Astronomy:17 Sagittarii
| Observation data Epoch J2000.0 Equinox (celestial coordinates) | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 16m 35.36860s[1] |
| Declination | −20° 32′ 40.1303″[1] |
| Apparent magnitude (V) | 6.89[2] (7.24 + 8.89[3]) |
| Characteristics | |
| Spectral type | G8/K0 III[4] + A4::[5] |
| B−V color index | 1.027±0.015[2] |
| Astrometry | |
| Radial velocity (Rv) | −13.88±0.51[1] km/s |
| Proper motion (μ) | RA: 10.978[1] mas/yr Dec.: −14.342[1] mas/yr |
| Parallax (π) | 4.8289 ± 0.0505[1] mas |
| Distance | 675 ± 7 ly (207 ± 2 pc) |
| Absolute magnitude (MV) | 0.68[2] |
| Details | |
| Luminosity | 73.21[6] L☉ |
| Temperature | 4700[6] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
17 Sagittarii is a binary star system in the zodiac constellation of Sagittarius, located 675 light years from the Sun. With a combined apparent visual magnitude of 6.89[2] it is below the normal limit of visibility to the naked eye. The system is moving closer to the Earth with a heliocentric radial velocity of −14 km/s.[1] J. Allen Hynek (1938) found an initial spectral type of G5 + A5 for the pair. It was first resolved by Harold A. McAlister (1978), who found an angular separation of 0.260″±0.002″ along a position angle of 133.0°±1.2°[8]
The magnitude 7.24[3] primary component is an evolved giant star with a stellar classification of G8/K0 III,[4] indicating it has exhausted the hydrogen at its core and expanded off the main sequence. It is radiating 73 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,700 K.[6] The companion is a hot A-type star of uncertain luminosity class,[5] with a visual magnitude of 8.89.[3]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G. Gaia DR2 record for this source at VizieR.
- ↑ 2.0 2.1 2.2 2.3 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A.
- ↑ 3.0 3.1 3.2 Mason, B. D. et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal 122 (6): 3466, doi:10.1086/323920, Bibcode: 2001AJ....122.3466M.
- ↑ 4.0 4.1 Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode: 1988mcts.book.....H.
- ↑ 5.0 5.1 Ginestet, N.; Carquillat, J. M. (2002), "Spectral Classification of the Hot Components of a Large Sample of Stars with Composite Spectra, and Implication for the Absolute Magnitudes of the Cool Supergiant Components", The Astrophysical Journal Supplement Series 143 (2): 513, doi:10.1086/342942, Bibcode: 2002ApJS..143..513G.
- ↑ 6.0 6.1 6.2 McDonald, I. et al. (2012), "Fundamental parameters and infrared excesses of Hipparcos stars", Monthly Notices of the Royal Astronomical Society 427 (1): 343–357, doi:10.1111/j.1365-2966.2012.21873.x, Bibcode: 2012MNRAS.427..343M.
- ↑ "17 Sgr". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=17+Sgr.
- ↑ McAlister, H. A. (November 1, 1978), "Speckle interferometric measurements of binary stars. II", Astrophysical Journal, Part 1 225: 932–938, doi:10.1086/156559, Bibcode: 1978ApJ...225..932M. See note #25.
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