Theta Ophiuchi
 Location of θ Ophiuchi(circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Ophiuchus |
| Right ascension | 17h 22m 00.57935s[1] |
| Declination | –24° 59′ 58.3670″[1] |
| Apparent magnitude (V) | +3.26[2] |
| Characteristics | |
| Spectral type | B2 IV[3] |
| U−B color index | –0.86[4] |
| B−V color index | –0.23[4] |
| Variable type | β Cep |
| Astrometry | |
| Radial velocity (Rv) | –2[5] km/s |
| Proper motion (μ) | RA: –7.37[1] mas/yr Dec.: –23.94[1] mas/yr |
| Parallax (π) | 7.48 ± 0.17[1] mas |
| Distance | 436 ± 10 ly (134 ± 3 pc) |
| Absolute magnitude (MV) | –2.4[2] |
| Details | |
| Mass | 8.8 ± 0.2[3] M☉ |
| Radius | 6.3[6] R☉ |
| Luminosity | 5,000[2] L☉ |
| Surface gravity (log g) | 3.950 ± 0.006[7] cgs |
| Temperature | 22,260 ± 280[7] K |
| Metallicity [Fe/H] | –0.15 ± 0.12[8] dex |
| Rotational velocity (v sin i) | 30[9] km/s |
| Age | 21.3 ± 5.8[3] Myr |
| Other designations | |
Theta Ophiuchi (θ Oph, θ Ophiuchi) is a multiple star system in the equatorial constellation of Ophiuchus. It lies on the "right foot" of the serpent-bearer, and is only a little to the southwest of the Kepler's Star, the nova of 1604. According to Richard H. Allen's, Star Names: Their Lore and Meaning (1899), θ Oph together with ξ Oph formed the Sogdian Wajrik "the Magician", the Khorasmian Markhashik "the Serpent-bitten" and with η Oph the Coptic Tshiō, "the Snake", and Aggia, "the Magician".[11] This star has an apparent visual magnitude of +3.26,[2] making it readily visible to the naked eye. Based upon parallax measurements from the Hipparcos mission, it is located at a distance of roughly 436 light-years (134 parsecs) from Earth.[1]
Theta Ophiuchi appears to be a triple star system. The brightest component is a spectroscopic binary with an orbital period of 56.71 days and an eccentricity of 0.17. The tertiary component is 5.5 magnitude star with a stellar classification of B5. It is located at an angular separation of 0.15 arcseconds from the binary pair.[12] This system is a proper motion member of the Upper Scorpius sub-group in the Scorpius-Centaurus OB association, the nearest such co-moving association of massive stars to the Sun.[2]
The primary component of this system is a variable star of the Beta Cephei type with a short period of just 3h 22m.[13] It has nearly nine[3] times the mass of the Sun and more than six[6] times the Sun's radius. Although only 21 million years old,[3] it has begun to evolve away from the main sequence and has become a subgiant star with a stellar classification of B2 IV.[3] This massive star is radiating around 5,000 times the luminosity of the Sun from its outer atmosphere at an effective temperature of about 22,260 K,[7] giving it the blue-white hue of a B-type star.[14]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Lua error in package.lua at line 80: module 'strict' not found. Note: see VizieR catalogue I/311.
- ↑ 2.0 2.1 2.2 2.3 2.4 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 4.0 4.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 6.0 6.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 7.0 7.1 7.2 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
