Alpha Doradus

Alpha Doradus
Location of α Doradus (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Dorado
A
Right ascension 04h 33m 59.778s
Declination −55° 02′ 41.91″[1]
Apparent magnitude (V) 3.27[2]
B
Right ascension 04h 33m 59.782s
Declination −55° 02′ 42.39″[3]
Apparent magnitude (V) 4.3[2]
Characteristics
U−B color index −0.35[2]
B−V color index −0.10[2]
R−I color index −0.09[2]
A
Spectral type A0IIIp[2]
Variable type ACV[4]
B
Spectral type B9IV[2]
Astrometry
A
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)
B
Proper motion (μ) RA: 42.83[3] mas/yr
Dec.: 12.94[3] mas/yr
Orbit[7]
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)
(secondary)		193°
Details
A
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]
B
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
SIMBADdata

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]

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