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.[11] With μ Virginis it forms one of the Akkadian lunar mansions Mulu-izi[12](meaning "Man-of-fire"[13]).
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Libra |
| Right ascension | 15h 00m 58.34830s[2] |
| Declination | −08° 31′ 08.2104″[2] |
| Apparent magnitude (V) | 4.93[3] |
| Characteristics | |
| Spectral type | B9.5V[4] |
| U−B color index | –0.10[5] |
| B−V color index | +0.00[5] |
| Variable type | Eclipsing binary of Algol type (EA/SD)[6] |
| Astrometry | |
| Radial velocity (Rv) | −38.7±2[7] km/s |
| Proper motion (μ) | RA: −63.051[2] mas/yr Dec.: −6.024[2] mas/yr |
| Parallax (π) | 9.2824 ± 0.4725 mas[2] |
| Distance | 350 ± 20 ly (108 ± 5 pc) |
| Absolute magnitude (MV) | +0.15[8] |
| Orbit[9] | |
| Period (P) | 2.3274 d |
| Eccentricity (e) | 0.07 |
| Semi-amplitude (K1) (primary) | 76.6 km/s |
| Semi-amplitude (K2) (secondary) | 218.7 km/s |
| Details | |
| δ Lib A | |
| Mass | 4.9±0.2[9] M☉ |
| Radius | 3.94[10] R☉ |
| Luminosity | 86[8] L☉ |
| Temperature | 8800[10] K |
| Age | 0.5[10] Gyr |
| δ Lib B | |
| Mass | 1.7±0.2[9] M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
δ Librae 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[3] and is moving closer to the Sun with a radial velocity of −39 km/s.[7] This is an Algol-like eclipsing binary star system, with a period of 2.3274 days and an eccentricity of 0.07.[9] Its apparent magnitude varies from 4.91m to 5.9m.[14] 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.[9]
Along with λ Tauri, it was one of the first stars on which rotational line broadening[15] was observed, by Frank Schlesinger in 1911.