Epsilon Carinae (ε Carinae, abbreviated Epsilon Car, ε Car), officially named Avior , is a

binary star A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in ...

in the southern constellation of Carina. At

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

+1.86 it is one of the brightest stars in the night sky, but is not visible from most of the northern hemisphere. The

False Cross An asterism is an observed pattern or group of stars in the sky. Asterisms can be any identified pattern or group of stars, and therefore are a more general concept than the formally defined 88 constellations. Constellations are based on asteris ...

is an asterism formed of

Delta Velorum Delta Velorum (δ Velorum, abbreviated Delta Vel, δ Vel) is a triple star system in the southern constellation of Vela, near the border with Carina, and is part of the False Cross. Based on parallax measurements, it is approximat ...

, Kappa Velorum,

Iota Carinae Iota Carinae (ι Carinae, abbreviated Iota Car, ι Car), officially named Aspidiske , is a star in the southern constellation of Carina. With an apparent visual magnitude of 2.2, it is one of the brighter stars in the night sky. Ap ...

and ε Carinae. It is so called because it is sometimes mistaken for the

Southern Cross Crux () is a constellation of the southern sky that is centred on four bright stars in a cross-shaped asterism commonly known as the Southern Cross. It lies on the southern end of the Milky Way's visible band. The name ''Crux'' is Latin for ...

, causing errors in

astronavigation Celestial navigation, also known as astronavigation, is the practice of position fixing using stars and other celestial bodies that enables a navigator to accurately determine their actual current physical position in space (or on the surface of ...

Epsilon Carinae is located roughly from the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared rad ...

. Measurements during the

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...

mission give the pair an

angular separation Angular distance \theta (also known as angular separation, apparent distance, or apparent separation) is the angle between the two sightlines, or between two point objects as viewed from an observer. Angular distance appears in mathematics (in pa ...

of 0.46

arcseconds A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

with a difference in magnitude of 2.0. At their estimated distance, this angle is equivalent to a physical separation of around 4

astronomical unit The astronomical unit (symbol: au, or or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to or 8.3 light-minutes. The actual distance from Earth to the Sun varies by about 3% as Earth orbi ...

s. The primary component has an apparent visual magnitude of 2.2, which by itself would still make it the third-brightest star in the constellation. It is an

evolved Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation te ...

giant star A giant star is a star with substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moore, New York: Oxford University Press ...

with a

stellar classification In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting t ...

of K0 III. However, examination of the ultraviolet flux from this star suggests it may instead be of spectral type K7. The fainter secondary companion has an apparent visual magnitude of 4.1, which, if it were a solitary star, would be bright enough to be seen with the naked eye. This is a hot, core

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

-fusing B-type main sequence star of spectral class B2 Vp. The secondary may itself have an orbiting stellar companion of spectral class F8. This pair may form an

eclipsing binary A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in ...

system with a period of 785 days (2.15 years), resulting in a magnitude change of 0.12 during each eclipse.

Etymology

''ε Carinae'' ( Latinised to ''Epsilon Carinae'') is the star's

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek or Latin letter followed by the genitive form of its parent constellation's Latin name. The original list of Bayer designations contained 1,564 stars. T ...

. The name ''Avior'' is not classical in origin. It was assigned to the star by HM Nautical Almanac Office in the late 1930s during the creation of The Air Almanac, a navigational almanac for the

Royal Air Force The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) an ...

. Of the fifty-seven navigation stars included in the new almanac, two had no classical names: Epsilon Carinae and

Alpha Pavonis Alpha Pavonis (α Pavonis, abbreviated Alpha Pav, α Pav), formally named Peacock , is a binary star in the southern constellation of Pavo, near the border with the constellation Telescopium. Nomenclature ''α Pavonis'' ( Latinised t ...

. The RAF insisted that all of the stars must have names, so new names were invented. Alpha Pavonis was named "Peacock", a translation of Pavo, whilst Epsilon Carinae was called "Avior". Donald Sadler, then Superintendent of HM Nautical Almanac Office, recounted this in his memoirs but failed to explain the etymology of the invented name. In 2016, the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

organized a

Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize List of proper names of stars, proper names for stars for the international astronomical community. It operates under ...

(WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included ''Avior'' for this star. In Chinese, (), meaning '' Sea Rock'', refers to an asterism consisting of ε Carinae,

, HD 83183, HD 84810 and Upsilon Carinae . Consequently, ε Carinae itself is known as (, en, the First Star of Sea Rock.)香港太空館 – 研究資源 – 亮星中英對照表
, Hong Kong Space Museum. Accessed on line November 23, 2010.

References

{{DEFAULTSORT:Epsilon Carinae Carina (constellation) Carinae, Epsilon Eclipsing binaries K-type giants B-type main-sequence stars Avior 3307 071129 041037 CD-59 01032