Alpha Doradus

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

Location of α Doradus (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Dorado
Component A B
Right ascension 04h 33m 04h 33m
  59.778s 59.782s
Declination −55° 02′[1] −55° 02′[2]
  41.91″ 42.39″
Apparent magnitude (V) 3.8[3] 4.3[3]
Spectral type A0IIIp[3] B9IV[3]
U-B color index −0.35[3]
B-V color index −0.10[3]
R-I color index −0.09[3]
Variable type ACV[4]
Radial velocity (Rv) 25.6 ± 0.9[5] km/s
Proper motion:  
RA α cos δ)  58.06[1] mas/yr  42.83[2] mas/yr 
Dec. δ)  12.73[1] mas/yr  12.94[2] mas/yr 
Parallax (π) 19.34 ± 0.31[6] mas
Distance 169 ± 3 ly
(51.7 ± 0.8 pc)
Mass 3.33 ± 0.10[7] M 2.7[8] M
Radius 3.5 ± 0.3[7] R 1.9[8] R
Surface gravity (log g) 4.02 ± 0.07[7]
Luminosity (bolometric) 195[7] L 70[8] L
Temperature 11,588[7] K 12,200[8] K
Rotation 2.94 days[7]
Period (P) 12.1 y
Semimajor axis (a) 0.18
Eccentricity (e) 0.80
Inclination (i) 31°
Longitude of node (Ω) 140°
Periastron epoch (T) B1986
Argument of periastron (ω)
Database references
Other designations
α Dor, Alpha Doradus, Alpha Dor, B 2092, CCDM J04340-5503AB, CD−55 916, CPD−55 663, FK5 171, GC 5600, HD 29305, HIP 21281, HR 1465, IDS 04318-5515 AB, PPM 333592, SAO 233564, WDS 04340-5503AB.[5]

Alpha Doradus (Alpha Dor, α Doradus, α Dor) is the brightest star in the southern constellation of Dorado. The distance to this system, as measured using the parallax method, is about 169 light-years (52 parsecs).[6]

This is a binary star system[8] with an overall apparent visual magnitude that varies between 3.26 and 3.30,[4] making this one of the brightest binary stars.[10] The system consists of a subgiant star of spectral type B revolving around a giant star with spectral type A in an eccentric orbit with a period of about 12 years.[3][9] The orbital separation varies from 2 astronomical units at periastron to 17.5 astronomical units at apastron. The primary, α Doradus A, is a chemically peculiar star whose atmosphere displays an abnormally high abundance of silicon, making this an Si star.[7]

Alpha Doradus has an optical companion, CCDM J04340-5503C, located 77 arcseconds away along a position angle of 94°. It has no physical relation to the other two stars.[3][11]


  1. ^ a b c HIP 21281, record for component 1, Hipparcos catalogue; CDS ID I/239.
  2. ^ a b c HIP 21281, record for component 2, Hipparcos catalogue; CDS ID I/239.
  3. ^ a b c d e f g h i HR 1465, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line September 3, 2008.
  4. ^ a b alf Dor, database entry, The combined table of GCVS Vols I-III and NL 67-78 with improved coordinates, General Catalogue of Variable Stars, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line September 3, 2008.
  5. ^ a b V* alf Dor -- Variable Star, database entry, SIMBAD. Accessed on line September 3, 2008.
  6. ^ a b 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. 
  7. ^ a b c d e f g North, P. (June 1998), "Do SI stars undergo any rotational braking?", Astronomy and Astrophysics 334: 181–187, arXiv:astro-ph/9802286, Bibcode:1998A&A...334..181N 
  8. ^ a b c d e Kaler, James B., Alpha Dor, retrieved 2012-03-04 
  9. ^ a b "Entry 04340-5503", Sixth Catalog of Orbits of Visual Binary Stars (United States Naval Observatory), retrieved 2008-09-03 
  10. ^ Heintz, W. D. (April 1984), "Note on the orbit of alpha Doradus", The Observatory 104: 88–89, Bibcode:1984Obs...104...88H 
  11. ^ "Entry 04340-5503, discoverer code HJ3668, components AB-C", The Washington Double Star Catalog (United States Naval Observatory), retrieved 2008-09-03