Zeta Aquarii (ζ Aquarii, ζ Aqr) is the

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. ...

for a

triple star A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A large group of stars bound by gravitation is generally called a '' star cluster'' or '' galaxy'', although, broadly speak ...

system, the central star of the "water jar" asterism in the

equatorial Equatorial may refer to something related to: *Earth's equator **the tropics, the Earth's equatorial region **tropical climate *the Celestial equator ** equatorial orbit **equatorial coordinate system ** equatorial mount, of telescopes * equatorial ...

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 ...

Aquarius Aquarius may refer to: Astrology * Aquarius (astrology), an astrological sign * Age of Aquarius, a time period in the cycle of astrological ages Astronomy * Aquarius (constellation) * Aquarius in Chinese astronomy Arts and entertainment ...

. The 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 this system is 3.65, which is readily visible to the naked eye.

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 ...

measurements yield a distance estimate of around from Earth.

Etymology

In the catalogue of stars in the ''Calendarium of Al Achsasi Al Mouakket'', this star was designated ''Achr al Achbiya'' (آخر ألأخبية - ''ākhir al-akhbiya''), which was translated into

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

as ''Postrema Tabernaculorum'', meaning ''the end of luck of the homes (tents)''. This star, along with γ Aqr (Sadachbia), π Aqr (Seat) and η Aqr (Hydria), were ''al-Akḣbiya'' (الأخبية), the Tents. 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 ''

Tomb A tomb ( grc-gre, τύμβος ''tumbos'') is a :wikt:repository, repository for the remains of the dead. It is generally any structurally enclosed interment space or burial chamber, of varying sizes. Placing a corpse into a tomb can be ...

'', refers to an asterism consisting of ζ Aquarii, γ Aquarii, η Aquarii and π Aquarii. 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 Aquarii itself is (, en, the First Star of Tomb.)AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 16 日
/ref>

Properties

The binary was measured by

William Herschel Frederick William Herschel (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline H ...

in 1779 however

Christian Mayer Christian Mayer may refer to: *Christian Mayer (astronomer) (1719–1783), Czech astronomer and teacher *Christian Mayer (skier) (born 1972), Austrian former alpine skier * Christian Mayer (Wisconsin politician) (1827–1910), Wisconsin manufacture ...

, listed an earlier observation in his first double-star catalog in 1784 so its true discoverer is not clear. The two stars have an orbital period of about 587 years. The

semimajor axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the longe ...

is 3.8

arcsecond 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 ...

s and they have 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 0.40. The

orbital plane The orbital plane of a revolving body is the geometric plane in which its orbit lies. Three non-collinear points in space suffice to determine an orbital plane. A common example would be the positions of the centers of a massive body (host) an ...

is inclined by 138.2° to the line of sight. The brighter component, ζ Aquarii A (also called ζ² Aquarii), is a yellow-white-hued

F-type main sequence star An F-type main-sequence star (F V) is a main-sequence, hydrogen-fusing star of spectral type F and luminosity class V. These stars have from 1.0 to 1.4 times the mass of the Sun and surface temperatures between 6,000 and 7,600 K.Tables VII ...

with an apparent magnitude of +4.42. Its companion, ζ Aquarii B (also called ζ¹ Aquarii), is a yellow-white-hued F-type

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 ...

with an apparent magnitude of +4.51. The fact that their brightness is so similar makes the pair easy to measure and resolve. Zeta Aquarii A is known to be an

astrometric 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 wh ...

system, as it undergoes regular perturbations from its orbit. It has a 26-year

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...

and a

of 0.11″. The secondary's mass is . Zeta Aquarii is currently a northern hemisphere object. In 2004 it was directly above the

celestial equator The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth. This plane of reference bases the equatorial coordinate system. In other words, the celestial equator is an abstract projectio ...

, and before that it was located south of it.

References

External links

Double Stars to Follow, Part IV: Zeta Aquarii and Mu Cygni.
by Martin Gaskell, Prairie Astronomy Club Home Page.

by Richard Jaworski.
Image ζ Aquarii
{{DEFAULTSORT:Zeta Aquarii Aquarius (constellation) Aquarii, Zeta Aquarii, 055 213051 Binary stars F-type main-sequence stars F-type subgiants 110960 8558/9 Durchmusterung objects