Tau Orionis

Tau Orionis (τ Ori, τ Orionis) is a solitary^[10] star in the constellation Orion. If an imaginary line is drawn north-west between the stars Rigel and Mintaka, Tau Orionis can be found roughly one-sixth of the way to Mintaka. It is visible to the naked eye with an apparent visual magnitude of 3.58.^[2] Based upon an annual parallax shift of 6.6 mas,^[1] it is located around 490 light years from the Sun.

τ Orionis

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Orion
Right ascension	05h 17m 36.38856s[1]
Declination	−06° 50′ 39.8702″[1]
Apparent magnitude (V)	3.58[2]
Characteristics
Spectral type	B5 III[3]
U−B color index	−0.47[2]
B−V color index	−0.11[2]
Astrometry
Radial velocity (Rv)	+20.1[4] km/s
Proper motion (μ)	RA: −17.61[1] mas/yr Dec.: −9.24[1] mas/yr
Parallax (π)	6.60 ± 0.15 mas[1]
Distance	490 ± 10 ly (152 ± 3 pc)
Details
Mass	6.2±0.1[5] M☉
Radius	5.4[6] R☉
Luminosity	933[7] L☉
Temperature	10,829[7] K
Rotational velocity (v sin i)	40[8] km/s
Age	63.1±15.6[5] Myr
Other designations
τ Ori, 20 Orionis, BD−07° 1028, HD 34503, HIP 24674, HR 1735, SAO 131952.[9]
Database references
SIMBAD	data

This is a B-type giant star with a stellar classification of B5III5 III.^[3] It has around 5.4^[6] times the radius of the Sun and 6.2^[5] times the Sun's mass. The star shines with 933^[7] times the solar luminosity from its outer atmosphere at an effective temperature of 10,829^[7] K. it is around 63^[5] million years old, with a peculiar velocity through space of 16.9 km/s.^[5]

Tau Orionis has three visual companions: magnitude 11.0 component B at an angular separation of 33.30″ along a position angle of 251°; magnitude 10.9 component C lying some 3.80″ from component B; and magnitude 10.9 component D at 36.0″ from τ Ori along a position angle of 51°, all as of 2011.^[11]

Proper names

According to Richard H. Allen, this star, along with β Eri, λ Eri and ψ Eri were Al Kursiyy al Jauzah, "the Chair (or "Footstool") of the Central One".^[12] However, per the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Kursiyy al Jauzah were the title for just three stars: β Eri as Cursa, ψ Eri as Al Kursiyy al Jauzah I and λ Eri as Al Kursiyy al Jauzah II, excluding this star.^[13]

In Chinese, 玉井 (Yù Jǐng), meaning Jade Well, refers to an asterism consisting of τ Orionis, β Eridani, λ Eridani and ψ Eridani.^[14] Consequently, the Chinese name for τ Orionis itself is 玉井四 (Yù Jǐng sì, English: the Fourth Star of Jade Well.).^[15] From this Chinese title, the name Yuh Tsing is derived.^[12]

References

1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. Crawford, D. L.; et al. (1971), "Four-color, H-beta, and UBV photometry for bright B-type stars in the northern hemisphere", The Astronomical Journal, 76: 1058, Bibcode:1971AJ.....76.1058C, doi:10.1086/111220.
3. Abt, H. A. (September 1985), "Visual multiples. VIII - 1000 MK types", Astrophysical Journal Supplement Series, 59: 95–112, Bibcode:1985ApJS...59...95A, doi:10.1086/191064.
4. Wilson, R. E. (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication, Carnegie Institute of Washington, D.C., Bibcode:1953GCRV..C......0W.
5. Tetzlaff, N.; et al. (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, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
6. Pasinetti Fracassini, L. E.; Pastori, L.; Covino, S.; Pozzi, A. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics, 367 (2): 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754.
7. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
8. Abt, Helmut A.; et al. (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590.
9. "tau Ori". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-11-24.{{cite web}}: CS1 maint: postscript (link)
10. 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.
11. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
12. Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 218. ISBN 0-486-21079-0. Retrieved 2010-12-12.
13. Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF), Jet Propulsion Laboratory, California Institute of Technology, retrieved 2016-11-24.
14. (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
15. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 15 日 Archived 2011-07-16 at the Wayback Machine

External links

• Kaler, James B. (January 23, 2009), "Tau Orionis", Stars, University of Illinois, retrieved 2016-11-18.