Astronomy:Theta Ophiuchi

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Short description: Star in the constellation Ophiuchus
Theta Ophiuchi
Ophiuchus IAU.svg
Red circle.svg
Location of θ Ophiuchi (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Ophiuchus
Right ascension  17h 22m 00.57935s[1]
Declination −24° 59′ 58.3670″[1]
Apparent magnitude (V) 3.25 - 3.31[2]
Characteristics
Spectral type B2 IV[3]
U−B color index −0.86[4]
B−V color index −0.23[4]
Variable type β Cep[2]
Astrometry
Radial velocity (Rv)−2[5] km/s
Proper motion (μ) RA: −7.37[1] mas/yr
Dec.: −23.94[1] mas/yr
Parallax (π)7.48 ± 0.17[1] mas
Distance436 ± 10 ly
(134 ± 3 pc)
Absolute magnitude (MV)−2.4[6]
Details
Mass8.8±0.2[3] M☉
Radius6.3[7] R☉
Luminosity5,000[6] L☉
Surface gravity (log g)3.950±0.006[8] cgs
Temperature22,260±280[8] K
Metallicity [Fe/H]−0.15±0.12[9] dex
Rotational velocity (v sin i)30[10] km/s
Age21.3±5.8[3] Myr
Other designations
42 Ophiuchi, CD–24 13292, FK5 644, GC 23451, HD 157056, HIP 84970, HR 6453, SAO 185320[11]
Database references
SIMBADdata

Theta Ophiuchi, Latinized from θ Ophiuchi, is a multiple star system in the equatorial constellation of Ophiuchus. It lies on the "right foot" of the serpent-bearer, just southwest of Kepler's Star, the nova of 1604. According to Richard H. Allen's Star Names: Their Lore and Meaning (1899), θ Oph together with ξ Oph formed the Sogdian Wajrik "the Magician", the Khorasmian Markhashik "the Serpent-bitten" and with η Oph the Coptic Tshiō, "the Snake", and Aggia, "the Magician".[12] This star has an apparent visual magnitude of +3.3,[6] making it readily visible to the naked eye. Based upon parallax measurements from the Hipparcos mission, it is roughly 436 light-years (134 parsecs) from Earth.[1] It is 1.8 degrees south of the ecliptic and therefore subject to lunar occultations and less frequently occulted by a planet.

Theta Ophiuchi appears to be a triple star system. The brightest component is a spectroscopic binary with an orbital period of 56.71 days and an eccentricity of 0.17. The third component is 5.5 magnitude star with a stellar classification of B5. Its angular separation from the binary pair is 0.15 arcseconds.[13] This system is a proper motion member of the Upper Scorpius sub-group in the Scorpius–Centaurus OB association, the nearest such co-moving association of massive stars to the Sun.[6]

A light curve for Theta Ophiuchi, plotted from Hipparcos data[14]

The primary component of this system is a variable star of the Beta Cephei type with a period of just 3h 22m.[15] It has nearly nine[3] times the mass of the Sun and more than six[7] times the Sun's radius. Although only 21 million years old,[3] it has begun to evolve away from the main sequence and has become a subgiant star with a stellar classification of B2 IV.[3] This massive star is radiating around 5,000 times the luminosity of the Sun from its outer atmosphere at an effective temperature of about 22,260 K,[8] giving it the blue-white hue of a B-type star.[16]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, Floor (November 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  Note: see VizieR catalogue I/311.
  2. ↑ 2.0 2.1 Samus, N. N. et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1 61 (1): 80–88. doi:10.1134/S1063772917010085. Bibcode: 2017ARep...61...80S. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society 410 (1): 190–200, doi:10.1111/j.1365-2966.2010.17434.x, Bibcode: 2011MNRAS.410..190T 
  4. ↑ 4.0 4.1 Johnson, H. L. et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory 4 (99): 99, Bibcode: 1966CoLPL...4...99J 
  5. ↑ Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick, eds., "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30 (University of Toronto: International Astronomical Union) 30: p. 57, Bibcode: 1967IAUS...30...57E 
  6. ↑ 6.0 6.1 6.2 6.3 de Geus, E. J.; de Zeeuw, P. T.; Lub, J. (June 1989), "Physical parameters of stars in the Scorpio-Centaurus OB association", Astronomy and Astrophysics 216 (1–2): 44–61, Bibcode: 1989A&A...216...44D 
  7. ↑ 7.0 7.1 Underhill, A. B. et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society 189 (3): 601–605, doi:10.1093/mnras/189.3.601, Bibcode: 1979MNRAS.189..601U 
  8. ↑ 8.0 8.1 8.2 Briquet, M.; Morel, T.; Thoul, A.; Scuflaire, R.; Miglio, A.; Montalbán, J.; Dupret, M.-A.; Aerts, C. (November 2007), "An asteroseismic study of the β Cephei star θ Ophiuchi: constraints on global stellar parameters and core overshooting", Monthly Notices of the Royal Astronomical Society 381 (4): 1482–1488, doi:10.1111/j.1365-2966.2007.12142.x, Bibcode: 2007MNRAS.381.1482B, http://orbi.ulg.ac.be/bitstream/2268/75394/1/j%252E1365-2966%252E2007%252E12142%252Ex.pdf 
  9. ↑ Daszyńska-Daszkiewicz, J.; Niemczura, E. (April 2005), "Metallicity of mono- and multiperiodic β Cephei stars", Astronomy and Astrophysics 433 (3): 1031–1035, doi:10.1051/0004-6361:20040397, Bibcode: 2005A&A...433.1031D 
  10. ↑ Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal 573 (1): 359–365, doi:10.1086/340590, Bibcode: 2002ApJ...573..359A 
  11. ↑ "tet Oph". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=tet+Oph. 
  12. ↑ Allen, R.H. (1899), Star Names: Their Lore and Meaning, p. 297, https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Ophiuchus*.html 
  13. ↑ 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 
  14. ↑ Light Curve, ESA, https://www.cosmos.esa.int/web/hipparcos/java-tools/light-curve, retrieved 20 August 2022 
  15. ↑ Burnham, Robert (1978), Burnham's celestial handbook: an observer's guide to the universe beyond the solar system, 3, Courier Dover Publications, p. 1372, ISBN 978-0-486-23673-5, https://archive.org/details/burnhamscelestia03burn/page/1372 
  16. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html, retrieved 2012-01-16 



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