Alpha Phoenicis
 Location of α Phoenicis (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Phoenix |
| Right ascension | 00h 26m 17.05140s[1] |
| Declination | –42° 18′ 21.5539″[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: +233.05[1] mas/yr Dec.: –356.30[1] mas/yr |
| Parallax (π) | 38.50 ± 0.73[1] mas |
| Distance | 85 ± 2 ly (26.0 ± 0.5 pc) |
| Orbit[5] | |
| Period (P) | 3848.8 days |
| Semi-major axis (a) | 103.5 m |
| 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 | |
| Radius | 15[6] R☉ |
| Surface gravity (log g) | 2.53[3] cgs |
| Temperature | 4,436[3] K |
| Metallicity [Fe/H] | –0.73[3] dex |
| Other designations | |
Alpha Phoenicis (α Phe, α Phoenicis), or Ankaa, is the brightest star in the constellation Phoenix.
Name
Alpha Phoenicis has been given the name Ankaa sometime after 1800, from the Arabic العنقاء al-ʿanqā’ "the phoenix" for the name of the constellation.[8] Medieval Arab astronomers formed the constellation of the dhow (where Phoenix is), so another popular name for the star is Nair al Zaurak[9] from النائر الزوق an-na’ir az-zawraq "the bright (star) of the skiff". The Latin translation is Cymbae, from lūcida cumbæ.[9]
Description
This is a spectroscopic binary star system with components that orbit each other every 3848.8 days (10.5 years).[5] The combined stellar classification of the system is K0.5 IIIb,[3] which matches the spectrum of a lower 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 Australis). Based upon parallax measurements, this system is at a distance of about 85 light-years (26 parsecs) from the Earth.[1] The interferometry-measured angular diameter of the primary component, after correcting for limb darkening, is 5.25 ± 0.06 mas,[10] which, at its estimated distance, equates to a physical radius of about 15 times the radius of the Sun.[6]
Ankaa is similar to many of the visible stars of the night sky, being an orange giant of relatively average stellar size. It is currently thought to be in the midst of a short but stable helium burning phase of its stellar evolution, although it probably won't be long in astronomical terms before it sheds its outer layers in a planetary nebula and ends its life quietly as a white dwarf. Ankaa has a small stellar companion, about which little is known.[citation needed]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 2.0 2.1 2.2 2.3 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 3.0 3.1 3.2 3.3 3.4 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 5.0 5.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 6.0 6.1 Lua error in package.lua at line 80: module 'strict' not found.. The radius (R*) is given by:
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 9.0 9.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
