Orion, the Hunter
Probably the most easily recognised constellation in the winter sky has got to be Orion the Hunter. Orion dominates the southern part of the sky with his distinct ‘butterfly’ or ‘bow tie’ shape.
Look toward the east and you will see him rising at around 8.00pm. He appears to rise lying on his side but during the night as he gets higher in the sky he begins to stand upright in the south.
The three stars in a line that make up Orion’s belt, the bright red star Betelgeuse that marks his right shoulder, Bellatrix marks his left shoulder, the dazzling white star Rigel is his left foot and the slightly fainter Saith marks the position of his right foot. The full constellation shows Orion holding a club above his head in his right hand and a shield held out in front in his left hand fighting off Taurus the Bull which is bearing down on him.
In history, Orion was a great hunter who boasted that he could kill any creature in the forest. This angered the gods who sent a scorpion to kill Orion. The scorpion stung Orion in the foot and killed him instantly. Both Orion and Scorpio were placed in the sky but at opposite ends so they are never in the sky together. Orion is only visible during the winter and Scorpio during the summer months.
The constellation of Orion is filled with interesting objects. The star Betelgeuse is a red giant star about 430 light years away. It is huge, almost 700 times bigger than the sun. It is a very old star close to the end of its life. It is predicted that Betelgeuse will explode into a supernova any day now. In fact it may already have exploded and as it takes 430 years for the light to travel from Betelgeuse we may be simply waiting to see it. If and when it does explode it will make a spectacular sight in the sky and could even become visible for a short time during daylight.
Compare the red colour of Betelgeuse to the blue/white colour of Rigel. Rigel is a quite youngish star at over 776 light years away. The light you are seeing left Rigel in the year 1235 and has been travelling through space all this time. Rigel is almost 100 times bigger than the sun and the intense blue white colour tells us a great deal about the temperature of the star. It is much hotter than our sun.
Although the three stars of Orion’s belt look to be similar and very close together, they are really very different and at vastly different distances from the earth. The middle star of the belt for example is 1359 light years away, the light left that star in the year 652 A.D!
But the most interesting object in Orion can be found just below his belt where his sword would be. Look very carefully at the middle star of three marking his sword and you will see that it has a slightly fuzzy appearance. This is M42 the famous Orion nebula. The Orion nebula is a vast gas cloud where new stars are being born. Even a small pair of binoculars will help you to see the gases of the nebula. The mainly hydrogen gas is slowly condensing under gravity and as it forms clumps these attract more gas which eventually becomes big enough to form a star. Over millions of years the Orion nebula will eventually vanish and a cluster of stars will take its place.
By using Orion as a signpost you will be able to find other stars and constellations near by. Follow the three stars of Orion’s belt down to the left and you will find Sirius, the brightest star in the whole sky. Sirius also happens to be one of the closest stars to Earth at just over eight light years away. If you follow the line of Orion’s belt up to the right it leads to a bright red star called Aldebaran which marks the red eye of Taurus the Bull with its two horns making a V shape off to the left.
By Ken Campbell
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