Alpha Tucanae (α Tuc, α Tucanae), also named Lang-Exster, is a

binary star 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 ...

system in the southern

circumpolar constellation A circumpolar star is a star that, as viewed from a given latitude on Earth, never sets below the horizon due to its apparent proximity to one of the celestial poles. Circumpolar stars are therefore visible from said location toward the nearest p ...

Tucana Tucana (The Toucan) is a constellation in the southern sky, named after the toucan, a South American bird. It is one of twelve constellations conceived in the late sixteenth century by Petrus Plancius from the observations of Pieter Dirkszoon K ...

. 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 2.86, it can be seen with the naked eye from the southern hemisphere. Using

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, the distance to this system can be estimated as . A cool star with a surface temperature of 4300 K, it is 424 times as luminous as the sun and 37 times its diameter. It is 2.5 to 3 times as massive. It is unclear what stage of evolution the star is in. This is a

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 means that the two stars have not been individually resolved using a telescope, but the presence of the companion has been inferred from measuring changes in 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 the primary. The orbital period of the binary system is 4197.7 days (11.5 years). The primary component 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 ...

of K3 III, which indicates it is a

giant star A giant star has a substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature. They lie above the main sequence (luminosity class V in the Yerkes spectral classification) on the Hertzsp ...

that has exhausted the supply of hydrogen at its core and

evolved Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...

away from the

main sequence In astronomy, the main sequence is a classification of stars which appear on plots of stellar color index, color versus absolute magnitude, brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or d ...

. It has the characteristic orange hue of a K-type star. The

IAU 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 ...

approved the name Lang-Exster for this star system on 19 September 2024 and it is now so entered in the IAU Catalog of Star Names. "Lang" is a Malay and

Indonesian Indonesian is anything of, from, or related to Indonesia, an archipelagic country in Southeast Asia. It may refer to: * Indonesians, citizens of Indonesia ** Native Indonesians, diverse groups of local inhabitants of the archipelago ** Indonesian ...

word meaning

hornbill Hornbills are birds found in tropical and subtropical Africa, Asia and Melanesia of the family Bucerotidae. They are characterized by a long, down-curved bill which is frequently brightly coloured and sometimes has a horny casque on the upper ...

, and "Exster" is a

Dutch Dutch or Nederlands commonly refers to: * Something of, from, or related to the Netherlands ** Dutch people as an ethnic group () ** Dutch nationality law, history and regulations of Dutch citizenship () ** Dutch language () * In specific terms, i ...

word meaning

magpie Magpies are birds of various species of the family Corvidae. Like other members of their family, they are widely considered to be intelligent creatures. The Eurasian magpie, for instance, is thought to rank among the world's most intelligent c ...

; both were historically used as names for the constellation Tucana. Since this star is a binary system it is given a double name, making it the second star system with multiple IAU-named components, after

Alpha Centauri Alpha Centauri (, α Cen, or Alpha Cen) is a star system in the southern constellation of Centaurus (constellation), Centaurus. It consists of three stars: Rigil Kentaurus (), Toliman (), and Proxima Centauri (). Proxima Centauri ...

References

{{DEFAULTSORT:Alpha Tucanae Tucanae, Alpha Tucana K-type giants Spectroscopic binaries 110130 211416 PD-60 7561 8502 Lang-Exster