Zeta Centauri, Latinized from ζ Centauri, 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 wh ...

system in the southern

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Centaurus Centaurus is a bright constellation in the southern sky. One of the 88 modern constellations by area, largest constellations, Centaurus was included among the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one o ...

. It has the proper name Alnair , from the

Arabic Arabic (, ' ; , ' or ) is a Semitic languages, Semitic language spoken primarily across the Arab world.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Streck, Janet C ...

''Nayyir Baṭan Qanṭūris'' (نير بطن قنطورس), meaning "The Bright (Star) of the Body of the

Centaur A centaur ( ; grc, κένταυρος, kéntauros; ), or occasionally hippocentaur, is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse. Centaurs are thought of in many Greek myths as being ...

". With a combined

apparent visual 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 lig ...

of +2.55, it is one of the brighter members of the constellation. This system is close enough to the Earth that its distance can be measured directly using the

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. Due to foreshortening, nearby objects ...

technique. This yields a value of roughly , with a 1.6%

margin of error The margin of error is a statistic expressing the amount of random sampling error in the results of a survey. The larger the margin of error, the less confidence one should have that a poll result would reflect the result of a census of the ent ...

. It is drifting further away with a

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

of +6.5 km/s. In

Chinese Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of va ...

, (), meaning ''

Arsenal An arsenal is a place where arms and ammunition are made, maintained and repaired, stored, or issued, in any combination, whether privately or publicly owned. Arsenal and armoury (British English) or armory (American English) are mostly ...

'', refers to an asterism consisting of ζ Centauri,

η Centauri Eta Centauri, Latinized from η Centauri, is a star in the southern constellation of Centaurus. It has an apparent visual magnitude of +2.35 and is located at a distance of around . The stellar classification of this star is B1.5 Vn ...

θ Centauri Theta Centauri or θ Centauri, officially named Menkent (), is a single star in the southern constellation of Centaurus, the centaur. With an apparent visual magnitude of +2.06, it is the fourth-brightest member of the constellation. Bas ...

2 Centauri 2 Centauri is a single star in the Southern celestial hemisphere, southern constellation of Centaurus, located approximately 183 light-years from Earth. It has the Bayer designation g Centauri; ''2 Centauri'' is the Flamsteed designation ...

HD 117440 HD 117440, also known by its Bayer designation d Centauri, is a binary star system in the southern constellation of Centaurus. It is visible to the naked eye with a combined apparent visual magnitude of 3.90. The distance to this syst ...

, ξ¹ Centauri, γ Centauri,

τ Centauri Tau Centauri, Latinized from τ Centauri, is a solitary star in the southern constellation of Centaurus. It is visible to the naked eye with an apparent visual magnitude of +3.86. The distance to this star, based upon an annual parallax s ...

D Centauri D Centauri is a double star in the southern constellation of Centaurus. The system is faintly visible to the naked eye as a point of light with a combined apparent magnitude of +5.31; the two components are of magnitude 5.78 and 6.98, res ...

and

σ Centauri Sigma Centauri, Latinized from σ Centauri, is the Bayer designation for a solitary star in the southern constellation of Centaurus. It is visible to the naked eye with an apparent visual magnitude of 3.91. A visual companion at an angular ...

. Consequently, the

Chinese name Chinese names or Chinese personal names are names used by individuals from Greater China and other parts of the Chinese-speaking world throughout East and Southeast Asia (ESEA). In addition, many names used in Japan, Korea and Vietnam are often a ...

for ζ Centauri itself is (, en, the First Star of Arsenal.)AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 25 日
/ref> ζ Cen is a double-lined

spectroscopic binary A binary star is a system of two star, stars that are gravity, 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 separa ...

system, which indicates that the orbital motion was detected by shifts in the

absorption line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...

s of their combined spectra caused by the

Doppler effect The Doppler effect or Doppler shift (or simply Doppler, when in context) is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who d ...

. The two stars orbit each other over a period of slightly more than eight days with an

orbital eccentricity In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values betwee ...

of about 0.5. The estimated

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 the pair is 1.4

mas Mas, Más or MAS may refer to: Film and TV * Más y Menos, fictional superhero characters, from the Teen Titans animated television series * Más (Breaking Bad), "Más" (''Breaking Bad''), a season three episode of ''Breaking Bad'' Songs * Más ( ...

. At an estimated age of 40 million years, the primary component of this system appears to be in the

subgiant A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution of ...

stage of its

evolution 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 ...

with a

stellar classification In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

of B2.5 IV. It is a large star with nearly 8 times the mass of the Sun and close to 6 times the Sun's radius. This star is rotating rapidly with a

projected rotational velocity Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulge ...

of .

References

{{DEFAULTSORT:Zeta Centauri B-type subgiants Spectroscopic binaries Centaurus (constellation) Centauri, Zeta Durchmusterung objects 121263 068002

5231 5 (five) is a number, numeral (linguistics), numeral and numerical digit, digit. It is the natural number, and cardinal number, following 4 and preceding 6, and is a prime number. It has attained significance throughout history in part because typ ...