mardi 23 septembre 2008

Orion 2

Orion is the most splendid of constellations, befitting a character who was in legend the tallest and most handsome of men. His right arm and left foot are marked by the brilliant stars Betelgeuse and Rigel, with a distinctive line of three stars forming his belt. ‘No other constellation more accurately represents the figure of a man’, says Germanicus Caesar.
Manilius calls it ‘golden Orion’ and ‘the mightiest of constellations’, and exaggerates its brilliance by saying that, when Orion rises, ‘night feigns the brightness of day and folds its dusky wings’. Manilius describes Orion as ‘stretching his arms over a vast expanse of sky and rising to the stars with no less huge a stride’. In fact, Orion is not an exceptionally large constellation, ranking only 26th in size (smaller, for instance, than Perseus according to the modern constellation boundaries), but the brilliance of its stars gives it the illusion of being much larger.
Orion is also one of the most ancient constellations, being among the few star groups known to the earliest Greek writers such as Homer and Hesiod. Even in the space age, Orion remains one of the few star patterns that non-astronomers can recognize.

In the sky, Orion is depicted facing the snorting charge of neighbouring Taurus the Bull, yet the myth of Orion makes no reference to such a combat. However, the constellation originated with the Sumerians, who saw in it their great hero Gilgamesh fighting the Bull of Heaven. The Sumerian name for Orion was URU AN-NA, meaning light of heaven. Taurus was GUD AN-NA, bull of heaven.
Gilgamesh was the Sumerian equivalent of Heracles, which brings us to another puzzle. Being the greatest hero of Greek mythology, Heracles deserves a magnificent constellation such as this one, but in fact is consigned to a much more obscure area of sky. So is Orion really Heracles in another guise? It might seem so, for one of the labours of Heracles was to catch the Cretan bull, which would fit the Orion–Taurus conflict in the sky. Ptolemy described him with club and lion’s pelt, both familiar attributes of Heracles, and he is shown this way on old star maps. Despite these facts, no mythologist hints at a connection between this constellation and Heracles.
According to myth, Orion was the son of Poseidon the sea god and Euryale, daughter of King Minos of Crete. Poseidon gave Orion the power to walk on water. Homer in the Odyssey describes Orion as a giant hunter, armed with an unbreakable club of solid bronze. In the sky, the hunter’s dogs (the constellations Canis Major and Canis Minor) follow at his heels, in pursuit of the hare (the constellation Lepus).
On the island of Chios, Orion wooed Merope, daughter of King Oenopion, apparently without much success, for one night while fortified with wine he tried to ravish her. In punishment, Oenopion put out Orion’s eyes and banished him from the island. Orion headed north to the island of Lemnos where Hephaestus had his forge. Hephaestus took pity on the blind Orion and offered one of his assistants, Cedalion, to act as his eyes. Hoisting the youth on his shoulders, Orion headed east towards the sunrise, which an oracle had told him would restore his sight. As the sun’s healing rays fell on his sightless eyes at dawn, Orion’s vision was miraculously restored.
Orion is linked in a stellar myth with the Pleiades star cluster in Taurus. The Pleiades were seven sisters, daughters of Atlas and Pleione. As the story is usually told, Orion fell in love with the Pleiades and pursued them with amorous intent. But according to Hyginus, it was actually their mother Pleione he was after. Zeus snatched the group up and placed them among the stars, where Orion still pursues them across the sky each night.
Stories of the death of Orion are numerous and conflicting. Astronomical mythographers such as Aratus, Eratosthenes and Hyginus were agreed that a scorpion was involved. In one version, told by Eratosthenes and Hyginus, Orion boasted that he was the greatest of hunters. He declared to Artemis, the goddess of hunting, and Leto, her mother, that he could kill any beast on Earth. The Earth shuddered indignantly and from a crack in the ground emerged a scorpion which stung the presumptuous giant to death.
Aratus, though, says that Orion attempted to ravish the virgin Artemis, and it was she who caused the Earth to open, bringing forth the scorpion. Ovid has still another account; he says that Orion was killed trying to save Leto from the scorpion. Even the location varies. Eratosthenes and Hyginus say that Orion’s death happened in Crete, but Aratus places it in Chios.
In both versions, the outcome was that Orion and the scorpion (the constellation Scorpius) were placed on opposite sides of the sky, so that as Scorpius rises in the east, Orion flees below the western horizon. ‘Wretched Orion still fears being wounded by the poisonous sting of the scorpion’, noted Germanicus Caesar.
A very different story, also recounted by Hyginus, is that Artemis loved Orion and was seriously considering giving up her vows of chastity to marry him. As the greatest male and female hunters they would have made a formidable couple. But Apollo, twin brother of Artemis, was against the match. One day, while Orion was swimming, Apollo challenged Artemis to demonstrate her skill at archery by hitting a small black object that he pointed out bobbing among the waves. Artemis pierced it with one shot – and was horrified to find that she had killed Orion. Grieving, she placed him among the constellations.
There is a strange and persistent story about the birth of Orion, designed to account for the early version of his name, Urion (even closer to the Sumerian original URU AN-NA). According to this story, there lived in Thebes an old farmer named Hyrieus. One day he offered hospitality to three passing strangers, who happened to be the gods Zeus, Neptune and Hermes. After they had eaten, the visitors asked Hyrieus if he had any wishes. The old man confessed that he would have liked a son, and the three gods promised to fulfil his wish. Standing together around the hide of the ox they had just consumed, the gods urinated on it and told Hyrieus to bury the hide. From it in due course was born a boy whom Hyrieus named Urion after the mode of his conception.
Orion is one of several constellations in which the star labelled Alpha is not the brightest. The brightest star in Orion is actually Beta Orionis, called Rigel from the Arabic rijl meaning ‘foot’ since Ptolemy described it as marking the left foot of Orion. Rigel is a brilliant blue-white supergiant.
Alpha Orionis is called Betelgeuse (pronounced BET-ell-juice), one of the most famous yet misunderstood star names. It comes from the Arabic yad al-jauza, often wrongly translated as ‘armpit of the central one’. In fact, it means ‘hand of al-jauza’. Who (or what) was al-jauza? It was the name given by the Arabs to the constellation figure that they saw in this area, seemingly a female figure encompassing the stars of both Orion and Gemini. The word al-jauza apparently comes from the Arabic jwz meaning ‘middle’, so the best translation that modern commentators can offer is that al-jauza means something like ‘the female one of the middle’. The reference to the ‘middle’ may be to do with the fact that the constellation lies astride the celestial equator. As Ptolemy described it in the Almagest, Betelgeuse represents the right shoulder of Orion. The Greeks did not give a name to either Betelgeuse or Rigel, surprisingly for such prominent stars, which is why we know them by their Arabic titles. Betelgeuse is a red supergiant star hundreds of times the diameter of the Sun. It expands and contracts over periods of months and years, changing brightness noticeably in the process.
The left shoulder of Orion is marked by Gamma Orionis, known as Bellatrix, a Latin name meaning ‘the female warrior’. The star at the hunter’s right knee, Kappa Orionis, is called Saiph. This name comes from the Arabic for ‘sword’, and is clearly misplaced. The three stars of the belt – Zeta, Epsilon and Delta Orionis – are called Alnitak, Alnilam and Mintaka. The names Alnitak and Mintaka both come from the Arabic word meaning ‘the belt’ or ‘girdle’. Alnilam comes from the Arabic meaning ‘the string of pearls’, another reference to the belt of Orion.
Below the belt lies a hazy patch marking the giant’s sword. This is the location of the Orion Nebula, one of the most-photographed objects in the sky, a mass of gas from which a cluster of stars is being born. The gas of the Nebula shines by the light of the hottest stars that have already formed within; it is visible to the naked eye on clear nights.

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