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The ever-changing north star.

Imagine living in Egypt 4,400 years ago. Along the Nile River, the Great Pyramid of Khufu towers above the sand-swept plains of Giza. And overhead shines the North Star, Thuban, in the constellation Draco the Dragon.

Today, the Great Pyramid remains, but we view a different North Star. It is Polaris in the constellation the Little Dipper. Wait, how can two stars be the North Star? In fact, why do nine stars in six different constellations take their turn as the North Star?

Draw an imaginary axis through Earth from the North Pole to the South Pole. Now, tilt this axis 23.5 degrees and spin it. With the gravitational tug from the moon, sun, and stars, the Earth's axis moves in a slow, wavy, wobbly circle through space. This wobbly circle, or what scientists call precession, takes approximately 26,000 years to complete!

So who took first honors at being the North Star? In 2700 B.C.E. (4,700 years ago), ancient astronomers focused on Thuban. By 1900 B.C.E. (3,900 years ago), the Earth's axis pointed closer to Kochab in the Little Dipper. Now called a Guardian of the North Star, Kochab truly did protect this celestial position.

In 45 B.C.E. (2,050 years ago), Kochab pulled away. Would you believe there were no North Stars for almost 1,000 years? Not until 1000 C.E. would a new star, Polaris, align close to our northern-sky pole.

In America, the Lakota Sioux call Polaris "Wicahpi Owanjila", meaning "a star that always stands in one place." Polaris, however, will only stand above Earth's northern axis for another 600 years. Like its luminescent cousins, Polaris will slide away from this celestial throne.

Who's next in line? Three not-very-bright but royal stars in the constellation Cepheus the King are the ones. By 4000 to 7500 C.E. (in 2,000 to 5,500 years), the stars Al Rai, Alfirk, and Alderamin, will each shine near this royal throne.

In 10000 C.E., the star Deneb, in the constellation Cygnus the Swan, will glide above as the North Star. Then, near 14,000 C.E., bright Vega in the constellation Lyra the Lyre will soar overhead, pointing north. Think we're done? Not yet! Near 18000 C.E., Tau Herculis, a weak, blue star in Hercules the Hero, will muscle in as the North Star.

Finally, in 23000 C.E., the Earth's wobbly path will return to Thuban, the Dragon star. Today, we are in the Age of Polaris. Astronomers predict Earth will have no other hot, gaseous body as bright or as close to true north as Polaris. Yet, time stands still for no man or star. So when you point to the North Star, remember that nine special stars in 26,000 years will mark this position.

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Author:Hill, Lisa
Publication:Fun For Kidz
Date:Sep 1, 2005
Words:472
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