HD 163840
Star in the constellation Hercules
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HD 163840 is a binary star[7] system in the northern constellation of Hercules. It has a combined apparent visual magnitude of 6.45,[2] which falls just below the brightness level that is visible to the naked eye for people with normal eyesight. An annual parallax shift of 35.40[2] mas provides a distance estimate of about 92 light years. The system is moving closer to the Sun with a radial velocity of −33 km/s.[5] In about 769,000 years, it will make perihelion at a separation of around 27.2 ly (8.33 pc).[9]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Hercules[1] |
| Right ascension | 17h 57m 14.33667s[2] |
| Declination | +23° 59′ 44.5562″[2] |
| Apparent magnitude (V) | 6.4543±0.0005[2] (6.30 + 7.90)[3] |
| Characteristics | |
| Spectral type | G2 V + K2 V[4] |
| B−V color index | 0.642±0.006[2] |
| Astrometry | |
| Radial velocity (Rv) | −32.83±0.07[5] km/s |
| Proper motion (μ) | RA: −17.79±0.33[2] mas/yr Dec.: +73.56±0.47[2] mas/yr |
| Parallax (π) | 35.40±0.62 mas[2] |
| Distance | 92 ± 2 ly (28.2 ± 0.5 pc) |
| Absolute magnitude (MV) | 4.05[6] |
| Orbit[7] | |
| Period (P) | 881.628±0.064 d |
| Semi-major axis (a) | 80.64 mas |
| Eccentricity (e) | 0.4165±0.0010 |
| Inclination (i) | 72.83±0.47° |
| Longitude of the node (Ω) | 175.32±0.44° |
| Periastron epoch (T) | 55650.39 ± 0.38 (BJD−2400000) |
| Argument of periastron (ω) (secondary) | 135.46±0.16° |
| Details | |
| HD 163840 A | |
| Mass | 1.132±0.014[7] M☉ |
| Luminosity | 2.031[4] L☉ |
| Temperature | 5,860[4] K |
| Metallicity [Fe/H] | 0.06[6] dex |
| Age | 7.4[6] Gyr |
| HD 163840 B | |
| Mass | 0.7421±0.0073[7] M☉ |
| Luminosity | 0.648[4] L☉ |
| Temperature | 4,780[4] K |
| Other designations | |
| BD+24°3283, GJ 4039, HD 163840, HIP 87895, HR 6697, SAO 85575, WDS J17572+2400A, Wolf 777[8] | |
| Database references | |
| SIMBAD | data |
R. K. Young of the Dominion Astrophysical Observatory was the first to recognize the variable radial velocity of this system.[10] In 1974, Harold A. McAlister and Philip A. Ianna identified it as a nearby G-type dwarf based on its spectroscopic properties.[11] McAlister et al. (1974) found it to be a spectroscopic binary[11] and the components were first resolved in 1976. A series of observations since that time allowed the system's orbital elements to be published by McAlister et al. (1995), along with estimates of the stellar masses of the two components.[12] These parameters have been further refined using improved instruments up through 2016.[7]
The pair of stars orbit each other with a period of 881.6 days (2.414 a) and an eccentricity of 0.417. The plane of their orbit is inclined by an angle of 73° to the line of sight from the Earth, with a semimajor axis having an angular value of 80.64 mas.[7] The close, eccentric orbit of the pair does not permit a stable planetary orbit in the habitable zone of either component.[4]
The primary, component A, is a magnitude 6.30[3] G-type main-sequence star with a stellar classification of G2 V.[4] It has 1.13[7] times the mass of the Sun and is radiating double the Sun's luminosity from its photosphere at an effective temperature of 5,860 K.[4] Component B, the magnitude 7.90[3] secondary, is a smaller K-type main-sequence star with a class of K2 V.[4] It has 0.74[7] times the Sun's mass and shines with 0.65[4] times the Sun's luminosity at an effective temperature of 4,780 K.[4] The system as a whole may be around 7.4[6] billion years old with a slightly higher metallicity than the Sun. The system displays solar-like variability.[13]