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 Virginis it forms one of the Akkadian lunar mansions Mulu-izi(meaning "Man-of-fire").
A light curve for Delta Librae, adapted from Shobbrook (2005) | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Libra |
| Right ascension | 15h 00m 58.34830s |
| Declination | −08° 31′ 08.2104″ |
| Apparent magnitude (V) | 4.93 |
| Characteristics | |
| Spectral type | B9.5V |
| U−B color index | –0.10 |
| B−V color index | +0.00 |
| Variable type | Eclipsing binary of Algol type (EA/SD) |
| Astrometry | |
| Radial velocity (Rv) | −38.7±2 km/s |
| Proper motion (μ) | RA: −63.051 mas/yr Dec.: −6.024 mas/yr |
| Parallax (π) | 9.2824 ± 0.4725 mas |
| Distance | 350 ± 20 ly (108 ± 5 pc) |
| Absolute magnitude (MV) | +0.15 |
| Orbit | |
| 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 M☉ |
| Radius | 3.94 R☉ |
| Luminosity | 86 L☉ |
| Temperature | 8800 K |
| Age | 0.5 Gyr |
| δ Lib B | |
| Mass | 1.7±0.2 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 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 Tauri, it was one of the first stars on which rotational line broadening was observed, by Frank Schlesinger in 1911.