# Theta Librae

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Star in the constellation Libra

θ Librae Location of θ Librae (circled) Observation data Epoch J2000 Equinox J2000 Constellation Libra Right ascension 15h 53m 49.53806s[1] Declination −16° 43′ 45.4582″[1] Apparent magnitude (V) 4.136[2] Characteristics Evolutionary stage red clump[2] Spectral type G9IIIb[3] U−B color index +0.82[4] B−V color index +1.01[4] Astrometry Radial velocity (Rv) 4.56±0.25[5] km/s Proper motion (μ) RA: +100.33[1] mas/yr Dec.: +135.02[1] mas/yr Parallax (π) 19.36±0.15 mas[6] Distance 168 ± 1 ly (51.7 ± 0.4 pc) Absolute magnitude (MV) 0.665[2] Details Mass 1.47[7] M☉ Radius 12.27[7] R☉ Luminosity 68.1[7] L☉ Surface gravity (log g) 2.44[7] cgs Temperature 4,739[7] K Metallicity [Fe/H] −0.35[7] dex Rotational velocity (v sin i) 0.0[5] km/s Age 3.4[7] Gyr Other designations θ Lib, 46 Librae, BD−16°4174, HD 142198, HIP 77853, HR 5908, SAO 159563[8] Database references SIMBAD data

**Theta Librae** is a single[9] [star](/source/Star) in the southern [zodiac](/source/Zodiac) [constellation](/source/Constellation) of [Libra](/source/Libra_(constellation)), near the constellation border with [Scorpius](/source/Scorpius). Its name is a [Bayer designation](/source/Bayer_designation) that is [Latinized](/source/Romanization_of_Greek) from **θ Librae**, and abbreviated Theta Lib or θ Lib. It is visible to the naked eye as a faint, orange-hued star with an [apparent visual magnitude](/source/Apparent_visual_magnitude) of 4.14.[2] The distance to this star is approximately 168 [light years](/source/Light_year), as determined by [parallax](/source/Stellar_parallax), and it is drifting further away with a [radial velocity](/source/Radial_velocity) of 5 km/s.[5] The position of this star near the [ecliptic](/source/Ecliptic) means it is subject to [lunar occultations](/source/Lunar_occultation).[10]

This object is an aging [giant star](/source/Giant_star) with a [stellar classification](/source/Stellar_classification) of G9IIIb.[3] Having exhausted the supply of hydrogen at its [core](/source/Stellar_core), it has cooled and expanded; at present it has 12.3 times the girth of the Sun.[7] The star has an estimated mass about 47% greater than the Sun. It is radiating about 68 times the [luminosity of the Sun](/source/Luminosity_of_the_Sun) from its [photosphere](/source/Photosphere) at an [effective temperature](/source/Effective_temperature) of about 4,739 [K](/source/Kelvin).[7] It is probably on the [red giant branch](/source/Red_giant_branch), which indicates it is generating energy through [hydrogen fusion](/source/Hydrogen_fusion) in a shell outside an inert helium core.[7] However, there is a 41% chance that it is a [red clump](/source/Red_clump) giant on the [horizontal branch](/source/Horizontal_branch),[2] which would mean it was somewhat older and less massive.[7] It has sometimes been classified spectroscopically as a [subgiant](/source/Subgiant), but detailed study shows that it is too cool and luminous to be on the [subgiant branch](/source/Subgiant_branch).[11]

## References

1. ^ [***a***](#cite_ref-GaiaDR2_1-0) [***b***](#cite_ref-GaiaDR2_1-1) [***c***](#cite_ref-GaiaDR2_1-2) [***d***](#cite_ref-GaiaDR2_1-3) [Brown, A. G. A.](/source/Anthony_Brown_(scientist)); et al. ([Gaia collaboration](/source/Data_Processing_and_Analysis_Consortium)) (August 2018). ["*Gaia* Data Release 2: Summary of the contents and survey properties"](https://doi.org/10.1051%2F0004-6361%2F201833051). *[Astronomy & Astrophysics](/source/Astronomy_%26_Astrophysics)*. **616**. A1. [arXiv](/source/ArXiv_(identifier)):[1804.09365](https://arxiv.org/abs/1804.09365). [Bibcode](/source/Bibcode_(identifier)):[2018A&A...616A...1G](https://ui.adsabs.harvard.edu/abs/2018A&A...616A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201833051](https://doi.org/10.1051%2F0004-6361%2F201833051). [Gaia DR2 record for this source](https://vizier.u-strasbg.fr/viz-bin/VizieR-S?Gaia%20DR2%206260822966106296704) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-Liu2007_2-0) [***b***](#cite_ref-Liu2007_2-1) [***c***](#cite_ref-Liu2007_2-2) [***d***](#cite_ref-Liu2007_2-3) [***e***](#cite_ref-Liu2007_2-4) Liu, Y. J.; et al. (2007). ["The abundances of nearby red clump giants"](https://doi.org/10.1111%2Fj.1365-2966.2007.11852.x). *Monthly Notices of the Royal Astronomical Society*. **382** (2): 553–66. [Bibcode](/source/Bibcode_(identifier)):[2007MNRAS.382..553L](https://ui.adsabs.harvard.edu/abs/2007MNRAS.382..553L). [doi](/source/Doi_(identifier)):[10.1111/j.1365-2966.2007.11852.x](https://doi.org/10.1111%2Fj.1365-2966.2007.11852.x).

1. ^ [***a***](#cite_ref-Keenan1989_3-0) [***b***](#cite_ref-Keenan1989_3-1) 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. [Bibcode](/source/Bibcode_(identifier)):[1989ApJS...71..245K](https://ui.adsabs.harvard.edu/abs/1989ApJS...71..245K). [doi](/source/Doi_(identifier)):[10.1086/191373](https://doi.org/10.1086%2F191373).

1. ^ [***a***](#cite_ref-clpl99_4-0) [***b***](#cite_ref-clpl99_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](/source/Bibcode_(identifier)):[1966CoLPL...4...99J](https://ui.adsabs.harvard.edu/abs/1966CoLPL...4...99J).

1. ^ [***a***](#cite_ref-Massarotti2008_5-0) [***b***](#cite_ref-Massarotti2008_5-1) [***c***](#cite_ref-Massarotti2008_5-2) Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", *The Astronomical Journal*, **135** (1): 209–231, [Bibcode](/source/Bibcode_(identifier)):[2008AJ....135..209M](https://ui.adsabs.harvard.edu/abs/2008AJ....135..209M), [doi](/source/Doi_(identifier)):[10.1088/0004-6256/135/1/209](https://doi.org/10.1088%2F0004-6256%2F135%2F1%2F209), [S2CID](/source/S2CID_(identifier)) [121883397](https://api.semanticscholar.org/CorpusID:121883397)

1. **[^](#cite_ref-vanLeeuwen2007_6-0)** 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-reffert2015_7-0) [***b***](#cite_ref-reffert2015_7-1) [***c***](#cite_ref-reffert2015_7-2) [***d***](#cite_ref-reffert2015_7-3) [***e***](#cite_ref-reffert2015_7-4) [***f***](#cite_ref-reffert2015_7-5) [***g***](#cite_ref-reffert2015_7-6) [***h***](#cite_ref-reffert2015_7-7) [***i***](#cite_ref-reffert2015_7-8) [***j***](#cite_ref-reffert2015_7-9) [***k***](#cite_ref-reffert2015_7-10) Reffert, Sabine; Bergmann, Christoph; Quirrenbach, Andreas; Trifonov, Trifon; Künstler, Andreas (2015). "Precise radial velocities of giant stars. VII. Occurrence rate of giant extrasolar planets as a function of mass and metallicity". *Astronomy and Astrophysics*. **574**: A116. [arXiv](/source/ArXiv_(identifier)):[1412.4634](https://arxiv.org/abs/1412.4634). [Bibcode](/source/Bibcode_(identifier)):[2015A&A...574A.116R](https://ui.adsabs.harvard.edu/abs/2015A&A...574A.116R). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201322360](https://doi.org/10.1051%2F0004-6361%2F201322360). [S2CID](/source/S2CID_(identifier)) [59334290](https://api.semanticscholar.org/CorpusID:59334290).

1. **[^](#cite_ref-SIMBAD_8-0)** ["tet Lib"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=tet+Lib). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2017-06-19.

1. **[^](#cite_ref-Eggleton2008_9-0)** Eggleton, P. P.; Tokovinin, A. A. (September 2008). ["A catalogue of multiplicity among bright stellar systems"](https://doi.org/10.1111%2Fj.1365-2966.2008.13596.x). *[Monthly Notices of the Royal Astronomical Society](/source/Monthly_Notices_of_the_Royal_Astronomical_Society)*. **389** (2): 869–879. [arXiv](/source/ArXiv_(identifier)):[0806.2878](https://arxiv.org/abs/0806.2878). [Bibcode](/source/Bibcode_(identifier)):[2008MNRAS.389..869E](https://ui.adsabs.harvard.edu/abs/2008MNRAS.389..869E). [doi](/source/Doi_(identifier)):[10.1111/j.1365-2966.2008.13596.x](https://doi.org/10.1111%2Fj.1365-2966.2008.13596.x). [S2CID](/source/S2CID_(identifier)) [14878976](https://api.semanticscholar.org/CorpusID:14878976).

1. **[^](#cite_ref-Edwards1980_10-0)** Edwards, D. A.; et al. (April 1980). "Photoelectric observations of lunar occultations. XI". *Astronomical Journal*. **85**: 478–489. [Bibcode](/source/Bibcode_(identifier)):[1980AJ.....85..478E](https://ui.adsabs.harvard.edu/abs/1980AJ.....85..478E). [doi](/source/Doi_(identifier)):[10.1086/112700](https://doi.org/10.1086%2F112700).

1. **[^](#cite_ref-thoren2004_11-0)** Thorén, P.; Edvardsson, B.; Gustafsson, B. (2004). "Subgiants as probes of galactic chemical evolution". *Astronomy and Astrophysics*. **425**: 187–206. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0407260](https://arxiv.org/abs/astro-ph/0407260). [Bibcode](/source/Bibcode_(identifier)):[2004A&A...425..187T](https://ui.adsabs.harvard.edu/abs/2004A&A...425..187T). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20040421](https://doi.org/10.1051%2F0004-6361%3A20040421). [S2CID](/source/S2CID_(identifier)) [2116895](https://api.semanticscholar.org/CorpusID:2116895).

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 [Theta Librae](https://en.wikipedia.org/wiki/Theta_Librae) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Theta_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.