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Canopus is the brightest star in the southern
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 origins of the e ...
of Carina and the second-brightest star in the night sky. It is also
designated Designation (from Latin ''designatio'') is the process of determining an incumbent's successor. A candidate that won an election for example, is the ''designated'' holder of the office the candidate has been elected to, up until the candidate's i ...
α Carinae, which is Latinised to Alpha Carinae. With a
visual apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction (astron ...
of −0.74, it is outshone only by Sirius. Located around from the Sun, Canopus is a bright giant of
spectral type A9 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 th ...
, so it is essentially white when seen with the naked eye. It has a luminosity over 10,000 times the luminosity of the Sun, is eight times as massive, and has expanded to 71 times the Sun's radius. Its enlarged
photosphere The photosphere is a star's outer shell from which light is radiated. The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it ...
has an
effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...
of around . Canopus is undergoing core helium burning and is currently in the so-called blue loop phase of its evolution, having already passed through the red-giant branch after exhausting the hydrogen in its core. Canopus is a source of X-rays, which are likely being emitted from its corona. The prominent appearance of Canopus means it has been the subject of mythological lore among many ancient peoples. Its proper name is generally considered to originate from the
mythological Myth is a folklore genre consisting of narratives that play a fundamental role in a society, such as foundational tales or origin myths. Since "myth" is widely used to imply that a story is not objectively true, the identification of a narrat ...
Canopus, who was a navigator for Menelaus, king of Sparta. The
acronychal rising The heliacal rising ( ) or star rise of a star occurs annually, or the similar phenomenon of a planet, when it first becomes visible above the eastern horizon at dawn just before sunrise (thus becoming "the morning star") after a complete orbit of ...
marked the date of the Ptolemaia festival in Egypt. In ancient India, it was named
Agastya Agastya ( kn, ಅಗಸ್ತ್ಯ, ta, அகத்தியர், sa, अगस्त्य, te, అగస్త్యుడు, ml, അഗസ്ത്യൻ, hi, अगस्त्य) was a revered Indian sage of Hinduism. In the I ...
after the revered Vedic sage. For Chinese astronomers, it was known as the Old Man of the South Pole.


Nomenclature

The name ''Canopus'' is a Latinisation of the Ancient Greek name Κάνωβος/Kanôbos, recorded in Claudius Ptolemy's ''
Almagest The ''Almagest'' is a 2nd-century Greek-language mathematical and astronomical treatise on the apparent motions of the stars and planetary paths, written by Claudius Ptolemy ( ). One of the most influential scientific texts in history, it canoni ...
'' (c.150 AD). Eratosthenes used the same spelling. Hipparchos wrote it as Κάνωπος. John Flamsteed wrote Canobus, as did Edmond Halley in his 1679 ''Catalogus Stellarum Australium''. The name has two possible derivations, both listed in Richard Hinckley Allen's seminal '' Star Names: Their Lore and Meaning''. * Argo Navis was the ship used by Jason and the Argonauts in the legend of the Trojan War. The brightest star in the constellation was given the name of a ship's pilot from another Greek legend: Canopus, pilot of Menelaus' ship on his quest to retrieve
Helen of Troy Helen of Troy, Helen, Helena, (Ancient Greek: Ἑλένη ''Helénē'', ) also known as beautiful Helen, Helen of Argos, or Helen of Sparta, was a figure in Greek mythology said to have been the most beautiful woman in the world. She was believe ...
after she was taken by Paris. * A ruined ancient Egyptian port named Canopus lies near the mouth of the Nile, site of the
Battle of the Nile The Battle of the Nile (also known as the Battle of Aboukir Bay; french: Bataille d'Aboukir) was a major naval battle fought between the British Royal Navy and the Navy of the French Republic at Aboukir Bay on the Mediterranean coast off the ...
. It is speculated that its name is derived from the Egyptian
Coptic Coptic may refer to: Afro-Asia * Copts, an ethnoreligious group mainly in the area of modern Egypt but also in Sudan and Libya * Coptic language, a Northern Afro-Asiatic language spoken in Egypt until at least the 17th century * Coptic alphabet ...
''Kahi Nub'' ("Golden Earth"), which refers to how Canopus would have appeared near the horizon in ancient Egypt, reddened by atmospheric extinction from that position. 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 ''Canopus'' for this star. Canopus is now included in the ''IAU Catalog of Star Names''. Canopus traditionally marked the rudder of the ship Argo Navis. German celestial cartographer
Johann Bayer Johann Bayer (1572 – 7 March 1625) was a German lawyer and uranographer (celestial cartographer). He was born in Rain, Lower Bavaria, in 1572. At twenty, in 1592 he began his study of philosophy and law at the University of Ingolstadt, a ...
gave it—as the brightest star in the constellation—the
designation Designation may refer to: * Designation (law), the process of determining an incumbent's successor * Professional certification * Designation (landmarks), an official classification determined by a government agency or historical society * Designa ...
of ''α Argus'' ( Latinised to ''Alpha Argus'') in 1603. In 1763, French astronomer Nicolas Louis de Lacaille divided the huge constellation into three smaller ones, and hence Canopus became ''α Carinae'' ( Latinised to ''Alpha Carinae''). It is listed in the Bright Star Catalogue as HR 2326, the Henry Draper Catalogue as HD 45348, and the Hipparcos catalogue as HIP 30438. Flamsteed did not number this southern star, but Benjamin Apthorp Gould gave it the number 7 (7 G. Carinae) in his ''Uranometria Argentina''. An occasional name seen in English is ''Soheil'', or the feminine Soheila; in Turkish is ''Süheyl'', or the feminine Süheyla, from the Arabic name for several bright stars, سهيل ''suhayl'', and Canopus was known as Suhel in medieval times. Alternative spellings include Suhail, Souhail, Suhilon, Suheyl, Sohayl, Suhayil, Shoel, Sohil, Soheil, Sahil, Suhayeel, Sohayil, Sihel, and Sihil. An alternative name was ''Wazn'' "weight" or ''Haḍar'' "ground", possibly related to its low position near the horizon. Hence comes its name in the '' Alfonsine tables'', Suhel ponderosus, a Latinization of ''Al Suhayl al Wazn''. Its Greek name was revived during the Renaissance.


Observation

The Spanish Muslim astronomer Ibn Rushd went to
Marrakesh Marrakesh or Marrakech ( or ; ar, مراكش, murrākuš, ; ber, ⵎⵕⵕⴰⴽⵛ, translit=mṛṛakc}) is the fourth largest city in the Kingdom of Morocco. It is one of the four Imperial cities of Morocco and is the capital of the Marrakes ...
(in Morocco) to observe the star in 1153, as it was invisible in his native Córdoba, Al-Andalus. He used the different visibility in different latitudes to argue that the earth is round, following Aristotle's argument which held that such an observation was only possible if the earth was a relatively small sphere. English explorer
Robert Hues Robert Hues (1553 – 24 May 1632) was an English mathematician and geographer. He attended St. Mary Hall at Oxford, and graduated in 1578. Hues became interested in geography and mathematics, and studied navigation at a school set up by Walte ...
brought Canopus to the attention of European observers in his 1592 work ''Tractatus de Globis'', along with
Achernar Achernar is the brightest star in the constellation of Eridanus, and the ninth-brightest in the night sky. It has the Bayer designation Alpha Eridani, which is Latinized from α Eridani and abbreviated Alpha Eri or α Eri. The name A ...
and
Alpha Centauri Alpha Centauri ( Latinized from α Centauri and often abbreviated Alpha Cen or α Cen) is a triple star system in the constellation of Centaurus. It consists of 3 stars: Alpha Centauri A (officially Rigil Kentaurus), Alpha Centaur ...
, noting:
"Now, therefore, there are but three Stars of the first magnitude that I could perceive in all those parts which are never seene here in England. The first of these is that bright Star in the sterne of
Argo In Greek mythology the ''Argo'' (; in Greek: ) was a ship built with the help of the gods that Jason and the Argonauts sailed from Iolcos to Colchis to retrieve the Golden Fleece. The ship has gone on to be used as a motif in a variety of sour ...
which they call Canobus. The second is in the end of Eridanus. The third is in the right foote of the Centaure."
In the Southern Hemisphere, Canopus and Sirius are both visible high in the sky simultaneously, and reach a
meridian Meridian or a meridian line (from Latin ''meridies'' via Old French ''meridiane'', meaning “midday”) may refer to Science * Meridian (astronomy), imaginary circle in a plane perpendicular to the planes of the celestial equator and horizon * ...
just apart. Brighter than
first magnitude In astronomy, magnitude is a unitless measure of the brightness of an object in a defined passband, often in the visible or infrared spectrum, but sometimes across all wavelengths. An imprecise but systematic determination of the magnitude o ...
, Canopus can be seen by naked eye in the early twilight. Mostly visible in mid to late summer in the Southern Hemisphere, Canopus culminates at midnight on December 27, and at 9 PM on February 11.Schaaf, p. 257. When seen from latitudes south of  S, Canopus is a circumpolar star. Since Canopus is so far south in the sky, it never rises in mid- to far-northern latitudes; in theory the northern limit of visibility is latitude north. This is just south of Athens,
Richmond, Virginia (Thus do we reach the stars) , image_map = , mapsize = 250 px , map_caption = Location within Virginia , pushpin_map = Virginia#USA , pushpin_label = Richmond , pushpin_m ...
(USA), and San Francisco, and very close to Seville and Agrigento. It is almost exactly the latitude of
Lick Observatory The Lick Observatory is an astronomical observatory owned and operated by the University of California. It is on the summit of Mount Hamilton, in the Diablo Range just east of San Jose, California, United States. The observatory is managed by th ...
on Mt. Hamilton, California, from which it is readily visible because of the effects of elevation and atmospheric refraction, which add another degree to its apparent altitude. Under ideal conditions, it can be spotted as far north as latitude from the Pacific coast. Another northernmost record of visibility came from Mount Nemrut in Turkey, latitude . It is more easily visible in places such as the Gulf Coast and Florida, and the island of Crete (Greece) where the best season for viewing it around 9 p.m. is during late January and early February. Canopus has a B–V color index of +0.15—where 0 is a blue-white—indicating it is essentially white, although it has been described as yellow-white. Canopus' spectral type has been given as F0 and the incrementally warmer A9. It is less yellow than Altair or Procyon, with indices measured as 0.22 and 0.42, respectively. Some observers may have perceived Canopus as yellow-tinged because it is low in the sky and hence subject to atmospheric effects.Schaaf, pp. 112–13.
Patrick Moore Sir Patrick Alfred Caldwell-Moore (; 4 March 1923 – 9 December 2012) was an English amateur astronomer who attained prominence in that field as a writer, researcher, radio commentator and television presenter. Moore was president of the Brit ...
said that it never appeared anything but white to him. The bolometric correction for Canopus is 0.00, indicating that the visual absolute magnitude and bolometric absolute magnitude are equal. Canopus was previously proposed to be a member of the
Scorpius–Centaurus association The Scorpius–Centaurus association (sometimes called Sco–Cen or Sco OB2) is the nearest OB association to the Sun. This stellar association is composed of three subgroups (Upper Scorpius, Upper Centaurus–Lupus, and Lower Centaurus–Crux) ...
, however it is not located near the subgroups of that association, and has not been included as a Sco-Cen member in kinematic studies that used
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 of celestial obj ...
astrometric data. Canopus is not thought to be a member of any nearby young stellar groups. In 2014, astronomer Eric Mamajek reported that an extremely magnetically active M dwarf (having strong coronal X-ray emission), 1.16 degrees south of Canopus, appears to share a
common proper motion This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of celestial objects and phenomena that originate outsid ...
with Canopus. The projected separation of the M dwarf 2MASS J06234738-5351131 ("Canopus B") is approximately 1.9 parsecs. However, despite this large separation, it is still within the estimated tidal radius (2.9 parsecs) for the massive star Canopus. No star closer than Canopus is more luminous than it, and it has been the brightest star in Earth's night sky during three epochs over the past four million years. Other stars appear brighter only during relatively temporary periods, during which they are passing the Solar System much closer than Canopus. About 90,000 years ago, Sirius moved close enough that it became brighter than Canopus, and that will remain so for another 210,000 years. But in 480,000 years, as Sirius moves further away and appears fainter, Canopus will once again be the brightest, and will remain so for a period of about 510,000 years.


Role in navigation

The southeastern wall of the
Kaaba The Kaaba (, ), also spelled Ka'bah or Kabah, sometimes referred to as al-Kaʿbah al-Musharrafah ( ar, ٱلْكَعْبَة ٱلْمُشَرَّفَة, lit=Honored Ka'bah, links=no, translit=al-Kaʿbah al-Musharrafah), is a building at the c ...
in Mecca is aligned with the rising point of Canopus, and is also named ''Janūb''. The
Bedouin The Bedouin, Beduin, or Bedu (; , singular ) are nomadic Arab tribes who have historically inhabited the desert regions in the Arabian Peninsula, North Africa, the Levant, and Mesopotamia. The Bedouin originated in the Syrian Desert and A ...
people of the Negev and
Sinai Sinai commonly refers to: * Sinai Peninsula, Egypt * Mount Sinai, a mountain in the Sinai Peninsula, Egypt * Biblical Mount Sinai, the site in the Bible where Moses received the Law of God Sinai may also refer to: * Sinai, South Dakota, a place ...
knew Canopus as ''Suhayl'', and used it and
Polaris 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 or Pole Star. With an apparent magnitude that ...
as the two principal stars for navigation at night. Because it disappears below the horizon in those regions, it became associated with a changeable nature, as opposed to always-visible Polaris, which was circumpolar and hence 'steadfast'. The south celestial pole can be approximately located using Canopus and another bright star,
Achernar Achernar is the brightest star in the constellation of Eridanus, and the ninth-brightest in the night sky. It has the Bayer designation Alpha Eridani, which is Latinized from α Eridani and abbreviated Alpha Eri or α Eri. The name A ...
, as the three make an equilateral triangle. Canopus sits on an imaginary line that extends one way to Sirius and to the south celestial pole. Canopus's brightness and location well off the ecliptic make it useful for space navigation. Many spacecraft carry a special camera known as a "Canopus Star Tracker" plus a Sun sensor for
attitude Attitude may refer to: Philosophy and psychology * Attitude (psychology), an individual's predisposed state of mind regarding a value * Metaphysics of presence * Propositional attitude, a relational mental state connecting a person to a pro ...
determination. Mariner 4 used Canopus for second axis stabilisation (after locking on the Sun) in 1964, the first time a star had been used.


Spectrum

Canopus was little-studied by western scientists before the 20th century. It was given a spectral class of F in 1897, an early use of this extension to
Secchi class 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 grati ...
I, applied to those stars where the hydrogen lines are relatively weak and the calcium K line relatively strong. It was given as a standard star of F0 in the Henry Draper Catalogue, with the spectral type F0 described as having hydrogen lines half the strength of an A0 star and the calcium K line three times as strong as Hδ. American astronomer
Jesse Greenstein Jesse Leonard Greenstein (October 15, 1909 – October 21, 2002) was an American astronomer. His parents were Maurice G. and Leah Feingold. He earned a Ph.D, with thesis advisor Donald H. Menzel, from Harvard University in 1937, having starte ...
was interested in stellar spectra and used the newly built Otto Struve Telescope at McDonald Observatory to analyze the star's spectrum in detail. In a 1942 paper, he reported that the spectrum is dominated by strong broad hydrogen lines. There are also
absorption line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...
s of carbon, nitrogen, oxygen, sulphur, iron, and many ionised metals. It was studied in the ultraviolet by an early astronomical satellite,
Gemini XI Gemini 11 (officially Gemini XI) With Gemini IV, NASA changed to Roman numerals for Gemini mission designations. was the ninth crewed spaceflight mission of NASA's Project Gemini, which flew from September 12 to 15, 1966. It was the 17th crewed ...
in 1966. The UV spectra were considered to be consistent with an F0 supergiant having a temperature of , the accepted parameters for Canopus at the time. New Zealand-based astronomers
John Hearnshaw John Bernard Hearnshaw (born 16 March 1946) is a New Zealand astronomer who is Emeritus Professor of Astronomy at the University of Canterbury. He served as director of the Mt John University Observatory at the University of Canterbury from 19 ...
and Krishna Desikachary examined the spectrum in greater detail, publishing their results in 1982. When luminosity classes were added to the MK spectral classification scheme, Canopus was assigned class Iab indicating an intermediate luminosity supergiant. This was based on the relative strengths of certain spectral lines understood to be sensitive to the luminosity of a star. In the Bright Star Catalogue 5th edition it is given the spectral class F0II, the luminosity class indicating a bright giant. Balmer line profiles and oxygen line strengths indicate the size and luminosity of Canopus. When the effects of stellar rotation speed on spectral lines are accounted for, the MK spectral class of Canopus is adjusted to A9II. Its spectrum consists mostly of absorption lines on a visible
continuum Continuum may refer to: * Continuum (measurement), theories or models that explain gradual transitions from one condition to another without abrupt changes Mathematics * Continuum (set theory), the real line or the corresponding cardinal number ...
, but some emission has been detected. For example, the calcium K line have weak emission wings on each side of the strong central absorption line, first observed in 1966. The emission line profiles are usually correlated with the luminosity of the star as described by the Wilson-Bappu effect, but in the case of Canopus they indicate a luminosity much lower than that calculated by other methods. More detailed observations have shown that the emission line profiles are variable and may be due to
plage Plage may refer to: *Plage (astronomy), a bright region in the chromosphere of the Sun *Plage (mycology), a clear, unornamented area on the basal area of an ornamented fungal spore * "Plage" (song), a 2011 song by English electronic band Crystal F ...
areas on the surface of the star. Emission can also be found in other lines such as the h and k lines of ionised magnesium.


Distance

Before the launch of 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 of celestial obj ...
satellite telescope, distance estimates for Canopus varied widely, from 96
light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s to 1200 light-years. The closer distance was derived from parallax measurements of around . The larger distance derives from the assumption of a very bright absolute magnitude for Canopus. Hipparcos established Canopus as being () from the Solar System; this is based on its 2007
parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...
measurement of . At 95 parsecs, the interstellar extinction for Canopus is low at 0.26 magnitudes. Canopus is too bright to be included in the normal observation runs of the
Gaia satellite ''Gaia'' is a space observatory of the European Space Agency (ESA), launched in 2013 and expected to operate until 2025. The spacecraft is designed for astrometry: measuring the positions, distances and motions of stars with unprecedented preci ...
and there is no published Gaia parallax for it. At present the star is drifting further away from the Sun with a
radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...
of 20 km/s. Some 3.1 million years ago it made the closest approach to the Sun at a distance of about . Canopus is orbiting the Milky Way with a heliocentric velocity of 24.5 km/s and a low eccentricity of 0.065.


Physical characteristics

The
absorption line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...
s in the spectrum of Canopus shift slightly with a period of . This was first detected in 1906 and the Doppler variations were interpreted as orbital motion. An orbit was even calculated, but no such companion exists and the small radial velocity changes are due to movements in the atmosphere of the star. The maximum observed radial velocities are only 0.7 to . Canopus also has a magnetic field that varies with the same period, detected by the
Zeeman splitting The Zeeman effect (; ) is the effect of splitting of a spectral line into several components in the presence of a static magnetic field. It is named after the Dutch physicist Pieter Zeeman, who discovered it in 1896 and received a Nobel prize ...
of its spectral lines. Canopus is bright at microwave wavelengths, one of the few F-class stars to be detected by radio. The
rotation period The rotation period of a celestial object (e.g., star, gas giant, planet, moon, asteroid) may refer to its sidereal rotation period, i.e. the time that the object takes to complete a single revolution around its axis of rotation relative to the ...
of the star is not accurately known, but may be over three hundred days. The
projected rotational velocity Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulge ...
has been measured at 9 km/s. An early
interferometric Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber op ...
measurement of its angular diameter in 1968 gave a limb-darkened value of , close to the accepted modern value.
Very-long-baseline interferometry Very-long-baseline interferometry (VLBI) is a type of astronomical interferometer, astronomical interferometry used in radio astronomy. In VLBI a signal from an astronomical radio source, such as a quasar, is collected at multiple radio telesco ...
has been used to calculate Canopus' angular diameter at . Combined with distance calculated from its Hipparcos parallax, this gives it a radius of 71 times that of the Sun. If it were at the centre of the Solar System, it would extend 90% of the way to the orbit of
Mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...
. The radius and temperature relative to the Sun means that it is 10,700 times more luminous than the Sun, and its position in the H-R diagram relative to theoretical evolutionary tracks means that it is times as massive as the Sun. Measurements of its shape find a 1.1° departure from spherical symmetry. Canopus is a source of X-rays, which are probably produced by its corona, magnetically heated to several million Kelvin. The temperature has likely been stimulated by fast rotation combined with strong convection percolating through the star's outer layers. The soft X-ray sub-coronal X-ray emission is much weaker than the hard X-ray coronal emission. The same behaviour has been measured in other F-class supergiants such as α Persei and is now believed to be a normal property of such stars.


Evolution

The spectrum of Canopus indicates that it has exhausted its core hydrogen and evolved away from the
main sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...
, where it spent some 30 million years of its existence as a blue-white star of around 10 solar masses. The position of Canopus in the H–R diagram indicates that it is currently in the core-helium burning phase. It is an intermediate mass star that has left the red-giant branch before its core became
degenerate Degeneracy, degenerate, or degeneration may refer to: Arts and entertainment * ''Degenerate'' (album), a 2010 album by the British band Trigger the Bloodshed * Degenerate art, a term adopted in the 1920s by the Nazi Party in Germany to descr ...
and is now in a blue loop. Models of stellar evolution in the blue loop phase show that the length of the blue loop is strongly affected by rotation and mixing effects inside the star. It is difficult to determine whether a star is currently evolving towards hotter temperature or returning to cooler temperatures, since the evolutionary tracks for stars with different masses overlap during the blue loops. Canopus lies on the warm side of the
instability strip The unqualified term instability strip usually refers to a region of the Hertzsprung–Russell diagram largely occupied by several related classes of pulsating variable stars: Delta Scuti variables, SX Phoenicis variables, and rapidly oscillati ...
and does not pulsate like
Cepheid variables A Cepheid variable () is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude. A strong direct relationship between a Cepheid vari ...
of a similar luminosity. However its atmosphere does appear to be unstable, showing strong signs of convection. Canopus may not be massive enough for its fusion chain to reach iron and trigger a core collapse and subsequent
supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...
, instead eventually becoming a neon-oxygen white dwarf.


Cultural significance

Canopus was known to the ancient Mesopotamians and given the name ''NUN-ki'' and represented the city of Eridu in the ''Three Stars Each'' Babylonian star catalogues and later MUL.APIN around 1100 BC. Today, the star
Sigma Sagittarii Sigma Sagittarii, Latinized from σ Sagittarii; formally named Nunki , is the second-brightest star in the constellation of Sagittarius. It has an apparent magnitude of +2.05, making it readily visible to the naked eye. The distanc ...
is known by the common name Nunki. Canopus was not visible to the mainland ancient Greeks and Romans; it was, however, visible to the ancient Egyptians.Schaaf, p. 107. Hence Aratus did not write of the star as it remained below the horizon, while
Eratosthenes Eratosthenes of Cyrene (; grc-gre, Ἐρατοσθένης ;  – ) was a Greek polymath: a mathematician, geographer, poet, astronomer, and music theorist. He was a man of learning, becoming the chief librarian at the Library of Alexandria ...
and Ptolemy—observing from Alexandria—did, calling it ''Kanōbos''. An Egyptian priestly poet in the time of Thutmose III mentions the star as ''Karbana,'' "the star which pours his light in a glance of fire, when he disperses the morning dew." Under the
Ptolemies The Ptolemaic dynasty (; grc, Πτολεμαῖοι, ''Ptolemaioi''), sometimes referred to as the Lagid dynasty (Λαγίδαι, ''Lagidae;'' after Ptolemy I's father, Lagus), was a Macedonian Greek royal dynasty which ruled the Ptolemaic K ...
, the star was known as ''Ptolemaion'' ( Greek: Πτολεμαῖον) and its
acronychal rising The heliacal rising ( ) or star rise of a star occurs annually, or the similar phenomenon of a planet, when it first becomes visible above the eastern horizon at dawn just before sunrise (thus becoming "the morning star") after a complete orbit of ...
marked the date of the Ptolemaia festival, which was held every four years, from 262 to 145 BC.


India

In Indian
Vedic literature upright=1.2, The Vedas are ancient Sanskrit texts of Hinduism. Above: A page from the '' Atharvaveda''. The Vedas (, , ) are a large body of religious texts originating in ancient India. Composed in Vedic Sanskrit, the texts constitute the ...
, Canopus is associated with the sage
Agastya Agastya ( kn, ಅಗಸ್ತ್ಯ, ta, அகத்தியர், sa, अगस्त्य, te, అగస్త్యుడు, ml, അഗസ്ത്യൻ, hi, अगस्त्य) was a revered Indian sage of Hinduism. In the I ...
, one of the ancient siddhars and
rishi ''Rishi'' () is a term for an accomplished and enlightened person. They find mentions in various Vedic texts. Rishis are believed to have composed hymns of the Vedas. The Post-Vedic tradition of Hinduism regards the rishis as "great yogis" or ...
s (the others are associated with the stars of the Big Dipper). To Agastya, the star is said to be the 'cleanser of waters', and its rising coincides with the calming of the waters of the Indian Ocean. It is thus considered the son of Pulastya, son of Brahma. Canopus is described by Pliny the Elder and Gaius Julius Solinus as the largest, brightest and only source of
starlight Starlight is the light emitted by stars. It typically refers to visible electromagnetic radiation from stars other than the Sun, observable from Earth at night, although a component of starlight is observable from Earth during daytime. Sunligh ...
for navigators near Tamraparni island (ancient Sri Lanka) during many nights.


China

Canopus was described as Shou Xing, the Star of Longevity, in the ''Shiji'' ( Records of the Grand Historian) completed in 94 BC by Chinese historian
Sima Qian Sima Qian (; ; ) was a Chinese historian of the early Han dynasty (206AD220). He is considered the father of Chinese historiography for his ''Records of the Grand Historian'', a general history of China covering more than two thousand years b ...
. Drawing on sources from the Warring States period, he noted it to be the southern counterpart of Sirius, and wrote of a sanctuary dedicated to it established by Emperor Qin Shi Huang between 221 and 210 BC. During the Han dynasty, the star was auspicious, its appearance in the southern sky heralding peace and absence war. From the imperial capital Chang'an, the star made a low transit across the southern sky, indicating true south to observers, and was often obscured by clouds. During this time it was also equated with Old Man of the South Pole (in ) Under this name, Canopus appears (albeit misplaced northwards) on the medieval Chinese manuscript the Dunhuang Star Chart, although it cannot be seen from the Chinese capital of Chang'an. The Chinese astronomer Yi Xing had journeyed south to chart Canopus and other far southern stars in 724 AD. Its personification as the Old Man Star was popularised in the Tang Dynasty, where it appeared often in poetry and memorials. Later still, during the Ming Dynasty, the star was established as one of the Three Stars (Fu Lo Shou), appearing frequently in art and literature of the time. This symbolism spread into neighbouring cultures in Asia. In Japan, Canopus is known as ''Mera-boshi'' and ''Roujin-sei'' (the old man star), and in Mongolia, it was personified as the White Old Man. Although the link was known in Tibet, with names such as ''Genpo karpo'' (''Rgan po dkar po'') or ''Genkar'' (''Rgan dkar'') "White Old Man", the symbolism was not popular. Instead, Canopus was more commonly named ''Karma Rishi སྐར་མ་རི་ཥི།'', derived from Indian mythology. Tibetans celebrated the star's heliacal rising with ritual bathing and associated it with morning dew.


Polynesia

Bright stars were important to the ancient
Polynesians Polynesians form an ethnolinguistic group of closely related people who are native to Polynesia (islands in the Polynesian Triangle), an expansive region of Oceania in the Pacific Ocean. They trace their early prehistoric origins to Island Sou ...
for navigation between the many islands and atolls of the Pacific Ocean. Low on the horizon, they acted as stellar compasses to assist mariners in charting courses to particular destinations. Canopus served as the southern wingtip of a "Great Bird" constellation called ''Manu'', with Sirius as the body and Procyon the northern wingtip, which divided the Polynesian night sky into two hemispheres. The
Hawaiian people Native Hawaiians (also known as Indigenous Hawaiians, Kānaka Maoli, Aboriginal Hawaiians, First Hawaiians, or simply Hawaiians) ( haw, kānaka, , , and ), are the Indigenous peoples of Oceania, indigenous ethnic group of Polynesians, Polynes ...
called Canopus ''Ke Alii-o-kona-i-ka-lewa'', "The chief of the southern expanse"; it was one of the stars used by
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 ...
and Ki when they traveled to the Southern Ocean. The Māori people of New Zealand/Aotearoa had several names for Canopus. '' Ariki'' ("High-born"), was known as a solitary star that appeared in the east, prompting people to weep and chant. They also named it ''
Atutahi In Māori mythology, Atutahi is the name of Canopus, ( Alpha Carinae). Atutahi is the second brightest star in the night-time sky, second only to Sirius (Takurua). ''Aotahi'', ''Autahi'', and ''Atutahi'', "First-light" or "Single-light", were eq ...
'', ''Aotahi'' or ''Atuatahi'', "Stand Alone". Its solitary nature indicates it is a '' tapu'' star, as ''tapu'' people are often solitary. Its appearance at the beginning of the ''Maruaroa'' season foretells the coming winter; light rays to the south indicate a cold wet winter, and to the north foretell a mild winter. Food was offered to the star on its appearance. This name has several mythologies attached to it. One story tells of how Atutahi was left outside the basket representing the Milky Way when Tāne wove it. Another related myth about the star says that Atutahi was the first-born child of Rangi, who refused to enter the Milky Way and so turned it sideways and rose before it. The same name is used for other stars and constellations throughout Polynesia. ''Kapae-poto'', "Short horizon", referred to it rarely setting as seen in New Zealand; ''Kauanga'' ("Solitary") was the name for Canopus only when it was the last star visible before sunrise. The people of the Society Islands had two names for Canopus, as did the Tuamotu people. The Society Islanders called Canopus ''Taurua-e-tupu-tai-nanu'', "Festivity-whence-comes-the-flux-of-the-sea", and ''Taurua-nui-o-te-hiti-apatoa'' "Great-festivity-of-the-border-of-the-south", and the Tuamotu people called the star ''Te Tau-rari'' and ''Marere-te-tavahi'', the latter said to be the true name for the former, "He-who-stands-alone".


Africa

In the Guanche mythology of the island of Tenerife (Spain), the star Canopus was linked with the goddess Chaxiraxi. The Tswana people of Botswana knew Canopus as ''Naka''. Appearing late in winter skies, it heralded increasing winds and a time when trees lose their leaves. Stock owners knew it was time to put their sheep with rams. In southern Africa, the Sotho, Tswana and Venda people called Canopus ''Naka'' or ''Nanga'', “the Horn Star”, while the Zulu and Swazi called it ''inKhwenkwezi'' "Brilliant star". It appears in the predawn sky in the third week of May. According to the Venda, the first person to see Canopus would blow a ''phalaphala'' horn from the top of a hill, getting a cow for a reward. The Sotho chiefs also awarded a cow, and ordered their medicine men to roll bone dice and read the fortune for the coming year. To the ǀXam-speaking
Bushmen The San peoples (also Saan), or Bushmen, are members of various Khoe, Tuu, or Kxʼa-speaking indigenous hunter-gatherer cultures that are the first cultures of Southern Africa, and whose territories span Botswana, Namibia, Angola, Zambia, ...
of South Africa, Canopus and Sirius signalled the appearance of termites and flying ants. They also believed that stars had the power to cause death and misfortune, and they would pray to Sirius and Canopus in particular to impart good fortune or skill. The ǃKung people of the Kalahari Desert in Botswana held Canopus and Capella to be the horns of ''tshxum'' (the Pleiades), the appearance of all three marking the end of the dry season and start of the rainy season.


Americas

The
Navajo The Navajo (; British English: Navaho; nv, Diné or ') are a Native American people of the Southwestern United States. With more than 399,494 enrolled tribal members , the Navajo Nation is the largest federally recognized tribe in the United ...
observed the star and named it ''Maʼii Bizòʼ'', the “Coyote Star”. According to legend, Maʼii (Coyote) took part in the naming and placing of the star constellations during the creation of the universe. He placed Canopus directly south, naming it after himself.Maryboy, Nancy D. (2004). ''A Guide to Navajo Astronomy.'' Indigenous Education Institute : Bluff, Utah. The
Kalapalo The Kalapalo are an indigenous people of Brazil. They are one of seventeen tribal groups who inhabit the Xingu National Park in the Upper Xingu River region of the state of Mato Grosso. They speak the Amonap language, a Cariban language, and o ...
people of
Mato Grosso Mato Grosso ( – lit. "Thick Bush") is one of the states of Brazil, the third largest by area, located in the Central-West region. The state has 1.66% of the Brazilian population and is responsible for 1.9% of the Brazilian GDP. Neighboring ...
state in Brazil saw Canopus and Procyon as ''Kofongo'' "Duck", with Castor and Pollux representing his hands. The asterism's appearance signified the coming of the rainy season and increase in manioc, a food staple fed to guests at feasts.


Australia

Canopus is identified as the moiety ancestor ''Waa'' "Crow" to some Koori people in southeastern Australia. The Boorong people of northwestern Victoria recalled that ''War'' (Canopus) was the brother of ''Warepil'' (Sirius), and that he brought fire from the heavens and introduced it to humanity. His wife was ''Collowgullouric War'' ( Eta Carinae). The Pirt-Kopan-noot people of western Victoria tell of ''Waa'' "Crow" falling in love with a queen, ''Gneeanggar'' "Wedge-tailed Eagle" (Sirius) and her six attendants (the Pleiades). His advances spurned, he hears that the women are foraging for grubs and so transforms himself into a grub. When the women dig him out, he changes into a giant and carries her off. The Kulin people know Canopus as ''Lo-an-tuka''. Objects in the sky are also associated with states of being for some tribes; the Wailwun of northern New South Wales know Canopus as ''Wumba'' "deaf", alongside Mars as ''Gumba'' "fat" and Venus as ''Ngindigindoer'' "you are laughing". Tasmanian aboriginal lore holds that Canopus is ''Dromerdene'', the brother of ''Moinee''; the two fought and fell out of the sky, with ''Dromerdene'' falling into Louisa Bay in southwest Tasmania.


Legacy

Canopus appears on the flag of Brazil, symbolising the state of Goiás. Two U.S. Navy submarine tenders have been named after Canopus, the
first First or 1st is the ordinal form of the number one (#1). First or 1st may also refer to: *World record, specifically the first instance of a particular achievement Arts and media Music * 1$T, American rapper, singer-songwriter, DJ, and rec ...
serving from 1922 to 1942 and the
second The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds ...
serving from 1965 to 1994. The Royal Navy built nine Canopus-class ships of the line in the early 19th century, and six s which entered services between 1899 and 1902. There are at least two mountains named after the star:
Mount Canopus The Nash Range () is a mainly ice-covered coastal range in the Churchill Mountains of Antarctica. Location The Nash Range is 40 nautical miles (70 km) long, bordering the west side of the Ross Ice Shelf between the Dickey and Nimrod Glacie ...
in Antarctica; and Mount Canopus or Canopus Hill in Tasmania, the location of the Canopus Hill astronomical observatory.


See also

* List of brightest stars *
List of most luminous stars This is a list of stars arranged by their absolute magnitude – their intrinsic stellar luminosity. This cannot be observed directly, so instead must be calculated from the apparent magnitude (the brightness as seen from Earth), the distance t ...
* Dune (novel)


References


Bibliography

* * {{DEFAULTSORT:Canopus Carinae, Alpha Carina (constellation) A-type bright giants 045348 030438
2326 In contemporary history, the third millennium of the anno Domini or Common Era in the Gregorian calendar is the current millennium spanning the years 2001 to 3000 ( 21st to 30th centuries). Ongoing futures studies seek to understand what is ...
Stars named from the Ancient Greek language Durchmusterung objects