Alpha Columbae
Star in the constellation Columba
From Wikipedia, the free encyclopedia
Alpha Columbae is a third magnitude star in the southern constellation of Columba. It has the proper name Phact (/ˈfækt/);[14][15] Alpha Columbae is the Bayer designation, which is Latinized from α Columbae. This star has an apparent visual magnitude of 2.6,[3] 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).[2]
 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Columba[1] |
| Right ascension | 05h 39m 38.94103s[2] |
| Declination | −34° 04′ 26.7950″[2] |
| Apparent magnitude (V) | 2.645[3] |
| Characteristics | |
| Spectral type | B9Ve[4] or B7 IV[5] |
| U−B color index | −0.44[3] |
| B−V color index | −0.125[3] |
| R−I color index | −0.09[6] |
| Variable type | γ Cas?[7] |
| Astrometry | |
| Radial velocity (Rv) | +35.0[8] km/s |
| Proper motion (μ) | RA: −1.58[2] mas/yr[2] Dec.: −24.82 mas/yr[2] |
| Parallax (π) | 12.48±0.36 mas[2] |
| Distance | 261 ± 8 ly (80 ± 2 pc) |
| Absolute magnitude (MV) | −1.87[1] |
| Details | |
| Mass | 4.5[9] M☉ |
| Radius | 7±0.14[10] R☉ |
| Luminosity | 3,311[11] L☉ |
| Surface gravity (log g) | 3.5±0.04[10] cgs |
| Temperature | 12,200±122[10] K |
| Rotational velocity (v sin i) | 176[12] km/s |
| Age | 93[4] Myr |
| Other designations | |
| Phact, α Col, NSV 2549, CD−34 2375, CPD−34 703, FK5 215, GC 7078, HD 37795, HIP 26634, HR 1956, SAO 196059, PPM 281732, CCDM J05396−3404 A[13] | |
| Database references | |
| SIMBAD | data |
Nomenclature
α Columbae, Latinized to Alpha Columbae, is the star's Bayer designation. It is abbreviated Alpha Col or α Col.
The traditional name of Phact (also rendered Phad, Phaet, Phakt)[16] derives from the Arabic فاختة fākhitah 'ring dove'. It was originally applied to the constellation Cygnus and later transferred to this star.[17][18][19][20] The etymology of its name hadāri (unknown meaning)[21] has also been suggested. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[22] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[23] included a table of the first two batches of names approved by the WGSN; which included Phact for this star.
In Chinese, 丈人 (Zhàng Rén), meaning Grandfather, refers to an asterism consisting of α Columbae and ε Columbae.[24] Consequently, α Columbae itself is known as 丈人一 (Zhàng Rén yī, English: the First Star of Grandfather).[25] From this Chinese name, the name Chang Jin has appeared.[26]
Properties
This is believed to be a solitary star,[12][27] although it has a faint optical companion at an angular separation of 13.5 arcseconds, making it a double star.[28] The stellar classification of Alpha Columbae is B9Ve,[4] 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.[16] 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.[12] It is a suspected Gamma Cassiopeiae type (GCAS) variable star, with its apparent magnitude varying from 2.62m to 2.66m.[7]