Zeta Eridani

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ζ Eridani
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Eridanus
Right ascension  03h 15m 50.02656s[1]
Declination −08° 49′ 11.0220″[1]
Apparent magnitude (V) 4.80[2]
Spectral type kA4hA9mA9V[3]
U−B color index +0.07[2]
B−V color index +0.24[2]
Radial velocity (Rv)−5.8±4.2[4] km/s
Proper motion (μ) RA: −0.35[1] mas/yr
Dec.: +46.10[1] mas/yr
Parallax (π)29.72 ± 0.29[1] mas
Distance110 ± 1 ly
(33.6 ± 0.3 pc)
Absolute magnitude (MV)1.97[5]
Period (P)17.9297±0.0039 d
Eccentricity (e)0.14±0.03
Periastron epoch (T)43,051.07±0.83 JD
Argument of periastron (ω)
Semi-amplitude (K1)
21.5±0.6 km/s
Mass1.85[7] M
Radius10.3[7] R
Luminosity10.3[8] L
Surface gravity (log g)4.05[7] cgs
Temperature7,575[7] K
Metallicity [Fe/H]0.04[7] dex
Rotational velocity (v sin i)82[5] km/s
Age800[9] Myr
Other designations
Zibal, ζ Eri, 13 Eri, FK5 1091, HD 20320, HIP 15197, HR 984, SAO 130387, BD−09° 624, WDS J03158-0849A[10]
Database references

Zeta Eridani (ζ Eridani, abbreviated Zeta Eri, ζ Eri) is a binary star in the constellation of Eridanus. With an apparent visual magnitude of 4.80,[2] it is visible to the naked eye on a clear dark night. Based on parallax measurements taken during the Hipparcos mission, it is approximately 110 light-years from the Sun.

Zeta Eridani is the primary or 'A' component of a multiple star system designated WDS J03158-0849 (the secondary or 'B' component is 14 Eridani).[11] Zeta Eridani's two components are therefore designated WDS J03158-0849 Aa and Ab. Aa is formally named Zibal /ˈzbəl/, the traditional name for the system.[12]


ζ Eridani (Latinised to Zeta Eridani) is the binary star's Bayer designation. WDS J03158-0849 A is its designation in the Washington Double Star Catalog. The designations of the two components as WDS J03158-0849 Aa and Ab derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[13]

Zeta Eridani bore the traditional name of Zibal. This is an old misreading of the Arabic رئل riʼal "ostrich chicks" (with the carrier letter for the glottal stop taken for a 'b', and ر 'r' taken for ز 'z'), originally applied to a number of stars near Beid and Keid.[14]

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[15] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[16] It approved the name Zibal for the component WDS J03158-0849 Aa on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[12]


Zeta Eridani is a single-lined[17] spectroscopic binary system with an orbital period of 17.9 days and an eccentricity of 0.14.[5] The primary is a mild Am star[5] with a stellar classification of kA4hA9mA9V.[3] This notation indicates this is a main-sequence star with the Ca-II K absorption line strength (k) of an A4 star, and the hydrogen lines (h) and metallic lines (m) of an A9 star. It has about 185% of the Sun's mass and 10.3 times the Sun's radius.[7] This is a relatively young star with an estimated age of 800 million years,[9] and it appears to have a moderately high rotation rate with a projected rotational velocity of 82 km/s.[5]

The system displays a statistically significant infrared excess at a wavelength of 70 μm. This suggests the presence of an orbiting debris disk. The temperature of the dust is 70 K, indicating an orbital distance of 31 AU. It has an estimated mass of about 0.26% of the Earth.[18]


  1. ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. ^ a b c d Mermilliod, J.-C. (1986), Compilation of Eggen's UBV data, transformed to UBV (unpublished), SIMBAD, Bibcode:1986EgUBV........0M.
  3. ^ a b Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637.
  4. ^ Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065.
  5. ^ a b c d e Iliev, I. Kh.; et al. (August 2006), "Abundance analysis of Am binaries and search for tidally driven abundance anomalies - II. HD861, HD18778, HD20320, HD29479, HD96528 and HD108651", Monthly Notices of the Royal Astronomical Society, 370 (2): 819–827, Bibcode:2006MNRAS.370..819I, doi:10.1111/j.1365-2966.2006.10513.x.
  6. ^ Abt, H. A.; Levy, S. G. (October 1985), "Improved study of metallic-line binaries", Astrophysical Journal Supplement Series, 59: 229–247, Bibcode:1985ApJS...59..229A, doi:10.1086/191070.
  7. ^ a b c d e f Pawellek, Nicole; et al. (September 2014), "Disk Radii and Grain Sizes in Herschel-resolved Debris Disks", The Astrophysical Journal, 792 (1): 19, arXiv:1407.4579, Bibcode:2014ApJ...792...65P, doi:10.1088/0004-637X/792/1/65, 65.
  8. ^ McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x.
  9. ^ a b Vican, Laura (June 2012), "Age Determination for 346 Nearby Stars in the Herschel DEBRIS Survey", The Astronomical Journal, 143 (6): 135, arXiv:1203.1966, Bibcode:2012AJ....143..135V, doi:10.1088/0004-6256/143/6/135.
  10. ^ "* zet Eri". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-10-10.
  11. ^ "Washington Double Star Catalog". United States Naval Observatory. Retrieved 23 February 2018.
  12. ^ a b "Naming Stars". IAU.org. Retrieved 16 December 2017.
  13. ^ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  14. ^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  15. ^ IAU Division C Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
  16. ^ "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
  17. ^ Abt, Helmut A. (January 2009), "MK Classifications of Spectroscopic Binaries", The Astrophysical Journal Supplement, 180 (1): 117–118, Bibcode:2009ApJS..180..117A, doi:10.1088/0067-0049/180/1/117.
  18. ^ Rhee, Joseph H.; et al. (May 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.

External links[edit]

  • Kaler, James B. (January 13, 2012), "Zibal", Stars, University of Illinois, retrieved 2016-10-11.