Editing Alpha Librae (section)

== Properties ==
Alpha Librae is about {{Convert|77|ly|pc|abbr=off|lk=on}} from the [[Sun]]. 
The two brightest components of Alpha Librae form a [[double star]] moving together through space as [[common proper motion]] companions. They are separated in the sky by an [[angular size|angular distance]] of 231" (3'51"). The [[position angle]] of the companion is 314 degrees. The brighter of the two is a white star of [[stellar classification|spectral type]] A3, with an [[apparent magnitude]] of 2.8. Its companion is a type F4 star of apparent brightness 5.2. They are probably members of the [[Castor Moving Group]] of stars that have a similar motion through space and share a common origin some 200 million years ago.<ref name=aaa514_A98/>

=== Alpha<sup>2</sup> Librae ===
The brightest member, α<sup>2</sup> Librae, is itself a [[spectroscopic binary]] system. The components have similar masses (mass ratio of 0.92) but the primary has a rotational velocity three times higher than its companion, which could be caused by them having significantly misaligned spin axes or if the primary is a merger product.<ref name=waisberg>{{Cite journal |last1=Waisberg |first1=Idel |last2=Klein |first2=Ygal |last3=Katz |first3=Boaz |date=2023-08-23 |title=Hidden Companions to Intermediate-mass Stars. X. Solving for the Mass Ratio in the Spectroscopic Binary Zubenelgenubi = α <sup>2</sup> Librae* |journal=Research Notes of the AAS |volume=7 |issue=8 |pages=180 |doi=10.3847/2515-5172/acf28f |bibcode=2023RNAAS...7..180W |issn=2515-5172|doi-access=free }}</ref> 
=== Alpha<sup>1</sup> Librae ===
The second member, α<sup>1</sup> Librae, is separated from the primary system by around {{val|5400|ul=AU}}. It too is a spectroscopic binary with an orbital period of 5,870&nbsp;days and an [[angular separation]] of 0.383&nbsp;arcseconds; equal to about 10&nbsp;AU. 
=== KU Librae ===
The system may have a fifth component, the star KU Librae at a separation of 2.6°, thus forming a hierarchical quintuple star system. KU Lib shares a similar motion through space to the Alpha Librae system, but is separated from the other stars by about a [[parsec]]. It is sufficiently close to be gravitationally bound to the other members,<ref name=aaa514_A98/> but has a substantially different [[metallicity]], making it unlikely to be physically bound to the system.<ref name=multiplicity/>