The "wobble" of the Earth's rotational axis, which sweeps out an imaginary cone, much like a spinning top, once every 26,000 years. Precession changes the pole star as seen from Earth. Thuban, the brightest star in the constellation Draco, was the pole star while the Egyptians built the Pyramids in Egypt. Since that time, the motion of precession has rotated the Earth's axis away from Thuban and towards Polaris, the current pole star. In 13,000 years, Earth's rotational axis will point towards Vega, the new pole star.

Radio Programs

Moon and Spica Eyeballing some changes in the sky Tuesday, December 16, 2014
Venus and Antares Losing a “summer” star Wednesday, October 16, 2013
Aries Moving the point of the vernal equinox Saturday, October 27, 2012
Future Beacons Lining up the North Stars Monday, July 23, 2012
Saturn and Spica Eyeballing some changes in the sky Sunday, October 30, 2011
North Stars II Turning right at the North Star Sunday, July 25, 2010
North Stars Lining up the North Stars Saturday, July 24, 2010
Thuban Lining up an ancient North Star Tuesday, June 22, 2010
The Dragon Twisting around the north pole Monday, June 21, 2010
March Ram March goes out like a grown-up lamb Saturday, March 27, 2010

Featured Images

Current and future pole stars
Moving On Monday, July 23, 2012


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