HD 163840 is a binary star[6] system in the northern constellation of Hercules. It has a combined apparent visual magnitude of 6.45,[1] 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[1] 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.[4] In about 769,000 years, it will make perihelion at a separation of around 27.2 ly (8.33 pc).[8]
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Hercules |
Right ascension | 17h 57m 14.33667s[1] |
Declination | +23° 59′ 44.5562″[1] |
Apparent magnitude (V) | 6.4543±0.0005[1] (6.30 + 7.90)[2] |
Characteristics | |
Spectral type | G2 V + K2 V[3] |
B−V color index | 0.642±0.006[1] |
Astrometry | |
Radial velocity (Rv) | −32.83±0.07[4] km/s |
Proper motion (μ) | RA: −17.79±0.33[1] mas/yr Dec.: +73.56±0.47[1] mas/yr |
Parallax (π) | 35.40 ± 0.62 mas[1] |
Distance | 92 ± 2 ly (28.2 ± 0.5 pc) |
Absolute magnitude (MV) | 4.05[5] |
Orbit[6] | |
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[6] M☉ |
Luminosity | 2.031[3] L☉ |
Temperature | 5,860[3] K |
Metallicity [Fe/H] | 0.06[5] dex |
Age | 7.4[5] Gyr |
HD 163840 B | |
Mass | 0.7421±0.0073[6] M☉ |
Luminosity | 0.648[3] L☉ |
Temperature | 4,780[3] K |
Other designations | |
Database references | |
SIMBAD | data |
R. K. Young of the Dominion Astrophysical Observatory was the first to recognize the variable radial velocity of this system.[9] In 1974, Harold A. McAlister and Philip A. Ianna identified it as a nearby G-type dwarf based on its spectroscopic properties.[10] McAlister et al. (1974) found it to be a spectroscopic binary[10] 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.[11] These parameters have been further refined using improved instruments up through 2016.[6]
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.[6] The close, eccentric orbit of the pair does not permit a stable planetary orbit in the habitable zone of either component.[3]
The primary, component A, is a magnitude 6.30[2] G-type main-sequence star with a stellar classification of G2 V.[3] It has 1.13[6] 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.[3] Component B, the magnitude 7.90[2] secondary, is a smaller K-type main-sequence star with a class of K2 V.[3] It has 0.74[6] times the Sun's mass and shines with 0.65[3] times the Sun's luminosity at an effective temperature of 4,780 K.[3] The system as a whole may be around 7.4[5] billion years old with a slightly higher metallicity than the Sun. The system displays solar-like variability.[12]