| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h38m 53.40151s[1] |
| Declination | −21° 03′ 06.7415″[1] |
| Apparent magnitude (V) | 5.85[2] |
| Characteristics | |
| Spectral type | G5 V[2] |
| B−V color index | 0.68[3] |
| Astrometry | |
| Radial velocity (Rv) | +37.14±0.20[1] km/s |
| Proper motion (μ) | RA: −75.128±0.163[1] mas/yr Dec.: −153.645±0.150[1] mas/yr |
| Parallax (π) | 76.6355 ± 0.1082 mas[1] |
| Distance | 42.56 ± 0.06 ly (13.05 ± 0.02 pc) |
| Absolute magnitude (MV) | 5.27[4] |
| Details | |
| Mass | 0.865[5] or 1.00[6] M☉ |
| Radius | 0.90[5] R☉ |
| Surface gravity (log g) | 4.65[2] cgs |
| Temperature | 5,638[2] K |
| Metallicity [Fe/H] | –0.21[2] dex |
| Rotational velocity (v sin i) | 0.32[7] km/s |
| Age | 4.1–4.8[8] Gyr |
| Other designations | |
86 G. Sagittarii, BD−21° 5081, GJ 722, HD 172051, HIP 91438, HR 6998, SAO 187086, WDS J18389-2103AB[9] | |
| Database references | |
| SIMBAD | data |
HD 172051 (86 G. Sagittarii) is a single,[10] yellow-hued star in the southern constellationofSagittarius. The star is barely bright enough to be seen with the naked eye, having an apparent visual magnitude of 5.85.[2] Based upon an annual parallax shift of 76.64 mas, it is located some 43 light years from the Sun. It is moving away from the Sun with a radial velocity of +37 km/s.[1]
This ordinary G-type main-sequence star is considered a solar analog, having physical properties sufficiently similar to the Sun. It has a stellar classification of G5 V[2] and is around 4.5 billion years old. The mass is similar to the Sun, although it is cooler and has a lower luminosity. Due to this similarity, HD 172051 has been selected as an early target star for both the Terrestrial Planet Finder and Darwin missions, which seek to find an Earth-like extrasolar planet.[11] During a search for brown dwarf companions using the Hale Telescope in 2004, two candidate companions were identified at angular separations of 5″ and 6″. However, these were determined to be background stars.[12]
