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82-498: Located around 310  light-years from the Sun , Canopus is a bright giant of spectral type A9 , 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 has an effective temperature of around 7400 K . Canopus

164-413: A common proper motion 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. Since it is more luminous than any star closer to Earth, Canopus has been the brightest star in the night sky during three epochs over

246-513: A limb-darkened value of 6.86  mas , close to the accepted modern value. Very-long-baseline interferometry has been used to calculate Canopus' angular diameter at 6.9  mas . 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 . The radius and temperature relative to

328-407: A star system tend to be small fractions of a light-year, and are usually expressed in astronomical units . However, smaller units of length can similarly be formed usefully by multiplying units of time by the speed of light. For example, the light-second , useful in astronomy, telecommunications and relativistic physics, is exactly 299 792 458 metres or ⁠ 1 / 31 557 600 ⁠ of

410-486: A unit of time . The light-year is most often used when expressing distances to stars and other distances on a galactic scale, especially in non-specialist contexts and popular science publications. The unit most commonly used in professional astronomy is the parsec (symbol: pc, about 3.26 light-years). As defined by the International Astronomical Union (IAU), the light-year

492-427: 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 two different bright stars. The first, Achernar , makes an equilateral triangle between the stars and the south pole. One can also locate the pole more roughly using an imaginary line between Sirius and Canopus; Canopus will be approximately at

574-408: A cow, and ordered their medicine men to roll bone dice and read the fortune for the coming year. To the ǀXam -speaking Bushmen 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

656-412: A light-year. Units such as the light-minute, light-hour and light-day are sometimes used in popular science publications. The light-month, roughly one-twelfth of a light-year, is also used occasionally for approximate measures. The Hayden Planetarium specifies the light month more precisely as 30 days of light travel time. Light travels approximately one foot in a nanosecond ; the term "light-foot"

738-506: A magnetic field that varies with the same period, detected by the Zeeman splitting 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 of the star is not accurately known, but may be over three hundred days. The projected rotational velocity has been measured at 9 km/s. An early interferometric measurement of its angular diameter in 1968 gave

820-520: 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

902-851: A name that is also commonly used to imply rareness of appearance (as the Canopus infrequently appeared to a gazer at Middle Eastern latitutes) The name Canopus is a Latinisation of the Ancient Greek name Κάνωβος/Kanôbos, recorded in Claudius Ptolemy's Almagest (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 . In 2016,

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984-467: A paper dating Tasmanian Aboriginal oral tradition to the late Pleistocene, when Canopus was much closer to the South celestial pole . 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 serving from 1922 to 1942 and the second serving from 1965 to 1994. The Royal Navy built nine Canopus-class ships of

1066-518: A star had been used. 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 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

1148-560: Is "ly", International standards like ISO 80000:2006 (now superseded) have used "l.y." and localized abbreviations are frequent, such as "al" in French, Spanish, and Italian (from année-lumière , año luz and anno luce , respectively), "Lj" in German (from Lichtjahr ), etc. Before 1984, the tropical year (not the Julian year) and a measured (not defined) speed of light were included in

1230-402: Is a unit of length used to express astronomical distances and is equal to exactly 9 460 730 472 580 .8 km , which is approximately 5.88 trillion mi. As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in vacuum in one Julian year (365.25 days). Despite its inclusion of the word "year", the term should not be misinterpreted as

1312-571: Is almost exactly the latitude of Lick Observatory 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 37° 31′ from the Pacific coast. Another northernmost record of visibility came from Mount Nemrut in Turkey, latitude 37° 59′. It

1394-533: Is an odd name. In 1868 an English journal labelled the light-year as a unit used by the Germans. Eddington called the light-year an inconvenient and irrelevant unit, which had sometimes crept from popular use into technical investigations. Although modern astronomers often prefer to use the parsec , light-years are also popularly used to gauge the expanses of interstellar and intergalactic space. Distances expressed in light-years include those between stars in

1476-621: Is generally considered to originate from the mythological Canopus , who was a navigator for Menelaus , king of Sparta . The acronycal rising marked the date of the Ptolemaia festival in Egypt. In ancient India, it was named Agastya after the revered Vedic sage. For Chinese astronomers, it was known as the Old Man of the South Pole . In Islamic astronomy , it is Suhail or Suhayl ,

1558-449: 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. Patrick Moore 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

1640-487: 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

1722-556: Is sometimes used as an informal measure of time. Alfonsine tables The Alfonsine Tables ( Spanish : Tablas Alfonsíes , Latin : Tabulae Alphonsinae ), sometimes spelled Alphonsine Tables , provided data for computing the position of the Sun , Moon and planets relative to the fixed stars . The tables were named after Alfonso X of Castile , who sponsored their creation. They were compiled in Toledo, Spain , and contain astronomical data starting on June 1, 1252,

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1804-564: Is that bright Star in the sterne of Argo 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 just 21 min apart. Brighter than first magnitude , Canopus can be seen by naked eye in the early twilight. Mostly visible in mid to late summer in

1886-570: Is the product of the Julian year (365.25 days, as opposed to the 365.2425-day Gregorian year or the 365.24219-day Tropical year that both approximate) and the speed of light ( 299 792 458  m/s ). Both of these values are included in the IAU (1976) System of Astronomical Constants , used since 1984. From this, the following conversions can be derived: The abbreviation used by the IAU for light-year

1968-549: Is the product of the J1900.0 mean tropical year and the defined speed of light. Abbreviations used for light-years and multiples of light-years are: The light-year unit appeared a few years after the first successful measurement of the distance to a star other than the Sun, by Friedrich Bessel in 1838. The star was 61 Cygni , and he used a 160-millimetre (6.2 in) heliometre designed by Joseph von Fraunhofer . The largest unit for expressing distances across space at that time

2050-421: 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

2132-715: 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

2214-678: The Alfonsine tables , Suhel ponderosus, a Latinization of Al Suhayl al Wazn . Its Greek name was revived during the Renaissance . The Arabic Muslim astronomer Ibn Rushd went to Marrakesh (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

2296-577: The Alfonsine tables were originally written in Castilian Spanish . The first printed edition of the Alfonsine tables appeared in 1483, and a second edition in 1492. Georg Purbach used the Alfonsine tables for his book, Theoricae novae planetarum ( New Theory of the Planets ). Nicolaus Copernicus used the second edition in his work. One use of these and similar astronomical tables

2378-485: The Gaia satellite and there is no published Gaia parallax for it. At present the star is drifting further away from the Sun with a radial velocity of 20 km/s. Some 3.1 million years ago it made the closest approach to the Sun at a distance of about 172 ly (53 pc). Canopus is orbiting the Milky Way with a heliocentric velocity of 24.5 km/s and a low eccentricity of 0.065. The absorption lines in

2460-707: 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

2542-511: 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 steering oar of

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2624-890: 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. The Navajo 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. The Kalapalo people of Mato Grosso state in Brazil saw Canopus and Procyon as Kofongo "Duck", with Castor and Pollux representing his hands. The asterism's appearance signified

2706-459: The main sequence . 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 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

2788-700: 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

2870-580: The Copernican heliocentric model of the solar system. Copernicus's publication, De revolutionibus , was not easy to use and the Prutenic tables were intended to make the heliocentric model more usable by astrologers and astronomers. However, the Prutenic tables were not widely adopted outside German speaking countries and new ephemerides based on the Alfonsine tables continued to be published until

2952-644: The Grand Historian ) completed in 94 BC by Chinese historian Sima Qian . 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

3034-496: The IAU (1964) System of Astronomical Constants, used from 1968 to 1983. The product of Simon Newcomb 's J1900.0 mean tropical year of 31 556 925 .9747 ephemeris seconds and a speed of light of 299 792 .5 km/s produced a light-year of 9.460 530 × 10  m (rounded to the seven significant digits in the speed of light) found in several modern sources was probably derived from an old source such as C. W. Allen 's 1973 Astrophysical Quantities reference work, which

3116-552: 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

3198-527: The Ptolemaia festival, which was held every four years, from 262 to 145 BC. The Greek astronomer Posidonius used observations of Canopus to calculate quite accurately the Earth's circumference , around 90 – 120 BC. In Indian Vedic literature , Canopus is associated with the sage Agastya , one of the ancient siddhars and rishis (the others are associated with the stars of the Big Dipper ). To Agastya,

3280-561: The Southern Hemisphere, Canopus culminates at midnight on December 27, and at 9 PM on February 11. When seen from latitudes south of 37° 18′ 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 37° 18′ north. This is just south of Athens , San Francisco , and Seoul , and very close to Seville and Agrigento . It

3362-568: 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 8.0 ± 0.3 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

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3444-563: 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". 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

3526-472: The assumption of a very bright absolute magnitude for Canopus. Hipparcos established Canopus as being 310 light-years ( 95  parsecs ) from the Solar System ; this is based on its 2007 parallax measurement of 10.43 ± 0.53  mas . 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

3608-526: The body and Procyon the northern wingtip, which divided the Polynesian night sky into two hemispheres. The Hawaiian people called Canopus Ke Alii-o-kona-i-ka-lewa , "The chief of the southern expanse"; it was one of the stars used by Hawaiʻiloa and Ki when they traveled to the Southern Ocean . The Māori people of New Zealand/Aotearoa had several names for Canopus. Ariki ("High-born"),

3690-581: The brightest, and will remain so for a period of about 510,000 years. The southeastern wall of the Kaaba in Mecca is aligned with the rising point of Canopus, and is also named Janūb . The Bedouin people of the Negev and Sinai knew Canopus as Suhayl , and used it and Polaris as the two principal stars for navigation at night. Because it disappears below the horizon in those regions, it became associated with

3772-400: The coming of the rainy season and increase in manioc , a food staple fed to guests at feasts. 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

3854-903: The date of the coronation of the King. Alfonso X assembled a team of scholars, known as the Toledo School of Translators , who among other translating tasks, were asked to produce new tables that updated the Tables of Toledo . The new tables were based on earlier astronomical works and observations by Islamic astronomers , adding observations by astronomers Alfonso had gathered in Toledo, among them several Jewish scholars, like Yehuda ben Moshe and Isaac ibn Sid . He also brought Aben Raghel y Alquibicio and Aben Musio y Mohamat, from Seville , Joseph Aben Alí and Jacobo Abenvena, from Córdoba , and fifty more from Gascony and Paris . The instructions for

3936-556: The father of modern astronomy, bought a copy while at the University of Cracow , and cared about it enough to have it professionally bound with pieces of wood and leather. Alexander Bogdanov maintained that these tables formed the basis for Copernicus's development of a heliocentric understanding in astronomy. In 1551, the Prutenic Tables (or Prussian Tables ) of Erasmus Reinhold 's were published. These tables used

4018-464: The horizon, while Eratosthenes 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 star was known as Ptolemaion ( Greek : Πτολεμαῖον) and its acronychal rising marked the date of

4100-565: 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 Chinese : 南极老人 ; pinyin : Nanji Lǎorén ) Under this name, Canopus appears (albeit misplaced northwards) on the medieval Chinese manuscript the Dunhuang Star Chart , although it cannot be seen from

4182-442: The launch of the Hipparcos satellite telescope, distance estimates for Canopus varied widely, from 96 light-years to 1200 light-years (or 30 to 370 parsecs). For example, an old distance estimate of 200 parsecs (652 light years) gave it a luminosity of 80,000  L ☉ , far higher than modern estimates. The closer distance was derived from parallax measurements of around 33  mas . The larger distance derives from

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4264-593: The line in the early 19th century, and six Canopus -class battleships which entered services between 1899 and 1902. There are at least two mountains named after the star: Mount Canopus in Antarctica; and Mount Canopus or Canopus Hill in Tasmania , the location of the Canopus Hill astronomical observatory . Light-years A light-year , alternatively spelled light year ( ly or lyr ),

4346-477: 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 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. Before

4428-438: The mental picture of the approximate transit time for light, but he refrained from using the light-year as a unit. He may have resisted expressing distances in light-years because it would reduce the accuracy of his parallax data due to multiplying with the uncertain parameter of the speed of light. The speed of light was not yet precisely known in 1838; the estimate of its value changed in 1849 ( Fizeau ) and 1862 ( Foucault ). It

4510-449: The midpoint, being 36° one way to Sirius and 37° to the 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 determination. Mariner 4 used Canopus for second axis stabilisation (after locking on the Sun) in 1964, the first time

4592-411: 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

4674-491: The planetary motions with no more than 34 circles has been taken to imply that a large number of additional epicycles had been subsequently introduced into the Ptolemaic system in an attempt to make it conform with observation. (There is a famous (but probably apocryphal) quote attributed to Alfonso upon hearing an explanation of the extremely complicated mathematics required to demonstrate Ptolemy 's geocentric model of

4756-530: The precession of the Earth's axis the first rising of the star Canopus in Mesopotamia could be observed only from there at the southern meridian at midnight. Today, the star Sigma Sagittarii 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 . Hence Aratus did not write of the star as it remained below

4838-493: The same general area, such as those belonging to the same spiral arm or globular cluster . Galaxies themselves span from a few thousand to a few hundred thousand light-years in diameter, and are separated from neighbouring galaxies and galaxy clusters by millions of light-years. Distances to objects such as quasars and the Sloan Great Wall run up into the billions of light-years. Distances between objects within

4920-437: The ship Argo Navis . German celestial cartographer Johann Bayer gave it—as the brightest star in the constellation—the designation 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,

5002-475: 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 , but some emission has been detected. For example, the calcium K line has weak emission wings on each side of the strong central absorption line, first observed in 1966. The emission line profiles are usually correlated with

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5084-535: 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. Astronomer Duane Hamacher has identified Canopus with Moinee in

5166-545: The solar system: "If the Lord Almighty had consulted me before embarking on creation thus, I should have recommended something simpler.") However, modern computations using Ptolemy's unmodified theory have replicated the published Alfonsine tables. The Alfonsine tables were the most popular astronomical tables in Europe and updated versions were regularly produced for three hundred years. Nicolaus Copernicus , known as

5248-412: The spectrum of Canopus shift slightly with a period of 6.9 d . 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 1.6  km/s . Canopus also has

5330-422: The star is said to be the 'cleanser of waters', and its rising coincides with the calming of the waters of the Indian Ocean . Canopus is described by Pliny the Elder and Gaius Julius Solinus as the largest, brightest and only source of starlight for navigators near Tamraparni island (ancient Sri Lanka) during many nights. Canopus was described as Shou Xing, the Star of Longevity, in the Shiji ( Records of

5412-434: The star's heliacal rising with ritual bathing and associated it with morning dew. Bright stars were important to the ancient Polynesians 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

5494-478: 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. The spectrum of Canopus indicates that it spent some 30 million years of its existence as a blue-white main sequence star of around 10 solar masses, before exhausting its core hydrogen and evolving away from

5576-542: 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 and does not pulsate like Cepheid variables of a similar luminosity. However its atmosphere does appear to be unstable, showing strong signs of convection. Canopus may be massive enough to explode by an iron-core collapse supernova . Canopus

5658-467: The strength of an A0 star and the calcium K line three times as strong as Hδ. American astronomer Jesse Greenstein 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 lines of carbon, nitrogen, oxygen, sulphur, iron, and many ionised metals. It

5740-490: 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

5822-464: 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

5904-402: Was known as Suhel / ˈ s uː h ɛ l / 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" , implying the anchor stone used by ship, rather than being related to its low position near the horizon. Hence comes its name in

5986-471: Was known as a solitary star that appeared in the east, prompting people to weep and chant. They also named it Atutahi , 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

6068-544: Was known to the ancient Mesopotamians and represented the city of Eridu in the Three Stars Each Babylonian star catalogues and later MUL.APIN around 1100 BC. Canopus was called MUL.NUN by the Babylonians, which translates as "star of the city of Eridu". Eridu was the southernmost and one of the oldest Sumerian cities. From there is a good view to the south, so that about 6000 years ago due to

6150-432: Was not yet considered to be a fundamental constant of nature, and the propagation of light through the aether or space was still enigmatic. The light-year unit appeared in 1851 in a German popular astronomical article by Otto Ule . Ule explained the oddity of a distance unit name ending in "year" by comparing it to a walking hour ( Wegstunde ). A contemporary German popular astronomical book also noticed that light-year

6232-465: Was only possible if the Earth was a relatively small sphere. English explorer Robert Hues brought Canopus to the attention of European observers in his 1592 work Tractatus de Globis , along with Achernar and Alpha Centauri , 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

6314-563: Was previously proposed to be a member of the Scorpius–Centaurus association , 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 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

6396-439: Was studied in the ultraviolet by an early astronomical satellite, Gemini XI in 1966. The UV spectra were considered to be consistent with an F0 supergiant having a temperature of 6,900 K , the accepted parameters for Canopus at the time. New Zealand-based astronomers John Hearnshaw and Krishna Desikachary examined the spectrum in greater detail, publishing their results in 1982. When luminosity classes were added to

6478-440: Was the astronomical unit , equal to the radius of the Earth's orbit at 150 million kilometres (93 million miles). In those terms, trigonometric calculations based on 61 Cygni's parallax of 0.314 arcseconds, showed the distance to the star to be 660 000 astronomical units (9.9 × 10  km; 6.1 × 10  mi). Bessel added that light takes 10.3 years to traverse this distance. He recognized that his readers would enjoy

6560-649: 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

6642-445: Was to calculate ephemerides , which were in turn used by astrologers to cast horoscopes . Canons on the tables included those by John of Saxony and his teacher John of Lignères (fl 1320 to 1335). The methods of Claudius Ptolemy were used to compute the table, dividing the year into 365 days, 5 hours, 49 minutes, 16 seconds—very close to the currently accepted figure. Copernicus's observation that his system could explain

6724-438: Was updated in 2000, including the IAU (1976) value cited above (truncated to 10 significant digits). Other high-precision values are not derived from a coherent IAU system. A value of 9.460 536 207 × 10  m found in some modern sources is the product of a mean Gregorian year (365.2425 days or 31 556 952  s ) and the defined speed of light ( 299 792 458  m/s ). Another value, 9.460 528 405 × 10  m ,

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