HD 190647 is a yellow-hued star with an exoplanetary companion, located in the southern constellation of Sagittarius. It has an apparent visual magnitude of 7.78,[2] making this an 8th magnitude star that is much too faint to be readily visible to the naked eye. The star is located at a distance of 178 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −40 km/s.[1] It is also called HIP 99115.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 20h 07m 19.6698s[1] |
| Declination | −35° 32′ 19.0786″[1] |
| Apparent magnitude (V) | 7.78[2] |
| Characteristics | |
| Spectral type | G5V[3] |
| B−V color index | 0.743±0.002[2] |
| Variable type | Constant[4] |
| Astrometry | |
| Radial velocity (Rv) | −40.33±0.12[1] km/s |
| Proper motion (μ) | RA: −26.622±0.079[1] mas/yr Dec.: −206.859±0.053[1] mas/yr |
| Parallax (π) | 18.3287 ± 0.0495 mas[1] |
| Distance | 177.9 ± 0.5 ly (54.6 ± 0.1 pc) |
| Absolute magnitude (MV) | 4.00[2] |
| Details | |
| Mass | 1.07±0.01[5] M☉ |
| Radius | 1.56±0.03[5] R☉ |
| Luminosity | 2.19±0.01[5] L☉ |
| Surface gravity (log g) | 4.07±0.02[5] cgs |
| Temperature | 5,630+48 −40[5] K |
| Metallicity [Fe/H] | 0.23[6] dex |
| Rotational velocity (v sin i) | 1.576[6] km/s |
| Age | 8.7±0.4[5] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
The stellar classification of this star is G5V,[3] matching a G-type main-sequence star. However, the low gravity and high luminosity of this star may indicate it is slightly evolved. It is chrompsherically inactive with a slow rotation,[4] having a projected rotational velocity of 1.6 km/s.[6] The star's metallicity is high, with nearly 1.5 times the abundance of iron compared to the Sun.[4]
In 2007, a Jovian planet was found to be orbiting the star. It was detected using the radial velocity method with the HARPS spectrograph in Chile. The object is orbiting at a distance of 2.0 AU from the host star with a period of 2.84 years and an eccentricity (ovalness) of 0.18. As the inclination of the orbital plane is unknown, only a lower bound on the planetary mass can be made. It has a minimum mass 1.9 times the mass of Jupiter.[4]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | >1.9 ± 0.06 MJ | 2.07 ± 0.06 | 1038.1 ± 4.9 | 0.18 ± 0.02 | — | — |