19h46m58.1130s, +34° 25′ 10.288″
| |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 19h46m 58.1122s[1] |
| Declination | +34° 25′ 10.281″[1] |
| Apparent magnitude (V) | 7.83[2] |
| Characteristics | |
| Spectral type | G2V[3] |
| B−V color index | 0.661±0.010[2] |
| Astrometry | |
| Radial velocity (Rv) | −16.91(12)[1] km/s |
| Proper motion (μ) | RA: 142.591(15) mas/yr[1] Dec.: −123.715(18) mas/yr[1] |
| Parallax (π) | 21.7166 ± 0.0157 mas[1] |
| Distance | 150.2 ± 0.1 ly (46.05 ± 0.03 pc) |
| Absolute magnitude (MV) | 4.41[2] |
| Details | |
| Mass | 1.06±0.02[4] M☉ |
| Radius | 1.17±0.03[4] R☉ |
| Luminosity | 1.44±0.02[4] L☉ |
| Surface gravity (log g) | 4.32±0.03[4] cgs |
| Temperature | 5,853±53[4] K |
| Metallicity [Fe/H] | 0.121±0.030[5] dex |
| Rotational velocity (v sin i) | 2.15±0.50[5] km/s |
| Age | 5.6±1.3[4] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
HD 187123 is a single,[7] yellow-hued star with two exoplanetary companions in the northern constellationofCygnus. It has an apparent visual magnitude of 7.83,[2] making it an 8th magnitude star that is too faint to be visible with the naked eye. However, it should be easy target with binoculars or small telescope. The system is located at a distance of 150 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −17 km/s.[1]
This is an ordinary G-type main-sequence star with a stellar classification of G2V.[3] The physical properties of this star are sufficiently similar to the Sun that it has been considered a solar analog, although the metallicity is higher.[8] It is estimated to be five or six billion years old and is spinning with a projected rotational velocity of 2 km/s.[5] The star has a similar mass to the Sun but is slightly larger with 117% of the Sun's radius. It is radiating 1.44 times the luminosity of the Sun from its photosphere at an effective temperature of 5,853 K.[4]
In 1998 the California and Carnegie Planet Search team, after following a suggestion by Kevin Apps, a Briton who at the time was an undergraduate student[9] found a possible planet orbiting the star.[10] There were also indications of another, more distant body orbiting the star and this claim was published in 2006.[11] This planet was confirmed in 2009.[12] The presence of water has been detected in the atmosphere of HD 187123 b with high confidence.[13]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | >0.5074±0.0026 MJ | 0.04213±0.00034 | 3.0965886±0.0000043 | 0.0093±0.0046 | — | — |
| c | >1.818±0.035 MJ | 4.417±0.054 | 3324±46 | 0.280±0.022 | — | — |
