42 Orionis

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42 Orionis
Orion constellation map.svg
Map pointer.svg

Location of 42 Orionis (marked red)
Observation data
Epoch J2000      Equinox J2000
Constellation Orion
Right ascension 05h 35m 23.16427s[1]
Declination −4° 50′ 18.0881″[1]
Apparent magnitude (V) 4.59[2]
Spectral type B1V[3]
U−B color index -0.94[2]
B−V color index -0.19[2]
Radial velocity (Rv) +28.40[4] km/s
Proper motion (μ) RA: +4.52[1] mas/yr
Dec.: -7.11[1] mas/yr
Parallax (π) 3.69 ± 1.20[1] mas
Distance approx. 900 ly
(approx. 270 pc)
Mass 12.0[5] M
Temperature 25,400[6] K
Rotational velocity (v sin i) 20[7] km/s
Other designations
c Orionis, BD-04°1185, CCDM J05354-0450AB, GC 6934, HIP 26237, HR 1892, HD 37018, NSV 2318, SAO 132320, WDS J05354-0450AB
Database references
42 Ori is the bright star at the centre of NGC 1977. (Mount Lemmon SkyCenter Schulman Telescope courtesy Adam Block

42 Orionis is a class B1V[3] (blue main-sequence) star in the constellation Orion. Its apparent magnitude is 4.59[2] and it is approximately 900 light years away based on parallax.[1]

The primary star, Aa, has one spectroscopic companion Ab of magnitude 6.3 and separation 0.16", and a more distant companion B of 7.5 magnitude at 1.6" separation.[8][9]

c Orionis is surrounded by NGC 1977 one of a smaller fainter group of named nebulae just north of the Orion Nebula. c Ori is the star which excites and illuminates NGC 1977.


  1. ^ a b c d e f Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. Bibcode:2007A&A...474..653V. arXiv:0708.1752Freely accessible. doi:10.1051/0004-6361:20078357.  Vizier catalog entry
  2. ^ a b c d Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D. 
  3. ^ a b Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally published in: 1964BS....C......0H. 5050. Bibcode:1995yCat.5050....0H. 
  4. ^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. 
  5. ^ Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (2011). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun". Monthly Notices of the Royal Astronomical Society. 410: 190. Bibcode:2011MNRAS.410..190T. arXiv:1007.4883Freely accessible. doi:10.1111/j.1365-2966.2010.17434.x.  Vizier catalog entry
  6. ^ Hohle, M.M.; Neuhäuser, R.; Schutz, B.F. (2010). "Masses and luminosities of O- and B-type stars and red supergiants". Astronomische Nachrichten. 331 (4): 349. Bibcode:2010AN....331..349H. arXiv:1003.2335Freely accessible. doi:10.1002/asna.200911355.  Vizier catalog entry
  7. ^ Abt, Helmut A.; Levato, Hugo; Grosso, Monica (2002). "Rotational Velocities of B Stars". The Astrophysical Journal. 573: 359. Bibcode:2002ApJ...573..359A. doi:10.1086/340590. 
  8. ^ Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.  Vizier catalog entry
  9. ^ Tokovinin, Andrei; Mason, Brian D.; Hartkopf, William I.; Mendez, Rene A.; Horch, Elliott P. (2015). "Speckle Interferometry at Soar in 2014". The Astronomical Journal. 150 (2): 50. Bibcode:2015AJ....150...50T. doi:10.1088/0004-6256/150/2/50.