Gamma Cephei

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Gamma Cephei

There’s one star in the night sky that you should never need help to find. In fact, it can help find you. It’s Polaris, the North Star. It always stands due north — every night of the year. And it’s always at the same altitude in the sky — an altitude that reveals your latitude in the northern hemisphere. If you’re at 40 degrees, for example, Polaris is 40 degrees above the horizon.

Polaris won’t always be the North Star, though. In a couple of thousand years, that honor will go to a fainter star, in Cepheus, the king.

Gamma Cephei is about 45 light-years away. It’s a good bit bigger, heavier, and brighter than the Sun. It has a small, faint companion star, plus a giant planet.

Gamma Cephei will take over “North Star” honors because Earth wobbles on its axis like a spinning gyroscope. As it does so, the north pole aims at different stars. Right now, it aims at Polaris. But around the year 4100, it’ll aim at Gamma Cephei. And around 7500, it’ll aim at Alpha Cephei, the constellation’s brightest star. Eventually, it’ll return to Polaris — in about 23,000 years.

Cepheus is to the lower right of Polaris as darkness falls. Its brightest stars form an outline that looks like a child’s drawing of a house, with Gamma Cephei at the peak. At nightfall, the house is turned on its side, so Gamma Cephei is the first star you come to as you head away from Polaris.

Script by Damond Benningfield

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