Eta Orionis

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Eta Orionis
Diagram showing star positions and boundaries of the Orion constellation and its surroundings
Cercle rouge 100%.svg

Location of ε Orionis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Orion
Right ascension 05h 24m 28.61672s[1]
Declination –02° 23′ 49.7311″[1]
Apparent magnitude (V) 3.42[2]
Spectral type B1 V + B3 V + B2 V[3]
U−B color index –0.90[2]
B−V color index −0.17[2]
Variable type Algol[4]
Radial velocity (Rv) +19.8[5] km/s
Proper motion (μ) RA: −0.71[1] mas/yr
Dec.: −3.46[1] mas/yr
Parallax (π) 3.34 ± 1.07[1] mas
Distance approx. 1,000 ly
(approx. 300 pc)
η Ori A
Mass 20[citation needed] M
Radius 10[citation needed] R
Luminosity 38,000[citation needed] L
Rotational velocity (v sin i) 60[6] km/s
η Ori B
Rotational velocity (v sin i) 45[6] km/s
Other designations
η Ori, 28 Ori, BD−02°1235, HD 35411, HIP 25281, HR 1788, SAO 132071.[7]
Database references

Eta Orionis (η Ori, η Orionis) is a star in the constellation Orion. Other names are Saiph[8] (Arabic for "sword"), Algjebbah[9] (Arabic for "scutum"), and Ensis[citation needed] (Latin for "sword", since the star is taken to represent Orion's sheathed weapon). Eta Orionis lies a little to the west of Orion's belt between Delta Orionis and Rigel, being closer to Delta Orionis than to Rigel. It lies at a distance of around 1,000 light years from Earth and is part of the Orion Arm.[citation needed]

This is a quadruple star system, of which three members can be resolved with a telescope. The primary component is an eclipsing binary star in a triple-star grouping. These stars have orbital periods of 8 days and 9.2 years. It includes a variable star with a pulsation period of around 8 hours. Three of the components are B-type main sequence stars with stellar classifications of B1 V, B3 V and B2 V.[3]

See also[edit]


  1. ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c Crawford, D. L.; Barnes, J. V.; Golson, J. C. (1971), "Four-color, H-beta, and UBV photometry for bright B-type stars in the northern hemisphere", The Astronomical Journal, 76: 1058, Bibcode:1971AJ.....76.1058C, doi:10.1086/111220 
  3. ^ a b Zasche, P.; et al. (August 2009), "A Catalog of Visual Double and Multiple Stars With Eclipsing Components", The Astronomical Journal, 138 (2): 664–679, arXiv:0907.5172Freely accessible, Bibcode:2009AJ....138..664Z, doi:10.1088/0004-6256/138/2/664 
  4. ^ AAVSO International Variable Star Index VSX (Watson+, 2006-2012) VizieR
  5. ^ Evans, D. S. (June 20–24, 1966). Batten, Alan Henry; Heard, John Frederick, eds. The Revision of the General Catalogue of Radial Velocities. University of Toronto: International Astronomical Union. Retrieved 2009-09-10. 
  6. ^ a b Levato, H. (January 1975), "Rotational velocities and spectral types for a sample of binary systems", Astronomy and Astrophysics Supplement Series, 19: 91–99, Bibcode:1975A&AS...19...91L 
  7. ^ "CCDM J05245-0223AB -- Double or multiple star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-02-09 
  8. ^ Allen, R. H. (1899). Star-Names and Their Meanings. New York: G. E. Stechert. p. 316. 
    Saiph was also used to indicate Kappa Orionis in the same constellation.
  9. ^ Moore, P. (1983). The Guinness Book of Astronomy: Facts and Feats (2nd ed.). Middlesex: Guinness Superlatives Limited. p. 230.