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Wednesday, June 10, 2009

Dragon Constellation: Draco

Mythology

During the time that Draco's star Thuban was the pole star, it would have appeared to ancient sky watchers that the Earth revolved around Draco. Dragons and other similar creatures often played a role in creation myths. In these stories the gods would often battle such creatures for control of the Earth. When defeated, the dragons were flung up into the skies.

Roman myth calls this dragon Ladon and he guarded the golden apples on a tree in a garden tended by the Hesperides, the daughters of Atlas. Hercules was sent to obtain the apples while under pledge to Eurystheus. He learned from Nereus that he could not pluck the apples himself, but must get help from Atlas. Hercules shot and killed Ladon with an arrow, making way for Atlas to enter and pluck the golden apples. The goddess Hera was greatly distressed by the death of Ladon and placed the dragon in the heavens.

A Greek legend tells the story of Draco as a horrible dragon that guarded a sacred spring and slew the soldiers of Cadmus (first king of Thebes) who had been sent to gather water. Cadmus then fought the dragon and won,. After the dragon died, Athena appeared and told Cadmus to sow the ground with the creature's teeth. The teeth immediately sprang up as a group of armed soldiers who helped Cadmus found Thebes.

A Babylonian creation story tells of Tiamat, who turned herself into a dragon but was later defeated and split into two parts. One part became the heavens and the other, the Earth.

A Chinese tale sees the stars as the dragon who eats the Sun or Moon (possible represented by the north star Polaris) in an eclipse. During a real eclipse, ancient Chinese would make as much noise as possible, banging on pots and pans to try and scare away the dragon which was eating the Sun or Moon.

A Norse creation myth tells of a dragon who gnaws at the roots of Ygdrasil, the tree that covers the world.

Because Thuban was the pole star 5000 years ago the ancient Egyptians keenly observed it. Some of Draco's stars were part of their constellation of Hippopotamus and some were of the Crocodile. They appear on the planisphere of Denderah and the walls of the Ramesseum at Thebes. The hieroglyph for the Hippopotamus was used for the heavens in general while the constellation is supposed to have been a symbol of Isis Rathor, Athor, or Athyr, the Egyptian Venus. Draco's stars were also said to represent the falcon headed god Horus.

Around 800 BC, the prehistoric Adena people who lived in the Ohio area of the United States created Serpent Mound which is believed to mirror the constellation Draco. This huge mound is nearly a quarter mile long.

The Persians have regarded Draco as a man-eating serpent called Azhdeha.

In early Hindu worship, Draco is given the form of an alligator known as Shi-shu-mara.


For the Observer
Sky Chart of North Circumpolar Stars



α Alpha Draconis, Thuban (14h03m +64° 37'0 has a magnitude of 3.64 and is a class A0 star about 215 light years distant. Thuban is a spectroscopic binary. The star is also along the Earth's precessional path and was the pole star 4800 years ago.

β Beta Draconis, Rastaban (17h29m.3 +52° 20') means the "head of the snake." Arabian lore calls Rastaban and Eltanin the Dragon's eyes. Rastaban has a magnitude of 2.78 and is a class G2 white giant, about 400 light years distant. Rastaban is a binary system with the companion being 11.5 magnitude.

γ Gamma Draconis, Eltanin (17h55m.4 +51° 30') is a 2.2 magnitude yellow giant class K5 star about 110 light years away. The surface temperature is 3,800 degrees K and the luminosity is 145 times that of our Sun.

η Eta Draconis (16h24m +61° 31') and its neighbor Zeta were sometimes known by the Arabs as the Two Wolves or Ravens. The star has a magnitude of 2.7and is a yellow giant class G8 star about 65 light years distant. The star has a very faint companion difficult in anything but large telescopes.

ν Nu Draconis (17h32m +55° 10') is a dim but attractive double star. It is found in the head of the dragon, about 5 degrees from Eltanin and 3 degrees from Rastaban. The pair have a separation of 62.3 arcseconds. Both stars are blue-white main sequence stars of magnitudes 4.88 and 4.87. The pair is 93 light years distant.




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