Alpha Fornacis (α Fornacis, abbreviated Alpha For, α For) is a triple star[12] system in the southern constellationofFornax. It is the brightest star in the constellation and the only one brighter than magnitude 4.0. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 46 light-years (14parsecs) distant from the Sun.
Its three components are designated Alpha Fornacis A (officially named Dalim/ˈdeɪlɪm/),[13]Alpha Fornacis Ba and Alpha Fornacis Bb.
α Fornacis (LatinisedtoAlpha Fornacis) is the system's Bayer designation. The designations of the three components as Alpha Fornacis A, Ba and Bb derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[14] Formerly it was designated as the 12th of Eridanus (12 Eri) by Flamsteed.[15]
Indigenous Arabs had named both Alpha Eridani and Fomalhaut ظَلِيم al-ẓalīm, a local word for 'ostrich'. Later, Arabian astronomer would transfer the appellation to Theta Eridani, as they could not see those other stars from their location.[16]
In recent times, Italian astronomer Giuseppe Piazzi applied it with the spelling Dalim to his "III 13" (= α For) in his Palermo Catalogue,[17][18][19] and Elijah Burritt labeled it Fornacis in his Atlas.[20]
In 2016, the IAU organized a Working Group on Star Names (WGSN)[21] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[22] It 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.[13]
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.[23] The space velocity components of this star are (U, V, W) = (−35, +20, +30) km/s.[24] Approximately 350,000 years ago, Alpha Fornacis experienced a close encounter with the A-type main-sequence starNu Horologii. The two came within an estimated 0.265 ly (0.081 pc) of each other, and both stars have debris disks.[25]
The secondary, Alpha Fornacis B, has been identified as a blue straggler, and has likely accumulated material from a third star in the past. It is a strong source of X-rays and is 78% as massive as the Sun.[27] Such a third star, designated Alpha Fornacis Bb, was detected in 2016. Alpha Fornacis Ba is enriched in barium relative to star A, suggesting that its companion is likely a white dwarf.[12]
^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.
^ abRakos, 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.
^Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick (eds.). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. Bibcode:1967IAUS...30...57E.
^ abNordström, 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/0405198. Bibcode:2004A&A...418..989N. doi:10.1051/0004-6361:20035959. S2CID11027621. See VizierR catalogue V/130.
^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:1012.0707 [astro-ph.SR].
^Wagman, Morton (2003). Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others. Blacksburg, Virginia: The McDonald & Woodward Publishing Company. Bibcode:2003lslm.book.....W. ISBN978-0-939923-78-6.
^Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. pp. 36–37. ISBN978-1-931559-44-7.
^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.
^Burritt, E. H. (1835). Atlas, Designed to Illustrate the Geography of the Heavens (new ed.). New York: F. J. Huntington. plate III.
^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.
^Gliese, W. (1969). "Catalogue of Nearby Stars". Veröffentlichungen des Astronomischen Rechen-Instituts Heidelberg. 22: 1. Bibcode:1969VeARI..22....1G.
