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Coordinates: Sky map 06h 23m 57.1099s, −52° 41′ 44.378″
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==Observational history==
==Observational history==
One of the least famous of the brightest stars, Canopus was not visible to the [[Ancient Greece|Ancient Greeks]] and [[Roman Empire|Romans]]; it was, however, visible to the [[Ancient Egypt]]ians,<ref name=Schaaf107>Schaaf, p. 107.</ref> as well as the [[http://en.wikipedia.org/wiki/Navajo_people|Navajo]], who named it ''Ma’ii Bizò‘''.<ref name=Maryboy>Maryboy, Nancy D. (2004). ''A Guide to Navajo Astronomy.'' Indigenous Education Institute : Bluff, Utah.</ref> It is also referred to by its [[Arabic language|Arabic]] name: سهيل (''Suhayl''), given by [[Astronomy in medieval Islam|Islamic scientists]] in the 7th Century AD.
One of the least famous of the brightest stars, Canopus was not visible to the [[Ancient Greece|Ancient Greeks]] and [[Roman Empire|Romans]]; it was, however, visible to the [[Ancient Egypt]]ians,<ref name=Schaaf107>Schaaf, p. 107.</ref> as well as the [[Navajo_people|Navajo]], who named it ''Ma’ii Bizò‘''.<ref name=Maryboy>Maryboy, Nancy D. (2004). ''A Guide to Navajo Astronomy.'' Indigenous Education Institute : Bluff, Utah.</ref> It is also referred to by its [[Arabic language|Arabic]] name: سهيل (''Suhayl''), given by [[Astronomy in medieval Islam|Islamic scientists]] in the 7th Century AD.


==Visibility==
==Visibility==

Revision as of 20:47, 9 August 2013

For other uses, see Canopus (disambiguation).
Canopus

An image of Canopus by Expedition 6
Observation data
Epoch J2000      Equinox J2000
Constellation Carina
Pronunciation /kəˈnoʊpəs/
Right ascension 06h 23m 57.1099s[1]
Declination −52° 41′ 44.378″
Apparent magnitude (V) −0.72
Characteristics
Spectral type F0 II or F0 Ib[2]
U−B color index 0.04
B−V color index 0.15
Variable type None
Astrometry
Radial velocity (Rv)20.5[1] km/s
Proper motion (μ) RA: 19.99 [1] mas/yr
Dec.: 23.67 [1] mas/yr
Parallax (π)10.43 ± 0.53 mas[1]
Distance310 ± 20 ly
(96 ± 5 pc)
Absolute magnitude (MV)–5.53[citation needed]
Details
Mass9.0–10.6[3] M☉
Radius71.4 ± 4.0[2] R☉
Luminosity15,100[3] L☉
Surface gravity (log g)2.10[3] cgs
Temperature7,350[4] K
Metallicity [Fe/H]–0.07[3] dex
Rotational velocity (v sin i)8.0[3] km/s
Other designations
Suhel, Suhail, Suhayl, Alpha Carinae, CD−52°914, FK5 245, GC 8302, HD 45348, HIP 30438, HR 2326, SAO 234480
Database references
SIMBADdata
Canopus seen from Tokyo, Japan. The latitude is 35°38′N.

Canopus (/kəˈnoʊpəs/; α Car, α Carinae, Alpha Carinae) is the brightest star in the southern constellation of Carina, 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.[1]

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,[5] as well as the Navajo, who named it Ma’ii Bizò‘.[6] It is also referred to by its Arabic name: سهيل (Suhayl), given by Islamic scientists in the 7th Century AD.

Visibility

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 because of 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.[7] 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.[8]

Most visible in the southern hemisphere summer, Canopus culminates at midnight on December 27,[8] and at 9PM on February 11.[9]

F-type supergiants have been described as yellow-white or white.[citation needed] 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 perceived it as yellow-tinged owing to its being located low in the sky and hence subject to atmospheric effects.[10]

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.[1] 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,[2] 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.[11] 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.[4]

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.[2] If it were placed at the centre of our solar system, it would extend 90% of the way to the orbit of Mercury.[12]

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.[13] 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 – discuss]

Canopus is part of the Scorpius-Centaurus Association, a group of stars which share similar origins.[11]

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.[11]

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.[14] The name has two common derivations, both listed in Richard Hinckley Allen's seminal Star Names: Their Lore and Meaning;[15] 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.[15] 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)[citation needed], 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.[16]

Other names

Egypt

An Egyptian priestly poet of the time of Thutmose III wrote of it as Karbana, "the star which pours his light in a glance of fire, When he disperses the morning dew."[15]

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.[17] Today, the star Sigma Sagittarii is known by the common name Nunki.[18]

An occasional name seen in English is Sohel, or the feminine Soheila; in Turkish is Süheyl, or the feminine Süheyla, from the Arabic name for several bright stars, سهيل suhayl,[15] and Canopus was known as Suhel in medieval times.[19] Alternate spellings include Suhil, Suhilon, Suheyl, Sohayl, Suhayil, Shoel, Sohil, Soheil, Sahil, Suhayeel, Sohayil, Sihel, and Sihil.[15] An alternate name was Wazn "weight" or Haḍar "ground", possibly related to its low position near the horizon.[15] Hence comes its name in the Alphonsine Tables, Suhel ponderosus, a Latinization of Al Suhail al Wazn.[15] Its Greek name was revived during the Renaissance.[19]

Asia

It is known as the Star of the Old Man (in Chinese: 老人星 or in Chinese: Lǎorénxīng) in Chinese. It is also personified as the Shou star.

In Japan, Canopus is known as Mera-boshi and Roujin-sei (the old man star).[20]

In Ancient Hindu astronomy and astrology, Canopus is named Agasti or Agastya.[15]

In traditional Tibetan astronomy and astrology, Canopus is named Karma Rishi སྐར་མ་རི་ཥི།

Kalīla o Damna, an influential Pahlavi (Middle Persian) book of animal fables was later known as Anvar-i-Suhaili or The Lights of Canopus.

Australia

Canopus was identified as the moiety ancestor Waa "Crow" to some Koori people in southeastern Australia.[21] 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).[22] The Kulin people knew Canopus as Lo-an-tuka.[22] 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".[23] 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.[24]

Polynesia

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.[25] They also named it Atutahi, Aotahi or Atuatahi, "Stand Alone".[26] 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.[27] 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.[28] Kapae-poto, "Short horizon", referred to the fact that it rarely sets from the vantage point of New Zealand;[29] Kauanga ("Solitary") was the name for Canopus only when it was the last star visible before sunrise.[30]

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",[31] 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".[32]

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.[33]

Role in navigation

To anyone living in the northern hemisphere, but far enough south to see the star, it served as a southern pole star. This lasted only until magnetic compasses became common.

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.

The effects of precession will take Canopus within 10° of the south celestial pole around the year 14,000 AD.[34]

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'.[35]

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.[36]

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.[37]

Modern legacy

Canopus appears on the flag of Brazil, symbolising the state of Goiás.[38]

The book series Canopus in Argos by Nobel Prize in Literature-winning author Doris Lessing which portray a number of societies at different stages of development, over a great period of time. The focus is on accelerated evolution being aided by advanced species for less advanced species and societies.

The fictional desert planet Arrakis featured in the Dune series of novels by Frank Herbert is the third planet orbiting Canopus.

In the MMORPG Eve Online, the titular wormhole that led to the galaxy in which the player's experience takes place was located in the Canopus system.

See also

References

  1. ^ a b c d e f g "Database entry for Canopus". SIMBAD, Centre de Données astronomiques de Strasbourg. Retrieved 8 July 2012.
  2. ^ a b c d Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1051/0004-6361:200810450, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1051/0004-6361:200810450 instead.
  3. ^ a b c d e Smiljanic, R.; et al. (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. {{citation}}: Unknown parameter |month= ignored (help)
  4. ^ a b Desikachary K, Hearnshaw JB (1982). "The spectrum of Canopus. II - Analysis and composition". Royal Astronomical Society, Monthly Notices. 201: 707–21. Bibcode:1982MNRAS.201..707D. {{cite journal}}: |format= requires |url= (help)
  5. ^ Schaaf, p. 107.
  6. ^ Maryboy, Nancy D. (2004). A Guide to Navajo Astronomy. Indigenous Education Institute : Bluff, Utah.
  7. ^ D. Gieringer, "Exploring the Tropic of Canopus," Astronomy, December 1985, p.24.
  8. ^ a b Motz, Lloyd (1991). The Constellations: An Enthusiast's Guide to the Night Sky. London, United Kingdom: Aurum Press. pp. 376–77. ISBN 1-85410-088-2. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  9. ^ Schaaf, p. 257.
  10. ^ Schaaf, pp. 112-13.
  11. ^ a b c Kaler, James B. (2002). The Hundred Greatest Stars. New York: Copernicus Books. p. 37. ISBN 0-387-95436-8.
  12. ^ Kaler, Jim (26 June 2009). "Canopus". Stars. University of Illinois. Retrieved 8 July 2012.
  13. ^ Sky and Telescope, April 1998 (p60), based on computations from HIPPARCOS data.
  14. ^ Flamsteed, John (1729). Atlas coelestis. London, United Kingdom. pp. Constellation Map of Southern Hemisphere.
  15. ^ a b c d e f g h Allen, Richard Hinckley (1963) [1899]. Star Names: Their Lore and Meaning (Revised ed.). New York: Dover Publications. pp. 67–72. ISBN 0-486-21079-0.
  16. ^ Islamic Awareness. "Astronomical Orientation Of Ka`bah".
  17. ^ 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.
  18. ^ Allen, Richard Hinckley, Star Names, their lore and meaning, p. 359
  19. ^ a b 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.{{cite book}}: CS1 maint: multiple names: authors list (link)
  20. ^ 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. {{cite conference}}: Unknown parameter |booktitle= ignored (|book-title= suggested) (help)
  21. ^ 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.
  22. ^ a b Hamacher, Duane W.; Frew, David J. (2010). "An Aboriginal Australian Record of the Great Eruption of Eta Carinae" (PDF). Journal of Astronomical History & Heritage. 13 (3): 220–34.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  23. ^ Johnson, Diane (1998). Night skies of aboriginal Australia: a noctuary. Darlington, New South Wales: University of Sydney. p. 84. ISBN 1-86451-356-X.
  24. ^ Haynes, Ros D. (2000). Astronomy and the Dreaming: The Astronomy of the Aboriginal Australians. Astronomy Across Cultures: The History of Non-Western Astronomy (PDF). Kluwer Academic Publishers. p. 57.
  25. ^ Makemson 1941, p. 201.
  26. ^ p. 419, Mythology: Myths, Legends and Fantasies, Janet Parker, Alice Mills, Julie Stanton, Durban, Struik Publishers, 2007.
  27. ^ Best, Elsdon (1922). Astronomical Knowledge of the Maori: Genuine and Empirical. Wellington, New Zealand: Dominion Museum. pp. 34–35.
  28. ^ Makemson 1941, pp. 200–202.
  29. ^ Makemson 1941, p. 217.
  30. ^ Makemson 1941, p. 218.
  31. ^ Makemson 1941, p. 259.
  32. ^ Makemson 1941, p. 229.
  33. ^ Makemson 1941, p. 198.
  34. ^ Kieron Taylor (1 March 1994). "Precession". myweb.tiscali.co.uk. Retrieved 2012-02-25.
  35. ^ Bailey, Clinton (1974). "Bedouin Star-Lore in Sinai and the Negev". Bulletin of the School of Oriental and African Studies, University of London. 37 (3): 580–96. doi:10.1017/S0041977X00127491. JSTOR 613801. {{cite journal}}: |access-date= requires |url= (help); |format= requires |url= (help)
  36. ^ Clegg, Andrew (1986). "Some Aspects of Tswana Cosmology". Botswana Notes and Records. 18: 33–37. JSTOR 40979758.
  37. ^ 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.
  38. ^ "Astronomy of the Brazilian Flag". FOTW Flags Of The World website.


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