Sigma Cassiopeiae
Star in the constellation Cassiopeia
From Wikipedia, the free encyclopedia
Sigma Cassiopeiae is a binary star[5] system in the northern constellation of Cassiopeia. Its name is a Bayer designation that is Latinized from σ Cassiopeiae, and abbreviated Sigma Cas or σ Cas. The pair have a combined apparent magnitude of +4.88,[10] making it visible to the naked eye. Based on Parallax measurements, it is located at a distance of 1,200 to 1,400 light years from Earth.
 | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| 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][6] |
| σ Cas B | |
| Spectral type | B3 V[4] |
| Astrometry | |
| σ Cas A | |
| Radial velocity (Rv) | −12.6[7] 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[7] 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 | |
| σ Cas, 8 Cassiopeiae, BD+54°3082, HD 224572, HIP 118243, HR 9071, SAO 35947, ADS 17140, CCDM J23591+5546[8] | |
| Database references | |
| SIMBAD | data |
| A | |
| B | |
The primary component, σ Cassiopeiae A, has an apparent magnitude of +5.01 and presents as a subgiant star with a stellar classification of B2 IV.[4] It is a candidate Beta Cephei variable and is rotating rapidly.[5] Its companion, σ Cassiopeiae B, is a main sequence dwarf with a class of B3 V[4] and an apparent magnitude of +7.14. The two stars are three arcseconds apart.[11]
Naming
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).[12]