Properties
Alpha Librae is located approximately 77 light years from the Sun. The two brightest components of Alpha Librae form a double star that share a similar motion through space, forming common proper motion companions. The brightest member, α2 Librae, is itself a spectroscopic binary system. The second member, α1 Librae, is separated from the primary system by around 5,400 AU. It too is a spectroscopic binary with an orbital period of 5,870 days and an angular separation of 0.383 arcseconds; equal to about 10 AU. 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. Still, it is sufficiently close to be gravitationally bound to the other members.
The two brightest members of Alpha Librae are separated in the sky by an 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 spectral type A3, with an apparent brightness 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.
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