Alpha Columbae or α Columbae, officially named Phact (), is a third magnitude

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

in the southern

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 ...

Columba Columba or Colmcille; gd, Calum Cille; gv, Colum Keeilley; non, Kolban or at least partly reinterpreted as (7 December 521 – 9 June 597 AD) was an Irish abbot and missionary evangelist credited with spreading Christianity in what is toda ...

. It has an apparent visual magnitude of 2.6, making it the brightest member of Columba. 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 made 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, Alpha Columbae is located at a distance of around .

Nomenclature

''α Columbae'', Latinized to ''Alpha Columbae'', 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 of ''Phact'' (also rendered ''Phad'', ''Phaet'', ''Phakt'') derives from the Arabic فاختة ''fākhitah'' ' ring dove'. It was originally applied to the constellation Cygnus and later transferred to this star. The etymology of its name ''hadāri'' (unknown meaning) has also been suggested. In 2016, the International Astronomical Union organized a Working Group on Star Names (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 ''Phact'' for this star. 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 '' Grandfather'', refers to an asterism consisting of α Columbae and ε Columbae. Consequently, α Columbae itself is known as (, en, the First Star of Grandfather.). From this Chinese name, the name ''Chang Jin'' has appearedRichard Hinckley Allen: Star Names — Their Lore and Meaning: Columbae
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Properties

This is believed to be a solitary star, although it has a faint optical companion at an

angular separation Angular distance \theta (also known as angular separation, apparent distance, or apparent separation) is the angle between the two sightlines, or between two point objects as viewed from an observer. Angular distance appears in mathematics (in pa ...

of 13.5 arcseconds, making it 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 ...

. The

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 Alpha Columbae is B9Ve, matching a B-type main-sequence star. The spectrum shows it to be a Be star surrounded by a hot gaseous disk, which is generating emission lines because of hydrogen recombination. Like most if not all such stars, it is rotating 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 . The azimuthal equatorial velocity may be . It is a suspected Gamma Cassiopeiae type (GCAS) variable star, with its apparent magnitude varying from 2.62^m to 2.66^m.

References

{{DEFAULTSORT:Alpha Columbae B-type main-sequence stars Be stars Columba (constellation) Columbae, Alpha Durchmusterung objects 037795 026634

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Phact