Canopus
Overview
 
Canopus is the brightest star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

 in the southern constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 of Carina
Carina (constellation)
Carina is a constellation in the southern sky. Its name is Latin for the keel of a ship, and it was formerly part of the larger constellation of Argo Navis until that constellation was divided in three.-Stars:...

 and Argo Navis
Argo Navis
Argo Navis was a large constellation in the southern sky that has since been divided into three constellations. It represented the Argo, the ship used by Jason and the Argonauts in Greek mythology...

, and the second brightest star in the night-time sky, after Sirius
Sirius
Sirius is the brightest star in the night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The name "Sirius" is derived from the Ancient Greek: Seirios . The star has the Bayer designation Alpha Canis Majoris...

. Canopus's visual magnitude is −0.72, and it has an absolute magnitude
Absolute magnitude
Absolute magnitude is the measure of a celestial object's intrinsic brightness. it is also the apparent magnitude a star would have if it were 32.6 light years away from Earth...

 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").
Encyclopedia
Canopus is the brightest star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

 in the southern constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 of Carina
Carina (constellation)
Carina is a constellation in the southern sky. Its name is Latin for the keel of a ship, and it was formerly part of the larger constellation of Argo Navis until that constellation was divided in three.-Stars:...

 and Argo Navis
Argo Navis
Argo Navis was a large constellation in the southern sky that has since been divided into three constellations. It represented the Argo, the ship used by Jason and the Argonauts in Greek mythology...

, and the second brightest star in the night-time sky, after Sirius
Sirius
Sirius is the brightest star in the night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The name "Sirius" is derived from the Ancient Greek: Seirios . The star has the Bayer designation Alpha Canis Majoris...

. Canopus's visual magnitude is −0.72, and it has an absolute magnitude
Absolute magnitude
Absolute magnitude is the measure of a celestial object's intrinsic brightness. it is also the apparent magnitude a star would have if it were 32.6 light years away from Earth...

 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
Declination
In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and...

 of −52° 42' (2000) and a right ascension
Right ascension
Right ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination.-Explanation:...

 of 06h24.0m.

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
Circumpolar star
A circumpolar star is a star that, as viewed from a given latitude on Earth, never sets , due to its proximity to one of the celestial poles...

 when seen from points that have latitude south of 37°18' south; for example, Victoria
Victoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....

 and Tasmania
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...

, Australia; Auckland
Auckland
The Auckland metropolitan area , in the North Island of New Zealand, is the largest and most populous urban area in the country with residents, percent of the country's population. Auckland also has the largest Polynesian population of any city in the world...

 and south of it, New Zealand; Bahía Blanca
Bahía Blanca
Bahía Blanca is a city located in the south-west of the province of Buenos Aires, Argentina, by the Atlantic Ocean, and seat of government of Bahía Blanca Partido. It has a population of 274,509 inhabitants according to the...

, Argentina; and Valdivia, Chile
Valdivia, Chile
Valdivia is a city and commune in southern Chile administered by the Municipality of Valdivia. The city is named after its founder Pedro de Valdivia and is located at the confluence of the Calle-Calle, Valdivia and Cau-Cau Rivers, approximately east of the coastal towns of Corral and Niebla...

 and south of these cities in South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

. 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
Athens
Athens , is the capital and largest city of Greece. Athens dominates the Attica region and is one of the world's oldest cities, as its recorded history spans around 3,400 years. Classical Athens was a powerful city-state...

, Richmond, and San Francisco, and very close to Seville
Seville
Seville is the artistic, historic, cultural, and financial capital of southern Spain. It is the capital of the autonomous community of Andalusia and of the province of Seville. It is situated on the plain of the River Guadalquivir, with an average elevation of above sea level...

. It is almost exactly the latitude of Lick Observatory
Lick Observatory
The Lick Observatory is an astronomical observatory, owned and operated by the University of California. It is situated on the summit of Mount Hamilton, in the Diablo Range just east of San Jose, California, USA...

 on Mt. Hamilton, California, from which it is readily visible due to the effects of elevation and atmospheric refraction
Atmospheric refraction
Atmospheric refraction is the deviation of light or other things like humanelectromagnetic wave from a straight line as it passes through the atmosphere due to the variation in air density as a function of altitude...

, 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 Gibraltar
Gibraltar
Gibraltar is a British overseas territory located on the southern end of the Iberian Peninsula at the entrance of the Mediterranean. A peninsula with an area of , it has a northern border with Andalusia, Spain. The Rock of Gibraltar is the major landmark of the region...

, Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...

, Albuquerque, and Atlanta.

Physical properties

Before the launching of the Hipparcos
Hipparcos
Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...

 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 parsec
Parsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....

s) from our solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

; this is based on a parallax
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. The term is derived from the Greek παράλλαξις , meaning "alteration"...

 measurement of 10.43 ± 0.53 mas. The difficulty in measuring Canopus' distance stemmed from its unusual nature. The spectral classification for Canopus is F0 Ib (Ib referring to "less luminous supergiant"), 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
Red giant
A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000 K and lower...

 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.

Canopus is 13,600 times more luminous than the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 and the most intrinsically bright star within approximately 700 light years. In fact, from 1 astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....

, Canopus would have an apparent magnitude of -37. Canopus appears less bright than Sirius
Sirius
Sirius is the brightest star in the night sky. With a visual apparent magnitude of −1.46, it is almost twice as bright as Canopus, the next brightest star. The name "Sirius" is derived from the Ancient Greek: Seirios . The star has the Bayer designation Alpha Canis Majoris...

 in our sky only because Sirius is much closer to the Earth (8.6 light years).

Its surface temperature has been estimated at 7350 ± 30 K. Its diameter has been measured at 0.6 astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....

s (the measured angular diameter being 0.006 arcseconds), 65 times that of the sun. If it were placed at the centre of the solar system, it would extend three-quarters of the way to Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...

. An Earth-like planet would have to lie three times the distance of Pluto
Pluto
Pluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet in the Solar System and the tenth-most-massive body observed directly orbiting the Sun...

 for its star to appear the same size in the sky as our own sun.

Canopus is part of the Scorpius-Centaurus Association
Scorpius-Centaurus Association
The Scorpius-Centaurus Association is the nearestOB Association to the Sun. This stellar association is composed of three subgroups The Scorpius-Centaurus Association (sometimes called Sco-Cen or Sco OB2) is the nearestOB Association to the Sun. This stellar association is composed of three...

, a group of stars which share similar origins.

Canopus is a strong source of X-rays, which are probably produced by its corona, magnetically heated to around 15 million K.

Etymology and cultural significance

The name "Canopus" is a Latinisation of the Greek name "Kanôbos", recorded in Claudius Ptolemy's Almagest
Almagest
The Almagest is a 2nd-century mathematical and astronomical treatise on the apparent motions of the stars and planetary paths. Written in Greek by Claudius Ptolemy, a Roman era scholar of Egypt,...

 (c150 AD). The name has two common derivations, both listed in Richard Hinckley Allen's seminal Star Names: Their Lore and Meaning
Star Names: Their Lore and Meaning
Star Names: Their Lore and Meaning is a book by Richard Hinckley Allen, published in 1899.It discusses the names of stars and constellations and their origin.-Author:...

; and one less so. All are matters of conjecture:
  • One from the legend of the Trojan War
    Trojan War
    In Greek mythology, the Trojan War was waged against the city of Troy by the Achaeans after Paris of Troy took Helen from her husband Menelaus, the king of Sparta. The war is among the most important events in Greek mythology and was narrated in many works of Greek literature, including the Iliad...

    , where the constellation Carina was once part of the now-obsolete constellation of Argo Navis
    Argo Navis
    Argo Navis was a large constellation in the southern sky that has since been divided into three constellations. It represented the Argo, the ship used by Jason and the Argonauts in Greek mythology...

    , which represented the ship used by Jason
    Jason
    Jason was a late ancient Greek mythological hero from the late 10th Century BC, famous as the leader of the Argonauts and their quest for the Golden Fleece. He was the son of Aeson, the rightful king of Iolcus...

     and the Argonauts. The brightest star in the constellation was given the name of a ship's pilot from another Greek legend: Canopus
    Canopus (mythology)
    In Greek mythology, Canopus was the pilot of the ship of King Menelaus of Sparta during the Trojan War. He is described as a young handsome man, who was loved by Theonoe, the Egyptian prophetess, but never answered her feelings. According to legend, while visiting the coasts of Egypt, he was...

    , pilot of Menelaus
    Menelaus
    Menelaus may refer to;*Menelaus, one of the two most known Atrides, a king of Sparta and son of Atreus and Aerope*Menelaus on the Moon, named after Menelaus of Alexandria.*Menelaus , brother of Ptolemy I Soter...

    ' ship on his quest to retrieve Helen of Troy after she was taken by Paris
    Paris (mythology)
    Paris , the son of Priam, king of Troy, appears in a number of Greek legends. Probably the best-known was his elopement with Helen, queen of Sparta, this being one of the immediate causes of the Trojan War...

    .
  • A second from the Egyptian Coptic
    Coptic language
    Coptic or Coptic Egyptian is the current stage of the Egyptian language, a northern Afro-Asiatic language spoken in Egypt until at least the 17th century. Egyptian began to be written using the Greek alphabet in the 1st century...

     Kahi Nub ("Golden Earth"), which refers how Canopus would have appeared near the horizon in ancient Egypt
    Egypt
    Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...

    , reddened by atmospheric extinction from that position. A ruined ancient Egyptian port named Canopus lies near the mouth of the Nile
    Nile
    The Nile is a major north-flowing river in North Africa, generally regarded as the longest river in the world. It is long. It runs through the ten countries of Sudan, South Sudan, Burundi, Rwanda, Democratic Republic of the Congo, Tanzania, Kenya, Ethiopia, Uganda and Egypt.The Nile has two major...

    , site of the Battle of the Nile
    Battle of the Nile
    The Battle of the Nile was a major naval battle fought between British and French fleets at Aboukir Bay on the Mediterranean coast of Egypt from 1–3 August 1798...

    .
  • A third is its possible origin from the Semitic
    Semitic languages
    The Semitic languages are a group of related languages whose living representatives are spoken by more than 270 million people across much of the Middle East, North Africa and the Horn of Africa...

     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

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, including Canopus and Regor.

It is known as the Star of the Old Man
Old Man of the South Pole
The Old Man of the South Pole is the Taoist deification of Canopus, the brightest star of the constellation Carina. It is the symbol of happiness and longevity in Far Eastern culture.-General:...

 (in or in ) in Chinese.

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

In Ancient Hindu astronomy and astrology, Canopus is named Agasti or Agastya
Agastya
Agastya was a Tamil/Vedic Siddhar or sage. Agastya and his clan are also generally credited with uncovering many mantras of the Rig Veda, the earliest and most revered Hindu scripture, in the sense of first having the mantras revealed in his mind by the Supreme Brahman...

.

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

Kalīla o Damna, an influential Pahlavi (Middle Persian
Persian literature
Persian literature spans two-and-a-half millennia, though much of the pre-Islamic material has been lost. Its sources have been within historical Persia including present-day Iran as well as regions of Central Asia where the Persian language has historically been the national language...

) book of animal fables was later known as Anvar-i-Suhaili or The Lights of Canopus.

Canopus was identified as the moiety ancestor Waa "Crow" to some Koori
Koori
The Koori are the indigenous Australians that traditionally occupied modern day New South Wales and Victoria....

 people in southeastern Australia.

The people of Maori
Māori
The Māori are the native or indigenous Polynesian people of New Zealand . They arrived in New Zealand from eastern Polynesia in several waves at some time before 1300 CE. Over several centuries in isolation, the Māori developed a unique culture with their own language, a rich mythology,...

 named Canopus as Atutahi or Atuatahi, "Stand Alone"

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
Pole star
The term "Pole Star" usually refers to Polaris, which is the current northern pole star, also known as the North Star.In general, however, a pole star is a visible star, especially a prominent one, that is approximately aligned with the Earth's axis of rotation; that is, a star whose apparent...

. This lasted only until magnetic compasses became common.

In modern times, Canopus serves another navigational use. Canopus' brightness and location well off the ecliptic makes it popular for space navigation. Many spacecraft carry a special camera known as a "Canopus Star Tracker" plus a sun sensor for attitude
Orientation (geometry)
In geometry the orientation, angular position, or attitude of an object such as a line, plane or rigid body is part of the description of how it is placed in the space it is in....

 determination.

The effects of precession
Precession
Precession is a change in the orientation of the rotation axis of a rotating body. It can be defined as a change in direction of the rotation axis in which the second Euler angle is constant...

 will take Canopus within 10° of the south celestial pole around the year 14,000 AD.

To the Bedouin
Negev Bedouins
The Negev Bedouin are traditionally pastoral semi-nomadic Arab tribes indigenous to the Negev region in Israel, who hold close ties to the Bedouin of the Sinai Peninsula. The move away from their traditional lifestyle in modern times has led to sedentarization.Estimated to number some 160,000,...

 people of the Negev
Negev
The Negev is a desert and semidesert region of southern Israel. The Arabs, including the native Bedouin population of the region, refer to the desert as al-Naqab. The origin of the word Neghebh is from the Hebrew root denoting 'dry'...

 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
Polaris
Polaris |Alpha]] Ursae Minoris, commonly North Star or Pole Star, also Lodestar) is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole, making it the current northern pole star....

, which was circumpolar and hence 'steadfast'.

See also


External links

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