# Upsilon Librae

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Binary star in the constellation Libra

Upsilon Librae Location of υ Librae (circled in red) Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) Constellation Libra Right ascension 15h 37m 01.45020s[1] Declination −28° 08′ 06.2926″[1] Apparent magnitude (V) 3.628[2] Characteristics Spectral type K3 III[3] U−B color index +1.586[2] B−V color index +1.374[2] Astrometry Radial velocity (Rv) −24.9±0.7[4] km/s Proper motion (μ) RA: −12.82[1] mas/yr Dec.: −4.15[1] mas/yr Parallax (π) 14.58±0.19 mas[1] Distance 224 ± 3 ly (68.6 ± 0.9 pc) Absolute magnitude (MV) −0.28[5] Details[6] Mass 1.67 M☉ Radius 31.5[7] R☉ Luminosity 309 L☉ Surface gravity (log g) 1.58 cgs Temperature 4,135±20 K Metallicity [Fe/H] −0.02 dex Age 3.14 Gyr Other designations υ Lib, 39 Lib, CD−27°10464, FK5 579, HD 139063, HIP 76470, HR 5794, SAO 183619[8] Database references SIMBAD data

**Upsilon Librae** (υ Lib, υ Librae) is the [Bayer designation](/source/Bayer_designation) for a [double star](/source/Double_star)[9] in the [zodiac](/source/Zodiac) [constellation](/source/Constellation) [Libra](/source/Libra_(constellation)). With an [apparent visual magnitude](/source/Apparent_visual_magnitude) of 3.628,[2] it is visible to the naked eye. The distance to this star, based upon an annual [parallax shift](/source/Stellar_parallax) of 14.58,[1] is around 224 [light years](/source/Light_year). It has a magnitude 10.8 companion at an [angular separation](/source/Angular_separation) of 2.0 [arc seconds](/source/Arc_second) along a [position angle](/source/Position_angle) of 151°, as of 2002.[10]

The brighter component is an [evolved](/source/Stellar_evolution) [K-type](/source/K-type_star) [giant star](/source/Giant_star) with a [stellar classification](/source/Stellar_classification) of K3 III.[3] The measured [angular diameter](/source/Angular_diameter), after correction for [limb darkening](/source/Limb_darkening), is 4.27±0.05 [mas](/source/Milliarcsecond).[11] At the estimated distance of the star, this yields a physical size of about 31.5 times the [radius of the Sun](/source/Solar_radius).[7] It has 1.67 times the [mass of the Sun](/source/Solar_mass) and radiates 309 times the [solar luminosity](/source/Solar_luminosity) from its [outer atmosphere](/source/Stellar_atmosphere) at an [effective temperature](/source/Effective_temperature) of 4,135 K.[6] The star is about three billion years old.[6]

Upsilon Librae will be [the brightest star](/source/Historical_brightest_stars) in the night sky in about 2.3 million years,[12] and will peak in brightness with an apparent magnitude of −0.46, or more than 40 times its present-day brightness.[12]

This star was originally designated by [Bayer](/source/Johann_Bayer) as **Omicron Scorpii**, but it was reassigned to Libra as Upsilon Librae.[13]: 196, 278 The star now known as [Omicron Scorpii](/source/Omicron_Scorpii) was a reinterpretation of o (Latin letter [o](/source/O)) Scorpii, a designation given by [Lacaille](/source/Nicolas-Louis_de_Lacaille).

## 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-Celis1975_2-0) [***b***](#cite_ref-Celis1975_2-1) [***c***](#cite_ref-Celis1975_2-2) [***d***](#cite_ref-Celis1975_2-3) Celis S., L. (October 1975), "Photoelectric photometry of late-type variable stars", *Astronomy and Astrophysics Supplement Series*, **22**: 9–17, [Bibcode](/source/Bibcode_(identifier)):[1975A&AS...22....9C](https://ui.adsabs.harvard.edu/abs/1975A&AS...22....9C).

1. ^ [***a***](#cite_ref-houk1979_3-0) [***b***](#cite_ref-houk1979_3-1) Houk, Nancy (1979), *Michigan catalogue of two-dimensional spectral types for the HD stars*, vol. 3, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, [Bibcode](/source/Bibcode_(identifier)):[1982mcts.book.....H](https://ui.adsabs.harvard.edu/abs/1982mcts.book.....H)

1. **[^](#cite_ref-deBruijne2012_4-0)** de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", *Astronomy & Astrophysics*, **546**: 14, [arXiv](/source/ArXiv_(identifier)):[1208.3048](https://arxiv.org/abs/1208.3048), [Bibcode](/source/Bibcode_(identifier)):[2012A&A...546A..61D](https://ui.adsabs.harvard.edu/abs/2012A&A...546A..61D), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201219219](https://doi.org/10.1051%2F0004-6361%2F201219219), [S2CID](/source/S2CID_(identifier)) [59451347](https://api.semanticscholar.org/CorpusID:59451347), A61.

1. **[^](#cite_ref-Ryon2009_5-0)** Ryon, Jenna; et al. (August 2009), "Comparing the Ca ii H and K Emission Lines in Red Giant Stars", *Publications of the Astronomical Society of the Pacific*, **121** (882): 842, [arXiv](/source/ArXiv_(identifier)):[0907.3346](https://arxiv.org/abs/0907.3346), [Bibcode](/source/Bibcode_(identifier)):[2009PASP..121..842R](https://ui.adsabs.harvard.edu/abs/2009PASP..121..842R), [doi](/source/Doi_(identifier)):[10.1086/605456](https://doi.org/10.1086%2F605456), [S2CID](/source/S2CID_(identifier)) [17821279](https://api.semanticscholar.org/CorpusID:17821279).

1. ^ [***a***](#cite_ref-Luck2015_6-0) [***b***](#cite_ref-Luck2015_6-1) [***c***](#cite_ref-Luck2015_6-2) Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", *The Astronomical Journal*, **150** (3): 23, [arXiv](/source/ArXiv_(identifier)):[1507.01466](https://arxiv.org/abs/1507.01466), [Bibcode](/source/Bibcode_(identifier)):[2015AJ....150...88L](https://ui.adsabs.harvard.edu/abs/2015AJ....150...88L), [doi](/source/Doi_(identifier)):[10.1088/0004-6256/150/3/88](https://doi.org/10.1088%2F0004-6256%2F150%2F3%2F88), [S2CID](/source/S2CID_(identifier)) [118505114](https://api.semanticscholar.org/CorpusID:118505114), 88.

1. ^ [***a***](#cite_ref-lang2006_7-0) [***b***](#cite_ref-lang2006_7-1) Lang, Kenneth R. (2006), [*Astrophysical formulae*](https://books.google.com/books?id=OvTjLcQ4MCQC&pg=PA41), Astronomy and astrophysics library, vol. 1 (3rd ed.), [Birkhäuser](/source/Birkh%C3%A4user), [ISBN](/source/ISBN_(identifier)) [3-540-29692-1](https://en.wikipedia.org/wiki/Special:BookSources/3-540-29692-1). The radius (R*) is given by: 1. 2 ⋅ R ∗ = ( 68.6 ⋅ 4.27 ⋅ 10 − 3 ) AU 0.0046491 AU / R ⨀ ≈ 63.0 ⋅ R ⨀ {\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(68.6\cdot 4.27\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 63.0\cdot R_{\bigodot }\end{aligned}}}

1. **[^](#cite_ref-SIMBAD_8-0)** ["ups Lib"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=ups+Lib). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2017-01-30.

1. **[^](#cite_ref-Eggleton2008_9-0)** Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", *[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-Mason2014_10-0)** Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", *The Astronomical Journal*, **122** (6): 3466, [Bibcode](/source/Bibcode_(identifier)):[2001AJ....122.3466M](https://ui.adsabs.harvard.edu/abs/2001AJ....122.3466M), [doi](/source/Doi_(identifier)):[10.1086/323920](https://doi.org/10.1086%2F323920)

1. **[^](#cite_ref-Richichi2005_11-0)** Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", *Astronomy and Astrophysics*, **431** (2): 773–777, [Bibcode](/source/Bibcode_(identifier)):[2005A&A...431..773R](https://ui.adsabs.harvard.edu/abs/2005A&A...431..773R), [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20042039](https://doi.org/10.1051%2F0004-6361%3A20042039).

1. ^ [***a***](#cite_ref-tomkin1998_12-0) [***b***](#cite_ref-tomkin1998_12-1) Tomkin, Jocelyn (April 1998). "Once and Future Celestial Kings". *Sky and Telescope*. **95** (4): 59–63. [Bibcode](/source/Bibcode_(identifier)):[1998S&T....95d..59T](https://ui.adsabs.harvard.edu/abs/1998S&T....95d..59T). based on computations from [HIPPARCOS](/source/HIPPARCOS) data. (The calculations exclude stars whose distance or [proper motion](/source/Proper_motion) is uncertain.) [PDF](ftp://tlgleonid.asuscomm.com/HITACHI/BOOK_ASTRO/S&T/SkyandTelescope_1998%20-%20astronomy/04/199804059063.pdf)[*[dead link](https://en.wikipedia.org/wiki/Wikipedia:Link_rot)*]

1. **[^](#cite_ref-LostStars_13-0)** Wagman, Morton (2003). *Lost Stars*. McDonald & Woodward. [ISBN](/source/ISBN_(identifier)) [0939923785](https://en.wikipedia.org/wiki/Special:BookSources/0939923785).

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 [Upsilon Librae](https://en.wikipedia.org/wiki/Upsilon_Librae) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Upsilon_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.