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
Distance 110 ± 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
Mass 1.85[7] M
Radius 10.3[7] R
Luminosity 10.3[8] L
Surface gravity (log g) 4.05[7] cgs
Temperature 7,575[7] K
Metallicity [Fe/H] 0.04[7] dex
Rotational velocity (v sin i) 82[5] km/s
Age 800[9] Myr
Other designations
Zibal, ζ Eri, 13 Eri, FK5 1091, HD 20320, HIP 15197, HR 984, SAO 130387, BD−09° 624[10]
Database references

ζ Eridani (Latinised as Zeta Eridani, abbreviated to ζ Eri or Zeta Eri) also named Zibal,[11] is a 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. The distance to this star, as determined via parallax measurements, is around 110 light years.

This is a single-lined[12] 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.[13]


ζ Eridani (Latinised to Zeta Eridani) is the star's Bayer designation.

It bore the traditional name of Zibal. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[14] to catalogue and standardize proper names for stars. The WGSN approved the name Zibal for this star on 12 September 2016 and it is now so entered in the IAU Catalog of Star Names.[11]


  1. ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752Freely accessible, 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, Bibcode:2006AJ....132..161G, arXiv:astro-ph/0603770Freely accessible, 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, 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, Bibcode:2014ApJ...792...65P, arXiv:1407.4579Freely accessible, 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, Bibcode:2012MNRAS.427..343M, arXiv:1208.2037Freely accessible, 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, Bibcode:2012AJ....143..135V, arXiv:1203.1966Freely accessible, doi:10.1088/0004-6256/143/6/135. 
  10. ^ "zet Eri – Spectroscopic binary", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-10-10. 
  11. ^ a b Mamajek, Eric, IAU Catalog of Star Names, International Astronomical Union, Division C Working Group on Star Names, retrieved 28 July 2016 
  12. ^ 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. 
  13. ^ Rhee, Joseph H.; et al. (May 2007), "Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs", The Astrophysical Journal, 660 (2): 1556–1571, Bibcode:2007ApJ...660.1556R, arXiv:astro-ph/0609555Freely accessible, doi:10.1086/509912. 
  14. ^ IAU Division C Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016. 

External links[edit]

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