Tau Cassiopeiae
K-type giant star in the constellation Cassiopeia
From Wikipedia, the free encyclopedia
Tau Cassiopeiae is a solitary,[11] orange hued star in the northern constellation of Cassiopeia. Its name is a Bayer designation that is Latinized from τ Cassiopeiae, and abbreviated Tau Cas or τ Cas. This star is bright enough to be seen with the naked eye, having an apparent visual magnitude of +4.86.[3] Based upon an annual parallax shift of 18.78 mas as seen from Earth,[2] this star is located about 173.7 light-years (53.3 pc) from the Sun. It is drifting closer with a radial velocity of −20 km/s.[6]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Cassiopeia[1] |
| Right ascension | 23h 47m 03.454s[2] |
| Declination | +58° 39′ 07.17″[2] |
| Apparent magnitude (V) | +4.86[3] |
| Characteristics | |
| Evolutionary stage | red giant branch[2] |
| Spectral type | K1 IIIa[4] |
| U−B color index | +1.05[3] |
| B−V color index | +1.11[3] |
| Variable type | Suspected[5] |
| Astrometry | |
| Radial velocity (Rv) | −20.48±0.31[6] km/s |
| Proper motion (μ) | RA: +60.379 mas/yr[2] Dec.: +56.828 mas/yr[2] |
| Parallax (π) | 18.7789±0.0802 mas[2] |
| Distance | 173.7 ± 0.7 ly (53.3 ± 0.2 pc) |
| Absolute magnitude (MV) | 1.269[7] |
| Details | |
| Mass | 1.44[8] M☉ |
| Radius | 10[6] R☉ |
| Luminosity | 40[8] L☉ |
| Surface gravity (log g) | 2.50±0.09[9] cgs |
| Temperature | 4,617±77[8] K |
| Metallicity [Fe/H] | +0.06±0.06[9] dex |
| Rotational velocity (v sin i) | 5.9[6] km/s |
| Age | 3.90[8] Gyr |
| Other designations | |
| τ Cas, 5 Cas, BD+57°2804, FK5 3909, GC 33010, HD 223165, HIP 117301, HR 9008, SAO 35763[10] | |
| Database references | |
| SIMBAD | data |
The spectrum of this star indicates it is an evolved, K-type giant star with a stellar classification of K1 IIIa.[4] It is a suspected variable star of unknown type.[5][12] Tau Cassiopeiae is 3.9[8] billion years old with about 1.44[8] times the mass of the Sun and 10[6] times the Sun's radius. It is radiating 40[8] times the Sun's luminosity from its expanded photosphere at an effective temperature of around 4,617 K.[8]
Naming
In Chinese, 螣蛇 (Téng Shé), meaning Flying Serpent, refers to an asterism consisting of τ Cassiopeiae, α Lacertae, 4 Lacertae, π2 Cygni, π1 Cygni, HD 206267, ε Cephei, β Lacertae, σ Cassiopeiae, ρ Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, λ Andromedae, κ Andromedae, ι Andromedae, and ψ Andromedae. Consequently, the Chinese name for τ Cassiopeiae itself is 螣蛇十三 (Téng Shé shísān, English: the Thirteenth Star of Flying Serpent).[13]