HD 164509
Binary star in the constellation Ophiuchi
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HD 164509 is a binary star system in the constellation of Ophiuchus.[1] The primary component has an orbiting exoplanet companion.[6] This system is located at a distance of 175 light years based on parallax measurements,[2] and is drifting further away with a radial velocity of 13.7 km/s.[5] It has an absolute magnitude of 4.64,[6] but at that distance the system has an apparent visual magnitude of 8.10,[1] which is too faint to be seen with the naked eye.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ophiuchus[1] |
| Right ascension | 18h 01m 31.228s[2] |
| Declination | +00° 06′ 16.40″[2] |
| Apparent magnitude (V) | 8.10[1] |
| Characteristics | |
| Evolutionary stage | main sequence |
| Spectral type | G2V[3] + M6.5V[4] |
| B−V color index | 0.665±0.018[2] |
| J−H color index | 0.28[2] |
| J−K color index | 0.36[2] |
| Astrometry | |
| Radial velocity (Rv) | 13.68±0.16[5] km/s |
| Proper motion (μ) | RA: −7.876 mas/yr[2] Dec.: −20.462 mas/yr[2] |
| Parallax (π) | 18.6155±0.0219 mas[2] |
| Distance | 175.2 ± 0.2 ly (53.72 ± 0.06 pc) |
| Absolute magnitude (MV) | 4.64[6] |
| Orbit[7] | |
| Primary | HD 164509 A |
| Name | HD 164509 B |
| Period (P) | ∼180 yr |
| Semi-major axis (a) | 36.5 ±1.9 au |
| Eccentricity (e) | 0.87 ±0.21 |
| Details | |
| HD 164509 A | |
| Mass | 1.103±0.004[8] M☉ |
| Radius | 1.041±0.003[8] R☉ |
| Luminosity | 1.150±0.001[8] L☉ |
| Surface gravity (log g) | 4.44±0.01[8] cgs |
| Temperature | 5,865±7[8] K |
| Metallicity [Fe/H] | 0.21[9] dex |
| Rotational velocity (v sin i) | 2.4±0.5[6] km/s |
| Age | 1.5±0.2[8] Gyr |
| HD 164509 B | |
| Mass | 0.45±0.01[4] M☉ |
| Temperature | 2,710[4] K |
| Other designations | |
| BD+00 3837, HD 164509, HIP 88268, 2MASS J18013121+0006163, DENIS J084619.3-080136, Gaia DR2 4275421969292868224[10] | |
| Database references | |
| SIMBAD | 164509 data |
The primary component is a Sun-like G-type main-sequence star[6] with a stellar classification of G2V.[3] It is young and metal rich, having heavy elements abundance 160% of solar.[9] The star has a modest level of magnetic activity in its chromosphere.[6] It has 1.10 times the mass of the Sun and 1.04 times the Sun's radius.[8] This star is radiating 1.15[8] times the luminosity of the Sun from its photosphere at an effective temperature of 5,865 K.[8]
Initially it was thought the system consisted of a single star, but in 2016 it was discovered the primary is accompanied by the M-class red dwarf star at a projected separation of 36.5±1.9 AU.[7] The evidence for this stellar companion being on a bound orbit was further fortified in 2017.[11][4]
Planetary system
In 2011, a gas giant, HD 164509 Ab, was discovered orbiting the primary of HD 164509 using Doppler spectroscopy.[6] Given the binary nature of this system, the planet HD 164509 Ab could not have formed on the current orbit, which is unstable in long term.[12] Instead, it may be a captured body formed elsewhere.[13]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| Ab | 0.48±0.09 MJ | 0.875±0.008 | 282.4±3.8 | 0.26±0.14 | — | — |