Snakes are often considered to be the inspiration for mythical dragons. The constellation Draco, shown here in a 1621 engraving, is in the shape of a giant snake winding between the Great and Little Bears, also known as the Big and Little Dippers. The Sumerians, who lived in what is now Iraq, thought that the constellation was the dragon Tiamat. The Greeks and Romans identified it as a monster killed by the hero Hercules.

The star Polaris, in the Little Dipper, is currently the north star—the star that is located directly above the north pole and therefore does not appear to move. But because the direction of the Earth's axis changes, the north star changes as well. Thuban, a faint star in Draco's tail, was the north star 5,000 years ago when the pyramids were being built. It will be the north star again 20,000 years from now.

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