| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18 25 01.42751 |
| Declination | −30° 45′ 23.6292″ |
| Apparent magnitude (V) | 5.58 |
| Characteristics | |
| Evolutionary stage | giant star |
| Spectral type | K0 III |
| B−V color index | 1.138 |
| Astrometry | |
| Radial velocity (Rv) | −18.7±2.9 km/s |
| Proper motion (μ) | RA: −135.019 mas/yr Dec.: −70.932 mas/yr |
| Parallax (π) | 5.9260 ± 0.2434 mas |
| Distance | 550 ± 20 ly (169 ± 7 pc) |
| Absolute magnitude (MV) | −0.93 |
| Details | |
| Radius | 8.9 R☉ |
| Luminosity | 309.45 L☉ |
| Surface gravity (log g) | 1.50 cgs |
| Temperature | 4,341 K |
| Metallicity | −0.79 dex |
| Rotational velocity (v sin i) | 1.0 km/s |
| Other designations | |
| 18 Sgr, CD−30°15661, HD 169233, HIP 90260, HR 6888, SAO 210116 | |
| Database references | |
| SIMBAD | data |
18 Sagittarii is a single star in zodiac constellation of Sagittarius, located around 550 light years away from the Sun based on parallax. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 5.58. This object is moving closer to the Earth with a heliocentric radial velocity of −19 km/s.
This is an aging giant star with a stellar classification of K0 III, which indicates it has exhausted the hydrogen at its core and evolved away from the main sequence. It has expanded to about 9 times the Sun's radius and is radiating 309 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,341. There is a much lower abundance of iron in the spectrum compared to the Sun.
References
- ^ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
- ^ Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 3, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1982mcts.book.....H.
- ^ Randich, S.; et al. (August 1999), "Lithium in population I subgiants", Astronomy and Astrophysics, 348: 487–500, Bibcode:1999A&A...348..487R
- ^ Pasinetti Fracassini, L. E.; Pastori, L.; Covino, S.; Pozzi, A. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics, 367 (Third ed.): 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754.
- ^ "18 Sgr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-03-24.
- Eggleton, P. P.; Tokovinin, A. A. (2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
