Lambda Tauri
Lambda Tauri (λ Tau, λ Tauri) is a triple star system in the constellation Taurus. In the Calendarium of Al Achsasi Al Mouakket, this star was designated Sadr al Tauri, which was translated into Latin as Pectus Tauri, meaning "the bull chest". In 1848, the light from this system was found to vary periodically and it was determined to be an eclipsing binary system—the third such discovered. The components of this system have a combined apparent visual magnitude of +3.37 at its brightest, making it one of the brighter members of the constellation. Based upon parallax measurements from the Hipparcos mission, the distance to this system is approximately 480 light-years (150 parsecs).
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Taurus |
| Right ascension | 04h 00m 40.81572s |
| Declination | +12° 29′ 25.2259″ |
| Apparent magnitude (V) | +3.37 (- 3.54) - 3.91 |
| Characteristics | |
| Spectral type | B3 V + A4 IV |
| U−B color index | −0.62 |
| B−V color index | −0.12 |
| Variable type | Algol |
| Astrometry | |
| Radial velocity (Rv) | +17.8 km/s |
| Proper motion (μ) | RA: −8.02 mas/yr Dec.: −14.42 mas/yr |
| Parallax (π) | 6.74 ± 0.17 mas |
| Distance | 480 ± 10 ly (148 ± 4 pc) |
| Absolute magnitude (MV) | −2.45 |
| Orbit | |
| Primary | λ Tau A |
| Companion | λ Tau B |
| Period (P) | 3.9529552 days |
| Semi-major axis (a) | 21.91 R☉ |
| Eccentricity (e) | 0.025±0.015 |
| Inclination (i) | 76° |
| Periastron epoch (T) | 2,444,667.3±2.1 HJD |
| Semi-amplitude (K1) (primary) | 56.9±0.6 km/s |
| Semi-amplitude (K2) (secondary) | 215.6±0.7 km/s |
| Details | |
| λ Tau A | |
| Mass | 7.18 M☉ |
| Radius | 6.40 R☉ |
| Luminosity | 5,801 L☉ |
| Surface gravity (log g) | 3.38 cgs |
| Temperature | 18,700 K |
| Rotational velocity (v sin i) | 85 km/s |
| Age | 33.2±3.9 Myr |
| λ Tau B | |
| Mass | 1.89 M☉ |
| Radius | 5.30 R☉ |
| Luminosity | 128 L☉ |
| Temperature | 8,405 K |
| Rotational velocity (v sin i) | 76 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
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