Draco is a large northern constellation located between Ursa Major and Ursa Minor. It lies north of Hercules, Lyra and Cygnus. Draco is a circumpolar constellation, meaning that it can be seen throughout the year. Draco can be hard to find because it has no bright stars. Its head is marked by a pattern of four stars, and its long body winds toward Cepheus, then turns and runs between Ursa Major and Ursa Minor.
History and Mythology
Draco is one of the oldest recorded constellations. It derives from a terrible battle between the Greek gods. The dragon was said to be on the side of the Titans. Near the end of the battle, the dragon started to battle with Athene, the goddess of wisdom. She seized the dragon and hurled him into the heavens. The spinning dragon sailed into the open sky, where he became entangled with the North Pole forever.
In Egyptian mythology, Draco was portrayed as a hippopotamus or a crocodile. It was thought to be an object of worship. The ancient Indians also saw Draco as a crocodile. The Hindus thought Draco was an alligator. Draco has also been identified as the crooked serpent in the Book of Job and the Book of Isaiah.
Notable Stars
Thuban, or Alpha Draconis, is a 4th magnitude star in the tail of Draco, whose Arabic name means "the basilisk". Thuban was the pole star in 3,000 BC. Some Egyptian pyramids were built so that the light of Thuban could be seen shining on their altars. Ancient Egyptians thought Thuban represented the center of the world. Due to precession, the Earth's axis now points toward Polaris, the modern North Star.
Etamin, or Gamma Draconis, is brightest star in Draco, and it is one of the four stars forming the dragon's head. The second-brightest is Rastaban, or Beta Draconis. It is a yellow supergiant 360 light years away, and its Arabic name means "head of the serpent".
Clusters, Nebulae, and Galaxies
There are no bright star clusters in Draco. There are several galaxies, but most are fainter than 10th magnitude. M 102 is one of the "missing" Messier objects that has not been identified unambiguously; it may have been a duplicate observation of M 101, but there are historical and observational reasons to believe otherwise. NGC 5866 is a fine, bright, 10th-magnitude galaxy, often called the "Spindle Galaxy" due to its shape, and a worthy object with which to fill this blank in Messier's catalogue.
NGC 5907 is a 10th magnitude, edge-on elliptical galaxy with a central dust lane visible in a modest telescope. NGC 4236 is a barred spiral galaxy, seldom-observed object among amateur astronomers. Having a very low surface brightness, this galaxy is a challenging object.
Draco includes the 8th magnitude planetary nebula NGC 6543, commonly called the Cat's Eye Nebula. It has a bright, bluish disk and a faint central star visible in large telescopes.
NGC 6543 is a young planetary nebula, about 3300 light years away. The great complexity of the Cat's Eye's structure - with its concentric gas shells, jets of high-speed gas, and unusual shock-induced knots of gas - suggests that the central star may be a binary system. Despite intensive study, the Cat's Eye Nebula still holds many mysteries.