49 Orionis
Orion constellation map.svg
Red circle.svg
Location of 49 Orionis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Orion
Right ascension 05h 38m 53.08332s[1]
Declination −07° 12′ 46.1667″[1]
Apparent magnitude (V) 4.80[2]
Evolutionary stage main sequence
Spectral type A4Vn[3]
U−B color index +0.11[2]
B−V color index +0.13[2]
Radial velocity (Rv)−5.30[4] km/s
Proper motion (μ) RA: −15.562[1] mas/yr
Dec.: −50.613[1] mas/yr
Parallax (π)23.1346 ± 0.2801 mas[1]
Distance141 ± 2 ly
(43.2 ± 0.5 pc)
Absolute magnitude (MV)1.52[5]
Mass1.78[6] M
Radius2.0[7] R
Luminosity22[8] L
Surface gravity (log g)4.06[6] cgs
Temperature8,416±286[6] K
Rotational velocity (v sin i)186[8] km/s
Age284[6] Myr
Other designations
d Ori, 49 Ori, BD−07°1142, GC 7039, GJ 9187, HD 37507, HIP 26563, HR 1937, SAO 132411[9]
Database references

49 Orionis is a single[10] star in the equatorial constellation of Orion. It has the Bayer designation d Orionis, while 49 Orionis is the Flamsteed designation. This object is visible to the naked eye as a faint, white-hued star with an apparent visual magnitude of 4.80.[2] It is located 141 light years away from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −5 km/s.[4]

49 Orionis (center)
49 Orionis (center)

In the past 49 Orionis was reported as a spectroscopic binary and an orbit was computed with a period of 445.74 days and an eccentricity of 0.549.[11] But it was later determined to be single.[10]

This object is an A-type main-sequence star with a stellar classification of A4Vn,[3] where the 'n' suffix indicates broadened "nebulous" lines caused by rapid rotation. It is around 284[6] million years old with a projected rotational velocity of 186 km/s.[8] This spin is giving the star an oblate shape with an equatorial bulge that is an estimated 8% larger than the polar radius.[12] The star has 1.8[6] times the mass of the Sun and double[7] the Sun's radius. It is radiating 22[8] times the Sun's luminosity from its photosphere at an effective temperature of 8,416 K.[6]


  1. ^ a b c d e f Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  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 Gray, R. O.; Garrison, R. F. (July 1989). "The Late A-Type Stars: Refined MK Classification, Confrontation with Stroemgren Photometry, and the Effects of Rotation". Astrophysical Journal Supplement. 70: 623. Bibcode:1989ApJS...70..623G. doi:10.1086/191349.
  4. ^ a b 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. ^ 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. S2CID 119257644. Vizier catalog entry
  6. ^ a b c d e f g David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146, S2CID 33401607.
  7. ^ a b Allende Prieto, C.; Lambert, D. L. (1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: Masses, radii and effective temperatures". Astronomy and Astrophysics. 352: 555–562. arXiv:astro-ph/9911002. Bibcode:1999A&A...352..555A. Vizier catalog entry
  8. ^ a b c d Zorec, J.; Royer, F. (2012). "Rotational velocities of A-type stars". Astronomy & Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691. S2CID 55586789. Vizier catalog entry
  9. ^ "49 Ori". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-07-29.
  10. ^ a b De Rosa, R. J.; et al. (2014). "The VAST Survey - III. The multiplicity of A-type stars within 75 pc". Monthly Notices of the Royal Astronomical Society. 437 (2): 1216. arXiv:1311.7141. Bibcode:2014MNRAS.437.1216D. doi:10.1093/mnras/stt1932. S2CID 88503488.
  11. ^ Abt, Helmut A. (June 1965). "The Frequency of Binaries among Normal A-Type Stars". Astrophysical Journal Supplement. 11: 429. Bibcode:1965ApJS...11..429A. doi:10.1086/190120.
  12. ^ Belle, G. T. (2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2, S2CID 119273474.