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Over a period of about 26,000 years, the Earth’s axis traces out a huge circle on the sky, and over time it points toward bright stars other than Polaris, as shown on the inset on our map. This means that the axis of the Earth does not always point at Polaris. It turns out that the Earth wobbles slightly as it spins through space, just as a spinning toy top wobbles as it slows down. On a cosmic time scale, different stars take turns as our North Star. These six circumpolar constellations perpetually chase one another around Polaris. Draco, the Dragon (whose four-sided head is especially distinctive).Cepheus, the King (looking like a child’s drawing of a house)  and.Cassiopeia, the Queen (with her distinctive Big W or M shape).Ursa Major, the Greater Bear (including its Big Dipper asterism).Ursa Minor, the Lesser Bear (including Polaris).There are six of them, highlighted in green on our map: The constellations close to Polaris are thus visible all night and every night of the year for observers at mid-northern latitudes, such as the 48 United States and much of Europe, and are known as circumpolar constellations. This movement is caused entirely by the rotation of the Earth on its axis.Ī few constellations are near enough to Polaris that they never drop below the horizon, as do constellations farther from the North Star. All of the other stars on the map will have moved, too. If you waited six hours-until 2:00 a.m.-and look at the northern sky again, the Big Dipper will have revolved to a position directly to the right of Polaris. Note the Big Dipper, located at the bottom of the map, directly below Polaris at 8:00 p.m.And just as with a clock, the movement is slow. The stars of the northern sky appear to rotate counter-clockwise around Polaris. Just as the hands of a clock revolve around the center of the clock’s face, so the sky appears to revolve around the Celestial Pole as the Earth rotates on its axis. Polaris always remains nearly stationary, while all of the other stars and constellations appear to slowly revolve around it. Polaris lies very near the North Celestial Pole, the point in the sky that lies directly above Earth’s north pole. The center of the “sky clock” in the northern sky is Polaris, the North Star. The apparent motion of the sky can be compared to the movement of the hands of a clock. For observers in the northern hemisphere, this motion is most obvious when you look to the north on a dark night. Or, to be more accurate, the sky *appears* to be in constant motion due to the rotation of the Earth on its axis. This Month’s Highlight: The Stars Go Round and Round

Note: You’ll need to do your star gazing from a very dark location to see many of the sights described here. Advertisement Just click here or on the image below to open the printable map-then bring outside!