Arcturus (other)
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, - bgcolor="#FFFAFA" , Note (category: variability): , , H and K emission vary. Arcturus is a
red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The stellar atmosphere, outer atmosphere is inflated and tenuous, making the radius large and the surface t ...
star in the
northern Northern may refer to the following: Geography * North North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating ...
constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...
of
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 , which comes from 'herder, herdsman' or 'plowman' (literally, 'o ...
, and the brightest star in the constellation. It has the
Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...
α Boötis, which is Latinized to Alpha Boötis and abbreviated Alf Boo or α Boo. With an
apparent visual magnitude Apparent magnitude () is a measure of the brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction of the object's light ca ...
of −0.05, it is the fourth-brightest star in the
night sky The night sky is the nighttime appearance of celestial objects like stars, planets, and the Moon, which are visible in a clear sky between sunset and sunrise, when the Sun is below the horizon. Natural light sources in a night sky include moonlig ...
and the brightest in the
northern celestial hemisphere The northern celestial hemisphere, also called the Northern Sky, is the Northern Hemisphere, northern half of the celestial sphere; that is, it lies north of the celestial equator. This arbitrary sphere diurnal motion, appears to rotate westward ...
. Arcturus forms one corner of the
Spring Triangle The Spring Triangle is an asterism_(astronomy), astronomical asterism involving an imaginary triangle drawn upon the celestial sphere, with its defining vertices at Arcturus, Spica, and Regulus. This triangle connects the constellations of Boötes ...
asterism. Located relatively close at 36.7
light-year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...
s from the
Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
, Arcturus is a
red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The stellar atmosphere, outer atmosphere is inflated and tenuous, making the radius large and the surface t ...
of
spectral type In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...
K1.5III—an aging star around 7.1 billion years old that has used up its
core Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (laboratory), a highly specialized shared research resource * Core (manufacturing), used in casting and molding * Core (optical fiber ...
hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
and
evolved Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...
off the
main sequence In astronomy, the main sequence is a classification of stars which appear on plots of stellar color index, color versus absolute magnitude, brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or d ...
. It is about the same mass as the Sun, but has expanded to 25 times its size (around 35 million kilometers) and is around 170 times as luminous.


Nomenclature

The traditional name ''Arcturus'' is Latinised from the
ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
''Ἀρκτοῦρος'' (Arktouros) and means "Guardian of the Bear", ultimately from ''ἄρκτος'' (''arktos''), "bear" and ''οὖρος'' (ouros), "watcher, guardian". As ''ἄρκτος'' also came to mean "north", the name can also translate to "Guardian of the North". The designation of Arcturus as ''α Boötis'' ( Latinised to ''Alpha Boötis'') was made by
Johann Bayer Johann Bayer (; 1572 – 7 March 1625) was a German lawyer and uranographer (celestial cartographer). He was born in Rain in 1572. In 1592, aged 20, he began his study of philosophy and law at the University of Ingolstadt, after which he ...
in 1603. In 2016, the
International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...
organized a
Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize proper names for stars for the international astronomical community. It operates under Division C – Education ...
(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 α Boötis.


Observational history

Arcturus and its distinctive red color have been mentioned since
antiquity Antiquity or Antiquities may refer to: Historical objects or periods Artifacts *Antiquities, objects or artifacts surviving from ancient cultures Eras Any period before the European Middle Ages (5th to 15th centuries) but still within the histo ...
and
medieval times In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and t ...
;
Ptolemy Claudius Ptolemy (; , ; ; – 160s/170s AD) was a Greco-Roman mathematician, astronomer, astrologer, geographer, and music theorist who wrote about a dozen scientific treatises, three of which were important to later Byzantine science, Byzant ...
described it as ''subrufa'' ("slightly red"), and
Geoffrey Chaucer Geoffrey Chaucer ( ; – 25 October 1400) was an English poet, author, and civil servant best known for ''The Canterbury Tales''. He has been called the "father of English literature", or, alternatively, the "father of English poetry". He w ...
referred to it as ''Alramih'' in ''
A Treatise on the Astrolabe ''A Treatise on the Astrolabe'' is a medieval instruction manual on the astrolabe by Geoffrey Chaucer. It was completed in 1391. It describes both the form and the proper use of the instrument, and stands out as a prose technical work from a wr ...
'' (1391). In 1635, the French mathematician and astronomer Jean-Baptiste Morin observed Arcturus in the daytime with a telescope. This was the first recorded full daylight viewing for any star other than the
Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
and
supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...
e.


Observation

With an
apparent visual magnitude Apparent magnitude () is a measure of the brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction of the object's light ca ...
of −0.05, Arcturus is the brightest star in the
northern celestial hemisphere The northern celestial hemisphere, also called the Northern Sky, is the Northern Hemisphere, northern half of the celestial sphere; that is, it lies north of the celestial equator. This arbitrary sphere diurnal motion, appears to rotate westward ...
and the fourth-brightest star in the night sky, after
Sirius Sirius is the brightest star in the night sky. Its name is derived from the Greek word (Latin script: ), meaning 'glowing' or 'scorching'. The star is designated  Canis Majoris, Latinized to Alpha Canis Majoris, and abbr ...
(−1.46 apparent magnitude),
Canopus Canopus is the brightest star in the southern constellation of Carina (constellation), Carina and the list of brightest stars, second-brightest star in the night sky. It is also Bayer designation, designated α Carinae, which is Rom ...
(−0.72) and
α Centauri Alpha Centauri (, α Cen, or Alpha Cen) is a star system in the southern constellation of Centaurus. It consists of three stars: Rigil Kentaurus (), Toliman (), and Proxima Centauri (). Proxima Centauri is the closest star to th ...
(combined magnitude of −0.27). However, α Centauri AB is a
binary star A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...
, whose components are each fainter than Arcturus. This makes Arcturus the third-brightest individual star, just ahead of α Centauri A (officially named ''Rigil Kentaurus''), whose apparent magnitude . Arcturus has been seen at or just before sunset with the naked eye. Arcturus is visible from both of
Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
's hemispheres as it is located 19° north of the
celestial equator The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth. By extension, it is also a plane of reference in the equatorial coordinate system. Due to Earth's axial tilt, the celestial ...
. The star culminates at midnight on April 27, and at 9 p.m. on June 10 being visible during the late northern spring or the southern autumn. From the
northern hemisphere The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...
, an easy way to find Arcturus is to follow the arc of the handle of the
Big Dipper The Big Dipper (American English, US, Canadian English, Canada) or the Plough (British English, UK, Hiberno-English, Ireland) is an asterism (astronomy), asterism consisting of seven bright stars of the constellation Ursa Major; six of them ar ...
(or Plough in the UK). By continuing in this path, one can find
Spica Spica is the brightest object in the constellation of Virgo and one of the 20 brightest stars in the night sky. It has the Bayer designation α Virginis, which is Latinised to Alpha Virginis and abbreviated Alpha Vir or α Vir. Analys ...
, "Arc to Arcturus, then spike (or speed on) to Spica". Together with the bright stars
Spica Spica is the brightest object in the constellation of Virgo and one of the 20 brightest stars in the night sky. It has the Bayer designation α Virginis, which is Latinised to Alpha Virginis and abbreviated Alpha Vir or α Vir. Analys ...
and
Regulus Regulus is the brightest object in the constellation Leo (constellation), Leo and one of the List of brightest stars, brightest stars in the night sky. It has the Bayer designation designated α Leonis, which is Latinisation of names, ...
(or
Denebola Denebola is the second-brightest individual star in the zodiac constellation of Leo.The two components of the γ Leonis double star, which are unresolved to the naked eye, have a combined magnitude brighter than it. It is the eastern ...
, depending on the source), Arcturus is part of the
Spring Triangle The Spring Triangle is an asterism_(astronomy), astronomical asterism involving an imaginary triangle drawn upon the celestial sphere, with its defining vertices at Arcturus, Spica, and Regulus. This triangle connects the constellations of Boötes ...
asterism. With
Cor Caroli Cor Caroli is a binary star in the northern constellation of Canes Venatici. It is the brightest star in the constellation, lying at the third magnitude. The International Astronomical Union uses the name "Cor Caroli" specifically for th ...
, these four stars form the
Great Diamond The Great Diamond, also called the Diamond of Virgo, is an asterism that can be seen during spring evenings in the Northern Hemisphere. It is composed of the following stars: *Cor Caroli (α CVn), in Canes Venatici * Denebola (β Leo), the tai ...
asterism. Arcturus has a B-V color index of +1.23, roughly midway between Pollux (B-V +1.00) and
Aldebaran Aldebaran () is a star in the zodiac constellation of Taurus. It has the Bayer designation α Tauri, which is Latinized to Alpha Tauri and abbreviated Alpha Tau or α Tau. Aldebaran varies in brightness from an apparent vis ...
(B-V +1.54).
η Boötis Eta ( ; uppercase , lowercase ; ''ē̂ta'' or ''ita'' ) is the seventh letter of the Greek alphabet, representing the close front unrounded vowel, . Originally denoting the voiceless glottal fricative, , in most dialects of Ancient Greek, its ...
, or Muphrid, is only 3.3
light-year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...
s distant from Arcturus, and would have a visual magnitude −2.5, about as bright as
Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
at its brightest from Earth, whereas an observer on the former system would find Arcturus with a magnitude -5.0, slightly brighter than
Venus Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...
as seen from Earth, but with an orangish color.


Physical characteristics

Based upon an annual
parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...
shift of 88.83 
milliarcseconds A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...
, as measured by the
Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions and distances of ...
satellite, Arcturus is from Earth. The parallax
margin of error The margin of error is a statistic expressing the amount of random sampling error in the results of a Statistical survey, survey. The larger the margin of error, the less confidence one should have that a poll result would reflect the result of ...
is 0.54 milliarcseconds, translating to a distance margin of error of ±. Because of its proximity, Arcturus has a high
proper motion Proper motion is the astrometric measure of changes in the apparent places of stars or other celestial objects as they move relative to the center of mass of the Solar System. It is measured relative to the distant stars or a stable referenc ...
, two
arcseconds A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...
a year, greater than any
first magnitude star First-magnitude stars are the brightest stars in the night sky, with apparent magnitudes lower (i.e. brighter) than +1.50. Hipparchus, in the 1st century BC, introduced the magnitude scale. He allocated the first magnitude to the 20 brightest star ...
other than α Centauri. It is the second-closest giant star to Earth, after Pollux. Arcturus is moving rapidly () 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 Vega is the brightest star in the northern constellation of Lyra. It has the Bayer designation α Lyrae, which is Latinised to Alpha Lyrae and abbreviated Alpha Lyr or α Lyr. This star is relatively close at only from the Sun, and ...
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 Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...
; total ( bolometric) power output is about 180 times that of the Sun. With a near-infrared J band
magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...
of −2.2, only
Betelgeuse Betelgeuse is a red supergiant star in the constellation of Orion (constellation), Orion. It is usually the List of brightest stars, tenth-brightest star in the night sky and, after Rigel, the second brightest in its constellation. It i ...
(−2.9) and
R Doradus R Doradus (HD 29712 or P Doradus) is a red giant variable star in the far-southern constellation Dorado, close to the border with Reticulum. Its distance from Earth is . Having a angular diameter, uniform disk diameter of , it is though ...
(−2.6) are brighter. The lower output in visible light is due to a lower
efficacy Efficacy is the ability to perform a task to a satisfactory or expected degree. The word comes from the same roots as '' effectiveness'', and it has often been used synonymously, although in pharmacology a distinction is now often made betwee ...
as the star has a lower surface temperature than the Sun. There have been suggestions that Arcturus might be a member of a binary system with a faint, cool companion, but no companion has been directly detected. In the absence of a binary companion, the mass of Arcturus cannot be measured directly, but models suggest it is slightly greater than that of the Sun. Evolutionary matching to the observed physical parameters gives a mass of , while the oxygen isotope ratio for a first
dredge-up A dredge-up is any one of several stages in the evolution of some stars. By definition, during a ''dredge-up'', a convection zone extends all the way from the star's surface down to the layers of material that have undergone fusion. Consequently, ...
star gives a mass of . The star, given its evolutionary state, is expected to have undergone significant mass loss in the past. The star displays
magnetic activity A stellar magnetic field is a magnetic field generated by the motion of conductive Plasma (physics), plasma inside a star. This motion is created through convection, which is a form of energy transport involving the physical movement of material ...
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 The photosphere is a star's outer shell from which light is radiated. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately , or equivalently, a depth from which 50% of light will esc ...
with a strength of around half a
gauss Johann Carl Friedrich Gauss (; ; ; 30 April 177723 February 1855) was a German mathematician, astronomer, Geodesy, geodesist, and physicist, who contributed to many fields in mathematics and science. He was director of the Göttingen Observat ...
. The magnetic activity appears to lie along four latitudes and is rotationally modulated. Arcturus is estimated to be around 6 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 The red-giant branch (RGB), sometimes called the first giant branch, is the portion of the giant branch before helium ignition occurs in the course of stellar evolution. It is a stage that follows the main sequence for low- to intermediate-mass st ...
and will continue to do so until it accumulates a large enough degenerate helium
core Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (laboratory), a highly specialized shared research resource * Core (manufacturing), used in casting and molding * Core (optical fiber ...
to ignite the
helium flash A helium flash is a very brief thermal runaway nuclear fusion of large quantities of helium into carbon through the triple-alpha process in the core of low-mass stars (between 0.5-0.44 solar masses () and 2.0 ) during their red giant phase. The Su ...
. It has likely exhausted the
hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
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 The horizontal branch (HB) is a stage of stellar evolution that immediately follows the red-giant branch in stars whose masses are similar to the Sun's. Horizontal-branch stars are powered by helium fusion in the core (via the triple-alpha proc ...
, and suggested it has already completed the helium flash stage.


Spectrum

Arcturus has
evolved Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...
off the main sequence to the
red giant branch The red-giant branch (RGB), sometimes called the first giant branch, is the portion of the giant branch before helium ignition occurs in the course of stellar evolution. It is a stage that follows the main sequence for low- to intermediate-mass st ...
, reaching an
early Early may refer to: Places in the United States * Early, Iowa, a city * Early, Texas, a city * Early Branch, a stream in Missouri * Early County, Georgia * Fort Early, Georgia, an early 19th century fort Music * Early B, stage name of Jamaican d ...
K-type
stellar classification In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction gratin ...
. It is frequently assigned the spectral type of K0III, but in 1989 was used as the spectral standard for type K1.5III Fe−0.5, with the suffix notation indicating a mild underabundance of iron compared to typical stars of its type. As the brightest K-type
giant In folklore, giants (from Ancient Greek: ''wiktionary:gigas, gigas'', cognate wiktionary:giga-, giga-) are beings of humanoid appearance, but are at times prodigious in size and strength or bear an otherwise notable appearance. The word ''gia ...
in the sky, it has been the subject of multiple
atlases An atlas is a collection of maps; it is typically a bundle of maps of Earth or of a continent or region of Earth. Advances in astronomy have also resulted in atlases of the celestial sphere or of other planets. Atlases have traditionally been ...
with coverage from the
ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...
to
infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...
. The spectrum shows a dramatic transition from
emission line A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used ...
s in the ultraviolet to atomic
absorption line Absorption spectroscopy is spectroscopy that involves techniques that measure the absorption (electromagnetic radiation), absorption of electromagnetic radiation, as a function of frequency or wavelength, due to its interaction with a sample. Th ...
s in the visible range and molecular absorption lines in the infrared. This is due to the optical depth of the atmosphere varying with wavelength. The spectrum shows very strong absorption in some molecular lines that are not produced in the
photosphere The photosphere is a star's outer shell from which light is radiated. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately , or equivalently, a depth from which 50% of light will esc ...
but in a surrounding shell. Examination of
carbon monoxide Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...
lines show the molecular component of the atmosphere extending outward to 2–3 times the radius of the star, with the chromospheric wind steeply accelerating to 35–40 km/s in this region. Astronomers term "metals" those elements with higher
atomic number The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of its atomic nucleus. For ordinary nuclei composed of protons and neutrons, this is equal to the proton number (''n''p) or the number of pro ...
s than
helium Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is ...
. The atmosphere of Arcturus has an enrichment of
alpha elements The alpha process, also known as alpha capture or the alpha ladder, is one of two classes of nuclear fusion reactions by which stars convert helium into heavier elements. The other class is a cycle of reactions called the triple-alpha process, wh ...
relative to
iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
but only about a third of solar
metallicity In astronomy, metallicity is the Abundance of the chemical elements, abundance of Chemical element, elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-Dark matter, dark) matt ...
. Arcturus is possibly a
Population II star In 1944, Walter Baade categorized groups of stars within the Milky Way into stellar populations. In the abstract of the article by Baade, he recognizes that Jan Oort originally conceived this type of classification in 1926. Baade observed that ...
.


Oscillations

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 Asteroseismology is the study of oscillations in stars. Stars have many Resonance, resonant modes and frequencies, and the path of sound waves passing through a star depends on the local speed of sound, which in turn depends on local temperature a ...
. 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 and . This form of modelling is still relatively inaccurate, but a useful check on other models.


Search for planets

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions and distances of ...
satellite
astrometry Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other Astronomical object, celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, th ...
suggested that Arcturus is a
binary star A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...
, 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 A substellar object, sometimes called a substar, is an astronomical object, the mass of which is smaller than the smallest mass at which hydrogen fusion can be sustained (approximately 0.08 solar masses). This definition includes brown dwarfs and f ...
would be nearly 12 times the
mass of Jupiter The Jupiter mass, also called Jovian mass, is the units of mass, unit of mass equal to the total mass of the planet Jupiter. This value may refer to the mass of the planet alone, or the mass of the entire Jovian system to include the moons of Jup ...
and be located roughly at the same orbital distance from Arcturus as the Earth is from the Sun, at 1.1 
astronomical unit The astronomical unit (symbol: au or AU) is a unit of length defined to be exactly equal to . Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its m ...
s. 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.


Mythology

One astronomical tradition associates Arcturus with the mythology around
Arcas In Greek mythology, Arcas (; Ancient Greek: Ἀρκάς) was a hunter who became king of Arcadia. He was remembered for having taught people the arts of weaving and baking bread and for spreading agriculture to Arcadia. Family Arcas was the ...
, who was about to shoot and kill his own mother
Callisto CALLISTO (''Cooperative Action Leading to Launcher Innovation in Stage Toss-back Operations'') is a reusable VTVL Prototype, demonstrator propelled by a small 40 kN Japanese LOX-LH2 rocket engine. It is being developed jointly by the CNES, French ...
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 Hyginus may refer to: People *Hyginus, the author of the '' Fabulae'', an important ancient Latin source for Greek mythology. *Hyginus, the author of the ''Astronomia'', a popular ancient Latin guide on astronomy, probably the same as the author ...
's ''
Astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...
''.
Aratus Aratus (; ; c. 315/310 240 BC) was a Greek didactic poet. His major extant work is his hexameter poem ''Phenomena'' (, ''Phainómena'', "Appearances"; ), the first half of which is a verse setting of a lost work of the same name by Eudoxus of Cn ...
in his ''Phaenomena'' said that the star Arcturus lay below the belt of Arctophylax, and according to
Ptolemy Claudius Ptolemy (; , ; ; – 160s/170s AD) was a Greco-Roman mathematician, astronomer, astrologer, geographer, and music theorist who wrote about a dozen scientific treatises, three of which were important to later Byzantine science, Byzant ...
in the ''Almagest'' it lay between his thighs. An alternative lore associates the name with the legend around
Icarius In Greek mythology, there were two people named Icarius (; ''Ikários''). * Icarius, a Spartan prince, son of Perieres. * Icarius, an Athenian who received Dionysus.Apollodorus, 3.14.7 See also *Icarus, whose wings failed in flight Notes Ref ...
, 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 that Icarius became Arcturus while his dog, Maira, became Canicula (
Procyon Procyon () is the brightest star in the constellation of Canis Minor and usually the list of brightest stars, eighth-brightest star in the night sky, with an apparent visual magnitude of 0.34. It has the Bayer designation α Canis Min ...
), although "Arcturus" here may be used in the sense of the constellation rather than the star.


Cultural significance

As one of the
brightest stars This is a list of stars arranged by their apparent magnitude – their brightness as observed from Earth. It includes all stars brighter than magnitude +2.50 in visible light, measured using a ''V''-band filter in the UBV photometric system. Stars ...
in the sky, Arcturus has been significant to observers since antiquity. In ancient
Mesopotamia Mesopotamia is a historical region of West Asia situated within the Tigris–Euphrates river system, in the northern part of the Fertile Crescent. Today, Mesopotamia is known as present-day Iraq and forms the eastern geographic boundary of ...
, it was linked to the god
Enlil Enlil, later known as Elil and Ellil, is an List of Mesopotamian deities, ancient Mesopotamian god associated with wind, air, earth, and storms. He is first attested as the chief deity of the Sumerian pantheon, but he was later worshipped by t ...
, and also known as Shudun, "yoke", or SHU-PA of unknown derivation in the ''Three Stars Each''
Babylonian star catalogues Babylonian astronomy collated earlier observations and divinations into sets of Babylonian star catalogues, during and after the Kassite rule over Babylonia. These star catalogues, written in cuneiform script, contained lists of constellations, ...
and later MUL.APIN around 1100 BC. In ancient Greek, the star is found in ancient astronomical literature, e.g. Hesiod's ''Work and Days'', circa 700 BC, as well as Hipparchus's and Ptolemy's star catalogs. The folk-etymology connecting the star name with the bears (Greek: ἄρκτος, arktos) was probably invented much later. It fell out of use in favour of Arabic names until it was revived in the
Renaissance The Renaissance ( , ) is a Periodization, period of history and a European cultural movement covering the 15th and 16th centuries. It marked the transition from the Middle Ages to modernity and was characterized by an effort to revive and sur ...
. Arcturus is also mentioned in Plato's "Laws" (844e) as a herald for the season of vintage, specifically figs and grapes. In
Arabic Arabic (, , or , ) is a Central Semitic languages, Central Semitic language of the Afroasiatic languages, Afroasiatic language family spoken primarily in the Arab world. The International Organization for Standardization (ISO) assigns lang ...
, Arcturus is one of two stars called ''al-simāk'' "the uplifted ones" (the other is
Spica Spica is the brightest object in the constellation of Virgo and one of the 20 brightest stars in the night sky. It has the Bayer designation α Virginis, which is Latinised to Alpha Virginis and abbreviated Alpha Vir or α Vir. Analys ...
). 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 Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
as ''Al Simak Lanceator''). This has been variously
romanized In linguistics, romanization is the conversion of text from a different writing system to the Roman (Latin) script, or a system for doing so. Methods of romanization include transliteration, for representing written text, and transcription, ...
in the past, leading to obsolete variants such as ''Aramec'' and ''Azimech''. For example, the name ''Alramih'' is used in
Geoffrey Chaucer Geoffrey Chaucer ( ; – 25 October 1400) was an English poet, author, and civil servant best known for ''The Canterbury Tales''. He has been called the "father of English literature", or, alternatively, the "father of English poetry". He w ...
's ''
A Treatise on the Astrolabe ''A Treatise on the Astrolabe'' is a medieval instruction manual on the astrolabe by Geoffrey Chaucer. It was completed in 1391. It describes both the form and the proper use of the instrument, and stands out as a prose technical work from a wr ...
'' (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". In
Indian astronomy Astronomy has a long history in the Indian subcontinent, stretching from History of India, pre-historic to History of India (1947–present), modern times. Some of the earliest roots of Indian astronomy can be dated to the period of Indus Valle ...
, Arcturus is called Swati or
Svati Svati () is a feminine Hindu name that is a compound of + ('great goer', in reference to its remoteness) meaning 'very beneficent'. It was the name of one of the wives of the Moon in Hindu epics and the Sanskrit name of Arcturus as well as of ...
(Devanagari स्वाति, Transliteration IAST svāti, svātī́), possibly 'su' + 'ati' ("great goer", in reference to its remoteness) meaning very beneficent. It has been referred to as "the real pearl" in
Bhartṛhari Bhartṛhari (Devanagari: ; Bhartrihari; fl. c. 5th century CE), was an Indian-Hindu linguistic philosopher and poet, known for his contributions to the fields of linguistics, grammar, and philosophy. He is believed to have been born in the 5t ...
's kāvyas. In
Chinese astronomy Astronomy in China has a long history stretching from the Shang dynasty, being refined over a period of more than 3,000 years. The Ancient China, ancient Chinese people have identified stars from 1300 BCE, as Chinese star names later categori ...
, Arcturus is called ''Da Jiao'' (), because it is the brightest star in the
Chinese constellation Traditional Chinese astronomy has a system of dividing the celestial sphere into asterisms or constellations, known as "officials" ( Chinese ''xīng guān''). The Chinese asterisms are generally smaller than the constellations of Hellenisti ...
called '' Jiao Xiu'' (). Later it became a part of another constellation '' Kang Xiu'' (). The
Wotjobaluk The Wotjobaluk are an Aboriginal Australian people of the state of Victoria. They are closely related to the Wergaia people. Language R. H. Mathews supplied a brief analysis of the Wotjobaluk language (now known as Wergaia), describing what ...
Koori Koori (also spelt koorie, goori or goorie) is a demonym for Aboriginal Australians from a region that approximately corresponds to southern New South Wales and Victoria. The word derives from the Indigenous language Awabakal. For some people ...
people of southeastern Australia knew Arcturus as ''Marpean-kurrk'', mother of ''Djuit'' (
Antares Antares is the brightest star in the constellation of Scorpius. It has the Bayer designation α Scorpii, which is Latinisation of names, Latinised to Alpha Scorpii. Often referred to as "the heart of the scorpion", Antares is flanked by ...
) and another star in Boötes, ''Weet-kurrk'' (Muphrid). Its appearance in the north signified the arrival of the larvae of the
wood ant The ''Formica rufa'' group is a subgeneric group within the genus ''Formica'', first proposed by William Morton Wheeler. This group contains the mound-building species of ''Formica'' commonly termed "wood ants" or "thatch-mound ants", which build ...
(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 Milingimbi Island, also Yurruwi, is the largest island of the Crocodile Islands group off the coast of Arnhem Land, Northern Territory, Australia. Location Milingimbi lies approximately east of Darwin and west of Nhulunbuy. History Aborigin ...
in
Arnhem Land Arnhem Land is a historical region of the Northern Territory of Australia. It is located in the north-eastern corner of the territory and is around from the territorial capital, Darwin, Northern Territory, Darwin. In 1623, Dutch East India Compa ...
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. The
Weilwan The Wayilwan (also rendered Weilwan or Wailwan; also known as Ngiyambaa Wayilwan and Ngemba Wayilwan) are an Aboriginal Australian people of the state of New South Wales. They are a clan of the Ngiyambaa (nee-yam-bar) nation. Name The Wayilwan ...
of northern New South Wales knew Arcturus as ''Guembila'' "red". Prehistoric Polynesian navigators knew Arcturus as ''Hōkūleʻa'', the "Star of Joy". Arcturus is the
zenith The zenith (, ) is the imaginary point on the celestial sphere directly "above" a particular location. "Above" means in the vertical direction (Vertical and horizontal, plumb line) opposite to the gravity direction at that location (nadir). The z ...
star of the
Hawaiian Islands The Hawaiian Islands () are an archipelago of eight major volcanic islands, several atolls, and numerous smaller islets in the Pacific Ocean, North Pacific Ocean, extending some from the Hawaii (island), island of Hawaii in the south to nort ...
. Using Hōkūleʻa and other stars, the Polynesians launched their double-hulled canoes from
Tahiti Tahiti (; Tahitian language, Tahitian , ; ) is the largest island of the Windward Islands (Society Islands), Windward group of the Society Islands in French Polynesia, an overseas collectivity of France. It is located in the central part of t ...
and the
Marquesas Islands The Marquesas Islands ( ; or ' or ' ; Marquesan language, Marquesan: ' (North Marquesan language, North Marquesan) and ' (South Marquesan language, South Marquesan), both meaning "the land of men") are a group of volcano, volcanic islands in ...
. Traveling east and north they eventually crossed the
equator The equator is the circle of latitude that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern Hemispheres of Earth, hemispheres. It is an imaginary line located at 0 degrees latitude, about in circumferen ...
and reached the
latitude In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...
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 The trade winds or easterlies are permanent east-to-west prevailing winds that flow in the Earth's equatorial region. The trade winds blow mainly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere ...
to landfall. If Hōkūleʻa could be kept directly overhead, they landed on the southeastern shores of the Big Island of Hawaii. For a return trip to Tahiti the navigators could use Sirius, the zenith star of that island. Since 1976, the
Polynesian Voyaging Society The Polynesian Voyaging Society (PVS) is a non-profit research and educational corporation based in Honolulu, Hawaii. PVS was established to research and perpetuate traditional Polynesian voyaging methods. Using replicas of traditional double-hul ...
's ''
Hōkūleʻa ''Hōkūlea'' is a performance-accurate ''waa kaulua'', a Polynesian culture, Polynesian double-hulled voyaging canoe. Launched on 8 March 1975 by the Polynesian Voyaging Society, it is best known for its 1976 Hawaii to Tahiti voyage com ...
'' has crossed the Pacific Ocean many times under navigators who have incorporated this
wayfinding Wayfinding (or way-finding) encompasses all of the ways in which people (and animals) Orientation (mental), orient themselves in physical space and navigation, navigate from place to place. Wayfinding software is a self-service computer program th ...
technique in their non-instrument navigation. The crew's successful landing in Waitangi, New Zealand on December 1985 earned them
iwi Iwi () are the largest social units in New Zealand Māori society. In Māori, roughly means or , and is often translated as "tribe". The word is both singular and plural in the Māori language, and is typically pluralised as such in English. ...
hood under the name of (“Tribe of the Arcturus” in Māori). Arcturus had several other names that described its significance to indigenous
Polynesia Polynesia ( , ) is a subregion of Oceania, made up of more than 1,000 islands scattered over the central and southern Pacific Ocean. The indigenous people who inhabit the islands of Polynesia are called Polynesians. They have many things in ...
ns. In the
Society Islands The Society Islands ( , officially ; ) are an archipelago in the South Pacific Ocean that includes the major islands of Tahiti, Mo'orea, Moorea, Raiatea, Bora Bora and Huahine. Politically, they are part of French Polynesia, an overseas country ...
, 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
Tahiti Tahiti (; Tahitian language, Tahitian , ; ) is the largest island of the Windward Islands (Society Islands), Windward group of the Society Islands in French Polynesia, an overseas collectivity of France. It is located in the central part of t ...
an afterlife. In
Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...
, the pattern of Boötes was called ''Hoku-iwa'', meaning "stars of the frigatebird". This constellation marked the path for
Hawaiʻiloa Hawaiiloa (alt. Hawaii Loa or Ke Kowa i Hawaii) is a mythical Hawaiian fisherman and navigator who is said to have discovered the island of Hawaii. Legend Hawaiiloa was an expert fisherman and navigator who was famous for his lengthy fishing ex ...
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 Frigatebirds are a Family (biology), family of seabirds called Fregatidae which are found across all tropical and subtropical oceans. The five extant species are classified in a single genus, ''Fregata''. All have predominantly black plumage, l ...
", 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 The Marquesas Islands ( ; or ' or ' ; Marquesan language, Marquesan: ' (North Marquesan language, North Marquesan) and ' (South Marquesan language, South Marquesan), both meaning "the land of men") are a group of volcano, volcanic islands in ...
, Arcturus was probably called ''Tau-tou'' and was the star that ruled the month approximating January. The
Māori Māori or Maori can refer to: Relating to the Māori people * Māori people of New Zealand, or members of that group * Māori language, the language of the Māori people of New Zealand * Māori culture * Cook Islanders, the Māori people of the Co ...
and
Moriori The Moriori are the first settlers of the Chatham Islands ( in Moriori language, Moriori; in Māori language, Māori). Moriori are Polynesians who came from the New Zealand mainland around 1500 AD, which was close to the time of the ...
called it ''Tautoru'', a variant of the Marquesan name and a name shared with
Orion's Belt Orion's Belt is an asterism in the constellation of Orion. Other names include the Belt of Orion, the Three Kings, and the Three Sisters. The belt consists of three bright and easily identifiable collinear star systems – Alnitak, Alnilam, ...
. In Inuit astronomy, Arcturus is called the Old Man (''Uttuqalualuk'' in
Inuit languages The Inuit languages are a closely related group of Indigenous languages of the Americas, indigenous American languages traditionally spoken across the North American Arctic and the adjacent subarctic regions as far south as Labrador. The Inuit ...
) and The First Ones (''Sivulliik'' in Inuit languages). The
Miꞌkmaq The Mi'kmaq (also ''Mi'gmaq'', ''Lnu'', ''Mi'kmaw'' or ''Mi'gmaw''; ; , and formerly Micmac) are an Indigenous group of people of the Northeastern Woodlands, native to the areas of Canada's Atlantic Provinces, primarily Nova Scotia, New Bru ...
of eastern Canada saw Arcturus as ''Kookoogwéss'', the owl. Early-20th-century Armenian scientist
Nazaret Daghavarian Nazaret Daghavarian (, Western Armenian: Նազարէթ Տաղաւարեան, 1862 in Sebastia, Western Armenia, Ottoman Empire – 1915) was an Ottoman Armenian medical doctor, agronomist and public activist, and one of the founders of the ...
theorized that the star commonly referred to in
Armenian folklore The culture of Armenia encompasses many elements that are based on the Geography of Armenia, geography, Armenian literature, literature, Armenian architecture, architecture, Armenian dance, dance, and Music of Armenia, music of the Armenians, A ...
as ''Gutani astgh'' (
Armenian Armenian may refer to: * Something of, from, or related to Armenia, a country in the South Caucasus region of Eurasia * Armenians, the national people of Armenia, or people of Armenian descent ** Armenian diaspora, Armenian communities around the ...
: Գութանի աստղ; lit. star of the plow) was in fact Arcturus, as the
constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...
of
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 , which comes from 'herder, herdsman' or 'plowman' (literally, 'o ...
was called "Ezogh" (
Armenian Armenian may refer to: * Something of, from, or related to Armenia, a country in the South Caucasus region of Eurasia * Armenians, the national people of Armenia, or people of Armenian descent ** Armenian diaspora, Armenian communities around the ...
: Եզող; lit. the person who is plowing) by Armenians.


In popular culture

In
Ancient Rome In modern historiography, ancient Rome is the Roman people, Roman civilisation from the founding of Rome, founding of the Italian city of Rome in the 8th century BC to the Fall of the Western Roman Empire, collapse of the Western Roman Em ...
, 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 Titus Maccius Plautus ( ; 254 – 184 BC) was a Roman playwright of the Old Latin period. His comedies are the earliest Latin literary works to have survived in their entirety. He wrote Palliata comoedia, the genre devised by Livius Andro ...
' comedy ''
Rudens ''Rudens'' is a play by Roman author Plautus. Its name translates from Latin as "The Rope;" in English translation it has been called ''The Shipwreck'' or ''The Fisherman's Rope''. It is a Roman comedy, which describes how a girl, Palaestra, st ...
'' (circa 211 BC). The ''
Kāraṇḍavyūha Sūtra The ''Kāraṇḍavyūha Sūtra'' ("''The Basket's Display''", Full Sanskrit: ''Āryakāraṇḍavyūhanāmamahāyānasūtra'', Tibetan: phags paza ma tog bkod pa zhes bya ba theg pa chen po'i mdo; zh, t=佛說大乘莊嚴寶王經, p=Fó s ...
'', compiled at the end of the 4th century or beginning of the 5th century, names one of
Avalokiteśvara In Buddhism, Avalokiteśvara (meaning "the lord who looks down", International Phonetic Alphabet, IPA: ), also known as Lokeśvara ("Lord of the World") and Chenrezig (in Tibetan), is a Bodhisattva#Bhūmis (stages), tenth-level bodhisattva associ ...
s meditative absorptions as "The face of Arcturus". One of the possible etymologies offered for the name "
Arthur Arthur is a masculine given name of uncertain etymology. Its popularity derives from it being the name of the legendary hero King Arthur. A common spelling variant used in many Slavic, Romance, and Germanic languages is Artur. In Spanish and Ital ...
" assumes that it is derived from "Arcturus" and that the late 5th to early 6th-century figure on whom the myth of
King Arthur According to legends, King Arthur (; ; ; ) was a king of Great Britain, Britain. He is a folk hero and a central figure in the medieval literary tradition known as the Matter of Britain. In Wales, Welsh sources, Arthur is portrayed as a le ...
is based was originally named for the star. In the
Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...
, Arcturus was considered a
Behenian fixed star The Behenian fixed stars are a selection of fifteen stars considered especially useful for magic (paranormal), magical applications in the medieval astrology of Europe and the Arab world. Their name derives from the Arabic ''bahman'', "root," as ...
and attributed to the stone
jasper Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases, is an opaque, impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to ...
and the plantain herb.
Cornelius Agrippa Heinrich Cornelius Agrippa von Nettesheim (; ; 14 September 1486 – 18 February 1535) was a German Renaissance polymath, physician, legal scholar, soldier, knight, theologian, and occult writer. Agrippa's ''Three Books of Occult Philosophy'' pub ...
listed its
kabbalistic Kabbalah or Qabalah ( ; , ; ) is an esoteric method, discipline and school of thought in Jewish mysticism. It forms the foundation of mystical religious interpretations within Judaism. A traditional Kabbalist is called a Mekubbal (). Jewi ...
sign under the alternate name ''Alchameth''. Arcturus's light was employed in the mechanism used to open the
1933 Chicago World's Fair A Century of Progress International Exposition, also known as the Chicago World's Fair, was a world's fair held in the city of Chicago, Illinois, United States, from 1933 to 1934. The fair, registered under the Bureau International des Exposit ...
. 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). At the height of the American Civil War, President Abraham Lincoln observed Arcturus through a 9.6-inch refractor telescope when he visited the Naval Observatory in Washington, D.C., in August 1863. An Anacondrai general from
Ninjago (TV series) ''Ninjago'' (previously known as ''Ninjago: Masters of Spinjitzu'' until 2019) is an animated High fantasy, epic-fantasy Superhero fiction, superhero television series produced by The Lego Group. It was created to coincide with the Lego Ninjago ...
is also named Arcturus. In the
Fallout 4 ''Fallout 4'' is a 2015 action role-playing game developed by Bethesda Game Studios and published by Bethesda Softworks. It is the fourth main game in the ''Fallout'' series and was released worldwide on November 10, 2015, for Microsoft Windo ...
DLC Nuka-World, an in-game location which was built by Vault-Tec to demonstrate how Vaults might be used for space colonisation uses the name “Arcturus I”.


References


Further reading

* * * * * * * * * * * * * * * * * *


External links


SolStation.com entry
{{DEFAULTSORT:Arcturus K-type giants Suspected variables Hypothetical planetary systems Arcturus moving group Boötes Bootis, Alpha BD+19 2777 Bootis, 16 0541 124897 069673 5340 TIC objects
Arcturus , - bgcolor="#FFFAFA" , Note (category: variability): , , H and K emission vary. Arcturus is a red giant star in the Northern celestial hemisphere, northern constellation of Boötes, and the brightest star in the constellation. It ha ...