{{short description|Star in the constellation Libra}} {{Starbox begin}} {{Starbox observe | epoch = J2000.0 | constell = [[Libra (constellation)|Libra]] | pronounce = | ra = {{RA|15|34|16.89835}}<ref name=GaiaDR2/> | dec = {{DEC|−10|03|05.07536}}<ref name=GaiaDR2/> | appmag_v = 4.97<ref name=Anderson2012/> }} {{Starbox character | type = | class = K3-III CN2<ref name=perkins1989/> | b-v = {{Val|1.302|0.056}}<ref name=Anderson2012/> | u-b = | variable = }} {{Starbox astrometry | radial_v = {{Val|−21.8|2.8}}<ref name=Anderson2012/> | prop_mo_ra = −16.872<ref name=GaiaDR2/> | prop_mo_dec = −17.820<ref name=GaiaDR2/> | parallax = 8.7152 | p_error = 0.2628 | parallax_footnote = <ref name=GaiaDR2/> | absmag_v = −0.37<ref name=Anderson2012/> }} {{Starbox detail | source = | mass = | radius = {{Val|25.9|0.4}}<ref name=GaiaDR2/> | gravity = 2.30<ref name=McWilliam1990/> | metal_fe = {{Val|−0.03|0.06}}<ref name=Anderson2012/> | luminosity = {{Val|213.6|7.3}}<ref name=GaiaDR2/> | temperature = {{Val|4332|34|fmt=commas}}<ref name=GaiaDR2/> | rotational_velocity = | age_gyr = }} {{Starbox catalog | names = {{odlist| F=42 Lib | CD=-23°12458 | FK5=3239 | GJ=9526 | HD=139663 | HIP=76742 | HR=5824 | SAO=183686 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = 42+Lib }} {{Starbox end}}
'''42 Librae''' is a single<ref name=Eggleton2008/> [[star]] located around 370<ref name=GaiaDR2/> [[light year]]s distant from the Sun in the southern [[zodiac]] [[constellation]] of [[Libra (constellation)|Libra]].<ref name=SIMBAD/> It is visible to the naked eye as a faint, orange-hued star with an [[apparent visual magnitude]] of 4.97.<ref name=Anderson2012/> This object is drifting closer to the Earth with a heliocentric [[radial velocity]] of −22 km/s.<ref name=Anderson2012/>
The [[Bayer designation]] Chi Librae has been associated with this star, despite [[Johann Bayer]] not marking it as such in his ''[[Uranometria]]''.<ref name=bayer/> [[Johann Elert Bode|Bode]] assigned the designation χ Librae to this star in his ''Uranographia''.<ref name=bode/> The designation is no longer in use.
This is an aging [[giant star]] with a [[stellar classification]] of K3-III CN2,<ref name=perkins1989/> where the suffix notation indicates this is a strong [[CN star]] with a high overabundance of [[cyano radical|cyanogen]] in its [[stellar spectrum|spectrum]]. Having exhausted the supply of hydrogen at its [[stellar core|core]], this star has expanded to 26 times the [[Sun's radius]].<ref name=GaiaDR2/> Within the [[margin of error]] it has near-solar abundances of iron,<ref name=Anderson2012/> suggesting a Sun–like [[metallicity]]. The star is radiating 214<ref name=GaiaDR2/> times the [[luminosity of the Sun]] from its swollen [[photosphere]] at an [[effective temperature]] of 4,332 K.<ref name=GaiaDR2/>
==References== <references>
<ref name=GaiaDR2>{{cite DR2|6238537823914049408}}</ref>
<ref name=SIMBAD>{{cite simbad | title=42 Lib | access-date=2019-07-17 }}</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="bode">{{cite book |last1=Bode |first1=Johann |url=https://www.google.co.uk/books/edition/Allgemeine_Beschreibung_und_Nachweisung/NUlRAAAAcAAJ?hl=en&gbpv=1&dq=bode&printsec=frontcover |title=Uranometria |date=1801 |publisher=Selbstverl. |page=57 |language=de |access-date=2026-01-21}}</ref>
<ref name=Anderson2012>{{citation | last1=Anderson | first1=E. | last2=Francis | first2=Ch. | title=XHIP: An extended hipparcos compilation | journal=Astronomy Letters | postscript=. | volume=38 | issue=5 | pages=331 | year=2012 | bibcode=2012AstL...38..331A | arxiv=1108.4971 | doi=10.1134/S1063773712050015 | s2cid=119257644 }}</ref>
<ref name=perkins1989>{{citation | last1=Keenan | first1=Philip C. | last2=McNeil | first2=Raymond C. | title=The Perkins catalog of revised MK types for the cooler stars | journal=Astrophysical Journal Supplement Series | volume=71 | pages=245 | year=1989 | postscript=. | bibcode=1989ApJS...71..245K | doi=10.1086/191373 }}</ref>
<ref name=Eggleton2008>{{citation | postscript=. | 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 | bibcode=2008MNRAS.389..869E | arxiv=0806.2878 | doi=10.1111/j.1365-2966.2008.13596.x | doi-access=free | s2cid=14878976 }}</ref>
<ref name=McWilliam1990>{{citation | postscript=. | last=McWilliam | first=Andrew | title=High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances | journal=Astrophysical Journal Supplement Series | volume=74 | pages=1075–1128 | date=December 1990 | doi=10.1086/191527 | bibcode=1990ApJS...74.1075M | doi-access=free}}</ref>
</references>
{{Stars of Libra}}
{{DEFAULTSORT:42 Librae}} [[Category:K-type giants]] [[Category:CN stars]] [[Category:Libra (constellation)]] [[Category:Durchmusterung objects]] [[Category:Flamsteed objects|Librae, 42]] [[Category:Gliese and GJ objects]] [[Category:Henry Draper Catalogue objects|139663]] [[Category:Hipparcos objects|076742]] [[Category:Bright Star Catalogue objects|5824]]