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Precession

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

Pole Stars Lining up the north stars March 5, 2017

Dog Days The dog days of summer August 13, 2016

Moon and Spica Shifting the starry background August 7, 2016

Future North Star Lining up a future north star July 27, 2016

On the Move The Sun circles through the zodiac September 5, 2015

Kochab A former pole star keeps watch June 13, 2015

Thuban Lining up an ancient wonder June 12, 2015

Moon in Balance Bringing a constellation into balance May 30, 2015

Moon and Spica Eyeballing some changes in the sky December 15, 2014

Venus and Antares Losing a “summer” star October 15, 2013

Aries Moving the point of the vernal equinox October 26, 2012

Future Beacons Lining up the North Stars July 22, 2012

Featured Images

Current and future pole stars

Moving On July 23, 2012