Epoch J2000.0 Equinox J2000.0 (ICRS)
|Right ascension||05h 39m 38.94103s|
|Declination||−34° 04′ 26.7950″|
|Apparent magnitude (V)||2.645|
|Spectral type||B7 IV|
|U−B color index||−0.44|
|B−V color index||−0.125|
|R−I color index||−0.09|
|Radial velocity (Rv)||+35.0 km/s|
|Proper motion (μ)||RA: −1.58 mas/yr
Dec.: −24.82 mas/yr
|Parallax (π)||12.48 ± 0.36 mas|
|Distance||261 ± 8 ly
(80 ± 2 pc)
|Absolute magnitude (MV)||−1.9|
|Luminosity (bolometric)||1,000 L☉|
|Surface gravity (log g)||3.73 cgs|
|Rotational velocity (v sin i)||176 km/s|
Alpha Columbae (α Columbae, α Col) is the Bayer designation for a third magnitude star in the southern constellation of Columba. It has the traditional name of Phact, which is derived from the Arabic term for "ring dove". It has an apparent visual magnitude of 2.6, making it the brightest member of Columba. Based upon parallax measurements made during the Hipparcos mission, Alpha Columbae is located at a distance of around 261 light-years (80 parsecs).
This is believed to be a solitary star, although it has a faint optical companion at an angular separation of 13.5 arcseconds, making it a double star. The stellar classification of Alpha Columbae is B7 IV, with the luminosity class of IV indicating it has evolved into a subgiant 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 of 176 km s–1. The azimuthal equatorial velocity may be 457 km s–1. It is a suspected Gamma Cassiopeiae type (GCAS) variable star, with its apparent magnitude varying from 2.62m to 2.66m.
The proper name "Phact" (also Phad, Phaet, Phakt) derived from the Arabic ألفاجتة - fākh(i)tah [fa:x(i)ta] which meaning "ring dove". It was originally applied to the constellation Cygnus as al-Fākhtah, but later transferred to this star. The etymology of its name hadāri (unknown meaning) has also been suggested.
In Chinese, 丈人 (Zhàng Rén), meaning Grandfather, refers to an asterism consisting of α Columbae and ε Columbae. Consequently, α Columbae itself is known as 丈人一 (Zhàng Rén yī, English: the First Star of Grandfather.). From this Chinese name, the name Chang Jin was appeared
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