Theta Herculis
 Historical view of the Hercules constellation showing Rukbalgethi Genubi (θ Her) as the "southern knee" |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Hercules |
| Right ascension | 17h 56m 15.1805s[1] |
| Declination | 37° 15′ 01.941″[1] |
| Apparent magnitude (V) | 3.851[1][2] |
| Characteristics | |
| Spectral type | K1IIaCN[1] |
| U−B color index | +1.40 [3] |
| B−V color index | +1.35[3] |
| R−I color index | +0.63[4] |
| Variable type | Irregular (suspected)[5] |
| Astrometry | |
| Radial velocity (Rv) | –28.32[1] km/s |
| Proper motion (μ) | RA: 2.74[1] mas/yr Dec.: 7.24[1] mas/yr |
| Parallax (π) | 4.87 ± 0.54[6] mas |
| Distance | approx. 670 ly (approx. 210 pc) |
| Absolute magnitude (MV) | −2.71+0.26 −0.23[7] |
| Details | |
| Mass | 6.5[8] M☉ |
| Radius | ~80[8] R☉ |
| Luminosity | 2,400[8] L☉ |
| Surface gravity (log g) | 1.28[7] cgs |
| Temperature | 4,330[2][8] K |
| Metallicity [Fe/H] | −0.24[2] dex |
| Rotational velocity (v sin i) | 3.4 ± 0.6[7] km/s |
| Age | 550-780[8] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Theta Herculis (θ Her, θ Herculis) is a fourth-magnitude star in the constellation Hercules. It has the traditional name Rukbalgethi Genubi.
Properties
Theta Her is a variable K-type giant star with stellar classification K1IIaCN. In 1935, French astronomer P. Muller identified Theta Herculis as an irregular variable with a range of magnitudes between 3.7 and 4.1 and a periodicity of roughly 8–9 days.[5]
Etymology
In the Calendarium of Al Achsasi Al Mouakket, this star was designated Rekbet al Jathih al Aisr, which was translated into Latin as Genu Sinistrum Ingeniculi, meaning the left knee of the kneeling man.[9] The traditional name Rukbalgethi Genubi that is encountered in various texts is etymologically similar to the stars Ruchbah and Zubenelgenubi, the term "ruchbah" meaning "knee" while "genubi" signifies "southern"—hence the "southern knee", a meaning which can be gleaned more easily by looking at the accompanying constellation map.[10]
In Chinese, 天紀 (Tiān Jì), meaning Celestial Discipline, refers to an asterism consisting of θ Herculis, ξ Coronae Borealis, ζ Herculis, ε Herculis, 59 Herculis, 61 Herculis, 68 Herculis and HD 160054.[11] Consequently, θ Herculis itself is known as 天紀九 (Tiān Jì jiǔ, English: the Ninth Star of Celestial Discipline.)[12]
See also
- Lists of stars in the constellation Hercules
- Class K Stars
- Variable star
- Irregular variable
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 2.0 2.1 2.2 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 3.0 3.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 5.0 5.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 7.0 7.1 7.2 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 8.0 8.1 8.2 8.3 8.4 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.
- ↑ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
- ↑ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 26 日
External links
- Spacedude's Constellation map: Stars in Hercules
