Gamma Aquarii, or γ Aquarii, is a suspected
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
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 ...
of
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 ...
. It has an
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 3.849,
[ making it one of the brighter members of the constellation. Based upon ]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 taken 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, this star is located at a distance of approximately 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 radi ...
.[ It is drifting closer to the Sun 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 −16 km/s.[ In 1998, Olin J. Eggen included this star as a candidate member of the ]Hyades Supercluster
The Hyades Stream (or Hyades moving group) is a large collection of scattered stars that also share a similar trajectory with the Hyades Cluster. In 1869, Richard A. Proctor observed that numerous stars at large distances from the Hyades share a ...
.[
Gamma Aquarii is the primary or 'A' component of a ]double star
In observational astronomy, a double star or visual double is a pair of stars that appear close to each other as viewed from Earth, especially with the aid of optical telescopes.
This occurs because the pair either forms a binary star (i.e. a bi ...
designated WDS J22217-0123.[ Gamma Aquarii A's two purported components are therefore designated WDS J22217-0123 Aa and Ab. Gamma Aquarii is traditionally also called Sadachbia ,][ a name now formally restricted to γ Aqr Aa.]
Nomenclature
''γ Aquarii'', Latinised to ''Gamma Aquarii'', is the system'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. ...
. WDS J22217-0123 A is its designation in the Washington Double Star Catalog
The Washington Double Star Catalog, or WDS, is a catalog of double stars, maintained at the United States Naval Observatory. The catalog contains positions, magnitudes, proper motions and spectral types and has entries for (as of June 2017) 141,7 ...
.
It bore the traditional name ''Sadachbia'', from an 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 ...
expression سعد الأخبية (''sa‘d al-’axbiyah''), meaning "luck of the homes (tents)". In Hindi
Hindi (Devanāgarī: or , ), or more precisely Modern Standard Hindi (Devanagari: ), is an Indo-Aryan language spoken chiefly in the Hindi Belt region encompassing parts of northern, central, eastern, and western India. Hindi has been de ...
it is also called ''Satabhishaj'' (a hundred physicians); it is called ''Sadhayam'' in Tamil
Tamil may refer to:
* Tamils, an ethnic group native to India and some other parts of Asia
**Sri Lankan Tamils, Tamil people native to Sri Lanka also called ilankai tamils
**Tamil Malaysians, Tamil people native to Malaysia
* Tamil language, nativ ...
. In the catalogue of stars in the ''Calendarium of Al Achsasi Al Mouakket'', this star was designated ''Aoul al Achbiya'' (''أول ألأجبية'' - ''awwil al ahbiyah''), 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 ''Prima Tabernaculorum'', meaning ''the first of luck of the homes (tents)''.[ 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, outreac ...
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 proper names for stars for the international astronomical community. It operates under Division C – Education ...
(WGSN)[
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 Gamma Aquarii, Zeta Aquarii, Eta Aquarii and Pi 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 Gamma Aquarii itself is (, en, the Second Star of Tomb).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.
Properties
In 1978 through 1984, H. A. McAlister listed this as a 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 ...
star system that is unresolved by speckle interferometry
Speckle imaging describes a range of high-resolution astronomical imaging techniques based on the analysis of large numbers of short exposures that freeze the variation of atmospheric turbulence. They can be divided into the shift-and-add ("''i ...
,[ and it is listed as such in the 1991 revision of the '']Bright Star Catalogue
The Bright Star Catalogue, also known as the Yale Catalogue of Bright Stars, Yale Bright Star Catalogue, or just YBS, is a star catalogue that lists all stars of stellar magnitude 6.5 or brighter, which is roughly every star visible to the na ...
''.[ In 2008, P. P. Eggleton and A. A. Tokovinin listed it as a single star in their catalogue of multiplicity.][
It presents as an ]A-type main sequence star
An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral type A and luminosity class V (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1 ...
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 A0 V,[ around two and a half times more massive than the Sun.][ It was a candidate ]Lambda Boötis star
A Lambda Boötis star is a type of chemically peculiar star which has an unusually low abundance of iron peak elements in its surface layers. One possible explanation for this is that it is the result of accretion of metal-poor gas from a circumste ...
, suggesting it may have accreted low-metallicity
In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...
circumstellar gas some time in the past.[ But it has since been excluded.][ The star is spinning relatively 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 .[ This value gives a lower bound on the actual ]azimuth
An azimuth (; from ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north.
Mathematicall ...
al velocity along the star's equator. The outer atmosphere of Gamma Aquarii is radiating energy at an effective temperature
The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...
of 10,500 K,[ which is nearly double the temperature at the surface of the Sun. This heat is what gives Gamma Aquarii the white-hot glow of an ]A-type star
An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral type A and luminosity class V (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1 ...
.[
]
References
External links
* http://aladin.u-strasbg.fr/AladinPreview?-c=22+21+39.3754-01+23+14.393&ident=*+gam+Aqr&
{{DEFAULTSORT:Gamma Aquarii
A-type main-sequence stars
Lambda Boötis stars
Spectroscopic binaries
Aquarius (constellation)
Aquarii, Gamma
Durchmusterung objects
Aquarii, 048
212061
110395
8518
Sadachbia