THE SOUTHWORTH PLANETARIUM 207-780-4249 www.usm.maine.edu/planet 70 Falmouth Street Portland, Maine 04103 43.6667° N, 70.2667° W Founded January 1970 "On the best cellars list." THE DAILY ASTRONOMER Thursday, March 3, 2016 Queen of the Road Circumpolarity is a funny thing. First, there's the word itself that, when spoken, seems circular, as though the syllables arrange themselves along a closed curve. Cirumpolarity, incidentally, refers to those stars and constellations that never set; well, at least not in our lifetimes. The Big and Little Dippers are the most famous circumpolar patterns. -We can't call them constellations because they are asterisms, defined as star patterns within constellations.* Secondly, the circumpolarity concept often proves troublesome to sky watchers because not all stars are circumpolar, unless you're a South Pole or North Pole observer. Determining which stars never descend below the horizons can prove a bit tricky. Here, in these balmy climes, the circumpolar stars are those clustered around the North Celestial Pole, the position of which Polaris, the North Star, approximates. The six wholly circumpolar constellations -as opposed to those only partially composed of circumpolar stars- are Ursa Major, Ursa Minor, Camelopardalis the Giraffe, Draco the Dragon, Cepheus the King and Cassiopeia the Queen. A select group amongst the more than fifty constellations visible from this latitude. The third problematic matter pertaining to circumpolar is visibility. Sometimes a circumpolar constellation is quite difficult to find when it lingers around its low point. All the circumpolars appear to travel along circular orbits centered on the North Celestial Pole. This circle expands with increasing distance from the pole. The stars close to Polaris describe small circles; those farther away, such as in the Big Dipper and Cassiopeia, follow much longer paths; paths that bring them close to the horizon and then almost directly overhead. Curiously, the Big Dipper and Cassiopeia occupy opposite points relative to Polaris. So, when one ascends toward the zenith, the other descends toward the horizon. Throughout late autumn and most of the winter, the Big Dipper begins the evening either resting on the horizon or low in the northeast. Conversely, Cassiopeia looms high overhead. Now that we're steaming toward spring with sloth-like fury, Cassiopeia's evening position is lower while the Big Dipper rises. By late evening (just before midnight), if one is hiking merrily across the glacial expanses of this heaven-forsaken wasteland because one has no other means of coping with a mid-life crises and damn it all to hell, I'm stupid, one will observe Cassiopeia on the road. Well, she'll appear to be lurking in the distant realm where the road boundaries appear to converge toward an unattainable point. Circumpolar Cassiopeia prepares for her warm weather repose while the great bear Ursa Major (Big Dipper) rises out of its hibernation dwelling. A sign -the only one- that the frigid season is destined for a much anticipated end. *The Little Dipper is part of Ursa Minor (the Minor Bear) the Big Dipper is in Ursa Major (the Great Bear.)