Article · Wikipedia archive · Last revised Jun 18, 2026

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.

Last revised
Jun 18, 2026
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Wikipedia ↗
δ Librae
Location of δ Librae (circled in red)
Observation data
Epoch J2000      Equinox J2000
Constellation Libra
Right ascension 15h 00m 58.34830s1
Declination −08° 31′ 08.2104″1
Apparent magnitude (V) 4.932
Characteristics
Evolutionary stage main sequence3
Spectral type B9.5V4
U−B color index −0.105
B−V color index +0.005
Variable type Algol eclipsing6
Astrometry
Radial velocity (Rv)−38.7±27 km/s
Proper motion (μ) RA: −63.0511 mas/yr
Dec.: −6.0241 mas/yr
Parallax (π)9.2824±0.4725 mas1
Distance350 ± 20 ly
(108 ± 5 pc)
Absolute magnitude (MV)+0.158
Orbit
Period (P)2.3273543 days9
Semi-major axis (a)12.73±0.34 mas9
Eccentricity (e)0.0710
Semi-amplitude (K1)
(primary)		76.610 km/s
Semi-amplitude (K2)
(secondary)		218.710 km/s
Details9
δ Lib A
Mass3.78±0.13 M☉
Radius3.60±0.13 R☉
Luminosity155+11
−10 L☉
Temperature10,520±110 K
Age0.511 Gyr
δ Lib B
Mass1.50±0.04 M☉
Radius3.79±0.04 R☉
Luminosity9.1+1.4
−1.2 L☉
Temperature5,150±175 K
Other designations
δ Lib, Zuben Elakribi, 19 Librae, BD−07°3938, HD 132742, HIP 73473, HR 5586, SAO 140270
Database references
SIMBADdata

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.12 With μ Virginis it forms one of the Akkadian lunar mansions Mulu-izi13 (meaning "Man-of-fire").14

A light curve for Delta Librae, adapted from Shobbrook (2005)15 source ↗

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 4.932 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 0.07.10 Its apparent magnitude varies from 4.91 to 5.90.16 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.10

Along with λ Tauri, it was one of the first stars on which rotational line broadening was observed, by Frank Schlesinger in 1911.17

References

References

  1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  3. Zorec, J.; Royer, F. (2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy and Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691.
  4. Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars, Vol. 5". Michigan Spectral Survey. 5. Bibcode:1999MSS...C05....0H.
  5. Johnson, H. L. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99. Bibcode:1966CoLPL...4...99J.
  6. "Del Lib". The International Variable Star Index. AAVSO – American Association of Variable Star Observers. Retrieved 27 September 2017.
  7. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Carnegie Institute Washington D.C. Publication. Bibcode:1953GCRV..C......0W.
  8. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
  9. Malkov, Oleg Yu (2020-02-01). "Semidetached double-lined eclipsing binaries: Stellar parameters and rare classes". Monthly Notices of the Royal Astronomical Society. 491 (4): 5489–5497. Bibcode:2020MNRAS.491.5489M. doi:10.1093/mnras/stz3363. ISSN 0035-8711.
  10. Tomkin, J. (April 1978). "Secondaries of eclipsing binaries. I. Detection of the secondary of Delta Librae". Astrophysical Journal. 221: 608–615. Bibcode:1978ApJ...221..608T. doi:10.1086/156064.
  11. Rhee, Joseph H.; Song, Inseok; Zuckerman, B.; McElwain, Michael (2007). "Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs". The Astrophysical Journal. 660 (2): 1556–1571. arXiv:astro-ph/0609555. Bibcode:2007ApJ...660.1556R. doi:10.1086/509912. S2CID 11879505.
  12. Becvar, Antonin (1964). Atlas coeli II - Katalog 1950.0. Bibcode:1964ack..book.....B.
  13. Allen, R. H. (1963). Star Names: Their Lore and Meaning (rep. ed.). New York, NY: Dover Publications Inc. pp. 277, 473.
  14. Brown Jr., R. (1891). "Remarks on the Euphratean Astronomical Names of the Signs of the Zodiac". Proceedings of the Society of Biblical Archaeology. 13: 194.
  15. Shobbrook, R. R. (December 2005). "Photometry of 20 eclipsing and ellipsoidal binary systems". The Journal of Astronomical Data. 11: 7. Bibcode:2005JAD....11....7S.
  16. Samus, N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (2017). "General Catalogue of Variable Stars". Astronomy Reports. GCVS 5.1. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869. Retrieved 2018-01-07.
  17. Schlesinger, F. (1909). "Rotation of Stars about their Axes". Monthly Notices of the Royal Astronomical Society. 71 (9): 719. Bibcode:1911MNRAS..71..719S. doi:10.1093/mnras/71.9.719.