape of Cairo; a new island, known as Geziret al-Fil , first appeared in 1174, but eventually became connected to the mainland. Today, the site of Geziret al-Fil is occupied by the Shubra district. The low periods created another island at the turn of the 14th century that now composes Zamalek and Gezira . Land reclamation efforts by
22320-513: Was first measured by Robert Hanbury Brown and Richard Q. Twiss in 1959 at Jodrell Bank using their stellar intensity interferometer . In 2005, using the Hubble Space Telescope , astronomers determined that Sirius B has nearly the diameter of the Earth, 12,000 kilometres (7,500 mi), with a mass 102% of the Sun's. Around the year 150 AD, Claudius Ptolemy of Alexandria, an ethnic Greek Egyptian astronomer of
22475-479: Was first published on 10 July 1924 in Cairo under the patronage of King Fuad . The goal of the government of the newly formed Kingdom of Egypt was not to delegitimize the other variant Quranic texts (" qira'at "), but to eliminate errors found in Qur'anic texts used in state schools. A committee of teachers chose to preserve a single one of the canonical qira'at "readings", namely that of the " Ḥafṣ " version, an 8th-century Kufic recitation . This edition has become
22630-449: Was generated by helium fusion in the progenitor star. This is overlaid by an envelope of lighter elements, with the materials segregated by mass because of the high surface gravity. The outer atmosphere of Sirius B is now almost pure hydrogen—the element with the lowest mass—and no other elements are seen in its spectrum. Although Sirius A and B compose a binary system that is reminiscent of those that can undergo Type Ia supernova ,
22785-446: Was listed by Heinrich Cornelius Agrippa . Many cultures have historically attached special significance to Sirius, particularly in relation to dogs . It is often colloquially called the "Dog Star" as the brightest star of Canis Major , the "Great Dog" constellation. Canis Major was classically depicted as Orion 's dog. The Ancient Greeks thought that Sirius's emanations could affect dogs adversely, making them behave abnormally during
22940-480: Was misty or faint then it foretold (or emanated) pestilence. Coins retrieved from the island from the 3rd century BC feature dogs or stars with emanating rays, highlighting Sirius's importance. The Romans celebrated the heliacal setting of Sirius around 25 April, sacrificing a dog, along with incense, wine, and a sheep, to the goddess Robigo so that the star's emanations would not cause wheat rust on wheat crops that year. Bright stars were important to
23095-713: Was nonetheless in this period that the largest Mamluk-era religious monument, the Madrasa-Mosque of Sultan Hasan , was built. In the late 14th century, the Burji Mamluks replaced the Bahri Mamluks as rulers of the Mamluk state, but the Mamluk system continued to decline. Though the plagues returned frequently throughout the 15th century, Cairo remained a major metropolis and its population recovered in part through rural migration . More conscious efforts were conducted by rulers and city officials to redress
23250-449: Was observed and recorded while close to the horizon. Other contemporary cultures, such as Chinese, lacking this tradition, recorded Sirius only as white. With an apparent magnitude of −1.46, Sirius is the brightest star in the night sky , almost twice as bright as the second-brightest star, Canopus . From Earth , Sirius always appears dimmer than Jupiter and Venus , and at certain times also dimmer than Mercury and Mars . Sirius
23405-500: Was rising at the time of the city's founding. Egyptians often refer to Cairo as Maṣr ( IPA: [mɑsˤɾ] ; مَصر ), the Egyptian Arabic name for Egypt itself, emphasizing the city's importance for the country. There are a number of Coptic names for the city. Tikešrōmi ( Coptic : Ϯⲕⲉϣⲣⲱⲙⲓ Late Coptic: [di.kɑʃˈɾoːmi] ) is attested in the 1211 text The Martyrdom of John of Phanijoit and
23560-503: Was said to be "star-struck" ( ἀστροβόλητος , astrobólētos ). It was described as "burning" or "flaming" in literature. The season following the star's reappearance came to be known as the "dog days". The inhabitants of the island of Ceos in the Aegean Sea would offer sacrifices to Sirius and Zeus to bring cooling breezes and would await the reappearance of the star in summer. If it rose clear, it would portend good fortune; if it
23715-492: Was sold and replaced by newer buildings, becoming a prestigious site for the construction of Mamluk religious and funerary complexes. Construction projects initiated by the Mamluks pushed the city outward while also bringing new infrastructure to the centre of the city. Meanwhile, Cairo flourished as a centre of Islamic scholarship and a crossroads on the spice trade route among the civilisations in Afro-Eurasia . Under
23870-421: Was the focal point of the 2011 Egyptian revolution against former president Hosni Mubarak . More than 50,000 protesters first occupied the square on 25 January, during which the area's wireless services were reported to be impaired. In the following days Tahrir Square continued to be the primary destination for protests in Cairo. The uprising was mainly a campaign of non-violent civil resistance, which featured
24025-399: Was the second-largest in the empire, behind Constantinople, and, although migration was not the primary source of Cairo's growth, twenty percent of its population at the end of the 18th century consisted of religious minorities and foreigners from around the Mediterranean . Still, when Napoleon arrived in Cairo in 1798, the city's population was less than 300,000, forty percent lower than it
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