Omicron1 Eridani

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ο¹ Eridani
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Eridanus
Right ascension 04h 11m 51.93956s[1]
Declination −06° 50′ 15.2864″[1]
Apparent magnitude (V) 4.04[2]
Spectral type F0 III[3]
U−B color index +0.10[2]
B−V color index +0.32[2]
Variable type δ Scuti[4]
Proper motion (μ) RA: +10.76[1] mas/yr
Dec.: +81.92[1] mas/yr
Parallax (π)26.80 ± 0.32[1] mas
Distance122 ± 1 ly
(37.3 ± 0.4 pc)
Absolute magnitude (MV)+1.18[5]
Mass1.95[4] M
Radius3.7±0.1[4] R
Luminosity27[4] L
Surface gravity (log g)3.39[3] cgs
Temperature6,963[3] K
Metallicity [Fe/H]−0.01[3] dex
Rotational velocity (v sin i)108.1[6] km/s
Other designations
Beid, ο¹ Eri, 38 Eri, BD−07° 764, FK5 154, HD 26574, HIP 19587, HR 1298, SAO 131019[7]
Database references

Omicron¹ Eridani (ο¹ Eridani, abbreviated Omicron¹ Eri, ο¹ Eri), also named Beid,[8] is a variable star in the constellation of Eridanus. With an average apparent visual magnitude of 4.04,[2] it is visible to the naked eye on a clear, dark night. Based upon parallax measurements, it lies approximately 122 light-years from the Sun.


ο¹ Eridani (Latinised to Omicron¹ Eridani) is the star's Bayer designation.

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[9] to catalogue and standardize proper names for stars. The WGSN approved the name Beid for this star on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[8]

In Chinese, 九州殊口 (Jiǔ Zhōu Shū Kǒu), meaning Interpreters of Nine Dialects, refers to an asterism consisting of Omicron¹ Eridani, 39 Eridani, Xi Eridani, Nu Eridani, 56 Eridani and 55 Eridani.[10] Consequently, Omicron¹ Eridani itself is known as 九州殊口二 (Jiǔ Zhōu Shū Kǒu èr, English: the Second Star of Interpreters of Nine Dialects).[11]


Omicron¹ Eridani is an evolved F-type giant star with a stellar classification of F0 III.[3] It is a Delta Scuti variable star that undergoes non-radial pulsations,[4] with a variation of just 0.03 magnitude over a period of 0.0747 days.[12] The star is spinning rapidly with a projected rotational velocity of 108.1 km/s[6] and a rotation period of less than around 1.9 days.[4] This is creating an equatorial bulge that is 11% wider than the polar radius.[13] Omicron¹ Eridani has nearly double the mass of the Sun, 3.7 times the Sun's radius, and shines with 27 times the solar luminosity[4] from an outer atmosphere at an effective temperature of 6,963 K.[3]


  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 c d e f 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. ^ a b c d e f g Balona, Luis A. (October 2000), "The δ Scuti star 38 o1 Eri", Monthly Notices of the Royal Astronomical Society, 318 (1): 289–293, Bibcode:2000MNRAS.318..289B, doi:10.1046/j.1365-8711.2000.03776.x.
  5. ^ 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.
  6. ^ a b Schröder, C.; et al. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo" (PDF), Astronomy and Astrophysics, 493 (3): 1099–1107, Bibcode:2009A&A...493.1099S, doi:10.1051/0004-6361:200810377.
  7. ^ "* omi01 Eri". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-10-11.
  8. ^ a b "Naming Stars". Retrieved 16 December 2017.
  9. ^ IAU Division C Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
  10. ^ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  11. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2010-08-11 at the Wayback Machine., Hong Kong Space Museum. Accessed on line November 23, 2010.
  12. ^ Rodríguez, E.; et al. (June 2000), "A revised catalogue of δ Sct stars", Astronomy and Astrophysics Supplement, 144: 469–474, Bibcode:2000A&AS..144..469R, doi:10.1051/aas:2000221.
  13. ^ Van Belle, Gerard T. (2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20: 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2.

External links[edit]

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