Last modified on March 27, 2019, at 23:13


Observational Data
Designation Gamma Orionis
24 Orionis
Right ascension 05h 25m 07.8633s[1]
Declination +06° 20′ 58.93.18″[1]
Constellation Orion
Magnitude Apparent Mag: +1.64[1]
Absolute Mag: -2.80[2]
Distance from Earth 252.45 ly[2]
Radial velocity 18.2±0.9 km/s[1]
Proper motion RA: -8.11 mas/yr[1]
Dec.: -12.11 mas/yr[1]
Parallax 12.92±0.52[1]

Bellatrix (Gamma Orionis, 24 Orionis, sometimes called the Amazon star) is a giant star in the constellation of Orion, the hunter.[2] Given its Bayer designation of Gamma, it is the third brightest star in Orion and the 27th brightest star in the nigh sky.[3] The name Bellatrix means "female warrior" and may come either a latin translation of the Arabic title al-najid meaning "the conqueor" or possibly a modification of an alternate name for the contellation of Orion.[4] it is one of the four stars used in celestial navigation, .[5]

Bellatrix is a hot, luminous blue star and is also an eruptive variable star.[3] These changes in the star's output are due to violent processes such as solar flares.[6] It's magnitude only varies slightly from +1.64 to a peak of +1.59, though since it only varies due eruptive events, it averages out to +1.64.[3] The star has a spectral type of B2 III and is one of the hottest stars visible to the naked eye; it has a temperature of 18,900 kelvin.[2] The star used to be used as a standard candle but this stopped after its variable nature was discovered.

The original Hipparcos data from 1997 listed Bellatrix as lying 243.04 light years from Earth.[2] However the more recent 2007 release suggests it is slightly further away at 252.45 light years. The star is fairly large, with a mass 8-9 that of the Sun and a radius 3.18 times greater. Being larger, it emits around 6,400 times as much energy as the Sun.[3]

On July 11, 2005 the occultation of Bellatrix by Enceladus (one of Saturn's many moons) was used to investigate Enceladus' atmosphere.[7] It revealed the atmosphere is not global in scope, but is probably local to the south polar region, where most of the venting takes place.


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Gamma Orionis from the SIMBAD Astronomical Database
  2. 2.0 2.1 2.2 2.3 2.4 Bellatrix, Gamma Orionis, 24 Orionis, HD35468, HIP25336, HR1790. Retrieved on 2018-12-28.
  3. 3.0 3.1 3.2 3.3 Orion Constellation. Retrieved on 2018-12-28.
  4. Star Names And Designations. Retrieved on 2018-12-28.
  5. Bellatrix – Star Facts. Retrieved on 2018-12-28.
  6. SuperWASP Observations of Variable Stars. Retrieved on 2018-12-28.
  7. "Enceladus Atmosphere Not Global." JPL, NASA, August 30, 2005. Accessed June 17, 2008.