Iota Eridani

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ι Eridani
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Eridanus
Right ascension  02h 40m 40.03501s[1]
Declination −39° 51′ 19.3541″[1]
Apparent magnitude (V) 4.11[2]
Spectral type K0 III[3]
U−B color index +0.74[2]
B−V color index +1.02[2]
Radial velocity (Rv)−9.30±0.70[4] km/s
Proper motion (μ) RA: +135.92[1] mas/yr
Dec.: −27.53[1] mas/yr
Parallax (π)21.65 ± 0.18[1] mas
Distance151 ± 1 ly
(46.2 ± 0.4 pc)
Absolute magnitude (MV)0.877[5]
Mass1.42[2] M
Radius11[6] R
Luminosity57.5[2] L
Surface gravity (log g)2.60±0.10[7] cgs
Temperature4,683±35[2] K
Metallicity [Fe/H]−0.33±0.10[7] dex
Age4.12[2] Gyr
Other designations
ι Eri, CD−40° 689, FK5 1075, HD 16815, HIP 12486, HR 794, SAO 215999.[8]
Database references

Iota Eridani (ι Eri) is a solitary star in the constellation Eridanus. It is visible to the naked eye with an apparent magnitude of 4.11.[2] With an annual parallax shift of 0.02165 arcseconds,[1] it lies at an estimated distance of about 151 light years.

This is a evolved red clump[5] giant star with a stellar classification of K0 III.[3] The measured angular diameter, after correcting for limb darkening, is 2.18±0.02 mas.[9] At an estimated distance of the star, this yields a physical size of around 11 times the radius of the Sun.[6] It has 1.42 times the mass of the Sun and radiates 57.5 times the solar luminosity from its outer atmosphere at an effective temperature of 4,683 K.[2] It is around four billion years old.[2]


  1. ^ a b c d e f 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 e f g h i j Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), arXiv:1507.01466, Bibcode:1966CoLPL...4...99J.
  3. ^ a b Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 2, Ann Arbor: Dept. of Astronomy, University of Michigan,
  4. ^ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
  5. ^ a b Liu, Y. J.; et al. (2007). "The abundances of nearby red clump giants". Monthly Notices of the Royal Astronomical Society. 382 (2): 553–66. Bibcode:2007MNRAS.382..553L. doi:10.1111/j.1365-2966.2007.11852.x.
  6. ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
  7. ^ a b Alves, S.; et al. (April 2015), "Determination of the spectroscopic stellar parameters for 257 field giant stars", Monthly Notices of the Royal Astronomical Society, 448 (3): 2749–2765, arXiv:1503.02556, Bibcode:2015MNRAS.448.2749A, doi:10.1093/mnras/stv189.
  8. ^ "iot Eri". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-10-29.
  9. ^ Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431: 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.