Astronomy:Omicron Sagittarii

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Short description: Star in the constellation Sagittarius
Omicron Sagittarii
Location of ο Sagittarii (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Sagittarius
Right ascension  19h 04m 40.98177s[1]
Declination −21° 44′ 29.3845″[1]
Apparent magnitude (V) +3.771[2]
Characteristics
Evolutionary stage horizontal branch[3]
Spectral type G9IIIb[4]
B−V color index +1.012±0.008[5]
Astrometry
Radial velocity (Rv)+26.1±0.6[5] km/s
Proper motion (μ) RA: +76.35±0.31[1] mas/yr
Dec.: −58.12±0.18[1] mas/yr
Parallax (π)22.96 ± 0.24[1] mas
Distance142 ± 1 ly
(43.6 ± 0.5 pc)
Absolute magnitude (MV)0.625[2]
Details
Mass1.80[6] M☉
Radius12.09+0.29
−0.17[7] R☉
Luminosity66.7±1.1[7] L☉
Surface gravity (log g)2.66[2] cgs
Temperature4,744+34
−57 K
Metallicity [Fe/H]−0.04[2] dex
Age2.39[6] Gyr
Other designations
ο Sgr, 39 Sagittarii, BD−21°5237, GC 26224, HD 177241, HIP 93683, HR 7217, SAO 187643, PPM 269274, ADS 11996, CCDM J19047-2144A, WDS J19047-2144A[8]
Database references
SIMBADdata

ο Sagittarii, Latinized as Omicron Sagittarii, is a single[9] star in the constellation Sagittarius. It is yellow in hue and visible to the naked eye with an apparent visual magnitude of +3.77.[2] The distance to this star is approximately 142 light years based on parallax.[1] It is drifting further away from the Sun with a radial velocity of +26 km/s, having come to within 86 ly around a million years ago.[5]

This object is position 0.86 degrees north of the ecliptic, so ο Sagittarii can be occulted by the Moon and very rarely by planets. The last occultation by a planet took place on 24 December 1937, when it was occulted by Mercury. It was almost eclipsed by the sun, which occupies a mean, rounded, half of one degree of the sky, on 5 January.[10] Thus the star can be viewed the whole night, crossing the sky, in early July.

This is an aging giant star with a stellar classification of G9IIIb.[4] It is classified as a red clump giant, suggesting it is on the horizontal branch undergoing core helium fusion.[3] The star is 2.39 billion years old[6] with 1.80 times the mass of the Sun.[6] It has expanded to 12 times the radius of the Sun and is radiating 67 times the Sun's luminosity from its swollen photosphere at an effective temperature of 4,744 K.[7]

It has a faint, magnitude 13.8 companion, designated component B and positioned 38.4″ away along a position angle of 252°, as of 2010.[11]

Name and etymology

In Chinese, 建 (Jiàn), meaning Establishment, refers to an asterism consisting of ο Sagittarii ξ² Sagittarii, π Sagittarii, 43 Sagittarii, ρ¹ Sagittarii and υ Sagittarii. Consequently, the Chinese name for ο Sagittarii itself is 建二 (Jiàn èr, English: the Second Star of Establishment.)[12]

This star is occasionally called by the name Manubrium, usually in an astrological context.[13]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Liu, Y. J. et al. (2007), "The abundances of nearby red clump giants", Monthly Notices of the Royal Astronomical Society 382 (2): 553–66, doi:10.1111/j.1365-2966.2007.11852.x, Bibcode: 2007MNRAS.382..553L. 
  3. ↑ 3.0 3.1 Alves, David R. (August 2000), "K-Band Calibration of the Red Clump Luminosity", The Astrophysical Journal 539 (2): 732–741, doi:10.1086/309278, Bibcode: 2000ApJ...539..732A. 
  4. ↑ 4.0 4.1 Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins Catalog of Revised MK Types for the Cooler Stars", The Astrophysical Journal Supplement Series 71: 245, doi:10.1086/191373, Bibcode: 1989ApJS...71..245K. 
  5. ↑ 5.0 5.1 5.2 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  6. ↑ 6.0 6.1 6.2 6.3 Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal 150 (3): 88, doi:10.1088/0004-6256/150/3/88, Bibcode: 2015AJ....150...88L. 
  7. ↑ 7.0 7.1 7.2 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.
  8. ↑ "omi Sgr". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=omi+Sgr. 
  9. ↑ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society 389 (2): 869–879, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E. 
  10. ↑ In the Sky Earth astronomy reference utility showing the ecliptic and relevant date as at J2000 - present
  11. ↑ Mason, Brian D. et al. (2001), "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog", The Astronomical Journal 122 (6): 3466, doi:10.1086/323920, Bibcode: 2001AJ....122.3466M. 
  12. ↑ Script error: The function "in_lang" does not exist. AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 11 日
  13. ↑ Robson, Vivian E. (1923). The Fixed Stars And Constellations In Astrology. p. 114. https://archive.org/details/in.ernet.dli.2015.128091/page/n107/mode/2up. 



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