Alpha Doradus
Star in the constellation Dorado
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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).[7]
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Dorado |
| A | |
| Right ascension | 04h 33m 59.778s |
| Declination | −55° 02′ 41.91″[1] |
| Apparent magnitude (V) | 3.236 – 3.276[2] |
| B | |
| Right ascension | 04h 33m 59.782s |
| Declination | −55° 02′ 42.39″[3] |
| Apparent magnitude (V) | 4.3[4] |
| Characteristics | |
| U−B color index | −0.35[4] |
| B−V color index | −0.10[4] |
| R−I color index | −0.09[4] |
| A | |
| Spectral type | A0IIIp[4] |
| Variable type | ACV[5] |
| B | |
| Spectral type | B9IV[4] |
| Astrometry | |
| A | |
| Radial velocity (Rv) | 25.6 ± 0.9[6] km/s |
| Proper motion (μ) | RA: 58.06[1] mas/yr Dec.: 12.73[1] mas/yr |
| Parallax (π) | 19.34±0.31 mas[7] |
| Distance | 169 ± 3 ly (51.7 ± 0.8 pc) |
| B | |
| Proper motion (μ) | RA: 42.83[3] mas/yr Dec.: 12.94[3] mas/yr |
| Orbit[8] | |
| 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 | |
| Mass | 3.33 ± 0.10[9] M☉ |
| Radius | 3.5 ± 0.3[9] R☉ |
| Luminosity (bolometric) | 195[9] L☉ |
| Surface gravity (log g) | 4.02 ± 0.07[9] cgs |
| Temperature | 11,588[9] K |
| Rotation | 2.94 days[9] |
| B | |
| Mass | 2.7[10] M☉ |
| Radius | 1.9[10] R☉ |
| Luminosity (bolometric) | 70[10] L☉ |
| Temperature | 12,200[10] 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[6] | |
| Database references | |
| SIMBAD | data |
This is a binary star system[10] with an overall apparent visual magnitude that varies between 3.26 and 3.30,[5] making this one of the brightest naked-eye 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.[4][8] 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.[9]
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.[4][13]