Alpha Fornacis

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Alpha Fornacis
Fornax constellation map.png
Location of α Fornacis (upper left).
Observation data
Epoch J2000      Equinox J2000
Constellation Fornax
Right ascension 3h 12m 04.5277s[1]
Declination –28° 59′ 15.425″[1]
Apparent magnitude (V) 3.85[2] (3.98/7.19)[3]
Spectral type F8IV[4]
U−B color index +0.082[5]
B−V color index +0.581[5]
Radial velocity (Rv) –20.5[6] km/s
Proper motion (μ) RA: 371.49[1] mas/yr
Dec.: 612.28[1] mas/yr
Parallax (π) 70.24 ± 0.45[1] mas
Distance 46.4 ± 0.3 ly
(14.24 ± 0.09 pc)
Absolute magnitude (MV) 3.08[7]
Period (P) 269 yr
Semi-major axis (a) 4.0″
Eccentricity (e) 0.73
Inclination (i) 81°
Longitude of the node (Ω) 117°
Periastron epoch (T) 1947
Argument of periastron (ω)
α For A
Mass 1.33 ± 0.01[8] M
Radius 2.04 ± 0.06[9] R
Luminosity 4.87 ± 0.16[9] L
Surface gravity (log g) 4.27[8] cgs
Temperature 6,240[8] K
Metallicity [Fe/H] –0.20[8] dex
Rotational velocity (v sin i) 3.9[9] km/s
Age 2.9[10] Gyr
Other designations
α For, 12 Eridani, CD−29° 1177, GJ 127, HD 20010, HIP 14879, HR 963, SAO 168373, LTT 1512[2]
Database references

Alpha Fornacis, Latinized from α Fornacis, also designated 12 Eridani, is a binary star[11] system in the southern constellation of Fornax. It is the brightest star in the constellation and the only one brighter than magnitude 4.0. Its two components are designated Alpha Fornacis A (also named Dalim[12]) and B.


α Fornacis (Latinised to Alpha Fornacis) is the system's Bayer designation, 12 Eridani its Flamsteed designation. The designations of the two components as Alpha Fornacis A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[13]

It was listed under the proper names Dalim (in Piazzi's Palermo Catalogue)[14][15][16] and Fornacis (in Burritt's Atlas).[17] In 2016, the IAU organized a Working Group on Star Names (WGSN)[18] to catalog and standardize proper names for stars, the WGSN approved the name Dalim for the component Alpha Fornacis A on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[12]


Alpha Fornacis has a high proper motion[2] and the system displays an excess of infrared emission, which may indicate the presence of circumstellar material such as a debris disk.[19] The space velocity components of this star are (U, V, W) = (–35, +20, +30) km/s.[20] Approximately 350,000 years ago, Alpha Fornacis experienced a close encounter with the A-type main-sequence star Nu Horologii, the two came within an estimated 0.265 ly (0.081 pc) of each other, and both stars have debris disks.[21]

Alpha Fornacis A has a stellar classification of F8IV, where the luminosity class IV indicates this is a subgiant star that has just evolved off the main sequence,[22] it has 33% more mass than the Sun and is an estimated 2.9 billion years old.[8][10] and

The secondary, Alpha Fornacis B, has been identified as a blue straggler, and has either accumulated material from, or merged with, a third star in the past, it is a strong source of X-rays and is 78% as massive as the Sun.[23]


  1. ^ a b c d e Perryman, M. A. C.; et al. (April 1997). "The HIPPARCOS Catalogue". Astronomy & Astrophysics. 323: L49–L52. Bibcode:1997A&A...323L..49P. 
  2. ^ a b c "LHS 1515 -- High proper-motion Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2010-05-10. 
  3. ^ a b Hartkopf, W. I.; et al. (June 30, 2006), Sixth Catalog of Orbits of Visual Binary Stars, United States Naval Observatory, retrieved 2017-06-02. 
  4. ^ Favata, F.; Micela, G.; Sciortino, S. (July 1997). "The [Fe/H] distribution of a volume limited sample of solar-type stars and its implications for galactic chemical evolution". Astronomy and Astrophysics. 323: 809–818. Bibcode:1997A&A...323..809F. 
  5. ^ a b Rakos, K. D.; et al. (February 1982). "Photometric and astrometric observations of close visual binaries". Astronomy and Astrophysics Supplement Series. 47: 221–235. Bibcode:1982A&AS...47..221R. 
  6. ^ Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick. Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. Bibcode:1967IAUS...30...57E. 
  7. ^ Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982Freely accessible, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191. 
  8. ^ a b c d e Santos, N. C.; Israelian, G.; Mayor, M. (July 2001). "The metal-rich nature of stars with planets". Astronomy and Astrophysics. 373 (3): 1019–1031. arXiv:astro-ph/0105216Freely accessible. Bibcode:2001A&A...373.1019S. doi:10.1051/0004-6361:20010648. 
  9. ^ a b c Bruntt, H.; et al. (July 2010), "Accurate fundamental parameters for 23 bright solar-type stars", Monthly Notices of the Royal Astronomical Society, 405 (3): 1907–1923, arXiv:1002.4268Freely accessible, Bibcode:2010MNRAS.405.1907B, doi:10.1111/j.1365-2966.2010.16575.x 
  10. ^ a b Nordström, B.; Mayor, M.; Andersen, J.; Holmberg, J.; Pont, F.; Jørgensen, B. R.; Olsen, E. H.; Udry, S.; Mowlavi, N. (May 2004). "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs". Astronomy and Astrophysics. 418 (3): 989–1019. arXiv:astro-ph/0405198Freely accessible. Bibcode:2004A&A...418..989N. doi:10.1051/0004-6361:20035959.  See VizierR catalogue V/130.
  11. ^ Söderhjelm, Staffan (January 1999). "Visual binary orbits and masses POST HIPPARCOS". Astronomy and Astrophysics. 341: 121–140. Bibcode:1999A&A...341..121S. 
  12. ^ a b "Naming Stars". Retrieved 16 December 2017. 
  13. ^ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707Freely accessible [astro-ph.SR]. 
  14. ^ Piazzi, G, ed. (1814). Praecipuarum Stellarum Inerrantium Positiones Mediae Ineunte Saeculo XIX: ex Observationibus Habitis in Specula Panormitana ab anno 1792 ad annum 1813. Palermo. p. 21. 
  15. ^ Kunitzsch, P. (1959). Arabische Sternnamen in Europa. Wiesbaden: Otto Harrassowitz. p. 155. 
  16. ^ Laffitte, R. (2005). Héritages arabes: Des noms arabes pour les étoiles (2éme revue et corrigée ed.). Paris: Librairie Orientaliste Paul Geunthner / Les Cahiers de l'Orient. p. 229. 
  17. ^ Burritt, E. H. (1835). Atlas, Designed to Illustrate the Geography of the Heavens (new ed.). New York: F. J. Huntington.  plate III.
  18. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016. 
  19. ^ Oudmaijer, Rene D.; et al. (December 1992). "SAO stars with infrared excess in the IRAS Point Source Catalog". Astronomy and Astrophysics Supplement Series. 96 (3): 625–643. Bibcode:1992A&AS...96..625O. 
  20. ^ Gliese, W. (1969). "Catalogue of Nearby Stars". Veröffentlichungen des Astronomischen Rechen-Instituts Heidelberg. Bibcode:1969VeARI..22....1G. 
  21. ^ Deltorn, J.-M.; Kalas, P. (2001). "Search for Nemesis Encounters with Vega, ε Eridani, and Fomalhaut". In Ray Jayawardhana; Thomas Greene. Young Stars Near Earth: Progress and Prospects. ASP Conference Series. 244. San Francisco: Astronomical Society of the Pacific. p. 227. arXiv:astro-ph/0105284Freely accessible. Bibcode:2001ASPC..244..227D. ISBN 1-58381-082-X. 
  22. ^ Lopez, Bruno; Schneider, Jean; Danchi, William C. (July 2005). "Can Life Develop in the Expanded Habitable Zones around Red Giant Stars?". The Astrophysical Journal. 627 (2): 974–985. arXiv:astro-ph/0503520Freely accessible. Bibcode:2005ApJ...627..974L. doi:10.1086/430416. 
  23. ^ Fuhrmann, K.; Chini, R. (August 2015), "Multiplicity among F-type Stars. II", The Astrophysical Journal, 809 (1): 19, Bibcode:2015ApJ...809..107F, doi:10.1088/0004-637X/809/1/107, 107. 

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