Southern Hemisphere Circumpolar Star Trails
June 30, 2009
Photographer: Laurent Fournet; Jean-Philippe Olive
Summary Authors: Jean-Philippe Olive; Jim Foster
The photo above showing circumpolar star trails in the Southern Hemisphere was taken from Reunion Island, in October 2008 (austral spring). For an observer on Earth, circumpolar stars trail in a counterclockwise direction around the north celestial pole but move clockwise about the south celestial pole. Because they’re so positioned, they’re visible all night long and, in fact, all year long. As observed from the viewer's latitude, they never set or dip below the horizon. At the North or South Pole, all constellations that can be seen are deemed circumpolar. However, there are no circumpolar constellations at the Equator.
The Big and Little Dippers are the most well-known circumpolar constellations (actually asterisms) of the Northern Hemisphere. In the Southern Hemisphere, although there's no bright star analogous to Polaris directly above the South Pole, several conspicuous circumpolar constellations brighten the southern sky. The two most prominent are the Southern Cross and Carina. Their striking star trails are at right center. Note: Some light pollution from the city of Saint Louis contaminates the view of the night sky here.
Photo Details: Olympus camera; 28mm f/8 lens; 2 hours and 40 minutes exposure time; Ektachrome 200 ASA film. Location: Les Makes Observatory, 55.3 degrees east and 21.5 degrees south latitude; altitude 1,200 m. Laurent Fournet and Jean-Philippe Olive are members of the Club Astro Astrium in Toulouse, France.
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