G Herculis
Star in the constellation Hercules
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g Herculis is a binary star[11] system in the northern constellation of Hercules, which makes part of a wide triple star system. It has the Flamsteed designation 30 Herculis, while g Herculis is the Bayer designation. This system is visible to the naked eye as a faint, red-hued point of light. Based upon a measured parallax of 9.2 mas, it is located around 354 light years away from the Sun. The system is moving further from the Earth with a heliocentric radial velocity of 1.5 km/s.[5]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Hercules |
| Right ascension | 16h 28m 38.54859s[1] |
| Declination | +41° 52′ 54.0406″[1] |
| Apparent magnitude (V) | 4.3 - 6.3[2] |
| Characteristics | |
| Evolutionary stage | AGB[3] |
| Spectral type | M6− III[4] |
| B−V color index | 1.289±0.024[5] |
| Variable type | SRb[2] |
| Astrometry | |
| Radial velocity (Rv) | 1.49±0.38[5] km/s |
| Proper motion (μ) | RA: +30.16[1] mas/yr Dec.: −5.14[1] mas/yr |
| Parallax (π) | 9.21±0.18 mas[1] |
| Distance | 354 ± 7 ly (109 ± 2 pc) |
| Absolute magnitude (MV) | −0.41[6] |
| Orbit[3] | |
| Period (P) | 843.7±21.1 d |
| Eccentricity (e) | 0.37±0.11 |
| Periastron epoch (T) | 2,451,918.2±43.9 HJD |
| Argument of periastron (ω) (secondary) | 246±21° |
| Semi-amplitude (K1) (primary) | 2.3±0.3 km/s |
| Details | |
| g Her A | |
| Mass | 1.65±0.30[7] M☉ |
| Radius | 230[8] R☉ |
| Luminosity | 5,395[8] L☉ |
| Surface gravity (log g) | 0.20[9] cgs |
| Temperature | 3,263±23[8] K |
| Metallicity [Fe/H] | −0.01[9] dex |
| Other designations | |
| g Her, 30 Her, BD+42°2714, FK5 3303, HD 148783, HIP 80704, HR 6146, SAO 46108[10] | |
| Database references | |
| SIMBAD | data |
Characteristics
This is a single-lined spectroscopic binary with an orbital period of 2.310 years and an eccentricity of 0.37.[3] The visible component is an aging red giant on the asymptotic giant branch[3] with a stellar classification of M6− III.[4] According to Samus et al. (2017), it is a semiregular variable of subtype SRb, which ranges between visual magnitudes 4.3 and 6.3 over 89.2 days.[2][13] It displays cyclical periods of 62.3, 89.5, and 888.9 days.[3] The star is surrounded by a circumstellar dust shell that seems primarily composed of oxides of iron, magnesium, and aluminium, rather than silicates.[14]
In addition to the spectroscopic pair, there is a much wider star sharing similar proper motion and distance. It is a so-called proper motion companion. This star has a projected separation of 1,060 astronomical units from the inner pair. Its mass is estimated at 0.4 solar masses, and its apparent magnitude is much fainter than that of g Herculis.[15]