49 Librae

{{short description|Star in the constellation Libra}} {{Starbox begin}} {{Starbox observe | epoch = J2000 | constell = [[Libra (constellation)|Libra]] | ra = {{RA|16|00|19.61087}}<ref name=GaiaDR2/> | dec = {{DEC|−16|32|00.5483}}<ref name=GaiaDR2/> | appmag_v = 5.47<ref name=aaass34_1/> }} {{Starbox character | component1 = 49 Lib Aa | type = [[Blue straggler]]<ref name=Fuhrmann2017/> | class = F8 V<ref name=Willmarth2016/> | b-v = +0.52<ref name=aaass34_1/> | u-b = +0.03<ref name=aaass34_1/> | variable = | component2 = 49 Lib Ab | type2 = [[White dwarf]]<ref name=Fuhrmann2017/> }} {{Starbox astrometry | radial_v = {{val|−20.1|4.0}}<ref name=aaa475_2_519/> | prop_mo_ra = −644.387<ref name=GaiaDR2/> | prop_mo_dec = −360.803<ref name=GaiaDR2/> | parallax = 34.2281 | p_error = 0.1906 | parallax_footnote = <ref name=GaiaDR2/> | absmag_v = 2.89<ref name=aaa475_2_519/> }} {{Starbox orbit | reference = <ref name=Willmarth2016/> | period_unitless = {{Val|1142.4|1.1|fmt=commas|u=days}} | axis_unitless = {{convert|585|solar radius|au|disp=number}} [[astronomical unit|AU]]<ref name=Fuhrmann2017/> | eccentricity = {{Val|0.110|0.012}} | inclination = {{Val|141.3|1.0|2.0}}<ref name=Fuhrmann2017/> | node = {{Val|163.5|2.8}} | periastron = {{Val|57025|22|ul=MJD|fmt=commas}} | periarg = {{Val|69.4|7.4}} | k1 = {{Val|3.847|0.051}} }} {{Starbox detail | component1 = 49 Lib Aa | mass = {{val|1.55|0.07|0.13}}<ref name=Fuhrmann2017/> | radius = {{Val|1.86|0.05|0.04}}<ref name=GaiaDR2/> | gravity = {{val|3.93|0.10}}<ref name=Fuhrmann2017/> | metal_fe = −0.02<ref name=aaa475_2_519/> | temperature = {{val|6190|80|fmt=commas}}<ref name=Fuhrmann2017/> | luminosity = {{Val|4.74|0.03}}<ref name=GaiaDR2/> | rotational_velocity = {{Val|9.2|0.4}}<ref name=Fuhrmann2017/> | rotation = | age_gyr = {{val|12|1}}<ref name=Fuhrmann2017/> | component2 = 49 Lib Ab | mass2 = {{val|0.50|0.03|0.04}}<ref name=Fuhrmann2017/> }} {{Starbox catalog | names = {{odlist| F=49 Lib | BD=−16°4196 | FK5=1419 | GJ=3931 | HD=143333 | HIP=78400 | HR=5954 | SAO=159625 | WDS=J16003-1632A }}<ref name="SIMBAD"/> }} {{Starbox reference | Simbad = 49+Lib }} {{Starbox end}}

'''49 Librae''' is a [[binary star]]<ref name=apjs180_1_117/> system in the [[Zodiac]] [[constellation]] of [[Libra (constellation)|Libra]]. It has an [[apparent visual magnitude]] of 5.47,<ref name=aaass34_1/> making it [[Bortle scale|faintly visible]] to the naked eye from dark suburban skies as a dim, yellow-white-hued star. The system is located 95 [[light-year]]s away from the Sun, based on [[stellar parallax|parallax]],<ref name=GaiaDR2/> but is drifting closer with a [[radial velocity]] of −20 km/s.<ref name=aaa475_2_519/>

The [[Bayer designation]] [[Phi Scorpii]] has been associated with this star. No star is found at the position marked φ Scorpii in [[Johann Bayer]]'s ''[[Uranometria]]''.<ref name=bayer/> The closest stars to that position are 48 and 49 Librae; [[48 Librae]] is clearly shown but not given a designation while no star is shown at the position of 49 Librae. In his Uranographia [[Johann Elert Bode|Bode]] assigned the designation φ Scorpii to the star now known as 49 Librae.<ref name=startales/> The designation is no longer in use.<ref name=kaler-sco/>

==Characteristics== This is a single-lined [[spectroscopic binary]] system, first spotted to have a variable radial velocity by [[Walter Sydney Adams|W. S. Adams]] in 1924. Both stars take {{Convert|1142.4|days|years|disp=out|abbr=off}} to orbit around the system's [[center of mass]] and have a rather low an [[orbital eccentricity|eccentricity]] of 0.11.<ref name=Willmarth2016/>

The primary component has a [[stellar classification]] of F8 V or F9 V,<ref name=Willmarth2016/> which at first would indicate it is an [[F-type main-sequence star]]. Such star would have an age around 2.3 billion years, consistent with a [[Population I star]]. However, the [[Stellar kinematics|space velocity]] and chemical composition of this star is inconsistent with that of a Pop I star, indicating it is a much older (over 12 billion years) [[Population II star]]. To account for its [[stellar evolution|evolutionary stage]], which is too young for such age, it has been proposed 49 Lib A is a [[blue straggler]] that was once smaller but gained mass after interacting gravitationally with the secondary.<ref name=Fuhrmann2017/>

The secondary is a [[white dwarf]] with half the mass of the Sun.<ref name=Fuhrmann2017/> The system is a source for radio and X-ray emissions, which may be coming from the secondary companion.<ref name=Lazio2010/>

==Evolution== Initially both components were [[G-type main-sequence star]]s separated by {{convert|323|solar radius|AU|disp=number}} AU. The primary had a mass of {{val|u=solar mass|1.00|0.03}}, while the secondary had {{val|u=solar mass|1.05|0.02}}. <ref name=Fuhrmann2017/>

The stars then started to evolve, becoming [[red giant]]s. [[Mass transfer]] between components started to happen. The end product was the secondary becoming the current white dwarf with half of its original mass, and the primary gaining {{solar mass|0.55}} and becoming a F-type star.<ref name=Fuhrmann2017/>

Within 500 million years, the primary will evolve and 49 Librae may become a double white-dwarf system. However, if the secondary accrete sufficient mass during the process, the system may instead undergo a [[Type Ia supernova]].<ref name=Fuhrmann2017/>

==See also== * [[List of supernova candidates]]

==References== {{Reflist|refs=

<ref name="Willmarth2016">{{citation |last1=Willmarth |first1=Daryl W. |title=Spectroscopic Orbits for 15 Late-type Stars |date=August 2016 |journal=The Astronomical Journal |volume=152 |issue=2 |pages=13 |postscript=. |url=https://dipot.ulb.ac.be/dspace/bitstream/2013/236718/3/Willmarth_2016_AJ_152_46.pdf |bibcode=2016AJ....152...46W |doi=10.3847/0004-6256/152/2/46 |s2cid=53648490 |id=46 |display-authors=1 |last2=Fekel |first2=Francis C. |last3=Abt |first3=Helmut A. |last4=Pourbaix |first4=Dimitri |doi-access=free}}</ref>

<ref name="bayer">{{cite book |last1=Bayer |first1=Johann |url=https://books.google.com/books?id=5NrCIF5mnysC&dq=bayer+uranometria&pg=IA1 |title=Uranometria |last2=Mair |first2=Alexander |date=1603 |publisher=Excvdit Christophorvs Mangvs |page= |language=la |access-date=2025-11-10}}</ref>

<ref name="startales">{{cite web |last=Ridpath |first=Ian |author-link=Ian Ridpath |title=Scorpius |url=http://www.ianridpath.com/startales/scorpius.html |access-date=2025-09-10 |website=Star Tales}}</ref>

<ref name="kaler-sco">{{Citation |title=Chi and Psi Scorpii |website=stars.astro.illinois.edu |postscript=. |url=http://stars.astro.illinois.edu/sow/chisco.html |access-date=2025-07-13}}</ref>

<ref name="aaa475_2_519">{{citation |last1=Nordström |first1=B. |title=The Geneva-Copenhagen survey of the Solar neighbourhood. II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk |date=November 2007 |journal=Astronomy & Astrophysics |volume=475 |issue=2 |pages=519–537 |postscript=. |arxiv=0707.1891 |bibcode=2007A&A...475..519H |doi=10.1051/0004-6361:20077221 |s2cid=119054949 |display-authors=1 |last2=Andersen |first2=J. |last3=Holmberg |first3=J.}}</ref>

<ref name="aaass34_1">{{citation |last=Nicolet |first=B. |title=Photoelectric photometric Catalogue of homogeneous measurements in the UBV System |date=October 1978 |journal=Astronomy and Astrophysics Supplement Series |volume=34 |pages=1–49 |postscript=. |bibcode=1978A&AS...34....1N}}</ref>

<ref name="apjs180_1_117">{{citation |last1=Abt |first1=Helmut A. |title=MK Classifications of Spectroscopic Binaries |date=January 2009 |journal=The Astrophysical Journal Supplement |volume=180 |issue=1 |pages=117–118 |postscript=. |bibcode=2009ApJS..180..117A |doi=10.1088/0067-0049/180/1/117 |s2cid=122811461}}</ref>

<ref name="SIMBAD">{{cite simbad|title=49 Lib|access-date=2013-11-06}}</ref>

<ref name="Fuhrmann2017">{{citation |last1=Fuhrmann |first1=K. |title=Bright Times for an Ancient Star |date=January 2, 2017 |journal=The Astrophysical Journal |volume=834 |issue=2 |pages=114 |postscript=. |language=en |bibcode=2017ApJ...834..114F |doi=10.3847/1538-4357/834/2/114 |s2cid=125888005 |last2=Chini |first2=R. |doi-access=free}}</ref>

<ref name="Lazio2010">{{citation |last1=Lazio |first1=T. Joseph W. |title=A Blind Search for Magnetospheric Emissions from Planetary Companions to Nearby Solar-Type Stars |date=January 2010 |journal=The Astronomical Journal |volume=139 |issue=1 |pages=96–101 |postscript=. |arxiv=0910.3938 |bibcode=2010AJ....139...96L |doi=10.1088/0004-6256/139/1/96 |s2cid=118537554 |display-authors=1 |last2=Carmichael |first2=S. |last3=Clark |first3=J. |last4=Elkins |first4=E. |last5=Gudmundsen |first5=P. |last6=Mott |first6=Z. |last7=Szwajkowski |first7=M. |last8=Hennig |first8=L. A.}}</ref>

}}

{{Stars of Libra}} {{Sky|16|00|19.594|-|16|32|00.22}}

[[Category:F-type main-sequence stars]] [[Category:Spectroscopic binaries]]  [[Category:Libra (constellation)]] [[Category:Durchmusterung objects]] [[Category:Flamsteed objects|Librae, 49]] [[Category:Gliese and GJ objects|3931]] [[Category:Henry Draper Catalogue objects|143333]] [[Category:Hipparcos objects|078400]] [[Category:Bright Star Catalogue objects|5954]] [[Category:Population II stars]]