Orion Constellation
orion constellation
The constellation of Orion, one of the most familiar constellations in the night sky.
Orion Constellation Facts
  • Orion is visible in both the Northern and Southern hemispheres.
  • In the Northern hemisphere the constellation can be seen from late autumn to early spring.
  • In the Southern hemisphere Orion can be seen in the summer months, note that it will appear upside down.
  • The constellation mainly consists of bright blue supergiant stars, the most notable exception being the red supergiant Betelgeuse which lies on Orion's shoulder.
  • Betelgeuse is also the largest star in the constellation, it has 1,000 times the radius of the sun.
  • The brightest star in the constellation is Rigel, which is 40,000 times brighter than the sun and emits 100,000 times the energy.
  • The three stars which form a line through the middle of the constellation are known as Orion's Belt.
  • If you follow an imaginary line down through Orion's Belt it will take you to the brightest star in the night sky, Sirius, follow the line up in the southern hemisphere.

Orion Mythology

orion mythology
Representation of Orion from Greek mythology, holding a lion pelt in his left hand.
Orion is a character from Greek mythology, a giant hunter who was placed in the stars by Zeus upon his death. In the night sky Orion was perceived by ancient Greeks as defending himself against the nearby constellation of Taurus the bull.
In one version of the myth Orion was the son of Poseidon, the Greek God of the sea, from whom he inherited an ability to walk on water. Orion walked across the sea to the island of Chios where he attacked the daughter of the island ruler in a drunken rage. Orion was blinded by the ruler in an act of retaliation but was later healed by Helios, the Greek personification of the sun. Orion later became arrogant with his great hunting abilities and vowed to kill every creature on the planet. The Goddess of the Earth, Gaia, responded by sending a giant scorpion to destroy him. In the ensuing battle Orion was killed and both he and the scorpion were placed amongst the stars.

Main Stars in the Orion Constellation
orion constellation
The number next to each star is its apparent magnitude, its brightness from our point of view on Earth, the lower the number the brighter the star in the night sky.
Betelgeuse
A red supergiant star around 640 light years from Earth, Betelgeuse, also known as Alpha Orionis, has a radius 1,000 times larger than the sun and is expected to explode as a supernova in the next million years.
Meissa
A blue giant star with surface temperatures around 5 times hotter than our sun, Meissa is actually a pair of binary stars, its companion is similar in size and mass to the sun.
Bellatrix
A blue giant star around 250 light years from Earth, Bellatrix is 6 times larger than our sun and 8 times more massive, the star is also known as Gamma Orionis.
Alnitak
Alnitak is a triple star system around 736 light years from Earth, the primary star is a blue supergiant star with a radius around 20 times larger than the sun, Alnitak is also known as Zeta Orionis.
Alnilam
A blue supergiant star around 1,400 light years from Earth, Alnilam is 24 times larger than the sun and more than 250,000 times as luminous, the star is also known as Epsilon Orionis.
Mintaka
Also known as Delta Orionis, Mintaka is actually a pair of blue giant stars with the largest having 16 times the radius of the sun, both stars are around 100,000 times more luminous than the sun.
Saiph
A blue supergiant star around 650 light years from Earth, Saiph is 16 times more massive and around 22 times larger in diameter than the sun.
Rigel
Also known as Beta Orionis, Rigel is around 800 light years from Earth and is the brightest star in the constellation, once again like most of the others it is a blue supergiant around 75 times larger in diameter than the sun and around 40,000 times brighter.
M42
Perhaps the most interesting component of the Orion constellation, M42 is not a star but is in fact the Orion nebula, a vast star forming region some 1,500 light years from Earth, the nebula makes up the sword of Orion along with two other stars. The Orion nebula has an apparent magnitude of 4.0, making it easily visible with the naked eye apart from those living in an around the center of large cities.

Finding Orion - Northern Hemisphere
finding orion northern hemisphere
The chart shows the position of Orion over most of the United States in mid-winter at 8 pm. This chart can also be applied to other areas of the Northern hemisphere such as Canada, the UK and Europe. Orion rises in the east and sets in the west, in December the constellation will appear in the eastern night sky around 8 pm and continue westward until around 6 am, from January to March it will first appear from the south east as night falls around 6 pm before setting around 2 am, and in April it will first appear in the south-west around 9 pm and dip below the horizon around midnight.

Finding Orion - Southern Hemisphere
finding orion southern hemisphere
The chart shows the position of Orion over most of Australia in mid-summer at 10 pm. This chart can also be applied to other areas of the Southern hemisphere such as New Zealand, South Africa and South America. In the Northern hemisphere Orion is visible in the northern night sky. In December the constellation will appear low on the horizon in the eastern night sky around 10 pm and continue westward until around 6 am, from January to March it will first appear north easterly as night falls around 10pm before disappearing below the horizon around 4 am, and in April it will first appear in the north-west around 8pm and dip below the horizon around midnight.


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