triple star
A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. It may sometimes be used to refer to a single star. A large group of stars bound by gravitation is generally called a ''sta ...
system in the 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 first constellati ...
of
Aquila
Aquila may refer to:
Arts, entertainment, and media
* ''Aquila'', a series of books by S.P. Somtow
* ''Aquila'', a 1997 book by Andrew Norriss
* ''Aquila'' (children's magazine), a UK-based children's magazine
* ''Aquila'' (journal), an orni ...
. Its name is a
Bayer designation
A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...
that is Latinized from β Aquilae, and abbreviated Beta Aql or β Aql. This system is visible to the naked eye as a point-like source with an
apparent visual magnitude
Apparent magnitude () is a measure of the brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction of the object's light ca ...
of 3.87. Based on
parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...
measurements, it is located at a distance of 44.4
light-years
A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astro ...
. It is drifting closer to the Sun with a
radial velocity
The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity ...
of −40 km/s, and is predicted to approach to within in roughly 207,000 years.
Its two visible components are designated Beta Aquilae A and B. The former is formally named Alshain , the traditional name for the system.
Nomenclature
''β Aquilae'' (Latinised to ''Beta Aquilae'') is the system's
Bayer designation
A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...
. The designations of the two components as ''Beta Aquilae A'' and ''B'' derive from the convention used by the Washington Multiplicity Catalog (WMC) for
multiple star system
A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. It may sometimes be used to refer to a single star. A large group of stars bound by gravitation is generally called a ''st ...
s, and adopted by the
International Astronomical Union
The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...
(IAU).
The system bore the traditional name ''Alshain'' derived from the Perso-
Arabic
Arabic (, , or , ) is a Central Semitic languages, Central Semitic language of the Afroasiatic languages, Afroasiatic language family spoken primarily in the Arab world. The International Organization for Standardization (ISO) assigns lang ...
term الشاهين, ''aš-šāhīn'', meaning "the (peregrine) falcon", perhaps by
folk etymology
Folk etymology – also known as (generative) popular etymology, analogical reformation, (morphological) reanalysis and etymological reinterpretation – is a change in a word or phrase resulting from the replacement of an unfamiliar form by a mo ...
from the
Persian
Persian may refer to:
* People and things from Iran, historically called ''Persia'' in the English language
** Persians, the majority ethnic group in Iran, not to be conflated with the Iranic peoples
** Persian language, an Iranian language of the ...
''šāhīn tarāzū'' (or possibly ''šāhīn tara zed''; see Gamma Aquilae), the Persian name for the asterismα, β and
γ Aquilae
Gamma Aquilae is a star in the constellation of Aquila. Its name is a Bayer designation that is Latinized from γ Aquilae, and abbreviated gamma Aql or γ Aql. The star is formally known as Tarazed, pronounced . It has an apparent visua ...
. In 2016, the IAU 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) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name ''Alshain'' for the component Beta Aquilae A on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.
In the catalogue of stars in the ''Calendarium'' of
Al Achsasi al Mouakket
Muḥammad al Achsasi al Mouakket () was a 17th century Egyptian astronomer whose and catalogue of stars, ("''Pearls of brilliance upon the solar operations''"), was written in Cairo in about 1650. Al-Achsasi was a shaykh, a learned elder, of th ...
, this star was designated ''Unuk al Ghyrab'' (عنق ألغراب - ''únuq al-ghuraab''), which was translated into
Latin
Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
as ''Collum Corvi'', meaning ''the crow's neck''.
In
Chinese
Chinese may refer to:
* Something related to China
* Chinese people, people identified with China, through nationality, citizenship, and/or ethnicity
**Han Chinese, East Asian ethnic group native to China.
**'' Zhonghua minzu'', the supra-ethnic ...
, (), meaning '' River Drum'', refers to an asterism consisting of Beta Aquilae,
Altair
Altair is the brightest star in the constellation of Aquila (constellation), Aquila and the list of brightest stars, twelfth-brightest star in the night sky. It has the Bayer designation Alpha Aquilae, which is Latinisation of name ...
Chinese name
Chinese may refer to:
* Something related to China
* Chinese people, people identified with China, through nationality, citizenship, and/or ethnicity
**Han Chinese, East Asian ethnic group native to China.
**'' Zhonghua minzu'', the supra-ethni ...
for Beta Aquilae itself is (, ).香港太空館 - 研究資源 - 亮星中英對照表 , Hong Kong Space Museum. Accessed on line November 26, 2008.
Properties
The primary, component A, is of
magnitude
Magnitude may refer to:
Mathematics
*Euclidean vector, a quantity defined by both its magnitude and its direction
*Magnitude (mathematics), the relative size of an object
*Norm (mathematics), a term for the size or length of a vector
*Order of ...
3.71 and
spectral class
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 the ...
G8IV. It has a very low level of surface magnetic activity and may be in a state similar to a Maunder minimum. The activity shows a cycle of . The star displays
solar-like oscillations
Solar-like oscillations are oscillations in star
A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many ot ...
. Since 1943, the
spectrum
A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...
of this star has served as one of the stable anchor points by which other stars are classified.
This is an aging
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 ...
star that has exhausted the supply of hydrogen at its core and is
evolving
Evolution is the change in the heritable characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certai ...
into a
giant
In folklore, giants (from Ancient Greek: ''wiktionary:gigas, gigas'', cognate wiktionary:giga-, giga-) are beings of humanoid appearance, but are at times prodigious in size and strength or bear an otherwise notable appearance. The word ''gia ...
. Its
angular diameter
The angular diameter, angular size, apparent diameter, or apparent size is an angular separation (in units of angle) describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the ''visual an ...
has been precisely determined using
interferometry
Interferometry is a technique which uses the ''interference (wave propagation), interference'' of Superposition principle, superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important inves ...
at the
Very Large Telescope
The Very Large Telescope (VLT) is an astronomical facility operated since 1998 by the European Southern Observatory, located on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each equipped with ...
and the
CHARA array
The CHARA (Center for High Angular Resolution Astronomy) array is an optical interferometer, located on Mount Wilson, California. The array consists of six telescopes operating as an astronomical interferometer. Construction was completed in ...
, the average of both measurements, combined with its estimated distance, result in a radius 3.096 times the
radius of the Sun
Solar radius is a unit of distance used to express the size of objects in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the optical depth equals 2/3:
1\,R_ = 6.957\ti ...
. It has a mass 24% greater than the Sun's, a luminosity 5.9 times that of the Sun, and 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 5,060 K.
The 12th magnitude secondary companion, designated component B, is a double-lined
spectroscopic binary
A binary star or binary star system 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 as separate stars us ...
, which is at an
angular separation
Angular distance or angular separation is the measure of the angle between the orientation of two straight lines, rays, or vectors in three-dimensional space, or the central angle subtended by the radii through two points on a sphere. When t ...
of 13
arcsecond
A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...
s from the primary. It has 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 gratin ...
red dwarf
A red dwarf is the smallest kind of star on the main sequence. Red dwarfs are by far the most common type of fusing star in the Milky Way, at least in the neighborhood of the Sun. However, due to their low luminosity, individual red dwarfs are ...
.
In culture
In the Chinese folk tale ''
The Cowherd and the Weaver Girl
''The Cowherd and the Weaver Girl'' are characters found in Chinese mythology and appear eponymously in a romantic Chinese folk tale. The story tells of the romance between Zhinü (; the weaver girl, symbolized by the star Vega) and Niulang ...
'', Beta and Gamma Aquilae are children of
Niulang
Niulang is a Chinese deity who is identified as the star Altair in the constellation Aquila. He was a legendary figure and main character in the popular Chinese folk tale ''The Cowherd and the Weaver Girl''. The earliest record of this myth is ...
(牛郎, The Cowherd,
Altair
Altair is the brightest star in the constellation of Aquila (constellation), Aquila and the list of brightest stars, twelfth-brightest star in the night sky. It has the Bayer designation Alpha Aquilae, which is Latinisation of name ...
) and
Zhinü
Zhinü is the goddess of weaving and the star Vega in Chinese mythology. She was the youngest of seven daughters of the Jade Emperor. It is believed that she wove her father’s royal robes out of the clouds. She is identified as the star Vega i ...
(織女, The Princess,
Vega
Vega is the brightest star in the northern constellation of Lyra. It has the Bayer designation α Lyrae, which is Latinised to Alpha Lyrae and abbreviated Alpha Lyr or α Lyr. This star is relatively close at only from the Sun, and ...
).
The Koori people of
Victoria
Victoria most commonly refers to:
* Queen Victoria (1819–1901), Queen of the United Kingdom and Empress of India
* Victoria (state), a state of Australia
* Victoria, British Columbia, Canada, a provincial capital
* Victoria, Seychelles, the capi ...
knew Beta and Gamma Aquilae as the
black swan
The black swan (''Cygnus atratus'') is a large Anatidae, waterbird, a species of swan which breeds mainly in the southeast and southwest regions of Australia. Within Australia, the black swan is nomadic, with erratic migration patterns dependent ...
wives of ''Bunjil'' (Altair), the
wedge-tailed eagle
The wedge-tailed eagle (''Aquila audax'') also known as the eaglehawk, is the largest bird of prey in the continent of Australia. It is also found in southern New Guinea to the north and is distributed as far south as the state of Tasmania. A ...