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Cassiopeia, Queen of the north

On these December evenings, turn toward the northern sky and see its famous constellation Cassiopeia the Queen. In early Decemer, Cassiopeia swings directly over Polaris, the North Star, at roughly 8 p.m. local clock time. Cassiopeia – sometimes called The Lady of the Chair – is famous for having the shape of a telltale W or M. You will find this configuration of stars as a starlit M whenever she reigns highest in the sky, hovering over Polaris.

Cassiopeia can also be seen from tropical and subtropical latitudes in the Southern Hemisphere, by the way. The constellation appears low in the north around 7 to 8 p.m. tonight. However, you can’t see Polaris from the Southern Hemisphere because it’s below the horizon in that part of the world.

Because Cassiopeia returns to the same spot in the sky about four minutes earlier with each passing day, or one-half earlier with each passing week, look for Cassiopeia to be at her high point over Polaris, the North Star, around 6 p.m. in early January.

View larger. | The constellation Cassiopeia has the distinct shape of a W, or M, depending on the time of night you see it. This nice photo from EarthSky Facebook friend Mike O’Neal.

From a dark country sky, you’ll see that Cassiopeia sits atop the luminous band of stars known as the Milky Way. Arching from horizon to horizon, this soft-glowing boulevard of stars represents an edgewise view into the flat disk of our own Milky Way galaxy. When Cassiopeia climbs above Polaris, the North Star, on these dark winter evenings, note that this hazy belt of stars that we call the Milky Way extends through the Northern Cross in the western sky and past Orion the Hunter in your eastern sky.

This Milky Way is fainter than the glorious broad band of the Milky Way we see in a Northern Hemisphere summer or Southern Hemisphere winter. That’s because we are looking toward the star-rich center of the galaxy at the opposite side of the year. On these December nights, we are looking toward the galaxy’s outer edge, not the center.

The famous Double Cluster in the constellation Perseus is not far from Cassiopeia on the sky’s dome. This chart shows how to use the W or M shape of Cassiopeia to find the Double Cluster. To appreciate the clusters fully, look with your binoculars in a dark sky! More about the Double Cluster here.

As the night marches onward, Cassiopeia – like the hour hand of a clock – circles around the North Star, though in a counter-clockwise direction.

By dawn, you will find Cassiopeia has swept down in the northwest – to a point below the North Star. At that time, if you’re at a southerly latitude, such as the far south U.S., you might not be able to see Cassiopeia. The constellation might be below your horizon. But if you’re located at a latitude like those in the northern U.S., you will still see Cassiopeia sitting on or near your northern horizon.

Look northward on these cold December evenings to see the Queen Cassiopeia sitting proudly on her throne, atop the northern terminus of the Milky Way!

Bottom line: Watch for Cassiopeia the Queen on these December evenings. The constellation is shaped like an M or W. You’ll find Cassiopeia in the northeast at nightfall, sweeping higher in the north as evening progresses.

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Bruce McClure