Astronomy:HD 171238
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Sagittarius[1] |
| Right ascension | 18h 34m 43.676s[2] |
| Declination | −28° 04′ 20.33″[2] |
| Apparent magnitude (V) | 8.606[3] |
| Characteristics | |
| Evolutionary stage | main sequence[2] |
| Spectral type | G8 V[4] |
| Apparent magnitude (B) | 9.40 |
| Apparent magnitude (J) | 7.244[5] |
| Apparent magnitude (H) | 6.868[5] |
| Apparent magnitude (K) | 6.831[5] |
| B−V color index | 0.74[6] |
| Astrometry | |
| Radial velocity (Rv) | 21.11±0.17[7] km/s |
| Proper motion (μ) | RA: −29.539[2] mas/yr Dec.: −109.580[2] mas/yr |
| Parallax (π) | 22.4809 ± 0.0324[2] mas |
| Distance | 145.1 ± 0.2 ly (44.48 ± 0.06 pc) |
| Absolute magnitude (MV) | 5.15[6] |
| Details | |
| Mass | 0.99±0.01[8] M☉ |
| Radius | 0.95±0.01[8] R☉ |
| Luminosity | 0.774±0.003[8] L☉ |
| Surface gravity (log g) | 4.47±0.01[8] cgs |
| Temperature | 5,570±21[8] K |
| Metallicity [Fe/H] | 0.17±0.007[6] dex |
| Rotational velocity (v sin i) | 1.48[6] km/s |
| Age | 4.0±1.2[8] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | 171238 data |
| Extrasolar Planets Encyclopaedia | data |
HD 171238 is a star with an orbiting exoplanet in the southern constellation of Sagittarius. It is located at a distance of 145 light years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of 21 km/s.[7] The star has an absolute magnitude of 5.15,[6] but at the distance of this system it is too faint to be viewed with the naked eye, having an apparent visual magnitude of 8.61.[3]
The spectrum of HD 171238 presents as an ordinary G-type main-sequence star with a stellar classification of G8 V.[4] At an estimated age of around four billion years,[8] it is spinning with a projected rotational velocity of 1.5 km/s.[6] The metallicity of the star – the abundance of elements more massive than helium – is 48% higher than solar, based on the abundance of iron.[6] There are indications of a significant level of magnetic activity in the chromosphere.[6] The star has 99% of the mass of the Sun and 95% of the Sun's girth. It is radiating just 77% of the luminosity of the Sun from its photosphere at an effective temperature of 5,570 K.[8]
Planetary system
In August 2009, it was announced that this star has a super-jovian exoplanet.[6] Using astrometry from Gaia, astronomers were able to deduce the true mass of HD 171238 b as 8.8 |♃|J}}}}}}; higher than the minimum mass estimated from Doppler spectroscopy.[10]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (years) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 8.8+3.6 −1.3 MJ |
2.518+0.032 −0.033 |
4.148+0.045 −0.046 |
0.358+0.028 −0.026 |
19.1+7.9 −8.5° |
— |
See also
References
- ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific 99 (617): 695. doi:10.1086/132034. Bibcode: 1987PASP...99..695R Constellation record for this object at VizieR.
- ↑ 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 3.0 3.1 Nordström, B. et al. (May 2004), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs", Astronomy and Astrophysics 418: 989–1019, doi:10.1051/0004-6361:20035959, Bibcode: 2004A&A...418..989N.
- ↑ 4.0 4.1 Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, 3, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode: 1982mcts.book.....H.
- ↑ 5.0 5.1 5.2 Cutri, R. M. et al. (June 2003), 2MASS All Sky Catalog of point sources, NASA/IPAC, Bibcode: 2003tmc..book.....C
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 Ségransan, D. et al. (2009), "The CORALIE survey for southern extrasolar planets. XVI. Discovery of a planetary system around HD 147018 and of two long period and massive planets orbiting HD 171238 and HD 204313", Astronomy & Astrophysics 511: A45, doi:10.1051/0004-6361/200912136, Bibcode: 2010A&A...511A..45S.
- ↑ 7.0 7.1 Soubiran, C. et al. (2018), "Gaia Data Release 2. The catalogue of radial velocity standard stars", Astronomy and Astrophysics 616: A7, doi:10.1051/0004-6361/201832795, Bibcode: 2018A&A...616A...7S.
- ↑ 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 Bonfanti, A. et al. (2016), "Age consistency between exoplanet hosts and field stars", Astronomy & Astrophysics 585: 14, doi:10.1051/0004-6361/201527297, A5, Bibcode: 2016A&A...585A...5B.
- ↑ "HD 171238". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+171238.
- ↑ 10.0 10.1 Li, Yiting et al. (2021), "Precise Masses and Orbits for Nine Radial-velocity Exoplanets", The Astronomical Journal 162 (6): 266, doi:10.3847/1538-3881/ac27ab, Bibcode: 2021AJ....162..266L.
Coordinates: 
18h 34m 43.6733s, −28° 04′ 20.328″
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