Gamma Orionis
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 Bellatrix is located to the upper right of center. |
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| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Orion |
| Right ascension | 05h 25m 07.9s |
| Declination | +06° 20' 59" |
| Apparent magnitude (V) | 1.64 |
| Characteristics | |
| Spectral type | B2 III |
| U-B color index | -0.87 |
| B-V color index | -0.22 |
| Variable type | Eruptive |
| Astrometry | |
| Radial velocity (Rv) | +18.2 km/s |
| Proper motion (μ) | RA: -8.75 mas/yr Dec.: -13.28 mas/yr |
| Parallax (π) | 13.42 ± 0.98 mas |
| Distance | 240 ± 20 ly (75 ± 5 pc) |
| Absolute magnitude (MV) | -2.72 |
| Details | |
| Mass | 8-9 M☉ |
| Radius | 5.7 R☉ |
| Luminosity | 4,000 L☉ |
| Temperature | 21,500 K |
| Metallicity | ? |
| Rotation | ? |
| Age | ? years |
| Other designations | |
Gamma Orionis (γ Ori / γ Orionis), or Bellatrix, is the third brightest star in the constellation Orion and the twenty-seventh brightest star in the nighttime sky.
The name Bellatrix is Latin for female warrior. It is also known as the Amazon Star or Gamma Orionis. It was once thought to belong to the physical association of stars that comprise much of the constellation of Orion. But this is no longer believed to be the case, as Gamma Orionis is much closer to us than the rest of the group.
Historically this star was used as a luminosity standard thatfecompare with other stars to check for variability. But it was later discovered that Bellatrix itself is an eruptive variable, changing in luminosity by a few percent over time. It ranges in magnitude from 1.59 to 1.64.
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