Tau Scorpii
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Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Scorpius |
Right ascension | 16h 35m 52.95285s[1] |
Declination | −28° 12′ 57.6615″[1] |
Apparent magnitude (V) | +2.82[2] |
Characteristics | |
Spectral type | B0.2 V[3] |
U−B color index | −1.039[2] |
B−V color index | −0.252[2] |
Astrometry | |
Radial velocity (Rv) | +2.0[4] km/s |
Proper motion (μ) | RA: −9.89[1] mas/yr Dec.: −22.83[1] mas/yr |
Parallax (π) | 6.88 ± 0.53[1] mas |
Distance | 470 ± 40 ly (150 ± 10 pc) |
Absolute magnitude (MV) | −4.2[5] |
Details | |
Mass | 15.0 ± 0.1,[6] 14.5–14.7[7] M☉ |
Radius | 6.5[3] R☉ |
Diameter | 6.5[3] D☉ |
Luminosity | 18,000,[8] 20,400[7] L☉ |
Surface gravity (log g) | 4.24[9] cgs |
Temperature | 31,440,[10] 29,850[7] K |
Metallicity [Fe/H] | −0.14[9] dex |
Rotation | 41 days[11] |
Rotational velocity (v sin i) | 24[12] km/s |
Age | 5.7 ± 1.0,[6] 5[7] Myr |
Other designations | |
Database references | |
SIMBAD | data |
Tau Scorpii (τ Sco, τ Scorpii) is a star in the southern zodiac constellation of Scorpius. The apparent visual magnitude of Tau Scorpii is +2.8,[2] while parallax measurements yield a distance estimate of roughly 470 light-years (150 parsecs) from Earth.[1]

Compared to the Sun, Tau Scorpii is a massive OB star with 15[6] times the Sun's mass and more than six times the radius of the Sun.[3] It is radiating about 20,400[7] times the Sun's luminosity from its outer envelope at an effective temperature of 31,440 K.[10] This gives it the blue-white hue characteristic of B-type stars.[14] As yet there is no evidence of a companion in orbit around τ Sco.[15] It is a magnetic star whose surface magnetic field was mapped by means of Zeeman–Doppler imaging.[16] Tau Scorpii is rotating relatively slowly with a period of 41 days.[11]
The spectrum of this star shows triply ionized oxygen (O IV) that is being generated by X-rays and the Auger ionization effect. Observations with the ROSAT space telescope showed it has a higher energy (harder) X-ray spectrum than is usual for B0 V stars. Over the energy range 0.8–1.2 keV, its X-ray luminosity is Lx = 1.8 × 1031 erg s−1 with a large Lx to Lbol of log Lx/Lbol = –6.53 from ASCA measurements. ROSAT measurements showed a log Lx/Lbol ≃ –5.93 for the range 0.1–2.4 keV.[15] The hard component of the X-ray spectrum from τ Sco as studied with XMM-Newton supports the presence of in-falling clumps of plasma in τ Sco.[15]
This star is a proper motion member of the Upper Scorpius subgroup of the Scorpius-Centaurus OB association, the nearest such co-moving association of massive stars to the Sun.[5][7] The Upper Scorpius subgroup contains thousands of young stars with mean age 11 million years at average distance of 470 light years (145 parsecs)[7] A more recent analysis[7] of the HR diagram position for Tau Scorpii estimates its effective temperature to be 29,850 kelvins with a luminosity of 20,400 Suns, consistent with an isochronal age of 5 million years and an estimated mass of 14.5–14.7 solar masses.
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (November 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
- ↑ 2.0 2.1 2.2 2.3 Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A Photometric Investigation of the Scorpio-Centaurus Association", Astrophysical Journal Supplement 15: 459, Bibcode 1968ApJS...15..459G, doi:10.1086/190168
- ↑ 3.0 3.1 3.2 Howk, J. Christopher et al. (May 2000), "Stagnation and Infall of Dense Clumps in the Stellar Wind of τ Scorpii", The Astrophysical Journal 534 (1): 348–358, arXiv:astro-ph/9912360, Bibcode 2000ApJ...534..348H, doi:10.1086/308730
- ↑ Wielen, R. et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions, Astronomisches Rechen-Institut Heidelberg, Bibcode 1999VeARI..35....1W
- ↑ 5.0 5.1 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
- ↑ 6.0 6.1 6.2 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, arXiv:1007.4883, Bibcode 2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x
- ↑ 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 Mark J. Pecaut et al. (February 2012). "A Revised Age for Upper Scorpius and the Star Formation History among the F-type Members of the Scorpius-Centaurus OB Association". Astrophysical Journal 746 (2): 154. arXiv:1112.1695. Bibcode 2012ApJ...746..154P. doi:10.1088/0004-637X/746/2/154.
- ↑ Kaler, James B., Al NIYAT (Tau Scorpii), University of Illinois, http://stars.astro.illinois.edu/sow/alniyat-t.html, retrieved 2010-08-01
- ↑ 9.0 9.1 Kilian, J. (February 1994), "Chemical abundances in early B-type stars. 5: Metal abundances and LTE/NLTE comparison", Astronomy and Astrophysics 282 (3): 867–873, Bibcode 1994A&A...282..867K
- ↑ 10.0 10.1 Zorec, J. et al. (July 2009), "Fundamental parameters of B supergiants from the BCD system. I. Calibration of the (λ_1, D) parameters into Teff", Astronomy and Astrophysics 501 (1): 297–320, arXiv:0903.5134, Bibcode 2009A&A...501..297Z, doi:10.1051/0004-6361/200811147
- ↑ 11.0 11.1 Strassmeier, Klaus G. (September 2009), "Starspots", The Astronomy and Astrophysics Review 17 (3): 251–308, Bibcode 2009A&ARv..17..251S, doi:10.1007/s00159-009-0020-6
- ↑ 6165, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID [1]. Accessed on line February 8, 2013.
- ↑ "tau Sco -- Star", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Tau+Sco, retrieved 2010-08-01
- ↑ "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
- ↑ 15.0 15.1 15.2 Mewe, R. et al. (2003), "High-resolution X-ray spectroscopy of τ Scorpii (B0.2V) with XMM-Newton", Astronomy & Astrophysics 398 (1): 203–11, Bibcode 2003A&A...398..203M, doi:10.1051/0004-6361:20021577, http://dare.uva.nl/document/40494
- ↑ Donati, J.-F. et al. (2006), "The surprising magnetic topology of τ Sco: fossil remnant or dynamo output?", Monthly Notices of the Royal Astronomical Society 370 (2): 629–644, arXiv:astro-ph/0606156, Bibcode 2006MNRAS.370..629D, doi:10.1111/j.1365-2966.2006.10558.x