Lambda Orionis
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| Observation data Epoch J2000 |
|
|---|---|
| Constellation (pronunciation) |
Orion |
| Right ascension | 05h35m08.28s |
| Declination | +09°56′02.96″ |
| Apparent magnitude (V) | 3.39 / 5.61 |
| Characteristics | |
| Spectral type | O8III / B0.5V |
| U-B color index | −1.03 / −0.77 |
| B-V color index | 0.18 / 0.04 |
| Variable type | none |
| Astrometry | |
| Radial velocity (Rv) | +33.5 km/s |
| Proper motion (μ) | RA: −2.1 mas/yr Dec.: −2.9 mas/yr |
| Parallax (π) | 3.09 ± 0.78 mas |
| Distance | approx. 1100 ly (approx. 320 pc) |
| Absolute magnitude (MV) | −4.25 / -1.94 |
| Other designations | |
| Database references | |
| SIMBAD | data |
Lambda Orionis (λ Ori / λ Orionis) is a star in the constellation Orion. It also has the traditional names Meissa or Heka. "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 λ Orionis and the name stuck. The original Arabic name for this star, "Al Hakah", the source for "Heka", means "a White Spot" and refers to the faint background light of the star[1] but is also perhaps indicative of Orion having been seen in early Arab astronomy as a black sheep with a white spot in the center.
Meissa is a blue spectral type O giant star and is part of the Collinder 69 star cluster. It has an apparent visible magnitude 3.39 and is one of the most luminous stars known.
Meissa is actually a binary star system. The fainter star is of magnitude 6 and is 4.4 seconds of arc away from the brighter. It is a hot blue-white dwarf of spectral type B0.5 V.
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