Delta Librae
Delta Librae, Latinized from δ Librae, is a variable star in the constellation Libra. It has the traditional name Zuben Elakribi, a variant of the traditional name of Gamma Librae. With μ Vir it forms one of the Akkadian :ja:月宿#シュメール|lunar mansions Mulu-izi.
δ Lib is approximately 300 light years from the Earth and the primary, component A, belongs to the spectral class B9.5V, indicating it is a B-type main-sequence star. It is visible to the naked eye with an apparent visual magnitude of 4.93 and is moving closer to the Sun with a radial velocity of −39 km/s. This is an Algol-like eclipsing binary star system, with a period of 2.3274 days and an eccentricity of 0.07. Its apparent magnitude varies from 4.91m to 5.9m. The secondary is filling its roche lobe and there is evidence of large-scale mass transfer in the past, with the star being more evolved than the primary.
Along with λ Tau, it was one of the first stars on which
rotational line broadening was observed, by Frank Schlesinger in 1911.
