Epsilon Canis Majoris
Encyclopedia
Epsilon Canis Majoris (ε CMa, ε 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 (sometimes spelled Adara). The name is from the Arabic word عذارى ‘aðāra’, "virgins".
In Chinese
, , meaning Bow and Arrow
, refers to an asterism consisting of ε Canis Majoris, δ Canis Majoris
, η Canis Majoris
, c Puppis, ZI 674, ο Puppis, κ Puppis, κ Canis Majoris
and π Puppis
. Consequently, ε Canis Majoris itself is known as
In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket
, this star was designated Aoul al Adzari (أول ألعذاري - awwil al-aðārii), which was translated into Latin
as Prima Virginum, meaning First of the Virgins. This star, along with δ CMa
(Wezen), η CMa
(Aludra) and ο2 CMa
(Thanih al Adzari), were Al ʽAdhārā (ألعذاري), the Virgins.
of +1.5 and belongs to the spectral classification B2. Its color is blue or blueish-white, due to the surface temperature of 25,000 K
. It emits a total radiation equal to 20,000 times that of the Sun
: if this star were at the same distance as Sirius
, it would appear 15 times brighter than the planet Venus
. This star is also one of the brightest known extreme ultraviolet sources in the sky.
It is the strongest source of photons capable of ionizing
hydrogen
atoms in interstellar gas near the sun, and is very important in determining the ionization state of the Local Interstellar Cloud
.
The +7.5 magnitude companion star (the absolute magnitude
amounts to +1.9) is at 7.5" away with a position angle of 161° of the main star. Despite the relatively large angular distance
the components can only be resolved in large telescopes, since the main star is approximately 250 times brighter than its companion.
A few million years ago, Adhara was much closer to the Sun than it is at present, causing it to be a much brighter star in the night sky. About 4,700,000 years ago, Adhara was 34 light years from the Sun, and was the brightest star in the sky with a magnitude of –3.99. No other star has attained this brightness since, nor will any other star attain this brightness for at least five million years.
.
was a United States Navy
Crater class cargo ship
named after the star.
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...
, and one of the brightest stars in the night sky. It has the Bayer designation
Bayer designation
A Bayer designation is a stellar designation in which a specific star is identified by a Greek letter, followed by the genitive form of its parent constellation's Latin name...
"epsilon" despite being the second brightest and not the fifth brightest star in its constellation. It has the traditional name Adhara (sometimes spelled Adara). The name is from the Arabic word عذارى ‘aðāra’, "virgins".
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 ε Canis Majoris, δ Canis Majoris
Delta Canis Majoris
Delta Canis Majoris is a star in the constellation Canis Major. It has the traditional name Wezen or Wesen...
, 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, 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, ε Canis Majoris itself is known as
In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket
Al Achsasi al Mouakket
Mohammad Al Achsasi Al Mouakket was an Egyptian astronomer whose calendarium and catalogue of stars, entitled Durret al Muddiah Fih al Aamal al Shamsiah , was written at Cairo about 1650.Al Achsasi was sheikh of the Grand Mosque of the University of Cairo, where his name al...
, this star was designated Aoul al Adzari (أول ألعذاري - awwil 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 Prima Virginum, meaning First of the Virgins. This star, along with δ CMa
Delta Canis Majoris
Delta Canis Majoris is a star in the constellation Canis Major. It has the traditional name Wezen or Wesen...
(Wezen), 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
Adhara is a binary star, about 430 light years away from Earth. The main star possesses an apparent magnitudeApparent 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 +1.5 and belongs to the spectral classification B2. Its color is blue or blueish-white, due to the surface temperature of 25,000 K
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
. It emits a total radiation equal to 20,000 times that of 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...
: if this star were at the same distance as 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...
, it would appear 15 times brighter than the planet Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
. This star is also one of the brightest known extreme ultraviolet sources in the sky.
It is the strongest source of photons capable of ionizing
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
atoms in interstellar gas near the sun, and is very important in determining the ionization state of the Local Interstellar Cloud
Local Interstellar Cloud
The Local Interstellar Cloud is the interstellar cloud roughly 30 light years across through which the Earth's solar system is currently moving. The Solar System is thought to have entered the Local Interstellar Cloud at some time between 44,000 and 150,000 years ago and is expected to remain...
.
The +7.5 magnitude companion star (the 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...
amounts to +1.9) is at 7.5" away with a position angle of 161° of the main star. Despite the relatively large angular distance
Angular distance
In mathematics and all natural sciences , the angular distance between two point objects, as observed from a location different from either of these objects, is the size of the angle between the two directions originating from...
the components can only be resolved in large telescopes, since the main star is approximately 250 times brighter than its companion.
A few million years ago, Adhara was much closer to the Sun than it is at present, causing it to be a much brighter star in the night sky. About 4,700,000 years ago, Adhara was 34 light years from the Sun, and was the brightest star in the sky with a magnitude of –3.99. No other star has attained this brightness since, nor will any other star attain this brightness for at least five million years.
Modern legacy
Adhara appears on the national flag of Brazil, symbolising the state of TocantinsTocantins (state)
Tocantins is one of the states of Brazil. . The state was formed in 1988 out of the northern part of Goiás, and construction began on the capital, Palmas, in 1989, in contrast to most of the other cities in the state which date back to the Portuguese colonial period...
.
Namesakes
USS Adhara (AK-71)USS Adhara (AK-71)
USS Adhara was a Crater-class cargo ship in the service of the United States Navy in World War II. Named after the star Adhara in the constellation Canis Major, it was the only ship of the Navy to bear this name....
was a United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
Crater class cargo ship
Crater class cargo ship
Crater-class cargo ship is a category of freighter that was constructed for use by the United States Navy during World War II under Maritime Commission EC2-S-C1 type....
named after the star.