# Tau Librae

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Star in the constellation Libra

Tau Librae Location of τ Librae (circled in red) Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) Constellation Libra Right ascension 15h 38m 39.36950s[1] Declination −29° 46′ 39.8956″[1] Apparent magnitude (V) 3.68[2] Characteristics Spectral type B2.5 V[3] U−B color index −0.717[2] B−V color index −0.179[2] Astrometry Radial velocity (Rv) +33.3±2.3[4] km/s Proper motion (μ) RA: −22.08[1] mas/yr Dec.: −24.46[1] mas/yr Parallax (π) 8.89±0.20 mas[1] Distance 367 ± 8 ly (112 ± 3 pc) Absolute magnitude (MV) −1.59[5] Orbit[6] Period (P) 3.2907 d Eccentricity (e) 0.28 Longitude of the node (Ω) 114° Periastron epoch (T) 2439272.312 JD Semi-amplitude (K1) (primary) 75 km/s Semi-amplitude (K2) (secondary) 167 km/s Details τ Lib A Mass 7.25±0.49[7] M☉ Radius 3.2[8] R☉ Luminosity (bolometric) 2,705[7] L☉ Surface gravity (log g) 4.33[9] cgs Temperature 17,990[9] K Metallicity [Fe/H] +0.17[9] dex Rotational velocity (v sin i) 134[4] km/s Age 31.5±5.6[10] Myr Other designations τ Lib, 40 Lib, CD−29°11837, HD 139365, HIP 76600, HR 5812, SAO 183649[11] Database references SIMBAD data

**Tau Librae**, [Latinized](/source/Latinisation_of_names) from τ Librae, is a [binary star](/source/Binary_star) system at the southern edge of the [zodiac](/source/Zodiac) [constellation](/source/Constellation) of [Libra](/source/Libra_(constellation)). It can be seen with the naked eye, having an [apparent visual magnitude](/source/Apparent_visual_magnitude) of 3.68.[2] The distance to this system is around 367 [light years](/source/Light_year), as determined from an annual [parallax shift](/source/Stellar_parallax) of 8.89 [mas](/source/Milliarcsecond).[1]

Judging by its motion through space and physical properties, this system is a member of the Upper Centaurus–Lupus group of the [Scorpius–Centaurus association](/source/Scorpius%E2%80%93Centaurus_association).[4] It is a double-lined [spectroscopic binary](/source/Spectroscopic_binary)[12] with an [orbital period](/source/Orbital_period) of just 3.3 days and an [eccentricity](/source/Orbital_eccentricity) of 0.28.[6] The primary, component A, is a [B-type main sequence star](/source/B-type_main_sequence_star) with a [stellar classification](/source/Stellar_classification) of B2.5 V.[3] It is estimated to hold more than seven times the [mass of the Sun](/source/Solar_mass)[7] and have over three times the [Sun's radius](/source/Solar_radius).[8] It is only 31.5 million years old[10] and is spinning relatively rapidly with a [projected rotational velocity](/source/Projected_rotational_velocity) of 134 km/s.[4] It is a [heartbeat star](/source/Heartbeat_star) system, with pulsations caused by tidal forces.[13]

The system is emitting an [infrared excess](/source/Infrared_excess), suggesting the presence of a [circumstellar disk](/source/Circumstellar_disk) of material.[9]

## References

1. ^ [***a***](#cite_ref-vanLeeuwen2007_1-0) [***b***](#cite_ref-vanLeeuwen2007_1-1) [***c***](#cite_ref-vanLeeuwen2007_1-2) [***d***](#cite_ref-vanLeeuwen2007_1-3) [***e***](#cite_ref-vanLeeuwen2007_1-4) [***f***](#cite_ref-vanLeeuwen2007_1-5) van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", *Astronomy and Astrophysics*, **474** (2): 653–664, [arXiv](/source/ArXiv_(identifier)):[0708.1752](https://arxiv.org/abs/0708.1752), [Bibcode](/source/Bibcode_(identifier)):[2007A&A...474..653V](https://ui.adsabs.harvard.edu/abs/2007A&A...474..653V), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20078357](https://doi.org/10.1051%2F0004-6361%3A20078357), [S2CID](/source/S2CID_(identifier)) [18759600](https://api.semanticscholar.org/CorpusID:18759600).

1. ^ [***a***](#cite_ref-apjs15_2-0) [***b***](#cite_ref-apjs15_2-1) [***c***](#cite_ref-apjs15_2-2) [***d***](#cite_ref-apjs15_2-3) Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", *Astrophysical Journal Supplement*, **15**: 459, [Bibcode](/source/Bibcode_(identifier)):[1968ApJS...15..459G](https://ui.adsabs.harvard.edu/abs/1968ApJS...15..459G), [doi](/source/Doi_(identifier)):[10.1086/190168](https://doi.org/10.1086%2F190168).

1. ^ [***a***](#cite_ref-Hiltner2969_3-0) [***b***](#cite_ref-Hiltner2969_3-1) Hiltner, W. A.; Garrison, R. F.; Schild, R. E. (July 1969), "MK Spectral Types for Bright Southern OB Stars", *Astrophysical Journal*, **157**: 313–326, [Bibcode](/source/Bibcode_(identifier)):[1969ApJ...157..313H](https://ui.adsabs.harvard.edu/abs/1969ApJ...157..313H), [doi](/source/Doi_(identifier)):[10.1086/150069](https://doi.org/10.1086%2F150069).

1. ^ [***a***](#cite_ref-Jilinski2006_4-0) [***b***](#cite_ref-Jilinski2006_4-1) [***c***](#cite_ref-Jilinski2006_4-2) [***d***](#cite_ref-Jilinski2006_4-3) Jilinski, E.; et al. (March 2006), "Radial velocity measurements of B stars in the Scorpius–Centaurus association", *Astronomy and Astrophysics*, **448** (3): 1001–1006, [arXiv](/source/ArXiv_(identifier)):[astro-ph/0601643](https://arxiv.org/abs/astro-ph/0601643), [Bibcode](/source/Bibcode_(identifier)):[2006A&A...448.1001J](https://ui.adsabs.harvard.edu/abs/2006A&A...448.1001J), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20041614](https://doi.org/10.1051%2F0004-6361%3A20041614), [S2CID](/source/S2CID_(identifier)) [17818058](https://api.semanticscholar.org/CorpusID:17818058).

1. **[^](#cite_ref-Anderson2012_5-0)** Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", *Astronomy Letters*, **38** (5): 331, [arXiv](/source/ArXiv_(identifier)):[1108.4971](https://arxiv.org/abs/1108.4971), [Bibcode](/source/Bibcode_(identifier)):[2012AstL...38..331A](https://ui.adsabs.harvard.edu/abs/2012AstL...38..331A), [doi](/source/Doi_(identifier)):[10.1134/S1063773712050015](https://doi.org/10.1134%2FS1063773712050015), [S2CID](/source/S2CID_(identifier)) [119257644](https://api.semanticscholar.org/CorpusID:119257644).

1. ^ [***a***](#cite_ref-Pourbaix2004_6-0) [***b***](#cite_ref-Pourbaix2004_6-1) Pourbaix, D.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", *Astronomy and Astrophysics*, **424** (2): 727–732, [arXiv](/source/ArXiv_(identifier)):[astro-ph/0406573](https://arxiv.org/abs/astro-ph/0406573), [Bibcode](/source/Bibcode_(identifier)):[2004A&A...424..727P](https://ui.adsabs.harvard.edu/abs/2004A&A...424..727P), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20041213](https://doi.org/10.1051%2F0004-6361%3A20041213), [S2CID](/source/S2CID_(identifier)) [119387088](https://api.semanticscholar.org/CorpusID:119387088).

1. ^ [***a***](#cite_ref-Hohle2010_7-0) [***b***](#cite_ref-Hohle2010_7-1) [***c***](#cite_ref-Hohle2010_7-2) Hohle, M. M.; et al. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", *Astronomische Nachrichten*, **331** (4): 349, [arXiv](/source/ArXiv_(identifier)):[1003.2335](https://arxiv.org/abs/1003.2335), [Bibcode](/source/Bibcode_(identifier)):[2010AN....331..349H](https://ui.adsabs.harvard.edu/abs/2010AN....331..349H), [doi](/source/Doi_(identifier)):[10.1002/asna.200911355](https://doi.org/10.1002%2Fasna.200911355), [S2CID](/source/S2CID_(identifier)) [111387483](https://api.semanticscholar.org/CorpusID:111387483).

1. ^ [***a***](#cite_ref-PasinettiFracassini2001_8-0) [***b***](#cite_ref-PasinettiFracassini2001_8-1) Pasinetti-Fracassini, L. E.; et al. (February 2001), "Catalog of Apparent Diameters and Absolute Radii of Stars (CADARS)", *Astronomy and Astrophysics*, **367** (3rd ed.): 521–524, [arXiv](/source/ArXiv_(identifier)):[astro-ph/0012289](https://arxiv.org/abs/astro-ph/0012289), [Bibcode](/source/Bibcode_(identifier)):[2001A&A...367..521P](https://ui.adsabs.harvard.edu/abs/2001A&A...367..521P), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20000451](https://doi.org/10.1051%2F0004-6361%3A20000451), [S2CID](/source/S2CID_(identifier)) [425754](https://api.semanticscholar.org/CorpusID:425754).

1. ^ [***a***](#cite_ref-Saffe2008_9-0) [***b***](#cite_ref-Saffe2008_9-1) [***c***](#cite_ref-Saffe2008_9-2) [***d***](#cite_ref-Saffe2008_9-3) Saffe, C.; Gómez, M.; Pintado, O.; González, E. (October 2008), "Spectroscopic metallicities of Vega-like stars", *Astronomy and Astrophysics*, **490** (1): 297–305, [arXiv](/source/ArXiv_(identifier)):[0805.3936](https://arxiv.org/abs/0805.3936), [Bibcode](/source/Bibcode_(identifier)):[2008A&A...490..297S](https://ui.adsabs.harvard.edu/abs/2008A&A...490..297S), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:200810260](https://doi.org/10.1051%2F0004-6361%3A200810260), [S2CID](/source/S2CID_(identifier)) [15059920](https://api.semanticscholar.org/CorpusID:15059920).

1. ^ [***a***](#cite_ref-Tetzlaff2011_10-0) [***b***](#cite_ref-Tetzlaff2011_10-1) 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](/source/Monthly_Notices_of_the_Royal_Astronomical_Society)*, **410** (1): 190–200, [arXiv](/source/ArXiv_(identifier)):[1007.4883](https://arxiv.org/abs/1007.4883), [Bibcode](/source/Bibcode_(identifier)):[2011MNRAS.410..190T](https://ui.adsabs.harvard.edu/abs/2011MNRAS.410..190T), [doi](/source/Doi_(identifier)):[10.1111/j.1365-2966.2010.17434.x](https://doi.org/10.1111%2Fj.1365-2966.2010.17434.x), [S2CID](/source/S2CID_(identifier)) [118629873](https://api.semanticscholar.org/CorpusID:118629873).

1. **[^](#cite_ref-SIMBAD_11-0)** ["tau Lib"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=tau+Lib). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2017-01-30.{{[cite web](https://en.wikipedia.org/wiki/Template:Cite_web)}}: CS1 maint: postscript ([link](https://en.wikipedia.org/wiki/Category:CS1_maint:_postscript))

1. **[^](#cite_ref-Strom2005_12-0)** Strom, Stephen E.; et al. (February 2005), "B Star Rotational Velocities in h and χ Persei: A Probe of Initial Conditions during the Star Formation Epoch?", *The Astronomical Journal*, **129** (2): 809–828, [arXiv](/source/ArXiv_(identifier)):[astro-ph/0410337](https://arxiv.org/abs/astro-ph/0410337), [Bibcode](/source/Bibcode_(identifier)):[2005AJ....129..809S](https://ui.adsabs.harvard.edu/abs/2005AJ....129..809S), [doi](/source/Doi_(identifier)):[10.1086/426748](https://doi.org/10.1086%2F426748), [S2CID](/source/S2CID_(identifier)) [15059129](https://api.semanticscholar.org/CorpusID:15059129).

1. **[^](#cite_ref-Sharma_13-0)** Sharma, Awshesh N.; Bedding, Timothy R.; Saio, Hideyuki; White, Timothy R. (2022). ["Pulsating B stars in the Scorpius–Centaurus Association with TESS"](https://doi.org/10.1093%2Fmnras%2Fstac1816). *Monthly Notices of the Royal Astronomical Society*. **515** (1): 828–840. [arXiv](/source/ArXiv_(identifier)):[2203.02582](https://arxiv.org/abs/2203.02582). [Bibcode](/source/Bibcode_(identifier)):[2022MNRAS.515..828S](https://ui.adsabs.harvard.edu/abs/2022MNRAS.515..828S). [doi](/source/Doi_(identifier)):[10.1093/mnras/stac1816](https://doi.org/10.1093%2Fmnras%2Fstac1816).

## External links

- Kaler, James B. (May 17, 2013), ["Tau Librae"](http://stars.astro.illinois.edu/sow/taulib.html), *Stars*, University of Illinois, retrieved 2017-02-02.

v t e Constellation of Libra List of stars in Libra Libra in Chinese astronomy Stars Bayer α1 α2 (Zubenelgenubi) β (Zubeneschamali) γ (Zubenelhakrabi) δ ε ζ1 ζ2 ζ3 ζ4 η θ ι1 ι2 κ λ μ ν ξ1 ξ2 ο σ (Brachium) τ υ Flamsteed 2 3 4 5 10 11 12 16 17 18 22 23 26 28 30 36 37 41 42 47 48 49 50 Variable HN HO KU KX HR 5504 5455 HD 133131 134439 134440 135485 137010 139139 140283 141569 141937 Other 2M1510 2MASS 1507−1627 CWISEP J1446−2317 HE 1523−0901 WASP-57 WISE 1534−1043 WISE 1541−2250 Exoplanets 23 Librae b c Gliese 581b c e HD 137010 b (unconfirmed) K2-315b WASP-189b Star clusters NGC 5897 Galaxies NGC 5597 5605 5716 5728 5792 5793 5861 5885 5890 5898 5915 5917 Other AP Librae IC 1059 IRAS 14348−1447 PKS 1510−089 PKS 1519−273 QSO B1524−136 RXC J1504.1−0248 BCG Category

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Adapted from the Wikipedia article [Tau Librae](https://en.wikipedia.org/wiki/Tau_Librae) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Tau_Librae?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.