Sigma Cassiopeiae (σ Cas, σ Cassiopeiae) is a binary star in the constellation Cassiopeia. It is 1,200 to 1,400 light years from Earth and has a combined apparent magnitude of +4.88.[7]
Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Cassiopeia |
σ Cas A | |
Right ascension | 23h 59m 00.538s[1] |
Declination | +55° 45′ 17.75″[1] |
Apparent magnitude (V) | 5.01[2] |
σ Cas B | |
Right ascension | 23h 59m 00.331s[3] |
Declination | +55° 45′ 20.37″[3] |
Apparent magnitude (V) | 7.24[2] |
Characteristics | |
σ Cas A | |
Spectral type | B2 IV[4] |
U−B color index | −0.82 |
B−V color index | −0.07 |
Variable type | β Cep?[5] |
σ Cas B | |
Spectral type | B3 V[4] |
Astrometry | |
σ Cas A | |
Radial velocity (Rv) | −12.6[6] km/s |
Proper motion (μ) | RA: +9.956[1] mas/yr Dec.: −4.492[1] mas/yr |
Parallax (π) | 2.7419 ± 0.1491 mas[1] |
Distance | 1,190 ± 60 ly (360 ± 20 pc) |
Absolute magnitude (MV) | −3.90[5] |
Radial velocity (Rv) | −5.0[6] km/s |
Proper motion (μ) | RA: +8.651[3] mas/yr Dec.: −3.739[3] mas/yr |
Parallax (π) | 2.2572 ± 0.0558 mas[3] |
Distance | 1,440 ± 40 ly (440 ± 10 pc) |
Absolute magnitude (MV) | −1.7[4] |
Details[5] | |
A | |
Mass | 12 M☉ |
Radius | 11.3 R☉ |
Luminosity | 25,000 L☉ |
Surface gravity (log g) | 3.6 cgs |
Temperature | 21,000 K |
Rotational velocity (v sin i) | 170 km/s |
Age | 15.8 Myr |
Other designations | |
Database references | |
SIMBAD | data |
The primary component, σ Cassiopeiae A, is a B2 subgiant with an apparent magnitude of +5.0. Its companion, σ Cassiopeiae B, is a B5 main sequence dwarf with an apparent magnitude of +7.1. The two stars are three arcseconds apart.[8]
In Chinese, 螣蛇 (Téng Shé), meaning Flying Serpent, refers to an asterism consisting of σ Cassiopeiae, α Lacertae, 4 Lacertae, π2 Cygni, π1 Cygni, HD 206267, ε Cephei, β Lacertae, ρ Cassiopeiae, τ 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 σ Cassiopeiae itself is 螣蛇十一 (Téng Shé shíyī, English: the Eleventh Star of Flying Serpent).[9]