HD 156846 is a binary star[5] system in the equatorial constellation of Ophiuchus, positioned a degree SSE of Messier 9.[8] It has a yellow hue and is just barely bright enough to be visible to the naked eye with an apparent visual magnitude of 6.5.[2] The system is located at a distance of 156 light years from the Sun based on parallax.[1] It is drifting closer with a radial velocity of −68.5 km/s, and is predicted to come to within 85.0 light-years in about 476,000 years.[6]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ophiuchus |
| Right ascension | 17h 20m 34.31093s[1] |
| Declination | −19° 20′ 01.4944″[1] |
| Apparent magnitude (V) | 6.506[2] + 14.10[3] |
| Characteristics | |
| Spectral type | G1V[4] + M4V[5] |
| B−V color index | 0.557[2] |
| Astrometry | |
| Radial velocity (Rv) | −68.50±0.22[6] km/s |
| Proper motion (μ) | RA: −137.102±0.097[1] mas/yr Dec.: −143.204±0.074[1] mas/yr |
| Parallax (π) | 20.9210 ± 0.0508 mas[1] |
| Distance | 155.9 ± 0.4 ly (47.8 ± 0.1 pc) |
| Absolute magnitude (MV) | 3.055[2] |
| Details[2] | |
| A | |
| Mass | 1.35±0.045 M☉ |
| Radius | 2.12±0.12 R☉ |
| Luminosity | 5.07[6] L☉ |
| Surface gravity (log g) | 3.92±0.08 cgs |
| Temperature | 5,969±44 K |
| Metallicity [Fe/H] | +0.17±0.04 dex |
| Rotational velocity (v sin i) | 5.05±0.50 km/s |
| Age | 2.8+0.1 −0.2[6] Gyr |
| B | |
| Mass | 0.59[5] M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
The primary, component A, is a G-type star with a stellar classification of G1V.[4] The absolute visual magnitude of this star is 1.13 magnitudes above the main sequence, indicating it has evolved slightly off the main sequence.[2] It has 1.35 times the mass of the Sun and 2.12 times the Sun's radius.[2] The star is an estimated 2.8[6] billion years old and is spinning with a projected rotational velocity of 5 km/s.[2] It is radiating five[6] times the luminosity of the Sun from its photosphere at an effective temperature of 5,969 K.[2]
The magnitude 14.4 secondary companion, component B, was discovered by the American astronomer R. G. Aitken in 1910.[3] It lies at an angular separation of 5.1″ from the primary, corresponding to a projected separation of 250 AU. This is a red dwarf with a class of M4V and has an estimated 59% of the Sun's mass.[5]
On 26 October 2007, a planet HD 156846 b was found orbiting the primary star by Tamuz, using the radial velocity method.[9] It has an orbital period of 0.98 years and a large eccentricity of 0.85. The estimated mass of this object is, at a minimum, 10.6 times the mass of Jupiter. If it were following the same orbit within the Solar System, it would have a perihelion within the orbit of Mercury and an aphelion outside the orbit of Mars.[2]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥10.57±0.29 MJ | 1.096±0.021 | 359.5546±0.0071 | 0.84785±0.00050 | — | — |
Stars of Ophiuchus | |
|---|---|
| Bayer | |
| Flamsteed | |
| Variable | |
| HR |
|
| HD |
|
| Gliese |
|
| Other |
|