Bellatrix

Gamma Orionis

Bellatrix is located to the upper right of center.
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
γ Orionis, Bellatrix, Amazon Star, warrioress, 24 Ori, Al Najid, HR 1790, BD +06°919, HD 35468, SAO 112740, FK5 201, HIP 25336, TD1 4558.

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 to compare 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.

References

• HR 1790

Interpretation of Gamma Orionis (left), Algol B (right), the Sun (center), and other objects, to scale

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