Sunday, December 30, 2007

Star Trails

These are star trails--slow, graceful arcs traced by the stars as Earth spins on its axis. "A full 180° rotation of the circumpolar stars can be obtained only at this time of year when the astronomical night lasts more than 12 hours," says photographer Lorenzo Comolli. "I took this all-night picture on Dec. 28-29 using my Canon 350D on a tripod in light polluted Tradate, Italy."

The stubby arc near the center of the swirl is Polaris, also known as "the North Star" because Earth's north pole points almost directly at it. Polaris may be the most famous star in the heavens--but fame is fleeting! Earth's spin axis is precessing and in 10,000 years or so white-hot Vega (six times brighter than Polaris) will take over as North Star. Star trail photos will look even prettier then, with an intense bright dot illuminating the core of the starry whirlpool.

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