Cassiopeia lies on the opposite side of the North Star from the Big Dipper. This map shows the sky in late March around 9 o’clock. During spring, Cassiopeia resembles the Greek letter Sigma. Two outstretched fists separate the Dipper Bowl from the North Star. Created with Stellarium.
The other night while watching the space station quietly pass through the constellation Cassiopeia the Queen, it occured to me how many guises this familiar group of stars wears. We usually refer to Cassiopeia as the W-shaped constellation, but in early spring, as it descends in the northwestern sky, those five stars remind me more of the the Greek letter Sigma (right). That recalls a story my older brother Mike told me about the requirements for acceptance in his college fraternity. For one of them, he had to recite the Greek alphabet three times — very quickly — while holding a burning match. Seeing the Sigma of Cassiopeia is far less nerve-wracking. The symbol is also widely used in math, where it represents the summation of groups of numbers.
Cassiopeia circles around the North Star during the year, showing us different "sides" of its personality. Illustrations: Bob King, Stellarium
Only in summer, when the queen skirts the northern horizon, does the constellation resemble the letter W. By fall, she morphs into a zigzag and then finally transforms into a letter of the alphabet again — this time an M — in early winter. All of this shape shifting happens because Cassiopeia is close enough to the North Star that it never sets for northern latitudes. Instead, we watch it describe a circle around steady-still Polaris, changing its orientation just as the seasons change.
Some of Cassiopeia’s several guises.