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,[1] 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.[2] It is considered a member of the Hyades cluster.[7]
Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
---|---|
Constellation | Taurus |
Right ascension | 04h 22m 56.09253s[1] |
Declination | +17° 32′ 33.0487″[1] |
Apparent magnitude (V) | +3.772[2] (3.90 + 9.50)[3] |
Characteristics | |
Spectral type | G9.5 III CN0.5[4] |
U−B color index | +0.801[2] |
B−V color index | +0.919[2] |
Astrometry | |
Proper motion (μ) | RA: +106.56[1] mas/yr Dec.: −29.18[1] mas/yr |
Parallax (π) | 20.96 ± 0.58 mas[1] |
Distance | 156 ± 4 ly (48 ± 1 pc) |
Absolute magnitude (MV) | +0.41[5] |
Orbit[6] | |
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[7] | |
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[8] 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)[10] and Ab.
δ¹ Tauri (Latinised to Delta¹ Tauri) is the system's Bayer designation. The designations of the two constituents as Delta¹ Tauri A and B, and those of A's components - Delta¹ Tauri Aa and Ab - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[11]
The system bore the traditional name Hyadum II, which is Latin for "Second of the Hyades".[12] In 2016, the IAU organized a Working Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[14] It approved the name Secunda Hyadum for the component Delta¹ Tauri Aa on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[10]
In Chinese, 畢宿 (Bì Xiù), meaning Net, refers to an asterism consisting of δ¹ Tauri, Epsilon Tauri, Delta³ Tauri, Gamma Tauri, Alpha Tauri (Aldebaran), 71 Tauri and Lambda Tauri.[15] Consequently, the Chinese name for Delta¹ Tauri itself is 畢宿三 (Bì Xiù sān), "the Third Star of Net".[16]
Delta¹ Tauri A is a single-lined spectroscopic binary with an orbital period of 529.8 days and an eccentricity of 0.42.[6] The visible member, component Aa, is an evolved G- or K-type giant star with a stellar classification of G9.5 III CN0.5.[4] The 'CN0.5' suffix indicates a mild overabundance of cyanogen in the outer atmosphere. It is chromospherically active and shows a radial velocity variation of 9.3±0.2 m/s with a period of 165±3 d.[7] The primary, component Aa, has 2.8 times the mass of the Sun, while the secondary, component Ab, has 1.3 times the Sun's mass.[7]
Delta¹ Tauri B is a magnitude 13.21 visual companion separated by 111.8 arcseconds from A.[3] It is most likely not physically related to the main star.[17]
{{cite web}}
: CS1 maint: postscript (link)