Alpha Phoenicis
Orange-hued star in the constellation Phoenix
From Wikipedia, the free encyclopedia
Alpha Phoenicis (α Phoenicis, abbreviated Alpha Phe or α Phe), formally named Ankaa /ˈæŋkə/,[11] (with the same pronunciation) is the brightest star in the constellation of Phoenix.
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Phoenix |
| Right ascension | 00h 26m 17.06309s[1] |
| Declination | −42° 18′ 21.7712″[1] |
| Apparent magnitude (V) | 2.377[2] |
| Characteristics | |
| Spectral type | K0.5 IIIb[3] |
| U−B color index | +0.903[2] |
| B−V color index | +1.092[2] |
| Astrometry | |
| Radial velocity (Rv) | +74.6[4] km/s |
| Proper motion (μ) | RA: +176.268[1] mas/yr Dec.: −398.872[1] mas/yr |
| Parallax (π) | 39.9183±0.7283 mas[1] |
| Distance | 82 ± 1 ly (25.1 ± 0.5 pc) |
| Absolute magnitude (MV) | 0.52[5][6] |
| Orbit[7] | |
| Period (P) | 3848.8 days |
| Semi-major axis (a) | 103.5 mas[note 1] |
| Eccentricity (e) | 0.34 |
| Inclination (i) | 128.0±5.4° |
| Longitude of the node (Ω) | 242.8±3.9° |
| Periastron epoch (T) | 2416201.8 HJD |
| Argument of periastron (ω) (primary) | 19.8° |
| Details | |
| Mass | 0.96±0.07[6] M☉ |
| Radius | 13.39±0.29[6] R☉ |
| Luminosity | 83[8] L☉ |
| Surface gravity (log g) | 2.53[3] cgs |
| Temperature | 4,770±250[6] K |
| Metallicity [Fe/H] | −0.73[3] dex |
| Rotational velocity (v sin i) | 1.0[9] km/s |
| Other designations | |
| Ankaa, Nair al Zaurak, Cymbae, Lucida Cymbae, CD−42°116, FK5 12, GCTP 71.00, HIP 2081, HR 99, HD 2261, LTT 231, SAO 215093.[10] | |
| Database references | |
| SIMBAD | data |
Nomenclature
Alpha Phoenicis is the star's Bayer designation. It also bore the traditional name Ankaa sometime after 1800, from the Arabic العنقاء al-ʽanqāʼ "the phoenix" for the name of the constellation.[11] The International Astronomical Union has formally adopted the Ankaa as the proper name for Alpha Phoenicis.[12]
Medieval Arab astronomers formed the constellation of the dhow (where Phoenix is), so another popular name for the star is Nair al Zaurak[13] from نائر الزورق nayyir az-zawraq "the bright (star) of the skiff". The Latin translation is Cymbae, from lūcida cumbae.[13]
In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, 火鳥 (Huǒ Niǎo), meaning Firebird, refers to an asterism consisting of α Phoenicis, ι Phoenicis, σ Phoenicis, ε Phoenicis, κ Phoenicis, μ Phoenicis, λ1 Phoenicis, β Phoenicis and γ Phoenicis . Consequently, α Phoenicis itself is known as 火鳥六 (Huǒ Niǎo liù, English: the Sixth Star of Firebird.)[14]
Description
Alpha Phoenicis is a spectroscopic binary star system with components that orbit each other every 3,848.8 days (10.5 years).[7] The combined stellar classification of the system is K0.5 IIIb,[3] which matches the spectrum of a normal luminosity giant star. It has an apparent visual magnitude of 2.4,[2] so it is somewhat outshone by its first magnitude neighbors Achernar (α Eridani) and Fomalhaut (α Piscis Austrini). Based upon parallax measurements, this system is at a distance of about 85 light-years (26 parsecs) from the Earth.[15]
Notes
- This is the photocentric semi-major axis, from the motion shown by the observed "star" relative to distant objects, and in practice relative to the barycentre. This is always smaller than the orbital semi-major axis, dramatically smaller when the primary star is much more massive than the secondary or when it is not much brighter.