Alpha Phoenicis

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Alpha Phoenicis
Diagram showing star positions and boundaries of the Phoenix constellation and its surroundings
Cercle rouge 100%.svg

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]
Spectral type K0.5 IIIb[3]
U−B color index +0.903[2]
B−V color index +1.092[2]
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)
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)
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
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.[7]

Alpha Phoenicis (α Phe, α Phoenicis), or Ankaa, is the brightest star in the constellation Phoenix.


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]


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]


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c d Gutierrez-Moreno, Adelina; et al. (1966), A System of photometric standards 1, Publicaciones Universidad de Chile, Department de Astronomy, pp. 1–17, Bibcode:1966PDAUC...1....1G 
  3. ^ a b c d e Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637 
  4. ^ Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick, eds., The Revision of the General Catalogue of Radial Velocities, University of Toronto: International Astronomical Union, retrieved 2009-09-10 
  5. ^ a b Jancart, S.; et al. (October 2005), "Astrometric orbits of SB^9 stars", Astronomy and Astrophysics 442 (1): 365–380, arXiv:astro-ph/0507695, Bibcode:2005A&A...442..365J, doi:10.1051/0004-6361:20053003 
  6. ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1 . The radius (R*) is given by:
    \begin{align} 2\cdot R_*
 & = \frac{(10^{-3}\cdot 26\cdot 5.25)\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\
 & \approx 29.4\cdot R_{\bigodot}
  7. ^ "alf Phe -- Spectroscopic binary", SIMBAD (Centre de Données astronomiques de Strasbourg), retrieved 2012-01-09 
  8. ^ Kunitsch, Paul; Smart, Tim (2006). A Dictionary of Modern Star names: A Short Guide to 254 Star Names and Their Derivations. Cambridge, Massachusetts: Sky Publishing Corp. p. 49. ISBN 978-1-931559-44-7. 
  9. ^ a b Allen, Richard Hinckley (1899), Star-names and their meanings, G. E. Stechert, p. 336 
  10. ^ Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics 431: 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039