42 Orionis

42 Orionis
Location of 42 Orionis (marked red)
Observation data
Epoch J2000      Equinox ICRS
Constellation Orion
Right ascension 05h 35m 23.16427s[1]
Declination −04° 50′ 18.0881″[1]
Apparent magnitude (V) 4.59[2]
Characteristics
Spectral type B1V[3]
U−B color index −0.94[2]
B−V color index −0.19[2]
Astrometry
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 mas[1]
Distanceapprox. 900 ly
(approx. 270 pc)
Orbit[5]
Period (P)69.2 yr
Semi-major axis (a)0.146″
Eccentricity (e)0.23
Inclination (i)28.1°
Longitude of the node (Ω)125.4°
Periastron epoch (T)1986.4
Argument of periastron (ω)
(secondary)		84.7°
Details
Mass12.0[6] M☉
Radius7.0[7] R☉
Luminosity10,737[8] L☉
Surface gravity (log g)3.82[7] cgs
Temperature25,400[8] K
Rotational velocity (v sin i)20[9] km/s
Age2.6[6] Myr
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
SIMBADdata
42 Ori is the bright star at the centre of NGC 1977.

42 Orionis, also known as c Orionis or c Ori, is a triple star system 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.[10][11] Preliminary results published in 2026 give an orbtal period of 69.2 years, an eccentricity of 0.23 and an inclination of 28.1° for the inner companion.[5]

42 Orionis is surrounded by NGC 1977 one of a smaller fainter group of named nebulae just north of the Orion Nebula. 42 Ori is the star which excites and illuminates NGC 1977.

References

  1. 1 2 3 4 5 6 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. S2CID 18759600. Vizier catalog entry
  2. 1 2 3 4 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. ↑ 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): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
  5. 1 2 Mason, Brian D.; Hartkopf, William I. (March 2026). "Unreported ICCD Speckle Interferometry Measures of Double Stars". The Astronomical Journal. 171 (3): 149. Bibcode:2026AJ....171..149M. doi:10.3847/1538-3881/ae3748. ISSN 0004-6256.
  6. 1 2 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 (1): 190–200. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x. S2CID 118629873. Vizier catalog entry
  7. 1 2 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  8. 1 2 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. arXiv:1003.2335. Bibcode:2010AN....331..349H. doi:10.1002/asna.200911355. S2CID 111387483. Vizier catalog entry
  9. ↑ Abt, Helmut A.; Levato, Hugo; Grosso, Monica (2002). "Rotational Velocities of B Stars". The Astrophysical Journal. 573 (1): 359–365. Bibcode:2002ApJ...573..359A. doi:10.1086/340590.
  10. ↑ 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
  11. ↑ 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. arXiv:1506.05718. Bibcode:2015AJ....150...50T. doi:10.1088/0004-6256/150/2/50. S2CID 30737411.
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