Delta Librae

δ Librae

File:DeltaLibLightCurve.png A light curve for Delta Librae, adapted from Shobbrook (2005)
Observation data Epoch J2000      Equinox J2000
Constellation	Libra
Right ascension	Template:RA
Declination	Template:DEC
Apparent magnitude (V)	4.93
Characteristics
Spectral type	B9.5V
U−B Template:Engvar	−0.10
B−V Template:Engvar	+0.00
Variable type	Algol eclipsing
Astrometry
Radial velocity (Rv)	Template:Val km/s
Proper motion (μ)	RA: −63.051 mas/yr Dec.: −6.024 mas/yr
Parallax (π)	9.2824±0.4725 mas
Distance	Template:Rnd ± Template:Rnd ly (Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)	+0.15
Orbit
Period (P)	2.3273543 days
Semi-major axis (a)	Template:Val
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	Template:Val Template:Solar mass
Radius	Template:Val Template:Solar radius
Luminosity	Template:Val Template:Solar luminosity
Temperature	Template:Val K
Age	0.5 Gyr
δ Lib B
Mass	Template:Val Template:Solar mass
Radius	Template:Val Template:Solar radius
Luminosity	Template:Val Template:Solar luminosity
Temperature	Template:Val K
Metallicity [Fe/H]	{{{metal_fe2}}} dex
Other designations
δ Lib, Zuben Elakribi, 19 Librae, BD−07°3938, HD 132742, HIP 73473, HR 5586, SAO 140270
Database references
SIMBAD	data

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").

δ Librae is approximately 350 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 4.91 to 5.90. The secondary is filling its Roche lobe and there is evidence of large-scale mass transfer in the past, with the secondary being more evolved than the primary despite now being less massive.

Along with λ Tauri, it was one of the first stars on which rotational line broadening was observed, by Frank Schlesinger in 1911.