Delta1 Tauri
Delta¹ Tauri (δ¹ Tauri, abbreviated Delta¹ Tau, δ¹ Tau) is a double star in the zodiac constellation of Taurus. Based upon an annual parallax shift of 20.96 mas as seen from Earth, it is located roughly 156 light-years distant from the Sun. The system is faintly visible to the naked eye with a combined apparent visual magnitude of +3.772. It is considered a member of the Hyades cluster.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Taurus |
| Right ascension | 04h 22m 56.09253s |
| Declination | +17° 32′ 33.0487″ |
| Apparent magnitude (V) | +3.772 (3.90 + 9.50) |
| Characteristics | |
| Spectral type | G9.5 III CN0.5 |
| U−B color index | +0.801 |
| B−V color index | +0.919 |
| Astrometry | |
| Proper motion (μ) | RA: +106.56 mas/yr Dec.: −29.18 mas/yr |
| Parallax (π) | 20.96 ± 0.58 mas |
| Distance | 156 ± 4 ly (48 ± 1 pc) |
| Absolute magnitude (MV) | +0.41 |
| Orbit | |
| Period (P) | 529.8 d |
| Eccentricity (e) | 0.42 |
| Periastron epoch (T) | 2434356.5 JD |
| Argument of periastron (ω) (secondary) | 335° |
| Semi-amplitude (K1) (primary) | 3.0 km/s |
| Details | |
| δ¹ Tau Aa | |
| Mass | 2.8±0.5 M☉ |
| Radius | 11.4 R☉ |
| Luminosity | 69 L☉ |
| Temperature | 5,000 K |
| Metallicity [Fe/H] | +0.10 dex |
| Rotation | 138.2 d |
| Rotational velocity (v sin i) | 4.2 km/s |
| Age | 620 Myr |
| δ¹ Tau Ab | |
| Mass | 1.28±0.1 M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
The two constituents are designated δ¹ Tauri A and B. A is itself a binary star with components designated δ¹ Tauri Aa (officially named Secunda Hyadum /sɪˈkʌndə ˈhaɪədəm/, the traditional name for the entire system) and Ab.
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