Gamma Andromedae, Latinized from γ Andromedae, is the third-brightest point of light in the northern constellation of Andromeda. It is a

multiple star system 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 speaking ...

approximately 350

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 101 ...

s from Earth. The system 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 rate of change of the distance or range between the two points. It is equivalent to the vector projection ...

in the range of −12 to −14 km/s.

Observation

In 1778, German physicist Johann Tobias Mayer discovered that γ Andromedae is 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 ...

. When examined in a small

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to obse ...

, it appears to be a bright, golden-yellow star next to a dimmer, indigo-blue star, separated by approximately 10

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 ...

. The pair is often considered by stargazers to be a beautiful double star with a striking contrast of color. The brighter member, γ¹ Andromedae, is the primary of the system, and is thus designated component γ Andromedae A. It has the official proper name Almach , which was used as the traditional name of the naked eye star, and thus the system as a whole. The fainter secondary is γ² Andromedae or γ Andromedae B. It was later discovered that γ² Andromedae is itself a triple star system. What appears as a single star to the naked eye is thus a quadruple star system.

Nomenclature

''γ Andromedae'' ( Latinised to ''Gamma Andromedae'') 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. T ...

; ''γ¹'' and ''γ² Andromedae'' those of its two constituents. The designations of those constituents as ''Gamma Andromedae 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. A large group of stars bound by gravitation is generally called a '' star cluster'' or ''galaxy'', although, broadly speakin ...

s, and adopted by 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 ...

(IAU). 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 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 approved the name ''Almach'' for the component Gamma Andromedae A on 20 July 2016 and it is now so included in the List of IAU-approved Star Names. ''Almach'' was the traditional name (also spelt as ''Almaach'', ''Almaack'', ''Almak'', ''Almaak'', or ''Alamak''), derived from the

Arabic Arabic (, ' ; , ' or ) is a 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. E.Watson; Walte ...

العناق (''al-‘anāq''), "the

caracal The caracal (''Caracal caracal'') () is a medium-sized wild cat native to Africa, the Middle East, Central Asia, and arid areas of Pakistan and northwestern India. It is characterised by a robust build, long legs, a short face, long tufted e ...

" (desert lynx). Another term for this star used by medieval astronomers writing in Arabic was رجل المسلسلة (''Rijl al Musalsalah''), "Foot of The hainedWoman". In the catalogue of stars in the ''Calendarium'' of

Al Achsasi al Mouakket Muḥammad al-Akhṣāṣī al-Muwaqqit ( ar, محمد الاخصاصي الموقت) was an Egyptian astronomer whose and catalogue of stars, ('Pearls of brilliance upon the solar operations'), was written at Cairo about 1650. Al-Akhsasi was a ...

, this star was designated الخامس النعامة (''Al Khamis al Na'amah''), 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 ...

as Quinta Struthionum, meaning ''the fifth ostrich''. In Chinese, (), meaning ''

Heaven's Great General ''Teen Ta Tseang Keun'' () or ''Tëen ta tsëang keun'' meaning "Heaven's Great General",Allen (1963): p.37. was a Chinese constellation () in the region of '' Lóu'' (). It contained stars of the western constellations Andromeda and Triangulum. ...

'', refers to an asterism consisting of γ Andromedae,

φ Persei Phi Persei (Phi Per, φ Persei, φ Per) is a Stellar classification, Class B2Vpe fourth-magnitude star in the constellation Perseus (constellation), Perseus, location about 720 light-years from Earth. System Phi Persei i ...

51 Andromedae 51 Andromedae, abbreviated 51 And and formally named Nembus , is the 5th brightest star in the northern constellation of Andromeda, very slightly dimmer than the Andromeda Galaxy also being of 4th magnitude. It is an orange K-type giant ...

49 Andromedae 49 Andromedae (abbreviated 49 And) is a star in the constellation Andromeda. ''49 Andromedae'' is the Flamsteed designation though it also bears the Bayer designation A Andromedae. It is visible to the naked eye under good viewing co ...

χ Andromedae Chi Andromedae ( Andromedae, And) is the Bayer designation for a star in the northern constellation of Andromeda. It has an apparent visual magnitude of +5.01, which is relatively faint for a naked-eye star. Based upon parallax meas ...

, υ Andromedae,

τ Andromedae Tau Andromedae, Latinized from τ Andromedae, is the Bayer designation for a single star in the northern constellation of Andromeda. It has an apparent visual magnitude of +4.94, which is bright enough to be viewed from dark suburban ...

56 Andromedae 56 Andromedae, abbreviated 56 And, is a probable binary star system in the northern constellation of Andromeda. ''56 Andromedae'' is the Flamsteed designation. It has a combined apparent visual magnitude of 5.69, which is just bright enou ...

β Trianguli Beta Trianguli (Beta Tri, β Trianguli, β Tri) is the Bayer designation for a binary star system in the constellation Triangulum, located about 127 light years from Earth. Although the apparent magnitude is only ...

γ Trianguli Gamma Trianguli (Gamma Tri, γ Trianguli, γ Tri) is a star in the constellation Triangulum located approximately 112 light years from Earth. It has an apparent magnitude of +4.01 and forms an optical (line-of-sight) triple ...

and

δ Trianguli Delta Trianguli, Romanization of Greek, Latinized from Delta Tri, is a spectroscopic binary star system approximately away in the constellation of Triangulum. The primary star is a Yellow dwarf star, yellow dwarf, while the seconda ...

. 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 oft ...

for γ Andromedae itself is (, en, the First Star of Heaven's Great General). In the Babylonian star catalogues, γ Andromedae, together with

Triangulum Triangulum is a small constellation in the northern sky. Its name is Latin for " triangle", derived from its three brightest stars, which form a long and narrow triangle. Known to the ancient Babylonians and Greeks, Triangulum was one of the 4 ...

, formed the constellation known as ^MULAPIN () "The Plough". Astrologically, this star was considered "honourable and eminent".

Stellar properties

γ¹ Andromedae (A component) is a massive

bright giant 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, ...

star A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth make ...

with a

spectral 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 K2+IIb, and is presently at an

evolutionary 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 t ...

stage following the

asymptotic giant branch The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) lat ...

. It does not display a chemical enhancement of

s-process The slow neutron-capture process, or ''s''-process, is a series of reactions in nuclear astrophysics that occur in stars, particularly asymptotic giant branch stars. The ''s''-process is responsible for the creation ( nucleosynthesis) of approxim ...

elements. The star has an apparent visual magnitude of approximately 2.26. It has an estimated 24 times the

mass of the Sun The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass of ...

with an age of 6.5 million years. γ² Andromedae (BC component), with an overall apparent visual magnitude of 4.84, is 9.6

away from γ¹ Andromedae at a

position angle In astronomy, position angle (usually abbreviated PA) is the convention for measuring angles on the sky. The International Astronomical Union defines it as the angle measured relative to the north celestial pole (NCP), turning positive into the ...

of 63 degrees. γ¹ and γ² have an orbital period of approximately 5,000 years. In October 1842, Wilhelm Struve found that γ² Andromedae was itself a double star whose components were separated by less than an arcsecond. The components are an object of apparent visual magnitude 5.5, γ Andromedae B, and 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 ...

with apparent visual magnitude 6.3, γ Andromedae C. They have an orbital period of about 64 years and a high eccentricity (ovalness) of 0.927. Spectrograms taken from 1957 to 1959 revealed that γ Andromedae B was itself a spectroscopic binary, composed of two

B-type main-sequence star A B-type main-sequence star (B V) is a main-sequence (hydrogen-burning) star of spectral type B and luminosity class V. These stars have from 2 to 16 times the mass of the Sun and surface temperatures between 10,000 and 30,000 K. B-type stars ...

s orbiting each other with a period of 2.67 days. The two orbits may be coplanar. At present the angular distance between both stars is 0.16 arcsecon

Almach as a name

was the name of United States navy ship.

References

External links