Hunting Orion: Epsilon 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.
Epsilon Orionis
Alnilam (Epsilon Orionis) is a massive B-type blue supergiant star found in the Belt of Orion. With an average apparent visual magnitude of +1.69, it is the 4th brightest star in the constellation, the 29th brightest star in the entire night sky, and one of the 58 stars used in celestial navigation and identifying one’s relative positions. Alnilam is so hot and bright that it is illuminating the molecular cloud (NGC 1990) that surrounds it to produce a reflection nebula.
Like most other supergiant stars, Alnilam is losing mass at a very high rate. Studies have shown that the star’s 2,000 km/sec solar wind is blasting material away from it at the rate of two millionths of a solar mass every year, which in absolute terms, translates into a mass loss of about 20 million times that at which the Sun is losing its mass. Eventually, Alnilam is expected to become a red supergiant even more luminous than Betelgeuse in the constellation’s top left hand corner, before one day exploding as a supernova.
Quick Facts
Name: Alnilam
Object: Star -- Super Giant
Distance: 1000 light years
Brightness: 18,000 times greater than the Sun
Surface Temp: 50,000 F
Color: White-blue
Mass: 20 x the mass of the Sun
