| Arabian Desert ٱلصَّحْرَاء ٱلْعَرَبِيَّة |
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Desert near Sharjah, United Arab Emirates
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Map of the Arabian Desert ecoregion
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| Ecology | |
| Realm | Palearctic |
| Biome | deserts and xeric shrublands |
| Borders |
List
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| Geography | |
| Area | 1,855,470[1] km2 (716,400 mi2) |
| Countries |
List
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| Conservation | |
| Conservation status | critical/endangered[2] |
| Protected | 4.368%[1] |
The Arabian Desert (Arabic: ٱلصَّحْرَاء ٱلْعَرَبِيَّة) is a vast desert wilderness in West Asia that occupies almost the entire Arabian Peninsula with an area of 2,330,000 square kilometers (900,000 sq mi).[3] It stretches from Yemen to the Persian Gulf and Oman to Jordan and Iraq. It is the fourth largest desert in the world and the largest in Asia. At its center is Ar-Rub' al-Khali (The Empty Quarter), one of the largest continuous bodies of sand in the world. It is an extension of the Sahara Desert.[4]
Gazelles, oryx, sand cats, and spiny-tailed lizards are just some of the desert-adapted species that survive in this extreme environment, which features everything from red dunes to deadly quicksand. The climate is mostly dry (the major part receives around 100 mm (3.9 in) of rain per year, but some very rare places receive as little as 50 mm), and temperatures oscillate between very high heat and seasonal night time freezes. It is part of the deserts and xeric shrublands biome and lie in biogeographical realms of the Palearctic (northern part) and Afrotropical (southern part).
The Arabian Desert ecoregion has little biodiversity, although a few endemic plants grow here. Many species, such as the striped hyena, jackal and honey badger, have died out as a result of hunting, habitat destruction, overgrazing by livestock, off-road driving, and human encroachment on their habitat. Other species, such as the Arabian sand gazelle, have been successfully re-introduced and are protected at reserves.
The desert lies mostly in Saudi Arabia and covers most of the country. It extends into neighboring southern Iraq, southern Jordan, central Qatar, most of the Abu Dhabi emirate in the United Arab Emirates, western Oman, and northeastern Yemen. The ecoregion also includes most of the Sinai Peninsula in Egypt and the adjacent Negev desert in southern Israel.[1]
The Rub' al-Khali desert is a sedimentary basin stretching along a south-west to north-east axis across the Arabian Shelf.[5] At an altitude of 1,000 metres (3,300 ft), rock landscapes yield to the Rub' al-Khali, a vast stretch of sand whose extreme southern point crosses the center of Yemen. The sand overlies gravel or gypsum plains and the dunes reach maximum heights of up to 250 m (820 ft). The sands are predominantly silicates, composed of 80 to 90% quartz and the remainder feldspar, whose iron oxide-coated grains color the sands orange, purple, and red.
A corridor of sandy terrain known as the Ad-Dahna desert connects the An-Nafud desert (65,000 km2 or 40,389 square miles) in the north of Saudi Arabia to the Rub' al-Khali in the south-east.[citation needed] The Tuwaiq escarpment is an 800 km (500 mi) arc that includes limestone cliffs, plateaus, and canyons.[citation needed] There are brackish salt flats, including the quicksands of Umm al Samim.[2] The Sharqiya Sands, formerly known as Wahiba Sands of Oman are an isolated sand sea bordering the east coast.[6][7]
The Arabian Desert has a subtropical, hot desert climate, similar to the climate of the Sahara Desert (the world's largest hot desert). The Arabian Desert is actually an extension of the Sahara Desert over the Arabian peninsula.
The climate is mainly dry. Most areas get around 100 mm (3.9 in) of rain per year. Unlike the Sahara Desert—more than half of which is hyperarid (having rainfall of less than 50 mm (2.0 in) per year)—the Arabian Desert has only a few hyperarid areas. These rare driest areas may get only 30 to 40 mm (1.6 in) of rain per year.
The Arabian Desert’s sunshine duration index is very high by global standards: between 2,900 hours (66.2% of daylight hours) and 3,600 hours (82.1% of daylight hours), but typically around 3,400 hours (77.6% of daylight hours). Thus clear-sky conditions with plenty of sunshine prevail over the region throughout the year, and cloudy periods are infrequent. Visibility at ground level is relatively low, despite the brightness of the sun and moon, because of dust and humidity.
Temperatures remain high year round. In the summer, in low-lying areas, average high temperatures are generally over 40 °C (104 °F). In extremely low-lying areas, especially along the Persian Gulf (near sea level), summer temperatures can reach 48 °C (118 °F). Average low temperatures in summer are typically over 20 °C (68 °F) and in the south can sometimes exceed 30 °C (86 °F). Record high temperatures above 50 °C (122 °F) have been reached in many areas of the desert, partly because its overall elevation is relatively low. [citation needed]
The Arabian Desert ecoregion has about 900 species of plants.[8] The Rub'al-Khali has very limited floristic diversity. There are only 37 plant species, 20 recorded in the main body of the sands and 17 around the outer margins. Of these 37 species, one or two are endemic. Vegetation is very diffuse but fairly evenly distributed, with some interruptions of near sterile dunes.[2] Some typical plants are Calligonum crinitum on dune slopes, Cornulaca arabica (saltbush), Salsola stocksii (saltbush), and Cyperus conglomeratus. Other widespread species are Dipterygium glaucum, Limeum arabicum, and Zygophyllum mandavillei. Very few trees are found except at the outer margin (typically Acacia ehrenbergiana and Prosopis cineraria). Other species are a woody perennial Calligonum comosum, and annual herbs such as Danthonia forskallii.[2]
There are 102 native species of mammals.[8] Native mammals include the Arabian oryx (Oryx leucoryx), sand gazelle (Gazella marica), mountain gazelle (G. gazella), Nubian ibex (Capra nubiana), Arabian wolf (Canis lupus arabs), striped hyaena (Hyaena hyaena), caracal (Caracal caracal), sand cat (Felis margarita), red fox (Vulpes vulpes), and Cape hare (Lepus capensis).[2] The Asiatic cheetah[9] and Asiatic lion[10] used to live in the Arabian Desert. The ecoregion is home to 310 bird species.[8]
The area is home to several different cultures, languages, and peoples, with Islam as the predominant faith. The major ethnic group in the region is the Arabs, whose primary language is Arabic.
In the center of the desert lies Riyadh, the capital of Saudi Arabia, with more than 7 million inhabitants.[11] Other large cities, such as Dubai, Abu Dhabi, or Kuwait City, lie on the coast of the Persian Gulf.
Natural resources available in the Arabian Desert include oil, natural gas, phosphates, and sulfur.[citation needed]
Threats to the ecoregion include overgrazing by livestock and feral camels and goats, wildlife poaching, and damage to vegetation by off-road driving.[2]
The conservation status of the desert is critical/endangered. In the UAE, the sand gazelle and Arabian oryx are threatened, and honey badgers, jackals, and striped hyaenas already extirpated.[2]
4.37% of the ecoregion is in protected areas.[1]
Saudi Arabia has established a system of reserves overseen by the National Commission for Wildlife Conservation and Development (NCWCD).[2]
Protected areas in the United Arab Emirates include Al Houbara Protected Area (2492.0 km2), Al Ghadha Protected Area (1087.51 km2), Arabian Oryx Protected Area (5974.47 km2), Ramlah Protected Area (544.44 km2), and Al Beda'a Protected Area (417.0 km2).[12]
|
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| Observation data Epoch J2000 Equinox J2000 |
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|---|---|
| Constellation | Ursa Minor |
| Pronunciation | /pəˈlɛərɪs, -ˈlær-/; UK: /pəˈlɑːrɪs/[1] |
| α UMi A | |
| Right ascension | 02h 31m 49.09s[2] |
| Declination | +89° 15′ 50.8″[2] |
| Apparent magnitude (V) | 1.98[3] (1.86 – 2.13)[4] |
| α UMi B | |
| Right ascension | 02h 30m 41.63s[5] |
| Declination | +89° 15′ 38.1″[5] |
| Apparent magnitude (V) | 8.7[3] |
| Characteristics | |
| α UMi A | |
| Spectral type | F7Ib + F6V[6] |
| U−B color index | 0.38[3] |
| B−V color index | 0.60[3] |
| Variable type | Classical Cepheid[4] |
| α UMi B | |
| Spectral type | F3V[3] |
| U−B color index | 0.01[7] |
| B−V color index | 0.42[7] |
| Variable type | suspected[4] |
| Astrometry | |
| Radial velocity (Rv) | −17[8] km/s |
| Proper motion (μ) | RA: 44.48±0.11[2] mas/yr Dec.: −11.85±0.13[2] mas/yr |
| Parallax (π) | 7.54±0.11 mas[2] |
| Distance | 446.5±1.1 ly (136.90±0.34 pc)[9] |
| Absolute magnitude (MV) | −3.6 (α UMi Aa)[3] 3.6 (α UMi Ab)[3] 3.1 (α UMi B)[3] |
| Position (relative to α UMi Aa) | |
| Component | α UMi Ab |
| Epoch of observation | 2005.5880 |
| Angular distance | 0.172″ |
| Position angle | 231.4° |
| Position (relative to α UMi Aa) | |
| Component | α UMi B |
| Epoch of observation | 2005.5880 |
| Angular distance | 18.217″ |
| Position angle | 230.540° |
| Orbit[9] | |
| Primary | α UMi Aa |
| Companion | α UMi Ab |
| Period (P) | 29.416±0.028 yr |
| Semi-major axis (a) | 0.12955±0.00205" (≥2.90±0.03 AU[10]) |
| Eccentricity (e) | 0.6354±0.0066 |
| Inclination (i) | 127.57±1.22° |
| Longitude of the node (Ω) | 201.28±1.18° |
| Periastron epoch (T) | 2016.831±0.044 |
| Argument of periastron (ω) (primary) |
304.54±0.84° |
| Semi-amplitude (K1) (primary) |
3.762±0.025 km/s |
| Details | |
| α UMi Aa | |
| Mass | 5.13±0.28[9] M☉ |
| Radius | 46.27±0.42[9] R☉ |
| Luminosity (bolometric) | 1,260[11] L☉ |
| Surface gravity (log g) | 2.2[12] cgs |
| Temperature | 6015[7] K |
| Metallicity | 112% solar[13] |
| Rotation | 119 days[6] |
| Rotational velocity (v sin i) | 14[6] km/s |
| Age | 45 - 67?[14][15] Myr |
| α UMi Ab | |
| Mass | 1.316[9] M☉ |
| Radius | 1.04[3] R☉ |
| Luminosity (bolometric) | 3[3] L☉ |
| Age | >500?[15] Myr |
| α UMi B | |
| Mass | 1.39[3] M☉ |
| Radius | 1.38[7] R☉ |
| Luminosity (bolometric) | 3.9[7] L☉ |
| Surface gravity (log g) | 4.3[7] cgs |
| Temperature | 6900[7] K |
| Rotational velocity (v sin i) | 110[7] km/s |
| Age | 1.5?[14][15] Gyr |
| Other designations | |
| Polaris, North Star, Cynosura, Alpha UMi, α UMi, ADS 1477, CCDM J02319+8915 | |
| α UMi A: 1 Ursae Minoris, BD+88°8, FK5 907, GC 2243, HD 8890, HIP 11767, HR 424, SAO 308 | |
| α UMi B: NSV 631, BD+88°7, GC 2226, SAO 305 | |
| Database references | |
| SIMBAD | α UMi A |
| α UMi B | |
Polaris is a star in the northern circumpolar constellation of Ursa Minor. It is designated α Ursae Minoris (Latinized to Alpha Ursae Minoris) and is commonly called the North Star. With an apparent magnitude that fluctuates around 1.98,[3] it is the brightest star in the constellation and is readily visible to the naked eye at night.[16] The position of the star lies less than 1° away from the north celestial pole, making it the current northern pole star. The stable position of the star in the Northern Sky makes it useful for navigation.[17]
Although appearing to the naked eye as a single point of light, Polaris is a triple star system, composed of the primary, a yellow supergiant designated Polaris Aa, in orbit with a smaller companion, Polaris Ab; the pair is almost certainly[14] in a wider orbit with Polaris B. The outer companion B was discovered in August 1779 by William Herschel, with the inner Aa/Ab pair only confirmed in the early 20th century.
As the closest Cepheid variable, Polaris Aa's distance is a foundational part of the cosmic distance ladder. The revised Hipparcos stellar parallax gives a distance to Polaris A of about 432 light-years (ly) (133 parsecs (pc)), while the successor mission Gaia gives a distance of 446.5 ly (136.9 pc) for Polaris B[9][a].
Polaris Aa is an evolved yellow supergiant of spectral type F7Ib with 5.4 solar masses (M☉). It is the first classical Cepheid to have a mass determined from its orbit. The two smaller companions are Polaris B, a 1.39 M☉ F3 main-sequence star orbiting at a distance of 2,400 astronomical units (AU),[18] and Polaris Ab (or P), a very close F6 main-sequence star with a mass of 1.26 M☉.[3] In January 2006, NASA released images, from the Hubble telescope, that showed the three members of the Polaris ternary system.[19][20]
Polaris B can be resolved with a modest telescope. William Herschel discovered the star in August 1779 using a reflecting telescope of his own, one of the best telescopes of the time.[21]
The variable radial velocity of Polaris A was reported by W. W. Campbell in 1899, which suggested this star is a binary system.[22] Since Polaris A is a known cepheid variable, J. H. Moore in 1927 demonstrated that the changes in velocity along the line of sight were due to a combination of the four-day pulsation period combined with a much longer orbital period and a large eccentricity of around 0.6.[23] Moore published preliminary orbital elements of the system in 1929, giving an orbital period of about 29.7 years with an eccentricity of 0.63. This period was confirmed by proper motion studies performed by B. P. Gerasimovič in 1939.[24]
As part of her doctoral thesis, in 1955 E. Roemer used radial velocity data to derive an orbital period of 30.46 y for the Polaris A system, with an eccentricity of 0.64.[25] K. W. Kamper in 1996 produced refined elements with a period of 29.59±0.02 years and an eccentricity of 0.608±0.005.[26] In 2019, a study by R. I. Anderson gave a period of 29.32±0.11 years with an eccentricity of 0.620±0.008.[10]
There were once thought to be two more widely separated components—Polaris C and Polaris D—but these have been shown not to be physically associated with the Polaris system.[18][27]
Polaris Aa, the supergiant primary component, is a low-amplitude population I classical Cepheid variable, although it was once thought to be a type II Cepheid due to its high galactic latitude. Cepheids constitute an important standard candle for determining distance, so Polaris, as the closest such star,[10] is heavily studied. The variability of Polaris had been suspected since 1852; this variation was confirmed by Ejnar Hertzsprung in 1911.[29]
The range of brightness of Polaris is given as 1.86–2.13,[4] but the amplitude has changed since discovery. Prior to 1963, the amplitude was over 0.1 magnitude and was very gradually decreasing. After 1966, it very rapidly decreased until it was less than 0.05 magnitude; since then, it has erratically varied near that range. It has been reported that the amplitude is now increasing again, a reversal not seen in any other Cepheid.[6]
The period, roughly 4 days, has also changed over time. It has steadily increased by around 4.5 seconds per year except for a hiatus in 1963–1965. This was originally thought to be due to secular redward evolution across the Cepheid instability strip, but it may be due to interference between the primary and the first-overtone pulsation modes.[20][30][31] Authors disagree on whether Polaris is a fundamental or first-overtone pulsator and on whether it is crossing the instability strip for the first time or not.[11][31][32]
The temperature of Polaris varies by only a small amount during its pulsations, but the amplitude of this variation is variable and unpredictable. The erratic changes of temperature and the amplitude of temperature changes during each cycle, from less than 50 K to at least 170 K, may be related to the orbit with Polaris Ab.[12]
Research reported in Science suggests that Polaris is 2.5 times brighter today than when Ptolemy observed it, changing from third to second magnitude.[33] Astronomer Edward Guinan considers this to be a remarkable change and is on record as saying that "if they are real, these changes are 100 times larger than [those] predicted by current theories of stellar evolution".
Torres 2023 published a broad historical compilation of radial velocity and photometric data. He concludes that the change in the Cepheid period has reversed and is now decreasing since roughly 2010. Torres notes that TESS data is of limited utility: as a survey telescope, TESS is optimized for dimmer stars than Polaris, so Polaris significantly over-saturates TESS's cameras. Determining an accurate total brightness for Polaris from TESS is extremely difficult, although it remains suitable for timing the period.[34]
Furthermore, apparent irregularities in Polaris Aa's behavior may coincide with the periastron passage of Ab, although imprecision in the data prevents a definitive conclusion.[34] At the Gaia distance, the Aa-Ab closest approach is 6.2 AU; the radius of the primary supergiant is 46 R☉, meaning that the periastron separation is about 29 times its radius. This implies tidal forcing upon Aa's upper atmosphere by Ab. Such binary tidal forcing is known from heartbeat stars, where eccentric periastron approaches cause rich multimode pulsation akin to an electrocardiogram.
Szabados 1992 suggests that, among Cepheids, "phase slips" similar to what happened to Polaris in the mid 1960s are associated with binary systems.[35]
In 2024, researchers led by Nancy Evans at the Harvard & Smithsonian published a study with fresh data on the inner binary using the interferometric CHARA Array. They improved the solution of the orbit: combining CHARA data with previous Hubble data, and in tandem with the Gaia distance of 446±1 light-years, they confirmed the Cepheid radius estimate of 46 R☉ and re-determined its mass at 5.13±0.28 M☉. The corresponding Polaris Ab mass is 1.316±0.028 M☉. Polaris remains overluminous compared to the best Cepheid evolution models, something also seen in V1334 Cygni. Polaris's rapid period change and pulsation amplitude variations are still peculiar compared to other Cepheids, but may be related to the first-overtone pulsations.[9]
Evans et al also tentatively succeeded in imaging features on the surface of Polaris Aa: large bright and dark patches appear in close-up images, changing over time. Follow up imaging campaigns are required to confirm this detection.[9] Polaris's age is difficult to model; current best estimates find the Cepheid to be much younger than the two main sequence components, seemingly enough to exclude a common origin, which would be quite unlikely for a triple star system.[14][15]
Torres 2023 and Evans et al 2024 both suggest that recent literature cautiously agree that Polaris is a first overtone pulsator.[34][9]
Because Polaris lies nearly in a direct line with the Earth's rotational axis above the North Pole, it stands almost motionless in the sky, and all the stars of the northern sky appear to rotate around it. It thus provides a nearly fixed point from which to draw measurements for celestial navigation and for astrometry. The elevation of the star above the horizon gives the approximate latitude of the observer.[16]
In 2018 Polaris was 0.66° (39.6 arcminutes) away from the pole of rotation (1.4 times the Moon disc) and so revolves around the pole in a small circle 1.3° in diameter. It will be closest to the pole (about 0.45 degree, or 27 arcminutes) soon after the year 2100.[37] Because it is so close to the celestial north pole, its right ascension is changing rapidly due to the precession of Earth's axis, going from 2.5h in AD 2000 to 6h in AD 2100. Twice in each sidereal day Polaris's azimuth is true north; the rest of the time it is displaced eastward or westward, and the bearing must be corrected using tables or a rule of thumb. The best approximation[36] is made using the leading edge of the "Big Dipper" asterism in the constellation Ursa Major. The leading edge (defined by the stars Dubhe and Merak) is referenced to a clock face, and the true azimuth of Polaris worked out for different latitudes.
The apparent motion of Polaris towards and, in the future, away from the celestial pole, is due to the precession of the equinoxes.[38] The celestial pole will move away from α UMi after the 21st century, passing close by Gamma Cephei by about the 41st century, moving towards Deneb by about the 91st century.[citation needed]
The celestial pole was close to Thuban around 2750 BCE,[38] and during classical antiquity it was slightly closer to Kochab (β UMi) than to Polaris, although still about 10° from either star.[39] It was about the same angular distance from β UMi as to α UMi by the end of late antiquity. The Greek navigator Pytheas in ca. 320 BC described the celestial pole as devoid of stars. However, as one of the brighter stars close to the celestial pole, Polaris was used for navigation at least from late antiquity, and described as ἀεί φανής (aei phanēs) "always visible" by Stobaeus (5th century), also termed Λύχνος (Lychnos) akin to a burner or lamp and would reasonably be described as stella polaris from about the High Middle Ages and onwards, both in Greek and Latin. On his first trans-Atlantic voyage in 1492, Christopher Columbus had to correct for the "circle described by the pole star about the pole".[40] In Shakespeare's play Julius Caesar, written around 1599, Caesar describes himself as being "as constant as the northern star", although in Caesar's time there was no constant northern star. Despite its relative brightness, it is not, as is popularly believed, the brightest star in the sky.[41]
Polaris was referenced in the classic Nathaniel Bowditch maritime navigation book American Practical Navigator (1802), where it is listed as one of the navigational stars.[42]
The modern name Polaris[43] is shortened from the Neo-Latin stella polaris ("polar star"), coined in the Renaissance when the star had approached the celestial pole to within a few degrees.[44][45]
Gemma Frisius, writing in 1547, referred to it as stella illa quae polaris dicitur ("that star which is called 'polar'"), placing it 3° 8' from the celestial pole.[44][45]
In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[46] 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 Polaris for the star α Ursae Minoris Aa.[47]
In antiquity, Polaris was not yet the closest naked-eye star to the celestial pole, and the entire constellation of Ursa Minor was used for navigation rather than any single star. Polaris moved close enough to the pole to be the closest naked-eye star, even though still at a distance of several degrees, in the early medieval period, and numerous names referring to this characteristic as polar star have been in use since the medieval period. In Old English, it was known as scip-steorra ("ship-star").[citation needed]
In the "Old English rune poem", the T-rune is apparently associated with "a circumpolar constellation", or the planet Mars.[48]
In the Hindu Puranas, it became personified under the name Dhruva ("immovable, fixed").[49]
In the later medieval period, it became associated with the Marian title of Stella Maris "Star of the Sea" (so in Bartholomaeus Anglicus, c. 1270s),[50] due to an earlier transcription error.[51]
An older English name, attested since the 14th century, is lodestar "guiding star", cognate with the Old Norse leiðarstjarna, Middle High German leitsterne.[52]
The ancient name of the constellation Ursa Minor, Cynosura (from the Greek κυνόσουρα "the dog's tail"),[53] became associated with the pole star in particular by the early modern period. An explicit identification of Mary as stella maris with the polar star (Stella Polaris), as well as the use of Cynosura as a name of the star, is evident in the title Cynosura seu Mariana Stella Polaris (i.e. "Cynosure, or the Marian Polar Star"), a collection of Marian poetry published by Nicolaus Lucensis (Niccolo Barsotti de Lucca) in 1655. [citation needed]
Its name in traditional pre-Islamic Arab astronomy was al-Judayy الجدي ("the kid", in the sense of a juvenile goat ["le Chevreau"] in Description des Etoiles fixes),[54] and that name was used in medieval Islamic astronomy as well.[55][56] In those times, it was not yet as close to the north celestial pole as it is now, and used to rotate around the pole.[citation needed]
It was invoked as a symbol of steadfastness in poetry, as "steadfast star" by Spenser. Shakespeare's sonnet 116 is an example of the symbolism of the north star as a guiding principle: "[Love] is the star to every wandering bark / Whose worth's unknown, although his height be taken."[57]
In Julius Caesar, Shakespeare has Caesar explain his refusal to grant a pardon: "I am as constant as the northern star/Of whose true-fixed and resting quality/There is no fellow in the firmament./The skies are painted with unnumbered sparks,/They are all fire and every one doth shine,/But there's but one in all doth hold his place;/So in the world" (III, i, 65–71). Of course, Polaris will not "constantly" remain as the north star due to precession, but this is only noticeable over centuries.[citation needed]
In Inuit astronomy, Polaris is known as Nuutuittuq (syllabics: ᓅᑐᐃᑦᑐᖅ).[58]
In traditional Lakota star knowledge, Polaris is named "Wičháȟpi Owáŋžila". This translates to "The Star that Sits Still". This name comes from a Lakota story in which he married Tȟapȟúŋ Šá Wíŋ, "Red Cheeked Woman". However, she fell from the heavens, and in his grief Wičháȟpi Owáŋžila stared down from "waŋkátu" (the above land) forever.[59]
The Plains Cree call the star in Nehiyawewin: acâhkos êkâ kâ-âhcît "the star that does not move" (syllabics: ᐊᒑᐦᑯᐢ ᐁᑳ ᑳ ᐋᐦᒌᐟ).[60]
In Mi'kmawi'simk the star is named Tatapn.[61]
In the ancient Finnish worldview, the North Star has also been called taivaannapa and naulatähti ("the nailstar") because it seems to be attached to the firmament or even to act as a fastener for the sky when other stars orbit it. Since the starry sky seemed to rotate around it, the firmament is thought of as a wheel, with the star as the pivot on its axis. The names derived from it were sky pin and world pin.[citation needed]
Since Leavitt's discovery of the Cepheid variable period-luminosity relationship, and corresponding utility as a standard candle, the distance to Polaris has been highly sought-after by astronomers. It is the closest Cepheid to Earth, and thus key to calibrating the Cepheid standard candle; Cepheids form the base of the cosmic distance ladder by which to probe the cosmological nature of the universe.[62]
Distance measurement techniques depend on whether or not components A and B are a physical pair, that is, gravitationally bound. If they are, then their estimated distance can be presumed to be equal.[b] Gravitational binding of this pair is well supported by observations, and the presumption of common distance is widely adopted in historical and recent estimates.[64][65][66][26][67][62][14][9]
For most of the 20th century, available observation technologies remained inadequate to precisely measure absolute parallax.[68][62] Instead, the main technique was to use theoretical models of stellar evolution for both main sequence and giant stars, combined with spectroscopic and photometric data to estimate distances. Such modeling relies on theoretical assumptions and guesses, and contains much systematic error and statistical uncertainties in population data. Even by 2013, these techniques were still struggling to achieve even 10% precision in either main sequence[69] or Cepheid[14] modeling.
Further progress was thus limited until the advent of Hipparcos, the first instrument able to engage in all-sky absolute parallax astrometry.[68] Its first data release was in 1997.
| Published | Component | Distance | Source | Notes | |
|---|---|---|---|---|---|
| ly | pc | ||||
| 1966 | B | (359)[c] | (110)[c] | Fernie[64] | Photometry and modeling of B[c] |
| 1977 | B | (399)[d] | (122)[d] | Turner[65] | Photometry and modeling of B[d] |
| 1978 | A | 356* | 109* | Gauthier and Fernie[66] | Modeling extinction and Cepheid evolution of A |
| 1996 | B | 359* | 110* | Kamper[26] | Photometry and modeling of B, reproducing prior estimates |
| 1997 | A | 431±29 | 132±9 | Hipparcos[70] | All-sky/absolute[68] parallax observations, of the primary variable[e] |
| 2004-2013 | A, B | 307±13 | 94±4 | Turner/Turner et al | Cepheid evolution modeling[30], cluster kinematics and ZAMS fitting[30][67], photometry and modeling of B[67], spectral line ratios of A calibrated on yellow supergiants[62] |
| 329±10 | 101±3 | ||||
| 323±7 | 99±2 | ||||
| 2007[f] | A | 432±6 | 133±2 | Hipparcos[2][69] | All-sky/absolute parallax observations, revised analysis, of the primary variable[f] |
| 2008 | B | 357* | 109.5* | Usenko & Klochkova[7] | Photometry and modeling of B |
| 2014 | A | >385 | >118 | Neilson[71] | Cepheid evolution modeling, independent of any distance prior |
| 2018 | B | 521±20 | 160±6 | Hubble, Bond et al.[14] | Relative[68] parallax of the wide component referencing photometrically-calibrated background stars |
| 2018 | B | 445.3±1.7 | 136.6±0.5 | Gaia DR2[72] | All-sky/absolute[68] parallax observations, of the wide component[g] |
| 2020 | B | 446.5±1.1 | 136.9±0.3 | Gaia DR3[5][9] | All-sky/absolute parallax observations, of the wide component[h] |
| ^ * This estimate didn't state its uncertainty |
After the arrival of the Hipparcos data, the distance to Polaris and consequent analysis of its Cepheid variation was controversial. The Hipparcos distance for Polaris was broadly but not universally adopted.[20] Immediately, the Hipparcos data for the nearest few hundred Cepheids appeared to clarify Cepheid models and to clear up then-tension in higher rungs of the distance ladder.[70] However alternatives remained; particularly by Turner et al, who published several papers between 2004 and 2013.[62]
In 2018, Bond et al[14] used the Hubble Space Telescope to provide an alternate direct measurement of Polaris's parallax; they summarize the back-and-forth:
However, Turner et al. (2013, hereafter TKUG13)[62] argue that the parallax of Polaris is considerably larger, 10.10 ± 0.20 mas (d = 99±2 pc). The evidence cited by TKUG13 for this “short” distance includes (1) a photometric parallax for Polaris B based on measured photometry, spectral classification, and main-sequence fitting; (2) a claim that there is a sparse cluster of A-, F-, and G-type stars within 3° of Polaris, with proper motions and radial velocities similar to that of the Cepheid, for which the Hipparcos parallaxes combined with main-sequence fitting give a distance of 99 pc; and (3) a determination of the absolute visual magnitude of Polaris based on line ratios in high-resolution spectra, calibrated against supergiants with well-established luminosities. [...]
[...]
In a critique of the TKUG13 paper, van Leeuwen (2013, hereafter L13)[69] defended the Hipparcos parallax by presenting details of the solution, concluding that “the Hipparcos data cannot in any way support” the large parallax advocated by TKUG13. Using Hipparcos data, L13 also questioned the reality of the sparse cluster proposed by TKUG13, presenting evidence against it both from the color versus absolute-magnitude diagram for stars within 3° of Polaris, and their non-clustered distribution of proper motions. Lastly, L13 examined the absolute magnitudes of nearly 400 stars of spectral type F3 V in the Hipparcos catalog with parallax errors of less than 10%, and showed that the absolute magnitude of Polaris B would fall well within the observed MV distribution for F3 V stars, based on either the Hipparcos parallax of A or the larger parallax proposed by TKUG13. Thus, he concluded that the photometric parallax of B does not give a useful discriminant.
— [14]
Bond et al go on to find a trigonometric parallax (independent of Hipparcos) that implies a distance further-still than the "long" Hipparcos distance, well outside the plausible range of the "short" distance estimates.
The next major step in high precision parallax measurements comes from Gaia, a space astrometry mission launched in 2013 and intended to measure stellar parallax to within 25 microarcseconds (μas).[74] Although it was originally planned to limit Gaia's observations to stars fainter than magnitude 5.7, tests carried out during the commissioning phase indicated that Gaia could autonomously identify stars as bright as magnitude 3. When Gaia entered regular scientific operations in July 2014, it was configured to routinely process stars in the magnitude range 3 – 20.[75] Beyond that limit, special procedures are used to download raw scanning data for the remaining 230 stars brighter than magnitude 3; methods to reduce and analyse these data are being developed; and it is expected that there will be "complete sky coverage at the bright end" with standard errors of "a few dozen μas".[76]
Gaia DR2 does not include a parallax for Polaris A, but a distance inferred from Polaris B is 136.6±0.5 pc (445.5±1.7 ly),[72] somewhat further than most previous estimates and (in principle) considerably more accurate. There are known to be considerable systematic uncertainties in DR2.[77]
Gaia DR3 significantly improved both the statistical and systematic uncertainties, although the latter remain numerous and on the order of 10–60 μas[63]; the new estimate is 136.9±0.3 pc (446.5±1.1 ly) using the baseline parallax zeropoint correction.[5][9][h]
Gaia DR4 (expected December 2026) will further improve the statistical and systematic uncertainties in general, and the data pipelines for variable and multiple stars in particular.[78] Multistar orbital solutions will become available, greatly aiding the study of Cepheids and Polaris, and in particular, may enable solving the outer AB orbit.[9]
Polaris is depicted in the flag and coat of arms of the Canadian Inuit territory of Nunavut,[79] the flag of the U.S. states of Alaska and Minnesota,[80] and the flag of the U.S. city of Duluth, Minnesota.[81][82]
Around 4800 years ago Thuban ( α Draconis) lay a mere 0°.1 from the pole. Deneb (
α Cygni) will be the brightest star near the pole in about 8000 years' time, at a distance of 7°.5.
cite book: ISBN / Date incompatibility (help)
A safari (/səˈfɑːri/; from Swahili safari 'journey' originally from Arabic safar 'to journey') is an overland journey to observe or hunt wild animals, especially in East Africa.[1][2][3] The so-called "Big Five" game animals of Africa – lion, leopard, rhinoceros, elephant, and Cape buffalo – particularly form an important part of the safari market, both for wildlife viewing and big-game hunting.[4]
The Swahili word safari means "journey", originally from the Arabic noun سفر, safar, meaning "journey",[5] "travel", "trip", or "tour"; the verb for "to travel" in Swahili is kusafiri. These words are used for any type of journey, e.g., by bus from Nairobi to Mombasa or by ferry from Dar es Salaam to Unguja. Safari entered the English language at the end of the 1850s thanks to explorer Richard Francis Burton.[6]
The Regimental March of the King's African Rifles was "Funga Safari", literally 'set out on a journey', or, in other words, pack up equipment ready for travel.
Funga safari, funga safari. Funga safari, funga safari. Amri ya nani? Amri ya nani? Amri ya Bwana Kapteni, Amri ya KAR.
Which is, in English:
Set out on a journey, Set out on a journey. On whose orders? On whose orders? On the order of the boss captain, On the order of the KAR.
On Kenya's independence from the United Kingdom, "Funga Safari" was retained as the Regimental March of the Kenya Rifles, the successor to the KAR.
The origins of safari can be traced back to the first arrivals of Europeans and Arabs in Africa, long before the colonization era, but the big history of it began in the 19th century, when academic and economic interest to Africa increased in Western society, and technological advances and medicine (most notably the discovery of quinine as a remedy against malaria) allowed foreigners to step up deep into the continent safely enough. These expeditions established the concept of safari-style travel. While the goal of most was geographical discovery, the search for minerals and new routes of communication, others were primarily aimed at hunting animals, and elephant tusks at the first.[7]
In 1836, William Cornwallis Harris led an expedition to observe and record wildlife and landscapes. Harris established the safari style of journey, starting with a not-too-strenuous rising at first light, an energetic day walking, an afternoon rest, and concluding with a formal dinner and telling stories in the evening over drinks and tobacco.[8] The hunting aspect traditionally associated with the safari is said to have its origins in the early 17th century in the region of Évora, Alentejo, where villagers got together to hunt wild boar and reclaim land for farming.[citation needed]
The firm of Newland & Tarlton Ltd (founded 1904) pioneered luxury tented safaris.[9]
Jules Verne's first novel Five Weeks in a Balloon published in 1863 and H. Rider Haggard's first novel King Solomon's Mines published in 1885, both describe journeys of English travellers on safari and were best sellers in their day. These two books gave rise to a genre of Safari adventure novels and films.[citation needed]
Ernest Hemingway wrote several fiction and nonfiction pieces about African safaris. His short stories "The Short Happy Life of Francis Macomber" and "The Snows of Kilimanjaro" are set on African safaris and were written after Hemingway's own experience on safari. His books Green Hills of Africa and True at First Light are both set on African safaris.
The safari provided countless hours of cinema entertainment in sound films from Trader Horn (1931) onwards. The safari was used in many adventure films such as the Tarzan, Jungle Jim, and Bomba the Jungle Boy film series up to The Naked Prey (1965) where Cornel Wilde, a white hunter, becomes game himself. The safari genre films were parodied in the Bob Hope comedies Road to Zanzibar and Call Me Bwana. A short 15-minute helicopter safari was shown in Africa Addio, where clients are armed, flown from their hotel, and landed in front of an unlucky and baffled elephant. Out of Africa has Karen Blixen and famous hunter Denys Finch Hatton travelling, with Denys refusing to abandon home comforts using fine china and crystal, and listening to Mozart recordings over the gramophone while on safari trip.
The safari style originated from British officers and the jackets worn during their campaigns in Africa.[10] There is a particular theme or style associated with the word, which includes khaki clothing, belted bush jackets, pith helmets or slouch hats, and animal skin patterns. Pith helmet was initially worn by the British military in the tropics and was adopted as streetwear between 1870 and 1950.[11] Condé Nast Traveler describes safari jackets as, "crisp drill cotton with pockets, buttons, epaulets, belt", and a part of Kenyan colonial style.[11]
Theodore Roosevelt was "outfitted" in safari-style by his friend Lord Cranworth during his post-presidential safari trip from 1909 to 1910.[12] Lord Cranworth ran Newland & Tarlton, a luxury safari outfitter credited with creating safari-style clothing.[13] Other sources state Roosevelt was outfitted by Willis & Geiger in 1908.[14] Roosevelt carried British style rifles produced by Holland & Holland or Westley Richards, as did other safari attendees such as Ernest Hemingway.[11] Safari-style jackets have been worn by Hemingway as well as Hollywood celebrities like Grace Kelly and Johnny Weissmuller, and they remain a part of contemporary fashion.[11]
In the 2005 spring/summer edition of British Vogue, an article titled "World Vision: the grown-up approach to global style" featured haute safari style clothing.[15] Contemporary American public figures such as Melania Trump have worn safari fashion. Mrs. Trump wore a safari-style dress and jackets during her 2018 trip to Africa.[16] On this trip Mrs. Trump went on a safari in Kenya, she wore a pith helmet. Some have criticized the choice as evoking colonial ideals.[16] In 2014, Harper's Bazaar announced trend alerts featuring animal prints and a “safari sleek" style.[17] Couture designers in their 2015 fashion shows featured variations of safari-style in their collections. Designer Yang Lei featured a silk safari-style evening gown in his Spring/Summer collection during Paris Fashion Week.[18] Alexander Wang's collection focused on a variety of white shirts, including a safari-style white shirt dress.[19] The New York Times described designer Alberta Ferretti's 2015 daywear collection as "safari-sleek".[20]
In John Molloy's history of the leisure suit, he details that safari-style originated from British Officers wearing their uniforms outside military uses as "a status symbol, but only in casual settings."[21] Molloy stated in 1975 that it continues to be a form of casual menswear.[10] Alternatively, in Malindi Kenya, professional wear in the 1990s included safari-style clothing.[22] Yves Saint Laurent's 1967 Africa collection featured the "Saharienne" safari jacket.[23] In later collections, Yves Saint Laurent produced an iconic safari top.[23] According to Harper's Bazaar, the collection was "a fantasy of primitive genius."[24] On the other hand, differing fashion historians believe He had the gift of borrowing from one culture without being condescending to the other.[24]
The term safari chic arose after the release of the film Out of Africa.[25] It included not only clothing but also interior design and architecture.[26] Safari-style interiors feature African decor,[27] various hues of brown, natural materials,[28] animal print furniture, rugs and wallpaper.[29] In 2005 Architectural Digest released a list of luxurious safari camps.[30] Newland, Tarlton & Co. Furniture Collection, creates luxury safari-style furniture in featured safari camps, hotels and private homes.[31] Safari fashion also extends to fragrance collections by American designer Ralph Lauren; The Safari fragrance created in 1990 was advertised as "a floral aroma with a light breeze scented by grasses, freedom, and the romance of vast open spaces."[32]
Media related to Safari at Wikimedia Commons
The dictionary definition of safari at Wiktionary
African flora and fauna travel guide from Wikivoyage
Arabian Nights Tours Camp in Abu Dhabi, UAE, offers an immersive desert adventure experience. Located in the heart of the Arabian desert, the camp provides guests with a traditional Bedouin-style setting, complete with comfortable tents and authentic decor. Visitors can enjoy a range of activities, including dune bashing, camel rides, and sandboarding. The camp also features cultural entertainment such as belly dancing, henna painting, and traditional music. Guests are treated to a sumptuous buffet of Arabic cuisine under the stars, making for a memorable and picturesque desert experience. Arabian Nights Tours Camp combines adventure, culture, and relaxation in a stunning desert landscape.
Yes, Buggy Dubai is completely safe when operated by licensed professionals like Dune Buggy Rentals Dubai. We provide certified guides, safety briefings, helmets, and well-maintained vehicles with full insurance coverage. Safety is our top priority.
Buggy Dubai refers to exhilarating off-road dune buggy experiences in Dubai's Arabian Desert. It involves driving powerful vehicles like Polaris RZR and Can-Am Maverick across golden sand dunes, offering tourists and adventure seekers an unforgettable desert adventure.
Buggy Dubai prices start from AED 600 for a 2-seater Polaris RZR 1000cc, AED 800 for a 4-seater Polaris, and AED 999 for a 2-seater Can-Am Maverick X3. All packages include guided tours, unlimited mineral water, and safety equipment.