18 Sagittarii

18 Sagittarii
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Sagittarius
Right ascension 18h 25m 01.42751s[1]
Declination −30° 45′ 23.6292″[1]
Apparent magnitude (V) 5.58[2]
Characteristics
Evolutionary stage giant star
Spectral type K0 III[3]
B−V color index 1.138[4]
Astrometry
Radial velocity (Rv)−18.7±2.9[2] km/s
Proper motion (μ) RA: −135.019[1] mas/yr
Dec.: −70.932[1] mas/yr
Parallax (π)5.9260 ± 0.2434 mas[1]
Distance550 ± 20 ly
(169 ± 7 pc)
Absolute magnitude (MV)−0.93[4]
Details
Radius8.9[5] R☉
Luminosity309.45[2] L☉
Surface gravity (log g)1.50[4] cgs
Temperature4,341[4] K
Metallicity [Fe/H]−0.79[4] dex
Rotational velocity (v sin i)1.0[4] km/s
Other designations
18 Sgr, CD−30°15661, HD 169233, HIP 90260, HR 6888, SAO 210116[6]
Database references
SIMBADdata

18 Sagittarii is a single[7] star in zodiac constellation of Sagittarius,[6] located around 550 light years away from the Sun based on parallax.[1] It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 5.58.[2] This object is moving closer to the Earth with a heliocentric radial velocity of −19 km/s.[2]

This is an aging giant star with a stellar classification of K0 III,[3] which indicates it has exhausted the hydrogen at its core and evolved away from the main sequence. It has expanded to about 9[5] times the Sun's radius and is radiating 309[2] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,341.[4] There is a much lower abundance of iron in the spectrum compared to the Sun.[4]

References

  1. ^ a b c d e f 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.
  2. ^ a b c d e f 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.
  3. ^ a b 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.
  4. ^ a b c d e f g h Randich, S.; et al. (August 1999), "Lithium in population I subgiants", Astronomy and Astrophysics, 348: 487–500, Bibcode:1999A&A...348..487R
  5. ^ a b 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.
  6. ^ a b "18 Sgr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-03-24.
  7. ^ 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.