MadSci Network: Astronomy |
Dear Dale: The Little Dipper (Ursa Minor) is a circumpolar constellation - a constellation close to the celestial pole and visible at any time of the year. The celestial pole is directly over the North Pole of Earth and, coincidentally, the star Polaris is almost exactly at the north celestial pole. Polaris marks the end of the handle of the Little Dipper. As Earth rotates it appears to us that the northern constellations rotate around Polaris. At the north pole, Polaris is directly overhead and all visible constellations are circumpolar, although they are only visible during the dark months. At the latitudes of the US, Polaris is one-third to one-half of the way up from the northern horizon and only a few constellations appear circumpolar. From Albuquerque, the constellations of Cassiopeia (the W) and Cepheus are also visible year-round, as well as most of Ursa Major, Draco, and Camelopardalis. There are also circumpolar constellations visible in the Southern Hemisphere. Richard T. De Van Salt Lake City, Utah rdevan@rtd1.com
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