Orion

Orion-lowVisible towards the south during winter evenings, roughly midway between the horizon and overhead point, Orion is arguably the most beautiful constellation in the sky. Its conspicuous pattern of bright stars is unmistakable and, once seen, is unlikely to be forgotten.

One of the most conspicuous stars in Orion is Betelgeuse, the name of this star being derived from the Arabic ‘Yad al-jauza’ meaning ‘the Hand of al-jauza’. Medieval translators mistakenly took the first letter as being a ‘B’ rather than a ‘Y’, from which the currently accepted name of this star eventually emerged. The exact identity of ‘al-jauza’ is not clear, although it appears to be a reference to a female figure that Arabic astronomers saw as being depicted by the stars that represent Orion.

Betelgeuse is a red supergiant and one of the largest stars known to astronomers. Shining from a distance of over 500 light years, its ruddy glow forms a sharp contrast with the brilliant white of Rigel, the name of which is derived from the Arabic ‘rijl’ meaning ‘the Foot’. Checking these two stars out with binoculars brings out the colour difference between them very well. Rigel has a diameter of around 40 million miles and lies at a distance of around 900 light years, which means the light we are seeing now set off on its immense journey towards us only a few years after the Domesday Book was compiled.

Along with Betelgeuse and Rigel, the two blue giant stars Bellatrix and Saiph form the conspicuous Rectangle of Orion. Bellatrix lies at a distance of around 250 light years, somewhat closer than Saiph which shines with a magnitude of 2.07 from a distance of over 650 light years. Its name is derived from the Arabic ‘Saif al-jabbar’ meaning ‘the Sword of the Giant.’

Alnitak is the easternmost of the three stars that form the Belt of Orion. Its name means ‘The Girdle’ and the area immediately surrounding Alnitak is fairly rich in stars and well worth a look through binoculars. The central star in the Belt of Orion is Alnilam, derived from the Arabic for ‘String of Pearls’, and just to the west is Mintaka, the name of which comes from the Arabic Al Mintakah meaning ‘The Belt’.

We know these three stars as the Belt of Orion, although they have been given other names in the past. Australian natives referred to them as ‘Young Men’, Greenlanders called them ‘The Seal Hunters’ and mariners often referred to them as ‘The Golden Yardarm’. More common names include ‘The Three Kings’ and ‘Jacob’s Rod’. Perhaps the silliest episode relating to the naming of these three stars took place in 1807 when the University of Leipzig christened them ‘Napoleon’, whereupon an irate Englishman promptly retaliated with the title ‘Nelson’. Needless to say, neither name managed to find its way onto star charts!

If the night is really clear, try to seek out the lion’s skin which acts as Orion’s shield. This is represented by a faint line of stars stretching from the northernmost Omicron 1 down to Pi 6. Arabian astronomers knew these stars collectively as Al Kumm, the Sleeve (of the garment in which Orion was dressed). The great hunter’s club is depicted by a triangle of faint stars above Betelgeuse, comprised of Mu, Nu and Xi.

Below the Belt of Orion can be seen a line of faint stars commonly referred to as the Sword of Orion and here can be found by far the most famous object in the constellation. M42, also known as the Great Nebula, can be seen as a hazy patch of diffuse light surrounding the group of stars at the lower end of the sword. M42 takes the form of a giant, irregular cloud and shines because of the stars embedded within it.

On really dark and clear nights the Great Nebula is visible as a faint glowing patch and it is remarkable that its existence was not noted until 1611. Since then it has never failed to impress, and it is safe to say that there is little in the heavens to equal it. The wide field of view of a pair of binoculars brings out the nebula very well, and the sight leaves the observer with a sense of wonder when it is realised that inside this glowing cloud stars are actually being formed.

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