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Starry Spokes

StarDate: 
May 15, 2015

Like the spokes on a wheel, two prominent star patterns circle around the North Star night after night. They’re on opposite sides of the hub, though, so when one is high in the sky, the other is low.

That’s how they start the night at this time of year. W-shaped Cassiopeia, the queen, is quite low in the northern sky as night falls. At the same time, the Big Dipper is high in the north.

As the hours roll by, though, Cassiopeia rotates up and around the celestial hub, so it’s well up in the northeast at first light.

The Big Dipper rotates on the opposite side of the hub, so it is in the northwest at the first blush of twilight.

As seen from the northern hemisphere, all of the constellations appear to rotate around the North Star. But most of them are far enough away from the North Star that we don’t see them making that circle — we see them setting in the west, disappearing for a while, then rising in the east. So for most nights of the year, they’re out of sight for at least part of the night.

But from much of the U.S., that’s not the case for Cassiopeia and the Big Dipper. They’re close enough to the celestial pole that they remain in view all night, every night.

From far-southern latitudes, some or all of both star patterns briefly dips below the northern horizon. Even from those latitudes, though, Cassiopeia and the Big Dipper are in view almost all night, every night of the year, circling the hub of the sky — the North Star.

 

Script by Damond Benningfield, Copyright 2015

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