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DRACO
The Dragon
Draco - Celestial Atlas by Alexander Jamieson - 1822
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Ancient lore contains many tales of dragons, and more than one has been associated with the constellation Draco. The most familiar myth involves the eleventh labour of Hercules, in which he was ordered by the gods to steal the golden apples from the garden of the Hersperides, which were guarded by a dragon. Naturally, the dragon had to be disposed of to obtain the apples, and its form was placed in the sky to commemorate the feat.
Draco is one of the circumpolar constellations that never sets for viewers in the northern hemisphere. It is destined to circle the north star, Polaris, - tail first - for eternity.
Thuban is the alpha star in Draco, but unlike most constellations, it did not earn its alpha designation because it is the brightest star. Thuban is, in fact, only the seventh brightest star in the constellation. The reason it is the alpha star is because of its historical significance. Due to the precession of Earth's axis, which slowly but surely shifts the positions of the stars over time, 4800 years ago Thuban was our North Star (the position now occupied by Polaris).
And 4800 years ago was when the great Egyptian pyramid of Khufu, at Gizeh was built. From the King's Chamber, where the Pharoh Khufu was entombed, two narrow shafts lead from the tomb to opposite sides of the pyramid. Initially thought to be air shafts, astronomers are now thinking these shafts were directed towards specific stars, that were to be aids in the Pharoh's journey to the afterlife. One shaft appears to point directly where Thuban (the north star) would have been at the time, and the other shaft appears to point to Orion's belt, which was associated with the all important goddess Isis.
Draco has ten stars with known planetary systems, and two of these stars are easily visible with the naked eye. The brightest is Edasich, a star about half way along the body of the dragon, about 199 light years from Earth. It has one known planet orbiting around it, about eight times the size of Jupiter. The other visible star is 42 Draconis, 316 light years away, with a planet almost four times the size of Jupiter. The most exciting star is beyond naked eye visibility at a magnitude of 10.96, and out at the very great distance of 562 light years. It has been named Kepler 10, after NASA's Kepler Space Telescope that discovered it. It is exciting because it is home to two small, rocky planets not much larger than Earth, which are much more likely to support life than gas giants larger than Jupiter. These smaller planets were discovered in part because of the unprecedented sensitivity of the Kepler telescope, along with the fortunate alignment of these planets passing directly in front of (transiting) their parent star. For more information on extrasolar planets visit NASA's Planet Quest.
Draco is also home to one of the most stunning nebulae in the heavens. The Cat's Eye Nebula is an expanding sphere of multimillion degree gas ejected by a dying star similar to our Sun. The extraordinary image captured by the Hubble Space Telescope below shows an astounding level of complexity never before seen. What looks like circular refraction rings is not an artifact of the camera lens at all, but actual spherical shells of gas, at least twelve of them, ejected from the star at regular intervals, surrounding it like layers of an onion. The Hubble photo is like looking at a cross section of these onion-skin layers - a truly remarkable sight. This is in addition to all the other detailed linear and spherical phenomena surrounding the dying star - enough to keep scientists busy for many years. The nebula has an apparent magnitude of 9.8, and is 3,300 light years away.
Hubble also captured the unique image of a far away galaxy aligned almost precisely edge-on to our view from Earth, showing us just how thin the disk of a spiral galaxy can be. NGC 5866 is classified as a lenticular spiral galaxy, because of its lack of obvious spiral structure. It is 60,000 light years across, about one third the size of our Milky Way galaxy, 44 million light years away, with an apparent magnitude of 10.7.
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