Delta Canis Majoris
Encyclopedia
Delta Canis Majoris (δ CMa, δ Canis Majoris) is a star
in the constellation
Canis Major
. It has the traditional name Wezen or Wesen. It is a yellow-white F-type
supergiant
with an apparent magnitude
of +1.83.
and Adhara, with an apparent magnitude
of +1.83, and is a white or yellow-white in colour. Lying about 10 degrees south southeast of Sirius, it only rises to about 11 degrees above the horizon at the latitude of the United Kingdom. The open cluster NGC 2354 is located only 1.3 degrees east of Delta Canis Majoris. As with the rest of Canis Major, Wezen is most visible in winter skies in the northern hemisphere, and summer skies in the southern. It theoretically makes up the Great Dog's hind quarter.
. It is unclear whether the pair of stars was originally Alpha
and Beta Centauri or Alpha
and Beta Columbae
. In any case, the name was somehow applied to both Delta Canis Majoris and Beta Columbae. Richard Hinckley Allen muses that the name alludes to the difficulty the star has rising above the (northern hemisphere) horizon. Astronomer Jim Kaler
has noted the aptness of the traditional name given the star's massive nature.
In Chinese
, , meaning Bow and Arrow
, refers to an asterism consisting of δ Canis Majoris, η Canis Majoris
, c Puppis, ZI 674, ο Puppis, κ Puppis, ε Canis Majoris
, κ Canis Majoris
and π Puppis
. Consequently, δ Canis Majoris itself is known as
In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Thalath al Adzari (تالت ألعذاري - taalit al-aðārii), which was translated into Latin
as Tertia Virginum, meaning the third virgin. This star, along with ε CMa
(Adhara), η CMa
(Aludra) and ο2 CMa
(Thanih al Adzari), were Al ʽAdhārā (ألعذاري), the Virgins.
of class F8
with a radius around 215 times that of the Sun. Its surface temperature is around 5818 K, and it weighs around 17 solar masses. Its absolute magnitude is -6.87, and it lies around 1800 light years away. It is rotating at a speed of around 28 km/s, and hence may take a year to rotate fully. Only around 10 million years old, Wezen has stopped fusing hydrogen in its core. Its outer envelope is beginning to expand and cool, and in the next 100,000 years it will become a red supergiant as its core fuses heavier and heavier elements. Once it has a core of iron, it will collapse and explode as a supernova
.
If Wezen were as close to Earth as Sirius is, it would be as bright as a half-full moon.
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 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....
Canis Major
Canis Major
Canis Major is one of the 88 modern constellations, and was included in the 2nd-century astronomer Ptolemy's 48 constellations. Its name is Latin for 'greater dog', and is commonly represented as one of the dogs following Orion the hunter...
. It has the traditional name Wezen or Wesen. It is a yellow-white F-type
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...
supergiant
Supergiant
Supergiants are among the most massive stars. They occupy the top region of the Hertzsprung-Russell diagram. In the Yerkes spectral classification, supergiants are class Ia or Ib . They typically have bolometric absolute magnitudes between -5 and -12...
with an apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of +1.83.
Visibility
δ Canis Majoris is the third brightest star in the constellation after SiriusSirius
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...
and Adhara, with an apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of +1.83, and is a white or yellow-white in colour. Lying about 10 degrees south southeast of Sirius, it only rises to about 11 degrees above the horizon at the latitude of the United Kingdom. The open cluster NGC 2354 is located only 1.3 degrees east of Delta Canis Majoris. As with the rest of Canis Major, Wezen is most visible in winter skies in the northern hemisphere, and summer skies in the southern. It theoretically makes up the Great Dog's hind quarter.
History and naming
The traditional name, Wezen, is derived from the medieval Arabic وزن al-wazn, which means "weight" in modern Arabic. The name was for one of a pair of stars, the other being Hadar, which has now come to refer to Beta CentauriBeta Centauri
Beta Centauri , also known as Hadar or Agena, is the second brightest star in the constellation Centaurus and the tenth brightest star in the night sky. Beta Centauri is a B1 III blue-white giant star that the astrometric Hipparcos satellite calculates as about 161 parsecs or 525 light-years from...
. It is unclear whether the pair of stars was originally Alpha
Alpha Centauri
Alpha Centauri is the brightest star in the southern constellation of Centaurus...
and Beta Centauri or Alpha
Alpha Columbae
Alpha Columbae is a 3rd magnitude and the brightest star in the constellation Columba. It is also known as Phact.- Physical charactericities :...
and Beta Columbae
Beta Columbae
Beta Columbae is a K-type giant star and is the second brightest star in the constellation of Columba. It has the traditional name Wezn , from the Arabic وزن "weight".In Chinese, , meaning Son, refers to an asterism consisting of β Columbae and λ Columbae...
. In any case, the name was somehow applied to both Delta Canis Majoris and Beta Columbae. Richard Hinckley Allen muses that the name alludes to the difficulty the star has rising above the (northern hemisphere) horizon. Astronomer Jim Kaler
James B. Kaler
James B. Kaler is an American astronomer and science writer.After elementary and high-school education in Albany, Kaler earned his A.B. at the University of Michigan in 1960...
has noted the aptness of the traditional name given the star's massive nature.
In Chinese
Chinese language
The Chinese language is a language or language family consisting of varieties which are mutually intelligible to varying degrees. Originally the indigenous languages spoken by the Han Chinese in China, it forms one of the branches of Sino-Tibetan family of languages...
, , meaning Bow and Arrow
Well (Chinese constellation)
The Well mansion is one of the Twenty-eight mansions of the Chinese constellations. It is one of the southern mansions of the Vermilion Bird.-Asterisms:...
, refers to an asterism consisting of δ Canis Majoris, η Canis Majoris
Eta Canis Majoris
Eta Canis Majoris is a star in the constellation Canis Major. It has the traditional name Aludra.The name Aludra originates from the Arabic: عذرا al-‘aðrā "the virgin"...
, c Puppis, ZI 674, ο Puppis, κ Puppis, ε Canis Majoris
Epsilon Canis Majoris
Epsilon Canis Majoris is the second brightest star in the constellation Canis Major, and one of the brightest stars in the night sky. It has the Bayer designation "epsilon" despite being the second brightest and not the fifth brightest star in its constellation. It has the traditional name Adhara...
, κ Canis Majoris
Kappa Canis Majoris
Kappa Canis Majoris is a star in the constellation Canis Major.κ Canis Majoris is a blue-white B-type subgiant with a mean apparent magnitude of +3.50. It is approximately 790 light years from Earth. It is classified as a Gamma Cassiopeiae type variable star and its brightness varies from...
and π Puppis
Pi Puppis
Pi Puppis is a star in the constellation Puppis.In Chinese, , meaning Bow and Arrow, refers to an asterism consisting of π Puppis, δ Canis Majoris, η Canis Majoris, c Puppis, ZI 674, ο Puppis, κ Puppis, ε Canis Majoris and κ Canis Majoris...
. Consequently, δ Canis Majoris itself is known as
In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Thalath al Adzari (تالت ألعذاري - taalit al-aðārii), which was translated into Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
as Tertia Virginum, meaning the third virgin. This star, along with ε CMa
Epsilon Canis Majoris
Epsilon Canis Majoris is the second brightest star in the constellation Canis Major, and one of the brightest stars in the night sky. It has the Bayer designation "epsilon" despite being the second brightest and not the fifth brightest star in its constellation. It has the traditional name Adhara...
(Adhara), η CMa
Eta Canis Majoris
Eta Canis Majoris is a star in the constellation Canis Major. It has the traditional name Aludra.The name Aludra originates from the Arabic: عذرا al-‘aðrā "the virgin"...
(Aludra) and ο2 CMa
Omicron2 Canis Majoris
Omicron2 Canis Majoris is a star in the constellation Canis Major. It is one of the most luminous stars known, a supergiant that has used up the hydrogen fuel in its core and has entered the evolutionary stage where it is fusing helium atoms to form carbon...
(Thanih al Adzari), were Al ʽAdhārā (ألعذاري), the Virgins.
Properties
Wezen is a supergiantSupergiant
Supergiants are among the most massive stars. They occupy the top region of the Hertzsprung-Russell diagram. In the Yerkes spectral classification, supergiants are class Ia or Ib . They typically have bolometric absolute magnitudes between -5 and -12...
of class F8
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...
with a radius around 215 times that of the Sun. Its surface temperature is around 5818 K, and it weighs around 17 solar masses. Its absolute magnitude is -6.87, and it lies around 1800 light years away. It is rotating at a speed of around 28 km/s, and hence may take a year to rotate fully. Only around 10 million years old, Wezen has stopped fusing hydrogen in its core. Its outer envelope is beginning to expand and cool, and in the next 100,000 years it will become a red supergiant as its core fuses heavier and heavier elements. Once it has a core of iron, it will collapse and explode as a supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
.
If Wezen were as close to Earth as Sirius is, it would be as bright as a half-full moon.