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Meissa A/B
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λ Orionis (Meissa) is the head of the constellation Orion.
Observation data
Epoch J2000      Equinox J2000
Constellation Orion
Right ascension 05h 35m 08.27761s[1]
Declination +09° 56′ 02.9611″[1]
Apparent magnitude (V) 3.54 / 5.61[2]
Spectral type O8 III + B0.5 V[2]
U−B color index –1.01 / –0.77[2]
B−V color index –0.21 / +0.04[2]
Radial velocity (Rv) +33.5 km/s
Dec.: –2.94[1] mas/yr
Parallax (π) 2.97 ± 0.55[1] mas
Distance approx. 1,100 ly
(approx. 340 pc)
Absolute magnitude (MV) –4.25 / -1.94
Meissa A
Mass 27.9 ± 3.3[3] M
Radius 10.0[4] R
Surface gravity (log g) 4.0[4] cgs
Temperature 35,046 ± 454[4] K
Age 3.0 ± 0.8[3] Myr
Other designations
λ Orionis, 39 Orionis, 101 G. Orionis, BD+09 879, HIP 26207, HR 1879, SAO 112921.
A: HD 36861, HR 1879.
B: HD 36862, HR 1880.
Database references

Meissa (Lambda Orionis, λ Ori) is a star in the constellation Orion. "Meissa" derives from the Arabic "Al-Maisan" which means "The Shining One". This term was used for Gamma Gemini (Alhena), but was somehow also mistakenly applied to Meissa and the name stuck. The original Arabic name for this star, "Al Hakah" (the source for another name for it, "Heka") refers to the Arabic lunar mansion that includes this star and the two of φ Ori (Al Haḳʽah, "a White Spot").[5]

In Chinese, 觜宿 (Zī Sù), meaning Turtle Beak (asterism), refers to an asterism consisting of Meissa and both of φ Ori[6] Consequently, Meissa itself is known as 觜宿一 (Zī Sù yī, English: the First Star of Turtle Beak.)[7]

Meissa is a giant star with a stellar classification of O8 III and an apparent visible magnitude 3.54.[2] It is an enormous star with about 28[3] times the mass of the Sun and 10 times the Sun's radius.[4] The outer atmosphere has an effective temperature of around 35,000 K,[4] giving it the characteristic blue glow of a hot O-type star.[8] Meissa is a soft X-ray source with a luminosity of 1032 erg s−1 and peak emission in the energy range of 0.2–0.3 keV, which suggests the X-rays are probably being generated by the stellar wind.[9]

This star is the dominant member of a 5-million-year-old star-forming region known as the λ-Orionis cluster,[10] or Collinder 69. The intense ultraviolet energy being radiated by this star is creating the Sh2-264[11] H II region in the neighboring volume of space, which in turn is surrounded by an expanding ring of cool gas that has an age of about 2–6 million years. The expansion of this gaseous ring may be explained by a former binary companion of Meissa that became a Type II supernova. Such an event would also explain the star's peculiar velocity with respect to the center of the expanding ring, as the explosion and resulting mass loss could have kicked Meissa out of the system. A potential candidate for the supernova remnant is the neutron star Geminga.[12] However, the last is unlikely given the distance between Geminga and the cluster.[13]

Meissa is actually a double star with a companion at an angular separation of 4.41 arcseconds along a position angle of 43.12° (as of 1937).[14] This fainter component is of magnitude 5.61 and it has a stellar classification of B0.5 V,[2] making it a B-type main sequence star. There is an outlying component, Meissa C, which is an F-type main sequence star with a classification of F8 V. This star in turn may have a very low mass companion that is probably a brown dwarf.[9]


  2. ^ a b c d e f Murdin, P.; Penston, M. V. (December 1977), "The Lambda Orionis association", Monthly Notices of the Royal Astronomical Society 181: 657–665, Bibcode:1977MNRAS.181..657M, doi:10.1093/mnras/181.4.657 
  5. ^ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York, NY: Dover Publications Inc, p. 318, ISBN 0486210790, retrieved 2011-07-16 
  6. ^ (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 9789867332257.
  9. ^ a b Franciosini, E.; Sacco, G. G. (June 2011), "XMM-Newton observations of the young open cluster around λ Orionis", Astronomy & Astrophysics 530: A150, arXiv:1104.3803, Bibcode:2011A&A...530A.150F, doi:10.1051/0004-6361/201015248 
  10. ^ Bouy, H. et al. (September 2009), "A deep look into the core of young clusters. II. λ-Orionis", Astronomy and Astrophysics 504 (1): 199–209, arXiv:0907.0322, Bibcode:2009A&A...504..199B, doi:10.1051/0004-6361/200912569 
  11. ^ Barrado Y Navascués, D. (December 2005), Hidalgo-Gámez, A. M.; González, J. J.; Espinosa, J. M. Rodríguez; Torres-Peimbert, S., eds., "II International GTC Workshop: Science with GTC 1st-light Instruments and the LMT", Revista Mexicana de Astronomía y Astrofísica (Serie de Conferencias) 24: 217–218, Bibcode:2005RMxAC..24..217B  |chapter= ignored (help)
  12. ^ Cunha, K.; Smith, V. V. (May 1996), "Is the expanding molecular cloud surrounding λ Orionis caused by a Supernova?", Astronomy and Astrophysics 309: 892–894, Bibcode:1996A&A...309..892C 
  13. ^ Pellizza, L. J. et al. (May 2005), "On the local birth place of Geminga", Astronomy and Astrophysics 435 (2): 625–630, arXiv:astro-ph/0502190, Bibcode:2005A&A...435..625P, doi:10.1051/0004-6361:20042377 
  14. ^ Scardia, M. (September 1983), "Micrometric measurements of binary stars (first list)", Astronomy and Astrophysics Supplement Series (in French) 53: 433–440, Bibcode:1983A&AS...53..433S