Alpha Doradus

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Alpha Doradus
Dorado IAU.svg
Red circle.svg
Location of α Doradus (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Dorado
Right ascension 04h 33m 59.778s
Declination −55° 02′ 41.91″[1]
Apparent magnitude (V) 3.27[2]
Right ascension 04h 33m 59.782s
Declination −55° 02′ 42.39″[3]
Apparent magnitude (V) 4.3[2]
U−B color index −0.35[2]
B−V color index −0.10[2]
R−I color index −0.09[2]
Spectral type A0IIIp[2]
Variable type ACV[4]
Spectral type B9IV[2]
Radial velocity (Rv)25.6 ± 0.9[5] km/s
Proper motion (μ) RA: 58.06[1] mas/yr
Dec.: 12.73[1] mas/yr
Parallax (π)19.34 ± 0.31 mas[6]
Distance169 ± 3 ly
(51.7 ± 0.8 pc)
Proper motion (μ) RA: 42.83[3] mas/yr
Dec.: 12.94[3] mas/yr
Period (P)12.1 y
Semi-major axis (a)0.18
Eccentricity (e)0.80
Inclination (i)31°
Longitude of the node (Ω)140°
Periastron epoch (T)B1986
Argument of periastron (ω)
Mass3.33 ± 0.10[8] M
Radius3.5 ± 0.3[8] R
Luminosity (bolometric)195[8] L
Surface gravity (log g)4.02 ± 0.07[8] cgs
Temperature11,588[8] K
Rotation2.94 days[8]
Mass2.7[9] M
Radius1.9[9] R
Luminosity (bolometric)70[9] L
Temperature12,200[9] K
Other designations
α Dor, Alpha Doradus, Alpha Dor, CD−55 916, CPD−55 663, FK5 171, GC 5600, HD 29305, HIP 21281, HR 1465, SAO 233564, PPM 333592, CCDM J04340-5503AB, WDS 04340-5503AB[5]
Database references

Alpha Doradus, Latinized from α Doradus, 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]

A light curve for Alpha Doradus, plotted from TESS data[10][11]

This is a binary star system[9] with an overall apparent visual magnitude that varies between 3.26 and 3.30,[4] making this one of the brightest binary stars.[12] 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.[2][7] 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.[8]

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.[2][13]


  1. ^ a b c HIP 21281, record for component 1, Hipparcos catalogue; CDS ID I/239.
  2. ^ 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.
  3. ^ a b c HIP 21281, record for component 2, Hipparcos catalogue; CDS ID I/239.
  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 Archived 2017-06-20 at the Wayback Machine, 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. S2CID 18759600.
  7. ^ a b "Entry 04340-5503", Sixth Catalog of Orbits of Visual Binary Stars, United States Naval Observatory, archived from the original on 2005-04-24, retrieved 2008-09-03
  8. ^ 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
  9. ^ a b c d e Kaler, James B., Alpha Dor, retrieved 2012-03-04
  10. ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
  11. ^ "alf Dor". The International Variable Star Index. AAVSO. Retrieved 2 July 2022.
  12. ^ Heintz, W. D. (April 1984), "Note on the orbit of alpha Doradus", The Observatory, 104: 88–89, Bibcode:1984Obs...104...88H
  13. ^ "Entry 04340-5503, discoverer code HJ3668, components AB-C", The Washington Double Star Catalog, United States Naval Observatory, archived from the original on 2008-04-12, retrieved 2008-09-03