8 Draconis
White-hued chemically unusual star in the constellation Draco
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8 Draconis, formally named Taiyi /ˌtaɪˈjiː/,[10] is a single[11] star in the northern circumpolar constellation of Draco. Based upon an annual parallax shift of 33.97 mas as seen from the Earth,[12] the star is located 96 light-years from the Sun. It is moving further away with a heliocentric radial velocity of +9 km/s,[6] having come within 40.6 ly some 2.6 million years ago.[4]
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Draco |
| Right ascension | 12h 55m 28.54856s[1] |
| Declination | +65° 26′ 18.5071″[1] |
| Apparent magnitude (V) | 5.225[2] |
| Characteristics | |
| Evolutionary stage | main sequence[1] |
| Spectral type | F1VmA7(n)[3] |
| B−V color index | 0.303±0.005[4] |
| Variable type | Gamma Doradus[5] |
| Astrometry | |
| Radial velocity (Rv) | +9.0[6] km/s |
| Proper motion (μ) | RA: −3.658[1] mas/yr Dec.: −30.126[1] mas/yr |
| Parallax (π) | 33.9667±0.0792 mas[1] |
| Distance | 96.0 ± 0.2 ly (29.44 ± 0.07 pc) |
| Absolute magnitude (MV) | 2.90[4] |
| Details | |
| Mass | 1.56[7] M☉ |
| Radius | 1.50[7] R☉ |
| Luminosity | 5.75[4] L☉ |
| Surface gravity (log g) | 4.01[3] cgs |
| Temperature | 7,129[3] K |
| Metallicity [Fe/H] | −0.14[3] dex |
| Rotational velocity (v sin i) | 119.6[8] km/s |
| Age | 250±200[7] Myr |
| Other designations | |
| Taiyi, 8 Dra, IR Draconis, BD+66°778, FK5 486, HD 112429, HIP 63076, HR 4916, SAO 15941[9] | |
| Database references | |
| SIMBAD | data |
This is an F-type main-sequence star with a stellar classification of F1VmA7(n).[3] It is a Gamma Doradus variable star with a brightness variation of about one tenth of a magnitude.[5] 8 Dra has a relatively high rate of rotation, showing a projected rotational velocity of 120 km/s.[8] The star has 1.56 times the mass of the Sun and 1.50 times the Sun's radius.[7] It is radiating 5.75[4] times the Sun's luminosity from its photosphere at an effective temperature of 7,129 K.[3] An infrared excess has been detected at wavelengths of 24 and 70μm, which suggests the presence of a circumstellar disk orbiting the star.[7]
Nomenclature
8 Draconis is the star's Flamsteed designation. It also received the variable star designation IR Draconis in 2000, after its variability had been discovered using Hipparcos photometry.[5]
The star bore the traditional Chinese name of Taiyi,[14][15] from 太乙 (Tài Yǐ) or 太一 (Tài Yī, the Great One), both of which refer to Tao. Alternatively, Taiyi may refer to HD 119476[17] or 4 Draconis,[18] with 7 and 8 Draconis forming Neichu, representing a private kitchen.[19] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[20] to catalogue and standardize proper names for stars. The WGSN approved the name Taiyi for this star on 30 June 2017 and it is now so entered in the IAU Catalog of Star Names.[21]