Hunting Orion: Gamma Orionis

Orion constellation is one of the brightest and best known constellations in the night sky. It lies on the celestial equator.

Orion has been known since ancient times. The constellation is also known as the Hunter, as it is associated with one in Greek mythology. It represents the mythical hunter Orion, who is often depicted in star maps as either facing the charge of Taurus, the bull, pursuing the Pleiades sisters, represented by the famous open cluster, or chasing after the hare (constellation Lepus) with his two hunting dogs, represented by the nearby constellations Canis Major and Canis Minor.

The constellation Orion contains two of the ten brightest stars in the sky – Rigel (Beta Orionis) and Betelgeuse (Alpha Orionis) – a number of famous nebulae – the Orion Nebula (Messier 42), De Mairan’s Nebula (Messier 43) and the Horsehead Nebula, among others – the well-known Trapezium Cluster, and one of the most prominent asterisms in the night sky – Orion’s Belt.

Gamma Orionis

Bellatrix, also designated Gamma Orionis (γ Orionis, abbreviated Gamma Ori, γ Ori), is the third-brightest star in the constellation of Orion, east of the red giant Alpha Orionis (Betelgeuse). Just between the first and second magnitude and slightly variable, it is about the 25th-brightest star in the night sky.  Bellatrix (“female warrior”) is a bluish-white giant star located 250 light years away in the constellation of Orion, where it marks the giant’s eastern “shoulder”. Its location close to the sky’s 10th brightest star, an enormous red giant called Betelgeuse, makes it one of the easiest stars to recognise, with Bellatrix best seen in December and January.   It is rapidly depleting its hydrogen fuel and has started to evolve off the main sequence on its way to becoming a true giant. It is expected to become an orange giant within a few million years, and has already developed a gaseous shell that signals the start of its transformation. At its present 8.4 solar masses, Bellatrix is also close to being considered a supernova candidate.

Quick Facts

Name:  Bellatrix

Object:  Star -- Blue Giant

Distance: 250 light years

Age: 20 million years

Surface Temp: 22,000K

Color: Blue-white

Mass: 8.6 x the mass of the Sun