{{short description|Binary star in the constellation Libra}} {{Starbox begin}} {{Starbox image | image = {{Location mark |image=Libra constellation map.svg|alt=|float=center|width=280 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=υ Librae |x=325|y=785 }} | caption = Location of υ Librae (circled in red) }} {{Starbox observe | epoch = [[J2000.0]] | equinox = [[J2000.0]] ([[International Celestial Reference System|ICRS]]) | constell = [[Libra (constellation)|Libra]] | ra = {{RA|15|37|01.45020}}<ref name=vanLeeuwen2007/> | dec = {{DEC|−28|08|06.2926}}<ref name=vanLeeuwen2007/> | appmag_v = 3.628<ref name=Celis1975/> }} {{Starbox character | class = K3 III<ref name=houk1979/> | b-v = +1.374<ref name=Celis1975/> | u-b = +1.586<ref name=Celis1975/> | r-i = | variable = }} {{Starbox astrometry | radial_v = {{Val|−24.9|0.7}}<ref name=deBruijne2012/> | prop_mo_ra = −12.82<ref name=vanLeeuwen2007/> | prop_mo_dec = −4.15<ref name=vanLeeuwen2007/> | parallax = 14.58 | p_error = 0.19 | parallax_footnote = <ref name=vanLeeuwen2007/> | absmag_v = −0.28<ref name=Ryon2009/> }} {{Starbox detail | source = <ref name=Luck2015/> | mass = 1.67 | radius = 31.5<ref name=lang2006/> | luminosity = 309 | temperature = {{Val|4135|20|fmt=commas}} | gravity = 1.58 | metal_fe = −0.02 | rotational_velocity = | age_gyr = 3.14 }} {{Starbox catalog | names = [[Bayer designation|υ Lib]], [[Flamsteed designation|39 Lib]], [[Durchmusterung|CD]]−27°10464, [[FK5]] 579, [[Henry Draper Catalogue|HD]] 139063, [[Hipparcos Catalogue|HIP]] 76470, [[Harvard Revised catalogue|HR]] 5794, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]] 183619<ref name=SIMBAD/> }} {{Starbox reference | Simbad = ups+Lib }} {{Starbox end}} '''Upsilon Librae''' (υ Lib, υ Librae) is the [[Bayer designation]] for a [[double star]]<ref name=Eggleton2008/> in the [[zodiac]] [[constellation]] [[Libra (constellation)|Libra]]. With an [[apparent visual magnitude]] of 3.628,<ref name=Celis1975/> it is visible to the naked eye. The distance to this star, based upon an annual [[stellar parallax|parallax shift]] of 14.58,<ref name=vanLeeuwen2007/> is around 224 [[light year]]s. It has a magnitude 10.8 companion at an [[angular separation]] of 2.0 [[arc second]]s along a [[position angle]] of 151°, as of 2002.<ref name=Mason2014/>
The brighter component is an [[stellar evolution|evolved]] [[K-type star|K-type]] [[giant star]] with a [[stellar classification]] of K3 III.<ref name=houk1979/> The measured [[angular diameter]], after correction for [[limb darkening]], is {{Val|4.27|0.05|u=[[milliarcsecond|mas]]}}.<ref name=Richichi2005/> At the estimated distance of the star, this yields a physical size of about 31.5 times the [[Solar radius|radius of the Sun]].<ref name=lang2006/> It has 1.67 times the [[solar mass|mass of the Sun]] and radiates 309 times the [[solar luminosity]] from its [[stellar atmosphere|outer atmosphere]] at an [[effective temperature]] of 4,135 K.<ref name=Luck2015/> The star is about three billion years old.<ref name=Luck2015/>
Upsilon Librae will be [[historical brightest stars|the brightest star]] in the night sky in about 2.3 million years,<ref name=tomkin1998>{{cite journal|last=Tomkin|first=Jocelyn|date=April 1998|title=Once and Future Celestial Kings|journal=Sky and Telescope|volume=95|issue=4|pages=59–63|bibcode=1998S&T....95d..59T}} based on computations from [[HIPPARCOS]] data. (The calculations exclude stars whose distance or [[proper motion]] is uncertain.) [ftp://tlgleonid.asuscomm.com/HITACHI/BOOK_ASTRO/S&T/SkyandTelescope_1998%20-%20astronomy/04/199804059063.pdf PDF]{{dead link|date=May 2025|bot=medic}}{{cbignore|bot=medic}}</ref> and will peak in brightness with an apparent magnitude of −0.46, or more than 40 times its present-day brightness.<ref name=tomkin1998 />
This star was originally designated by [[Johann Bayer|Bayer]] as '''Omicron Scorpii''', but it was reassigned to Libra as Upsilon Librae.<ref name="LostStars"/>{{rp|pp=196,278}} The star now known as [[Omicron Scorpii]] was a reinterpretation of o (Latin letter [[o]]) Scorpii, a designation given by [[Nicolas-Louis de Lacaille|Lacaille]].
==References== <references>
<ref name=vanLeeuwen2007>{{citation | title=Validation of the new Hipparcos reduction | last1=van Leeuwen | first1=F. | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | date=2007 | arxiv=0708.1752 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 | s2cid=18759600 | postscript=. }}</ref>
<ref name=Mason2014>{{citation | display-authors=1 | last1=Mason | first1=B. D. | last2=Wycoff | first2=G. L. | last3=Hartkopf | first3=W. I. | last4=Douglass | first4=G. G. | last5=Worley | first5=C. E. | title=The Washington Visual Double Star Catalog | journal=The Astronomical Journal | year=2014 | volume=122 | issue=6 | page=3466 | bibcode=2001AJ....122.3466M | doi=10.1086/323920 | doi-access=free }}</ref>
<ref name=Ryon2009>{{citation | title=Comparing the Ca ii H and K Emission Lines in Red Giant Stars | postscript=. | display-authors=1 | last1=Ryon | first1=Jenna | last2=Shetrone | first2=Matthew D. | last3=Smith | first3=Graeme H. | journal=Publications of the Astronomical Society of the Pacific | volume=121 | issue=882 | page=842 | date=August 2009 | doi=10.1086/605456 | bibcode=2009PASP..121..842R |arxiv = 0907.3346 | s2cid=17821279 }}</ref>
<ref name=Richichi2005>{{citation | display-authors=1 | last1=Richichi | first1=A. | last2=Percheron | first2=I. | last3=Khristoforova | first3=M. | title=CHARM2: An updated Catalog of High Angular Resolution Measurements | journal=Astronomy and Astrophysics | postscript=. | volume=431 | issue=2 | pages=773–777 | date=February 2005 | doi=10.1051/0004-6361:20042039 | bibcode=2005A&A...431..773R | doi-access=free }}</ref>
<ref name=lang2006>{{citation | first1=Kenneth R. | last1=Lang | title=Astrophysical formulae | volume=1 | series=Astronomy and astrophysics library | edition=3rd | publisher=[[Birkhäuser]] | date=2006 | isbn=3-540-29692-1 | postscript=. | url=https://books.google.com/books?id=OvTjLcQ4MCQC&pg=PA41 }} The radius (R<sub>*</sub>) is given by: :<math>\begin{align} 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{align}</math></ref>
<ref name=houk1979>{{citation | title=Michigan catalogue of two-dimensional spectral types for the HD stars | volume=3 | last1=Houk | first1=Nancy | publication-place=Ann Arbor, Michigan | publisher=Dept. of Astronomy, University of Michigan | date=1979 | bibcode=1982mcts.book.....H }}</ref>
<ref name=Celis1975>{{citation | last1=Celis S. | first1=L. | title=Photoelectric photometry of late-type variable stars | journal=Astronomy and Astrophysics Supplement Series | volume=22 | pages=9–17 | date=October 1975 | bibcode=1975A&AS...22....9C | postscript=. }}</ref>
<ref name=deBruijne2012>{{citation | last1=de Bruijne | first1=J. H. J. | last2=Eilers | first2=A.-C. | title=Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project | journal=Astronomy & Astrophysics | volume=546 | id=A61 | pages=14 | date=October 2012 | doi=10.1051/0004-6361/201219219 | bibcode=2012A&A...546A..61D | arxiv=1208.3048 | s2cid=59451347 | postscript=. }}</ref>
<ref name=Eggleton2008>{{citation | last1=Eggleton | first1=P. P. | last2=Tokovinin | first2=A. A. | title=A catalogue of multiplicity among bright stellar systems | journal=[[Monthly Notices of the Royal Astronomical Society]] | volume=389 | issue=2 | pages=869–879 | date=September 2008 | doi=10.1111/j.1365-2966.2008.13596.x | doi-access=free | bibcode=2008MNRAS.389..869E | arxiv=0806.2878 | s2cid=14878976 | postscript=. }}</ref>
<ref name=Luck2015>{{citation | title=Abundances in the Local Region. I. G and K Giants | last1=Luck | first1=R. Earle | journal=The Astronomical Journal | volume=150 | issue=3 | id=88 | pages=23 | date=September 2015 | doi=10.1088/0004-6256/150/3/88 | bibcode=2015AJ....150...88L | arxiv=1507.01466 | s2cid=118505114 | postscript=. }}</ref>
<ref name=SIMBAD>{{cite simbad | title=ups Lib | access-date=2017-01-30 }}</ref>
<ref name="LostStars">{{cite book |last = Wagman |first = Morton |date = 2003 |title = Lost Stars |publisher = McDonald & Woodward |isbn = 0939923785 }}</ref>
</references>
{{Stars of Libra|state=collapsed}}
{{DEFAULTSORT:Upsilon Librae}} [[Category:K-type giants]] [[Category:Double stars]] [[Category:Libra (constellation)]] [[Category:Bayer objects|Librae, Upsilon]] [[Category:Durchmusterung objects|CD-27 10464]] [[Category:Flamsteed objects|Librae, 39]] [[Category:Henry Draper Catalogue objects|139063]] [[Category:Hipparcos objects|076470]] [[Category:Bright Star Catalogue objects|5794]]