Editing Libra (constellation) (section)

==The constellation==
[[File:Libra constellation map.svg|thumb|Libra constellation map]]
[[File:NGC 5897GCL01a.jpg|right|thumb|NGC 5897]]
[[File:NGC5885 - SDSS DR14.jpg|right|thumb|NGC 5885]]
Libra is bordered by the head of [[Serpens]] to the north, Virgo to the northwest, Hydra to the southwest, the corner of [[Centaurus]] to the southwest, Lupus to the south, [[Scorpius]] to the east and  [[Ophiuchus]] to the northeast. Covering 538.1&nbsp;square degrees and 1.304% of the night sky, it ranks 29th of the 88 constellations in size.<ref name=tirionconst>{{cite web| url=http://www.ianridpath.com/constellations2.html | title=Constellations: Lacerta–Vulpecula | work= Star Tales |author=Ridpath, Ian|publisher=Self-published | access-date= 3 April 2016| author-link=Ian Ridpath }}</ref> The three-letter abbreviation for the constellation, as adopted by the [[International Astronomical Union]] in 1922, is "Lib".<ref name="pa30_469">{{cite journal | last=Russell | first=Henry Norris |author-link=Henry Norris Russell | title=The New International Symbols for the Constellations | journal=[[Popular Astronomy (US magazine)|Popular Astronomy]] | volume=30 | page=469 | bibcode=1922PA.....30..469R | date=1922}}</ref> The official constellation boundaries, as set by [[Eugène Joseph Delporte|Eugène Delporte]] in 1930, are defined by a polygon of 12 segments (''illustrated in infobox''). In the [[equatorial coordinate system]], the [[right ascension]] coordinates of these borders lie between {{RA|14|22|08.08}} and {{RA|16|02|17.23}}, while the [[declination]] coordinates are between −0.47° and −30.00°.<ref name="boundary">{{Cite journal | title=Libra, Constellation Boundary | journal=The Constellations | publisher=[[International Astronomical Union]] | url=https://www.iau.org/public/themes/constellations/#lib| access-date=3 April 2016}}</ref> The whole constellation is visible to observers south of latitude 60°N.{{efn|1=While parts of the constellation technically rise above the horizon to observers between 60°N and 89°N, stars within a few degrees of the horizon are to all intents and purposes unobservable.<ref name=tirionconst/>}}

===Planetary systems===
Libra is home to the [[Gliese 581]] planetary system, which consists of the star Gliese 581 and three confirmed planets. This system gained attention in the late 2000s and early 2010s as the subject of some of the earliest claims of potentially habitable exoplanets,<ref>{{cite web|url=http://www.space.com/scienceastronomy/070424_hab_exoplanet.html|title=Major Discovery: New Planet Could Harbor Water and Life|website=space.com|date=24 April 2007 }}</ref><ref>{{Citation |last=Shiga |first=David |url=https://www.newscientist.com/article/dn19519-found-first-rocky-exoplanet-that-could-host-life.html |title=Found: first rocky exoplanet that could host life |publisher=[[New Scientist]]|date=September 29, 2010|access-date=September 30, 2010}}</ref> but it is now known that [[Gliese 581c]] is too hot to be potentially habitable, and the planet candidates [[Gliese 581d]] and [[Gliese 581g|g]] likely do not exist.<ref name="Robertson2014">{{cite journal |last1=Robertson |first1=Paul |author2-link=Suvrath Mahadevan |last2=Mahadevan |first2=Suvrath |last3=Endl |first3=Michael |last4=Roy |first4=Arpita |title=Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581 |journal=[[Science (journal)|Science]] |date=3 July 2014 |doi=10.1126/science.1253253 |pmid=24993348 |arxiv=1407.1049 |bibcode=2014Sci...345..440R |volume=345 |issue=6195 |pages=440–444 |citeseerx=10.1.1.767.2071 |s2cid=206556796 }}</ref> At the time of its discovery in 2009, [[Gliese 581e]] was the smallest mass [[exoplanet]] known orbiting a normal star.<ref name="mayor">{{cite journal |doi=10.1051/0004-6361/200912172 |bibcode=2009A&A...507..487M |journal=[[Astronomy and Astrophysics]] |volume=507 |issue=1 |year=2009 |pages=487–494 |last1=Mayor |first1=Michel |last2=Bonfils |first2=Xavier |last3=Forveille |first3=Thierry |last4=Delfosse |first4=Xavier |last5=Udry |first5=Stéphane |last6=Bertaux |first6=Jean-Loup |last7=Beust |first7=Hervé |last8=Bouchy |first8=François |last9=Lovis |first9=Christophe |last10=Pepe |first10=Francesco |last11=Perrier |first11=Christian |last12=Queloz |first12=Didier |last13=Santos |first13=Nuno C. |title=The HARPS search for southern extra-solar planets, XVIII. An Earth-mass planet in the GJ 581 planetary system |arxiv=0906.2780 |display-authors=3 |url=http://obswww.unige.ch/~udry/Gl581_preprint.pdf |s2cid=2983930 |url-status=dead |archive-url=https://web.archive.org/web/20090521052641/http://obswww.unige.ch/~udry/Gl581_preprint.pdf |archive-date=21 May 2009 }}</ref>

===Deep-sky objects===
Libra is home to one bright [[globular cluster]], [[NGC 5897]]. It is a loose cluster, 50,000 light-years from Earth; it is fairly large and has an integrated magnitude of 9.{{sfn|Ridpath|Tirion|2001|pp=172-173}} [[IC 1059]] is a [[galaxy]] in the constellation Libra.<ref>[http://cseligman.com/text/atlas/ic10a.htm#ic1059 csligman.com]</ref>