An image of Canopus by Expedition 6
Epoch J2000 Equinox J2000
|Right ascension||06h 23m 57.1099s|
|Declination||-52° 41′ 44.378″|
|Apparent magnitude (V)||−0.72|
|Spectral type||F0 II or F0 Ib|
|U−B color index||0.04|
|B−V color index||0.15|
|Radial velocity (Rv)||20.5 km/s|
|Proper motion (μ)||RA: 19.99  mas/yr
Dec.: 23.67  mas/yr
|Parallax (π)||10.43 ± 0.53 mas|
|Distance||310 ± 20 ly
(96 ± 5 pc)
|Absolute magnitude (MV)||−5.53|
|Surface gravity (log g)||2.10|
|Metallicity [Fe/H]||–0.07 dex|
|Rotational velocity (v sin i)||8.0 km/s|
Canopus (//; α Car, α Carinae, Alpha Carinae) is the brightest star in the southern constellation of Carina and Argo Navis, and the second brightest star in the night-time sky, after Sirius. Canopus's visual magnitude is −0.72, and it has an absolute magnitude of −5.53.
Canopus is a supergiant of spectral type F. Canopus is essentially white when seen with the naked eye (although F-type stars are sometimes listed as "yellowish-white"). It is located in the far southern sky, at a declination of −52° 42' (2000) and a right ascension of 06h24.0m.
Observational history 
One of the least famous of the brightest stars, Canopus was not visible to the Ancient Greeks and Romans; it was, however, visible to the Ancient Egyptians. It is also referred to by its Arabic name: سهيل (Suhayl), given by Islamic scientists in the 7th Century AD.
In the southern hemisphere, Canopus and Sirius are both visible high in the sky simultaneously, and reach the meridian just 21 minutes apart. It is a circumpolar star when seen from points that have latitude south of 37°18' south; for example, Victoria and Tasmania, Australia; Auckland and south of it, New Zealand; Bahía Blanca, Argentina; and Valdivia, Chile and south of these cities in South America. Since Canopus is so far south in the sky, it never rises in mid- or far-northern latitudes; in theory the northern limit of visibility is latitude 37°18' north. This is just south of Athens, Richmond (USA), and San Francisco, and very close to Seville. It is almost exactly the latitude of Lick Observatory on Mt. Hamilton, California, from which it is readily visible due to the effects of elevation and atmospheric refraction, which add another degree to its apparent altitude. Under ideal conditions it has been spotted as far north as latitude 37°31' from the Pacific coast. It is more easily visible in places such as the Gulf Coast and Florida, and is best viewed around 9 p.m. on February 6.
F-type supergiants have been described as yellow-white or white. Canopus has a B-V color index of 0.16 where 0 is a blue-white, indicating it is essentially white, although has been described as yellow-white. Its spectral type has been recorded as either F0 or sometimes A9. It has less yellow than Altair or Procyon, whose color indexes have been measured at 0.22 and 0.42 respectively. It may be that some observers have seen it yellow-tinged due to it being located low in the sky and hence subject to atmospheric effects.
Physical properties 
Before the launch of the Hipparcos satellite telescope, distance estimates for the star varied widely, from 96 light years to 1200 light years. Had the latter distance been correct, Canopus would have been one of the most luminous stars in our galaxy. Hipparcos established Canopus as lying 310 light years (96 parsecs) from our solar system; this is based on a parallax measurement of 10.43 ± 0.53 mas. The difficulty in measuring Canopus' distance stemmed from its unusual nature. Canopus has been classified as a F0 II or F0 Ib (Ib referring to "less luminous supergiant") star, and such stars are rare and poorly understood; they are stars that can be either in the process of evolving to or away from red giant status. This in turn made it difficult to know how intrinsically bright Canopus is, and therefore how far away it might be. Direct measurement was the only way to solve the problem. Canopus is too far away for Earth-based parallax observations to be made, so the star's distance was not known with certainty until the early 1990s.
The surface temperature of Canopus has been estimated at 7350 ± 30 K.
Infrared interferometry was used to calculate its angular diameter at 6.93 ± 0.15 mas. Combined with distance calculated by Hipparcos, this gives it a diameter of 71.4 ± 0.4 times that of the sun. If it were placed at the centre of our solar system, it would extend 90% of the way to the orbit of Mercury.
Canopus is the most intrinsically bright star within approximately 700 light years, and it has been the brightest star in Earth's sky during three different epochs over the past four million years. Other stars appear brighter only during relatively temporary periods, during which they are passing our solar system at a much closer distance than Canopus. About 90,000 years ago, Sirius moved close enough that it became brighter than Canopus, and that will remain the case for another 210,000 years. But in 480,000 years, Canopus will once again be the brightest, and will remain so for a period of about 510,000 years.[dubious ]
Canopus is a strong source of X-rays, which are probably produced by its corona, magnetically heated to around 15 million K. The temperature has likely been stimulated by fast rotation combined with strong convection percolating through the star's outer layers. The star's surface temperature is too cool to account for the X-rays.
Etymology and cultural significance 
The name "Canopus" is a Latinisation of the Ancient Greek name Κάνωβος/"Kanôbos", recorded in Claudius Ptolemy's Almagest (c150 AD). Eratosthenes used this spelling, however Hipparchos wrote it as Κάνωπος. John Flamsteed wrote Canobus. The name has two common derivations, both listed in Richard Hinckley Allen's seminal Star Names: Their Lore and Meaning; and one less so. All are matters of conjecture:
- One from the legend of the Trojan War, where the constellation Carina was once part of the now-obsolete constellation of Argo Navis, which represented the ship used by Jason and the Argonauts. 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 after she was taken by Paris.
- A second from the Egyptian Coptic Kahi Nub ("Golden Earth"), which refers how Canopus would have appeared near the horizon in ancient Egypt, reddened by atmospheric extinction from that position. A ruined ancient Egyptian port named Canopus lies near the mouth of the Nile, site of the Battle of the Nile.
- A third is its possible origin from the Semitic root G(C)-N-B (Gimmel-Nun-Beth), from which the Arabic word for south, janūb ( جنوب ), is derived. The southeastern wall of the Muslim Ka'bah points to Canopus, and is named Janūb ("south") as well.
Other names 
Middle East 
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 is known by the common name Nunki.
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. Alternate spellings include Suhil, Suhilon, Suheyl, Sohayl, Suhayil, Shoel, Sohil, Soheil, Sahil, Suhayeel, Sohayil, Sihel, and Sihil. An alternate name was Wazn "weight" or Haḍar "ground", possibly related to its low position near the horizon. Hence comes its name in the Alphonsine Tables, Suhel ponderosus, a Latinization of Al Suhail al Wazn. Its Greek name was revived during the Renaissance.
In Japan, Canopus is known as Mera-boshi and Roujin-sei (the old man star).
In traditional Tibetan astronomy and astrology, Canopus is named Karma Rishi སྐར་མ་རི་ཥི།
Canopus was 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 mankind. His wife was Collowgullouric War (Eta Carinae). The Kulin people knew Canopus as Lo-an-tuka. Objects in the sky were also associated with states of being for some tribes; the Wailwun of northern New South Wales knew Canopus as Wumba "deaf", alongside Mars as Gumba "fat" and Venus as Ngindigindoer "you are laughing". Tasmanian aboriginal lore held that Canopus was Dromerdene, the brother of Moinee; the two fought and fell out of the sky, with Dromerdene falling into Louisa Bay in southwest Tasmania.
The Maori people of New Zealand/Aotearoa had several different 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, 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 different mythologies attached to it as well. One story tells of how Atutahi was left outside of the basket representing the Milky Way when Tane wove it. Another related myth surrounding the star says that Autahi 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 the fact that it rarely sets from the vantage point of 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".
The Hawaiian people called Canopus by just one name, Ke Alii-o-kona-i-ka-lewa, "The Chief of the southern expanse". Ke Alii-o-kona-i-ka-lewa was one of the stars used by Hawaii-loa and Ki when they traveled to the Southern Ocean.
In modern times, Canopus serves another navigational use. Canopus's brightness and location well off the ecliptic make it popular for space navigation. Many spacecraft carry a special camera known as a "Canopus Star Tracker" plus a sun sensor for attitude determination.
To the Bedouin people of the Negev and Sinai, Canopus is known as Suhayl. It and Polaris are the two principal stars used for navigation at night. Due to the fact that it disappears below the horizon, it became associated with a cowardly or changeable nature, as opposed to always-visible Polaris, which was circumpolar and hence 'steadfast'.
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 mate their sheep with a ram.
To the ǀXam-speaking Bushmen of South Africa, Canopus and Sirius signalled the appearance of termites and flying ants. They also believed 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.
Modern legacy 
In popular culture 
See also 
- "Database entry for Canopus". SIMBAD, Centre de Données astronomiques de Strasbourg. Retrieved 8 July 2012.
- Domiciano De Souza, A.; Bendjoya, P.; Vakili, F.; Millour, F.; Petrov, R. G. (2008). "Diameter and photospheric structures of Canopus from AMBER/VLTI interferometry". Astronomy and Astrophysics 489 (2): L5–L8. doi:10.1051/0004-6361:200810450.
- Smiljanic, R. et al. (April 2006), "CNO in evolved intermediate mass stars", Astronomy and Astrophysics 449 (2): 655–671, arXiv:astro-ph/0511329, Bibcode:2006A&A...449..655S, doi:10.1051/0004-6361:20054377
- Desikachary K, Hearnshaw JB (1982). "The spectrum of Canopus. II - Analysis and composition". Royal Astronomical Society, Monthly Notices (PDFBibcode:1982MNRAS.201..707D.) 201: 707–21.
- Schaaf, p. 107.
- D. Gieringer, "Exploring the Tropic of Canopus," Astronomy, December 1985, p.24.
- Motz, Lloyd; Nathanson, Carol (1991). The Constellations: An Enthusiast's Guide to the Night Sky. London, United Kingdom: Aurum Press. pp. 376–77. ISBN 1-85410-088-2.
- Schaaf, p. 257.
- Schaaf, pp. 112-13.
- Kaler, James B. (2002). The Hundred Greatest Stars. New York: Copernicus Books. p. 37. ISBN 0-387-95436-8.
- Kaler, Jim (26 June 2009). "Canopus". Stars. University of Illinois. Retrieved 8 July 2012.
- Sky and Telescope, April 1998 (p60), based on computations from HIPPARCOS data.
- Flamsteed, John (1729). Atlas coelestis. London, United Kingdom. pp. Constellation Map of Southern Hemisphere.
- Allen, Richard Hinckley (1963) . Star Names: Their Lore and Meaning (Revised ed.). New York: Dover Publications. pp. 67–72. ISBN 0-486-21079-0.
- Islamic Awareness. "Astronomical Orientation Of Ka`bah".
- Rogers, John H. (1998). "Origins of the Ancient Constellations: I. The Mesopotamian Traditions". Journal of the British Astronomical Association 108 (1): 9–28. Bibcode:1998JBAA..108....9R.
- Allen, Richard Hinckley, Star Names, their lore and meaning, p. 359
- Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, MA: Sky Pub. p. 23. ISBN 978-1-931559-44-7.
- Takao Ibaraki (1996-07-14). "Stellar Iconology and Astronomical Folklore in Japan". International Planetarium Society (IPS) Conferences 1996. Osaka: International Planetarium Society. Retrieved 2012-02-25.
- Mudrooroo (1994). Aboriginal mythology : an A-Z spanning the history of aboriginal mythology from the earliest legends to the present day. London: HarperCollins. p. 27. ISBN 1-85538-306-3.
- Hamacher, Duane W.; Frew, David J. (2010). "An Aboriginal Australian Record of the Great Eruption of Eta Carinae". Journal of Astronomical History & Heritage 13 (3): 220–34.
- Johnson, Diane (1998). Night skies of aboriginal Australia: a noctuary. Darlington, New South Wales: University of Sydney. p. 84. ISBN 1-86451-356-X.
- Haynes, Ros D. (2000). Astronomy and the Dreaming: The Astronomy of the Aboriginal Australians. Astronomy Across Cultures: The History of Non-Western Astronomy. Kluwer Academic Publishers. p. 57.
- Makemson 1941, p. 201.
- p. 419, Mythology: Myths, Legends and Fantasies, Janet Parker, Alice Mills, Julie Stanton, Durban, Struik Publishers, 2007.
- Best, Elsdon (1922). Astronomical Knowledge of the Maori: Genuine and Empirical. Wellington, New Zealand: Dominion Museum. pp. 34–35.
- Makemson 1941, pp. 200-202.
- Makemson 1941, p. 217.
- Makemson 1941, p. 218.
- Makemson 1941, p. 259.
- Makemson 1941, p. 229.
- Makemson 1941, p. 198.
- Kieron Taylor (1 March 1994). "Precession". myweb.tiscali.co.uk. Retrieved 2012-02-25.
- Bailey, Clinton (1974). "Bedouin Star-Lore in Sinai and the Negev". Bulletin of the School of Oriental and African Studies, University of London (abstractdoi:10.1017/S0041977X00127491. JSTOR 613801.) 37 (3): 580–96.
- Clegg, Andrew (1986). "Some Aspects of Tswana Cosmology". Botswana Notes and Records 18: 33–37. JSTOR 40979758.
- Hollman, J. C. ""The Sky's Things", |xam Bushman 'Astrological Mythology' as recorded in the Bleek and Lloyd Manuscripts". African Sky 11: 8. Bibcode:2007AfrSk..11....8H.
- "Astronomy of the Brazilian Flag". FOTW Flags Of The World website.