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 |
| 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) (secondary) |
19.8° |
| Details | |
| Radius | 15[6] R☉ |
| Surface gravity (log g) | 2.53[3] |
| Temperature | 4,436[3] K |
| Metallicity [Fe/H] | –0.73[3] dex |
| Other designations | |
Alpha Phoenicis (α Phe, α Phoenicis) is the brightest star in the constellation Phoenix. It has the traditional name Ankaa,[8] from the Arabic العنقاء al-‘anqā’ "the phoenix". Medieval Arab astronomers formed the constellation of the dhow (small boat) where Phoenix is, so another popular name for the star is Nair al-Zaurak[9] from النائر الزورق an-na’ir az-zawraq "the bright (star) of the skiff". The Latin translation is Cymbae, from lūcida cumbæ.[citation needed]
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]
[edit] References
- ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, Bibcode 2007A&A...474..653V, doi:10.1051/0004-6361:20078357
- ^ 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
- ^ 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, Bibcode 2006AJ....132..161G, doi:10.1086/504637
- ^ Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick, ed., The Revision of the General Catalogue of Radial Velocities, University of Toronto: International Astronomical Union, http://adsabs.harvard.edu/abs/1967IAUS...30...57E, retrieved 2009-09-10
- ^ a b Jancart, S. et al. (October 2005), "Astrometric orbits of SB^9 stars", Astronomy and Astrophysics 442 (1): 365–380, Bibcode 2005A&A...442..365J, doi:10.1051/0004-6361:20053003
- ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3 ed.), Birkhäuser, ISBN 3540296921, http://books.google.com/books?id=OvTjLcQ4MCQC&pg=PA41. The radius (R*) is given by:
- ^ "alf Phe -- Spectroscopic binary", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Alpha+Phoenicis, retrieved 2012-01-09
- ^ Ridpath, Ian; Tirion, Wil (2007), Stars and planets: the most complete guide to the stars, planets, galaxies, and the solar system, Princeton field guides (4th ed.), Princeton University Press, p. 206, ISBN 0691135568
- ^ Allen, Richard Hinckley (1899), Star-names and their meanings, G. E. Stechert, p. 336, http://books.google.com/books?id=5xQuAAAAIAAJ&pg=PA336
- ^ Richichi; 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
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