Gamma Geminorum (γ Geminorum, abbreviated Gamma Gem, γ Gem), formally named Alhena , is the third-brightest object 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 ...

Gemini Gemini may refer to: Space * Gemini (constellation), one of the constellations of the zodiac ** Gemini in Chinese astronomy * Project Gemini, the second U.S. crewed spaceflight program * Gemini Observatory, consisting of telescopes in the Northern ...

. 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 1.9, making it easily visible to the naked eye even in urban regions. 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 with 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 ...

satellite, it is located at a distance of roughly 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 ...

Properties

Alhena is an

evolving 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 ...

star that is exhausting the supply of hydrogen at its core and has entered 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. The

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors i ...

matches 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 IV. Compared to the Sun it has 2.8 times the mass and 3.3 times the radius. It is radiating around 123 times the luminosity of the Sun from its outer envelope 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 9,260 K. This gives it a white hue typical of an A-class star. Alhena is 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 ...

system with a period of 12.6 years (4,614.51 days) in a highly

eccentric Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-center, in geometry * Eccentricity (graph theory) of a v ...

Keplerian orbit Johannes Kepler (; ; 27 December 1571 – 15 November 1630) was a German astronomer, German mathematician, mathematician, astrologer, Natural philosophy, natural philosopher and writer on music. He is a key figure in the 17th-century Scienti ...

. The secondary, with 1.07 times the mass of the Sun, is likely a

G-type main-sequence star A G-type main-sequence star (Spectral type: G-V), also often, and imprecisely called a yellow dwarf, or G star, is a main-sequence star (luminosity class V) of spectral type G. Such a star has about 0.9 to 1.1 solar masses and an effective temp ...

Etymology

''γ Geminorum'' ( Latinised to ''Gamma Geminorum'') is the star'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. ...

. The traditional name ''Alhena'' is derived 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 ...

الهنعة ''Al Han'ah'', 'the brand' (on the neck of the camel), whilst the alternate name ''Almeisan'' is from the Arabic المیسان ''Al Maisan'', 'the shining one.' ''Al Hanʽah'' was the name of star association consisting of this star, along with

Mu Geminorum Mu Geminorum or μ Geminorum, formally named Tejat (), is a single star in the northern constellation of Gemini. From parallax measurements obtained during the Hipparcos mission, it is roughly distant from the Sun. The position of the st ...

(Tejat Posterior),

Nu Geminorum Nu Geminorum, Latinized from ν Geminorum, is a triple star system in the constellation Gemini. It has an apparent visual magnitude of 4.16, which is bright enough to be visible to the naked eye on a dark night. Based upon an annual ...

Eta Geminorum Eta Geminorum (η Geminorum, abbreviated Eta Gem, η Gem), formally named Propus , is a triple star system in the constellation of Gemini. It is a naked-eye variable star around 380 light years from the Sun. Nomenclature ''Eta Gemin ...

(Tejat Prior) and

Xi Geminorum Xi Geminorum (ξ Geminorum, abbreviated Xi Gem, ξ Gem), formally named Alzirr , is a star in the zodiac constellation of Gemini. It forms one of the four feet of the outline demarcating the Gemini twins. The star has an apparent visua ...

(Alzirr). They also were associated in ''Al Nuḥātai'', the dual form of ''Al Nuḥāt'', 'a Camel's Hump'. 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) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included ''Alhena'' for this star. In the catalogue of stars in the ''Calendarium of Al Achsasi Al Mouakket'', this star was designated ''Nir al Henat'', 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 του al Henat'', meaning 'the brightest of Al Henat'. 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 ''

Well A well is an excavation or structure created in the ground by digging, driving, or drilling to access liquid resources, usually water. The oldest and most common kind of well is a water well, to access groundwater in underground aquifers. The ...

(asterism)'', refers to an asterism consisting of γ Geminorum, ε Geminorum,

ζ Geminorum Zeta Geminorum (ζ Geminorum, abbreviated Zeta Gem, ζ Gem) is a bright star with cluster components, distant optical components and a likely spectroscopic partner in the zodiac constellation of Gemini — in its south, on the left 'leg' ...

, λ Geminorum, μ Geminorum, ν Geminorum, ξ Geminorum and

36 Geminorum 36 may refer to: * 36 (number), the natural number following 35 and preceding 37 * One of these years of Gregorian or Julian calendars: ** 36 BC, 1st century BCE ** AD 36, 1st century ** 1936, 20th century ** 2036, 21st century Arts and entertai ...

. Consequently, γ Geminorum itself is known as (, en, the Third Star of Well.)

In culture

''Alhena'' was the name of a

Dutch Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () Dutch may also refer to: Places * Dutch, West Virginia, a community in the United States * Pennsylvania Dutch Country People E ...

ship that rescued many people from an Italian cruise liner, the ''

SS Principessa Mafalda The SS ''Principessa Mafalda'' was an Italian transatlantic ocean liner built for the Navigazione Generale Italiana (NGI) company. Named after Princess Mafalda of Savoy, second daughter of King Victor Emmanuel III, the ship was completed and ente ...

'', in October 1927.http://www.markos.it/quaderni/plata.htm Italian account of the Principessa Malfeda. In addition, the American

attack cargo ship Attack may refer to: Warfare and combat * Offensive (military) * Charge (warfare) * Attack (fencing) * Strike (attack) * Attack (computing) * Attack aircraft Books and publishing * ''The Attack'' (novel), a book * '' Attack No. 1'', comic an ...

was named after the star.

References

{{DEFAULTSORT:Gamma Geminorum Geminorum, Gamma Geminorum, 24 Gemini (constellation) A-type subgiants Spectroscopic binaries Alhena 2421 047105 031681 Durchmusterung objects