Gamma Cassiopeiae
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cassiopeia |
| Right ascension | 00h 56m 42.50108s |
| Declination | +60° 43′ 00.2984″ |
| Apparent magnitude (V) | 2.39 (varies by±0.01) |
| Characteristics | |
| Evolutionary stage | main sequence |
| Spectral type | B0.5IVe |
| U−B color index | −1.08 |
| B−V color index | −0.15 |
| Variable type | γ Cas |
| Astrometry | |
| Radial velocity (Rv) | −6.8 km/s |
| Proper motion (μ) | RA: +25.17 mas/yr Dec.: −3.92 mas/yr |
| Parallax (π) | 5.94±0.12 mas |
| Distance | 550 ± 10 ly (168 ± 3 pc) |
| Absolute magnitude (MV) | −3.98 |
| Orbit | |
| Primary | Aa |
| Name | Ab |
| Period (P) | 203.523±0.076 d |
| Semi-major axis (a) | 1.632+0.002 −0.001 AU |
| Eccentricity (e) | 0 |
| Inclination (i) | 45° |
| Semi-amplitude (K1) (primary) | 4.297±0.090 km/s |
| Orbit | |
| Primary | Aab |
| Name | Ac |
| Period (P) | 60.0 yr |
| Semi-major axis (a) | 0.233″ |
| Details | |
| Aa | |
| Mass | 15±2 M☉ |
| Radius | 10.9+0.8 −0.6 (equatorial) 7.9±0.4 (polar) R☉ |
| Luminosity | 19,000±500 L☉ |
| Surface gravity (log g) | 3.50 cgs |
| Temperature | 26,500 (polar) 17,300 (equatorial) K |
| Rotational velocity (v sin i) | 389±20 km/s |
| Age | 8.0±0.4 Myr |
| Ab | |
| Mass | 0.93+0.04 −0.01 M☉ |
| Radius | 6,000+65 −320 km |
| Other designations | |
| Tiansi, Tsih, Navi, γ Cas, 27 Cassiopeiae, AAVSO 0050+60, BD+59°144, FK5 32, HD 5394, HIP 4427, HR 264, SAO 11482, ADS 782, WDS 00567+6043 | |
| Database references | |
| SIMBAD | data |
Gamma Cassiopeiae, officially named Tiansi, is a multiple star system at the center of the distinctive "W" asterism in the northern circumpolar constellation of Cassiopeia. It was observed in 1866 by Angelo Secchi, the first star ever observed with emission lines. It is now considered a Be star.
Gamma Cassiopeiae is a variable star system. Based upon parallax measurements made by the Hipparcos satellite, it is located at a distance of roughly 550 light-years from Earth. Together with its common-proper-motion companion, HD 5408, the system could contain a total of eight stars. It is one of the highest multiplicity systems known.