Tau Cassiopeiae (τ Cassiopeiae) is a solitary, orange hued star in the northern constellation of Cassiopeia. It is bright enough to be seen with the naked eye, having an apparent visual magnitude of +4.86. Based upon an annual parallax shift of 18.75 mas as seen from Earth, this system is located about 174 light years from the Sun.
The spectrum of this star indicates it is an evolved, K-type giant star with a stellar classification of K1 IIIa. It is a suspected variable star of unknown type. Tau Cassiopeiae is 3.9 billion years old with about 1.44 times the mass of the Sun and 10 times the Sun's radius. It is radiating 40 times the Sun's luminosity from its expanded photosphere at an effective temperature of around 4,617 K.
Map of the Bayer-designated stars in Cassiopeia. Tau Cassiopeiae is circled.
Epoch J2000.0 Equinox J2000.0 (ICRS)
|Right ascension||00h 55m 00.15523s|
|Declination||+58° 58′ 21.7108″|
|Apparent magnitude (V)||+4.86|
|Spectral type||K1 IIIa|
|U−B color index||+1.05|
|B−V color index||+1.11|
|Radial velocity (Rv)||−20.48±0.31 km/s|
|Proper motion (μ)||RA: +60.81±0.19 mas/yr
Dec.: +56.47±0.17 mas/yr
|Parallax (π)||18.75 ± 0.20 mas|
|Distance||174 ± 2 ly
(53.3 ± 0.6 pc)
|Absolute magnitude (MV)||1.269|
|Surface gravity (log g)||2.50±0.09 cgs|
|Metallicity [Fe/H]||+0.06±0.06 dex|
|Rotational velocity (v sin i)||5.9 km/s|
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, τ Cassiopeiae itself is known as 螣蛇十三 (Téng Shé shísān, English: the Thirteenth Star of Flying Serpent)