Aldebaran
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Taurus |
| Pronunciation | /ælˈdɛbərən/ ⓘ |
| α Tauri A | |
| Right ascension | 04h 35m 55.23907s |
| Declination | +16° 30′ 33.4885″ |
| Apparent magnitude (V) | 0.86 (0.75–0.95) |
| α Tauri B | |
| Right ascension | 04h 35m 57.24674s |
| Declination | +16h 30m 21.3433s |
| Apparent magnitude (V) | 13.21 |
| Characteristics | |
| α Tauri A | |
| Evolutionary stage | Red giant branch |
| Spectral type | K5+ III |
| Apparent magnitude (J) | −2.095 |
| U−B color index | +1.92 |
| B−V color index | +1.44 |
| Variable type | LB |
| α Tauri B | |
| Evolutionary stage | Main sequence |
| Spectral type | M2.5 |
| Astrometry | |
| α Tauri A | |
| Radial velocity (Rv) | +54.26±0.03 km/s |
| Proper motion (μ) | RA: 63.45 mas/yr Dec.: −188.94 mas/yr |
| Parallax (π) | 48.94±0.77 mas |
| Distance | 67 ± 1 ly (20.4 ± 0.3 pc) |
| Absolute magnitude (MV) | −0.641±0.034 |
| α Tauri B | |
| Proper motion (μ) | RA: +58.919 mas/yr Dec.: −198.841 mas/yr |
| Parallax (π) | 47.2526 ± 0.0964 mas |
| Distance | 69.0 ± 0.1 ly (21.16 ± 0.04 pc) |
| Details | |
| α Tauri A | |
| Mass | 1.16±0.07 M☉ |
| Radius | 45.1±0.1 R☉ |
| Luminosity | 439±17 L☉ |
| Surface gravity (log g) | 1.45±0.3 cgs |
| Temperature | 3,900±50 K |
| Metallicity [Fe/H] | −0.33±0.1 dex |
| Rotation | 520 days |
| Rotational velocity (v sin i) | 3.5±1.5 km/s |
| Age | 6.4+1.4 −1.1 Gyr |
| α Tauri B | |
| Mass | 0.400±0.084 M☉ |
| Radius | 0.347±0.039 R☉ |
| Surface gravity (log g) | 4.96±0.17 cgs |
| Temperature | 3,398±89.5 K |
| Other designations | |
| Aldebaran, Alpha Tau, α Tau, 87 Tauri, BD+16°629, GJ 171.1, GJ 9159, HD 29139, HIP 21421, HR 1457, SAO 94027 | |
| Database references | |
| SIMBAD | Aldebaran |
| B | |
| Exoplanet Archive | data |
| ARICNS | Aldebaran |
| B | |
Aldebaran (Arabic: الدَّبَران, lit. 'The Follower') is a star in the zodiac constellation of Taurus. It has the Bayer designation α Tauri, which is Latinized to Alpha Tauri and abbreviated Alpha Tau or α Tau. Aldebaran varies in brightness from an apparent visual magnitude of 0.75 down to 0.95, making it the brightest star in the constellation, as well as (typically) the fourteenth-brightest star in the night sky. It is at a distance of approximately 67 light-years. The star lies along the line of sight to the nearby Hyades cluster.
Aldebaran is a red giant, meaning that it is cooler than the Sun with a surface temperature of 3,900 K, but its radius is about 45 times the Sun's, so it is over 400 times as luminous. As a giant star, it has moved off the main sequence on the Hertzsprung–Russell diagram after depleting its supply of hydrogen in the core. The star spins slowly and takes 520 days to complete a rotation.
Together with the star Alpha Tauri B (Alderbaran B), it makes a star system with an orbital separation of at least 680 astronomical units, or 680 times the average distance from Earth to the Sun. The companion has an apparent magnitude of 13.21, hence is 80,000 to 96,000 times fainter than Aldebaran.