Alpha Doradus
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).
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Dorado |
| A | |
| Right ascension | 04h 33m 59.778s |
| Declination | −55° 02′ 41.91″ |
| Apparent magnitude (V) | 3.27 |
| B | |
| Right ascension | 04h 33m 59.782s |
| Declination | −55° 02′ 42.39″ |
| Apparent magnitude (V) | 4.3 |
| Characteristics | |
| U−B color index | −0.35 |
| B−V color index | −0.10 |
| R−I color index | −0.09 |
| A | |
| Spectral type | A0IIIp |
| Variable type | ACV |
| B | |
| Spectral type | B9IV |
| Astrometry | |
| A | |
| Radial velocity (Rv) | 25.6 ± 0.9 km/s |
| Proper motion (μ) | RA: 58.06 mas/yr Dec.: 12.73 mas/yr |
| Parallax (π) | 19.34 ± 0.31 mas |
| Distance | 169 ± 3 ly (51.7 ± 0.8 pc) |
| B | |
| Proper motion (μ) | RA: 42.83 mas/yr Dec.: 12.94 mas/yr |
| Orbit | |
| 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 M☉ |
| Radius | 3.5 ± 0.3 R☉ |
| Luminosity (bolometric) | 195 L☉ |
| Surface gravity (log g) | 4.02 ± 0.07 cgs |
| Temperature | 11,588 K |
| Rotation | 2.94 days |
| B | |
| Mass | 2.7 M☉ |
| Radius | 1.9 R☉ |
| Luminosity (bolometric) | 70 L☉ |
| Temperature | 12,200 K |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is a binary star system with an overall apparent visual magnitude that varies between 3.26 and 3.30, making this one of the brightest binary stars. 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. 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.
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.