Jimmy Westlake: The eyes of the Dragon
July 15, 2007
Steamboat Springs — Peering at us from out of the darkness on July evenings are the twinkling eyes of Draco the Dragon. Draco is one of several constellations in the sky that pictures a creature killed by Hercules, the great, strong man from mythology. The two stars marking Draco’s eyes are remarkable in that they appear close together and are nearly the same brightness, making them easy to spot. Their names are Eltanin and Rastaban.
Draco represents the dragon Ladon, who guarded the Golden Apples of the Hesperides. After murdering his wife and children in a fit of madness induced by queen of the gods Hera, Hercules was forced to pay penance by completing 12 missions impossible, known as the Twelve Labors of Hercules. In his 11th labor, Hercules was commanded to find and bring back the Golden Apples, located in the Garden of the Hesperides. No big deal, except that the apples were guarded by a dragon with 100 eyes, half of which were always awake and on the lookout. Hercules managed to kill the dragon with a poisoned arrow, after which Hera placed the dragon in the sky as our constellation of Draco.
The Eyes of the Dragon – Eltanin and Rastaban – can be found passing nearly overhead on July evenings. The very bright star Vega lies less than a hand span to the east of the Dragon’s Eyes, making them particularly easy to locate.
The name Eltanin is derived from the Arabic words meaning “the serpent.” It is the brightest star in the entire constellation of Draco, even though it was given the Greek letter designation of “gamma,” indicating the third brightest. Eltanin is moving toward our solar system, and although it now lies 148 light years away, in one and a half million years it will be only 28 light years away and will become the brightest star in Earth’s sky.
The name Rastaban is derived from the Arabic words meaning “the serpent’s head.” Rastaban is a yellow giant star that pumps out 900 times more energy than our sun. An Earth-like planet around Rastaban would have to orbit 30 times farther out than the Earth orbits in order to bask in comfortable, Earth-like temperatures.
Another interesting star located near the Dragon’s eyes is simply named Nu Draconis. A person with exceptionally acute vision can barely tell this star is double. Binoculars make this obvious, and a small telescope reveals two nearly identical suns, separated by 1,900 times the Earth-sun distance and requiring at least 44,000 years to complete one orbit.
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The head of Draco the Dragon, including Eltanin and Rastaban, is circumpolar as seen from Northwest Colorado. This means the stars are located so close to the north celestial pole that their daily circles remain entirely above our horizon. In other words, the Eyes of the Dragon never set below our horizon but are always visible. Could this be the origin of the legend that Ladon, the Dragon of the Hesperides, never slept? The Eyes of the Dragon are always watching.
Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. He is an avid astronomer whose photographs and articles have been published on the Web sites of CNN.com, NASA’s “Astronomy Picture of the Day,” Spaceweather.com, Space.com, Discover.com, and in Sky & Telescope, Astronomy, Night Sky, Discover, and WeatherWise magazines.
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