Arcturus, also designated α Boötis (Latinized to Alpha Boötis, abbreviated Alpha Boo, α Boo), is the brightest star in the constellation of Boötes, the fourth-brightest in the night sky, and the brightest in the northern celestial hemisphere. Together with Spica and Denebola (or Regulus, depending on the source), Arcturus is part of the Spring Triangle asterism and, by extension, also of the Great Diamond along with the star Cor Caroli.
Relatively close at 36.7 light-years from the Sun, Arcturus is a red giant of spectral type K0III—an ageing star around 7.1 billion years old that has used up its core hydrogen and moved off the main sequence. It is 1.08±0.06 times as massive as the Sun, but has expanded to 25.4±0.2 times its diameter and is around 170 times as luminous.
Arcturus in the constellation of Boötes (circled)
Epoch J2000 Equinox J2000
|Right ascension||14h 15m 39.7s|
|Declination||+19° 10′ 56″|
|Apparent magnitude (V)||−0.05|
|Spectral type||K0 III|
|Apparent magnitude (J)||−2.25|
|U−B color index||+1.28|
|B−V color index||+1.23|
|R−I color index||+0.65|
|Note (category: variability):||H and K emission vary.|
|Radial velocity (Rv)||−5.19 km/s|
|Proper motion (μ)|| RA: −1093.45 mas/yr |
Dec.: −1999.40 mas/yr
|Parallax (π)||88.83 ± 0.54 mas|
|Distance||36.7 ± 0.2 ly |
(11.26 ± 0.07 pc)
|Absolute magnitude (MV)||−0.30±0.02|
|Surface gravity (log g)||1.66±0.05 cgs|
|Metallicity [Fe/H]||−0.52±0.04 dex|
|Rotational velocity (v sin i)||2.4±1.0 km/s|
Bright Star Catalogue (5th rev. ed.),
VizieR catalog entry
The traditional name Arcturus derives from Ancient Greek Ἀρκτοῦρος (Arktouros) and means "Guardian of the Bear", ultimately from ἄρκτος (arktos), "bear" and οὖρος (ouros), "watcher, guardian". It has been known by this name since at least the time of Hesiod.
One astronomical tradition associates Arcturus with the mythology around Arcas, who was about to shoot and kill his own mother Callisto who had been transformed into a bear. Zeus averted their imminent tragic fate by transforming the boy into the constellation Boötes, called Arctophylax "bear guardian" by the Greeks, and his mother into Ursa Major (Greek: Arctos "the bear"). The account is given in Hyginus's Astronomy.
An alternative lore associates the name with the legend around Icarius, who gave the gift of wine to other men, but was murdered by them, because they had had no experience with intoxication and mistook the wine for poison. It is stated this Icarius, became Arcturus, while his dog, Maira, became Canicula (Procyon), although "Arcturus" here may be used in the sense of the constellation rather than the star.
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 Arcturus for this star. It is now so entered in the IAU Catalog of Star Names.
With an apparent visual magnitude of −0.05, Arcturus is the brightest star in the northern celestial hemisphere and the fourth-brightest star in the night sky, after Sirius (−1.46 apparent magnitude), Canopus (−0.72) and α Centauri (combined magnitude of −0.27). However, α Centauri AB is a binary star, whose components are both fainter than Arcturus. This makes Arcturus the third-brightest individual star, just ahead of α Centauri A (officially named Rigil Kentaurus), whose apparent magnitude is −0.01. The French mathematician and astronomer Jean-Baptiste Morin observed Arcturus in the daytime with a telescope in 1635, a first for any star other than the Sun and supernovae. Arcturus has been seen at or just before sunset with the naked eye.
Arcturus is visible from both of Earth's hemispheres as it is located 19° north of the celestial equator. The star culminates at midnight on 27 April, and at 9 p.m. on June 10 being visible during the late northern spring or the southern autumn. From the northern hemisphere, an easy way to find Arcturus is to follow the arc of the handle of the Big Dipper (or Plough). By continuing in this path, one can find Spica, "Arc to Arcturus, then spike (or speed on) to Spica".
η Boötis, or Muphrid, is only 3.3 light-years distant from Arcturus, and would have a visual magnitude −2.5, about as bright as Mercury from Earth, whereas an observer on the former system would find Arcturus as bright as Venus as seen from Earth.
Based upon an annual parallax shift of 88.83 milliarcseconds as measured by the Hipparcos satellite, Arcturus is 36.7 light-years (11.26 parsecs) from the Sun. The parallax margin of error is 0.54 milliarcseconds, translating to a distance margin of error of ±0.23 light-years (0.069 parsecs). Because of its proximity, Arcturus has a high proper motion, two arcseconds a year, greater than any first magnitude star other than α Centauri.
Arcturus is moving rapidly (122 km/s) relative to the Sun, and is now almost at its closest point to the Sun. Closest approach will happen in about 4,000 years, when the star will be a few hundredths of a light-year closer to Earth than it is today. (In antiquity, Arcturus was closer to the centre of the constellation.) Arcturus is thought to be an old-disk star, and appears to be moving with a group of 52 other such stars, known as the Arcturus stream.
With an absolute magnitude of −0.30, Arcturus is, together with Vega and Sirius, one of the most luminous stars in the Sun's neighborhood. It is about 110 times brighter than the Sun in visible light wavelengths, but this underestimates its strength as much of the light it gives off is in the infrared; total (bolometric) power output is about 180 times that of the Sun. With a near-infrared J band magnitude of −2.2, only Betelgeuse (−2.9) and R Doradus (−2.6) are brighter. The lower output in visible light is due to a lower efficacy as the star has a lower surface temperature than the Sun.
Arcturus is an evolved red giant star with a stellar classification of K0 III. As the brightest K-type giant in the sky, it was the subject of an atlas of its visible spectrum, made from photographic spectra taken with the coudé spectrograph of the Mt. Wilson 2.5m telescope published in 1968, a key reference work for stellar spectroscopy. Subsequent spectral atlases with greater wavelength coverage and superior signal-to-noise ratio made with digital detectors have supplanted the older work, but the Arcturus spectrum remains an important standard for stellar spectroscopy.
As a single star, the mass of Arcturus cannot be measured directly, but models suggest it is slightly larger than that of the Sun. Evolutionary matching to the observed physical parameters gives a mass of 1.08±0.06 M☉, while the oxygen isotope ratio for a first dredge-up star gives a mass of 1.2 M☉. The star displays magnetic activity that is heating the coronal structures, and it undergoes a solar-type magnetic cycle with a duration that is probably less than 14 years. A weak magnetic field has been detected in the photosphere with a strength of around half a gauss. The magnetic activity appears to lie along four latitudes and is rotationally-modulated.
Arcturus is estimated to be around 6 billion to 8.5 billion years old, but there is some uncertainty about its evolutionary status. Based upon the color characteristics of Arcturus, it is currently ascending the red-giant branch and will continue to do so until it accumulates a large enough degenerate helium core to ignite the helium flash. It has likely exhausted the hydrogen from its core and is now in its active hydrogen shell burning phase. However, Charbonnel et al. (1998) placed it slightly above the horizontal branch, and suggested it has already completed the helium flash stage.
As one of the brightest stars in the sky, Arcturus has been the subject of a number of studies in the emerging field of asteroseismology. Belmonte and colleagues carried out a radial velocity (Doppler shift of spectral lines) study of the star in April and May 1988, which showed variability with a frequency of the order of a few microhertz (μHz), the highest peak corresponding to 4.3 μHz (2.7 days) with an amplitude of 60 ms−1, with a frequency separation of c. 5 μHz. They suggested that the most plausible explanation for the variability of Arcturus is stellar oscillations.
Asteroseismological measurements allow direct calculation of the mass and radius, giving values of 0.8±0.2 M☉ and 27.9±3.4 R☉. This form of modelling is still relatively inaccurate, but a useful check on other models.
Astronomers term "metals" those elements with higher atomic numbers than helium. Arcturus has an enrichment of alpha elements relative to iron but only about a third of solar metallicity. Arcturus is possibly a Population II star.
Hipparcos also suggested that Arcturus is a binary star, with the companion about twenty times dimmer than the primary and orbiting close enough to be at the very limits of humans' current ability to make it out. Recent results remain inconclusive, but do support the marginal Hipparcos detection of a binary companion.
In 1993, radial velocity measurements of Aldebaran, Arcturus and Pollux showed that Arcturus exhibited a long-period radial velocity oscillation, which could be interpreted as a substellar companion. This substellar object would be nearly 12 times the mass of Jupiter and be located roughly at the same orbital distance from Arcturus as the Earth is from the Sun, at 1.1 astronomical units. However, all three stars surveyed showed similar oscillations yielding similar companion masses, and the authors concluded that the variation was likely to be intrinsic to the star rather than due to the gravitational effect of a companion. So far no substellar companion has been confirmed.
In Arabic, Arcturus is one of two stars called al-simāk "the uplifted ones" (the other is Spica). Arcturus is specified as السماك الرامح as-simāk ar-rāmiħ "the uplifted one of the lancer". The term Al Simak Al Ramih has appeared in Al Achsasi Al Mouakket catalogue (translated into Latin as Al Simak Lanceator).
This has been variously romanized in the past, leading to obsolete variants such as Aramec and Azimech. For example, the name Alramih is used in Geoffrey Chaucer's A Treatise on the Astrolabe (1391). Another Arabic name is Haris-el-sema, from حارس السماء ħāris al-samā’ "the keeper of heaven". or حارس الشمال ħāris al-shamāl’ "the keeper of north".
Arcturus was once again called by its classical name from the Renaissance onwards.
In Chinese astronomy, Arcturus is called Da Jiao (Chinese: 大角; pinyin: Dàjiǎo; literally: 'great horn"), because it is the brightest star in the Chinese constellation called Jiao Xiu (Chinese: 角宿; pinyin: Jiǎo Xiǔ; literally: 'horn star"). Later it become a part of another constellation Kang Xiu (Chinese: 亢宿; pinyin: Kàng Xiǔ).
In Indian Astrology or Vedic Astrology or Sidereal Astrology, Arcturus is called Swati which is a word meaning "very beneficent" derived from the language Sanskrit. It is the eponymous star of one of the nakshatras (lunar mansions) of Hindu astrology.
The Wotjobaluk Koori people of southeastern Australia knew Arcturus as Marpean-kurrk, mother of Djuit (Antares) and another star in Boötes, Weet-kurrk (Muphrid). Its appearance in the north signified the arrival of the larvae of the wood ant (a food item) in spring. The beginning of summer was marked by the star's setting with the Sun in the west and the disappearance of the larvae. The people of Milingimbi Island in Arnhem Land saw Arcturus and Muphrid as man and woman, and took the appearance of Arcturus at sunrise as a sign to go and harvest rakia or spikerush.:24,69,112 The Wailwun of northern New South Wales knew Arcturus as Guembila "red".:84
Arcturus had several names that described its significance to indigenous Polynesians. In the Society Islands, Arcturus, called Ana-tahua-taata-metua-te-tupu-mavae ("a pillar to stand by"), was one of the ten "pillars of the sky", bright stars that represented the ten heavens of the Tahitian afterlife. In Hawaii, the pattern of Boötes was called Hoku-iwa, meaning "stars of the frigatebird". This constellation marked the path for Hawaiiloa on his return to Hawaii from the South Pacific Ocean. The Hawaiians called Arcturus Hoku-leʻa. It was equated to the Tuamotuan constellation Te Kiva, meaning "frigatebird", which could either represent the figure of Boötes or just Arcturus. However, Arcturus may instead be the Tuamotuan star called Turu. The Hawaiian name for Arcturus as a single star was likely Hoku-leʻa, which means "star of gladness", or "clear star". In the Marquesas Islands, Arcturus was probably called Tau-tou and was the star that ruled the month approximating January. The Māori and Moriori called it Tautoru, a variant of the Marquesan name and a name shared with Orion's Belt.
As one of the brightest stars in the sky, Arcturus has been significant to observers since antiquity.
Prehistoric Polynesian navigators knew Arcturus as Hōkūleʻa, the "Star of Joy". Arcturus is the zenith star of the Hawaiian Islands. Using Hōkūleʻa and other stars, the Polynesians launched their double-hulled canoes from Tahiti and the Marquesas Islands. Traveling east and north they eventually crossed the equator and reached the latitude at which Arcturus would appear directly overhead in the summer night sky. Knowing they had arrived at the exact latitude of the island chain, they sailed due west on the trade winds to landfall. If Hōkūleʻa could be kept directly overhead, they landed on the southeastern shores of the Big Island of Hawaiʻi. For a return trip to Tahiti the navigators could use Sirius, the zenith star of that island. Since 1976, the Polynesian Voyaging Society's Hōkūleʻa has crossed the Pacific Ocean many times under navigators who have incorporated this wayfinding technique in their non-instrument navigation.
In ancient Mesopotamia, it was linked to the god Enlil, and also known as Shudun, "yoke", or SHU-PA of unknown derivation in the Three Stars Each Babylonian star catalogues and later MUL.APIN around 1100 BC.
In Ancient Rome, the star's celestial activity was supposed to portend tempestuous weather, and a personification of the star acts as narrator of the prologue to Plautus' comedy Rudens (circa 211 BC).
In the Hebrew scriptures Arcturus is referred to in Job 38:32.
In the Middle Ages, Arcturus was considered a Behenian fixed star and attributed to the stone Jasper and the plantain herb. Cornelius Agrippa listed its kabbalistic sign under the alternate name Alchameth.
Arcturus achieved fame when its light was rumored to be the mechanism used to open the 1933 Chicago World's Fair. The star was chosen as it was thought that light from Arcturus had started its journey at about the time of the previous Chicago World's Fair in 1893 (at 36.7 light-years away, the light actually started in 1896).
The star is mentioned in the 1977 documentary film Powers of Ten, in which it is seen when a camera zooms from Earth to the whole of the known universe.
27 Cancri is a star in the constellation Cancer.
27 Cancri is a M-type red giant with a mean apparent magnitude of +5.56. It is approximately 1050 light years from Earth. It is classified as a semiregular variable star and its brightness varies from magnitude +5.41 to +5.75 with a period of 40 days.
It has been analysed as a member of the Arcturus stream, a group of stars with high proper motion and metal-poor properties thought to be the remnants of a small galaxy consumed by the Milky Way.A Voyage to Arcturus
A Voyage to Arcturus is a novel by the Scottish writer David Lindsay, first published in 1920. It combines fantasy, philosophy, and science fiction in an exploration of the nature of good and evil and their relationship with existence. Described by critic, novelist, and philosopher Colin Wilson as the "greatest novel of the twentieth century", it was a central influence on C. S. Lewis' Space Trilogy, and through him on J. R. R. Tolkien, who said he read the book "with avidity". Clive Barker called it "a masterpiece" and "an extraordinary work ... quite magnificent."An interstellar voyage is the framework for a narrative of a journey through fantastic landscapes. The story is set at Tormance, an imaginary planet orbiting Arcturus, which in the novel (but not in reality) is a double star system, consisting of stars Branchspell and Alppain. The lands through which the characters travel represent philosophical systems or states of mind, through which the main character, Maskull, passes on his search for the meaning of life.
The book sold poorly during Lindsay's lifetime, but was republished in 1946 and many times thereafter. It has been translated into at least ten languages. Critics such as the novelist Michael Moorcock have noted that the book is unusual, but has been highly influential with its qualities of "commitment to the Absolute" and "God-questioning genius".Alpha Vulpeculae
Alpha Vulpeculae (α Vulpeculae, abbreviated Alfa Vul, α Vul), also named Anser, is the brightest star in the constellation of Vulpecula. It is approximately 297 light-years from Earth. It forms a wide optical binary with 8 Vulpeculae.Alpha Vulpeculae is a red giant of spectral class M1 and has apparent magnitude +4.4. It has been analysed as a member of the Arcturus stream, a group of stars with high proper motion and metal-poor properties thought to be the remnants of a small galaxy consumed by the Milky Way.Arcturus, Virginia
Arcturus is a neighborhood within the unincorporated community of Fort Hunt, Virginia in Fairfax County, Virginia, United States. Arcturus lies south of Alexandria between the George Washington Memorial Parkway and the Potomac River.Arcturus-class attack cargo ship
The Arcturus-class attack cargo ships were converted from other ship types by Sun Shipbuilding & Drydock Co. in Chester, Pennsylvania, Tampa Shipbuilding Co. in Tampa, Florida, and Federal Shipbuilding & Drydock Co. in Kearny, New Jersey during World War II.
Like all attack cargo ships (AKAs), they were designed to carry combat loaded military cargo and landing craft, and to use the latter to land weapons, supplies, and troops on enemy shores during amphibious operations.
All these ships were built on the same standard hull design, but there were some differences from ship to ship:
The armament varied, as did that of the other ships of the day. During 1944-1945, the 5"/38 caliber gun was recognized as the best gun for the dual role of antiaircraft and naval gunfire support, and the 40 mm was seen as the best antiaircraft gun. The older 20 mm and .50 caliber guns had been recognized to be of limited value, and were being phased out, though they appeared on some of these ships. The 20 mm guns were later removed from all of them, but it is not clear just when this happened.
The complement varied as well, but the DANFS figures sometimes seem to confuse ship's company with embarked troops in determining a ship's complement.Arcturus (band)
Arcturus is a Norwegian avant-garde black metal band formed in 1991. Their name, which means "Bear Guardian", references the Behenian fixed star Arcturus.Boötes
Boötes is a constellation in the northern sky, located between 0° and +60° declination, and 13 and 16 hours of right ascension on the celestial sphere. The name comes from the Greek Βοώτης, Boōtēs, meaning “herdsman” or “plowman” (literally, “ox-driver”; from βοῦς bous “cow”).
One of the 48 constellations described by the 2nd-century astronomer Ptolemy, Boötes is now one of the 88 modern constellations. It contains the fourth-brightest star in the night sky, the orange giant Arcturus. Epsilon Bootis, or Izar, is a colourful multiple star popular with amateur astronomers. Boötes is home to many other bright stars, including eight above the fourth magnitude and an additional 21 above the fifth magnitude, making a total of 29 stars easily visible to the naked eye.Hugh Mingay
Hugh Steven James Mingay (born 12 December 1974), also known by his stage name Skoll is a heavy
metal musician.ICS Vortex
Simen Hestnæs, better known by his stage name I.C.S. Vortex or simply Vortex, is a Norwegian musician. He is the vocalist of the similarly named band ICS Vortex, the avant-garde metal band Arcturus, and the doom metal band Lamented Souls. He is also the vocalist and bass guitarist to the progressive black metal band Borknagar, and the former bass guitarist and backing vocalist for the Norwegian symphonic black metal band Dimmu Borgir.Jan Axel Blomberg
Jan Axel "Hellhammer" Blomberg (born August 2, 1969) is a Norwegian heavy metal drummer. He is best known as the drummer of Mayhem, which he joined in 1988. In 1987 Blomberg formed the avant-garde black metal band Arcturus (under the name Mortem) with Steinar Sverd Johnsen, which broke up in April 2007 and reunited in 2011. He named himself after the Swiss extreme metal band Hellhammer. Praised as a talented musician, Blomberg is a three-time winner of the Spellemannprisen award.List of Foundation universe planets
This is a list of Foundation universe planets featured or mentioned in the Robot series, Empire series, and Foundation series created by Isaac Asimov.Lockheed CP-140 Aurora
The Lockheed CP-140 Aurora is a maritime patrol aircraft operated by the Royal Canadian Air Force. The aircraft is based on the Lockheed P-3 Orion airframe, but mounts the electronics suite of the Lockheed S-3 Viking. "Aurora" refers to the Roman goddess of dawn who flies across the sky each morning ahead of the sun. Aurora also refers to the Aurora Borealis, the "northern lights", that are prominent over northern Canada and the Arctic Ocean.
The CP-140A Arcturus was a related variant used primarily for pilot training and coastal surface patrol missions.Samoth
Samoth (born Thomas Thormodsæter Haugen; 9 June 1974) is a musician and multi-instrumentalist in the Norwegian black metal scene. He is well known for his distinct guitar work and drumming in the band Emperor, as well as his formation of the death metal band Zyklon. In very early Emperor releases, he was called Samot (his name "Tomas" backward), and with the formation of Zyklon he became known as Zamoth. Samoth was the owner of the record label Nocturnal Art Productions and had a close relationship with Candlelight Records.Starhawk (comics)
Starhawk (Stakar of the House of Ogord) is a fictional character appearing in American comic books published by Marvel Comics. He was created by Steve Gerber (writer) and Sal Buscema (artist). He is an antihero in the Earth-691 timeline of the Marvel Comics universe.
Stakar was fated to eventually re-inhabit his infant body, reliving his life over countless times. Because of the knowledge of things to come, he manipulated events to affect what he felt would be the best outcome, referring to himself as "One Who Knows". He made many enemies in doing so, but his tampering and guidance also led to the formation of the Guardians of the Galaxy in the 31st Century.Sylvester Stallone plays Stakar in the Marvel Cinematic Universe, with his first appearance being in Guardians of the Galaxy Vol. 2.Svati
Swati (Devanagari स्वाति, Transliteration IAST svāti, also found svātī́) According to some is a feminine noun of unknown derivation or ′su′ + ′ati′ (″Great goer″, in reference to its remoteness) meaning very beneficent. Probably referring to its brightness call ″the real pearl″ in Bhartṛhari's kāvyas. It was the name of one of the wives of the Sun in Hindu Epics and the Sanskrit name of Arcturus as well as of the nakshatra (lunar mansion) associated with Arcturus in Hindu astrology.
Swati is a very common Hindu name. Also spelled Swathi.USS Arcturus (AF-52)
USS Arcturus (AF-52) was an Alstede class stores ship stores ship acquired by the U.S. Navy. Her task was to carry stores, refrigerated items, and equipment to ships in the fleet, and to remote stations and staging areas.
The fifth Navy vessel to be named Arcturus, AF-52 was laid down on 8 December 1941 at Oakland, California, by the Moore Dry Dock Co. under a Maritime Commission contract (MC hull 184) as Golden Eagle; launched on 15 March 1942; sponsored by Mrs. John B. McKee; and delivered to the War Shipping Administration (WSA) on 23 April 1943. She was operated under WSA charter by the United Fruit Co. until 1946 and, thereafter by the Sword Line and the United States Lines.USS Arcturus (AKA-1)
USS Arcturus (AK-18/AKA-1) was an Arcturus-class attack cargo ship named after Arcturus, a star in the constellation Boötes. She served as a commissioned ship for 5 years and 5 months.USS Artemis (SP-593)
USS Artemis (SP-593), later known as USS Arcturus (SP 593) was a yacht acquired by the United States Navy during World War I. Artemis was armed with guns and depth charges, and was sent to Europe as a patrol craft to protect Allied ships from German submarines and other dangers. Post-war she was returned to the United States and turned over to the United States Coast and Geodetic Survey. Later, back in civilian operation, she was burned and sank in 1927.USS Electra (AKA-4)
USS Electra (AKA-4) was an Arcturus-class attack cargo ship named after Electra, a star in the Pleiades star cluster in the constellation Taurus. She served as a commissioned ship for seven years.
Electra (AK-21) was launched 18 November 1941 as Meteor by Tampa Shipbuilding Co., Tampa, Fla., under a Maritime Commission contract; sponsored by Mrs. C. O. Andrews, wife of the Senator from Florida; transferred to the Navy 16 April 1941; and commissioned 17 March 1942, Commander J. J. Hughes in command. She was reclassified AKA-4, 1 February 1943.