Jupiter continues to shine bright in February’s evening skies, and the winter constellations Orion and Taurus are bright on clear nights. But let’s focus on something else this winter month, called circumpolar constellations.
As the Earth spins, we are used to seeing stars rise in the east and set in the west, just as the Sun and Moon do. But did you realize that there are some stars, like insomniacs, that are up all night? They are called circumpolar stars, there to be seen in the evening, midnight, and early morning.
What makes a star circumpolar? It all relates to our latitude. The farther north (or south) you are from the equator, the more stars you have that are always above the horizon. In our area, slightly closer to the north pole than the equator, we have a good number of circumpolar stars and their associated constellations.
Probably the most famous circumpolar star in the northern hemisphere is Polaris, the north star. Polaris is located almost exactly over Earth’s north pole, and occupies an almost exact, fixed location in our skies year-round. If you go out at night, look due north, and up about 45 degrees in the sky, you’ll see Polaris. The north star is fairly bright, and is at the end of the handle of the Little Dipper, Ursa Minor. It shows you where true north is, and also how far you are above the equator. Mariners have long used it as a means to tell how far north they are; if Polaris is 30 degrees above the northern horizon, you are 30 degrees north of the equator.
Ursa minor’s neighbor, Ursa Major and its included Big Dipper, are also circumpolar, always in the night sky at our latitude. Actually, the great bear’s feet dip below the horizon at times, but the Big Dipper never sets for us. Here in February, in the evening, the Dipper is on the northeast, with its handle pointing down. Brave the chill at midnight, and you’ll find it high overhead. Just before sunrise, at 6am, you’ll find the Dipper in the northwest, with the handle pointing up. The Dipper has a number of bright stars, including Alkaid and Mizar, in the handle, and Dubhe and Merak, on the far side of the Dipper’s bowl.
Another bright, circumpolar constellation is the familiar “W” shape of Cassiopeia. The Greek mythology queen lies on the other side of Polaris from the Big Dipper. On February evenings it lies in the northwest, to the left of Polaris as you face north. At 6am it will be low in the northern sky, but still above the horizon.
Three other relatively faint constellations in our sky are also circumpolar. Cepheus, the King, lies just to the left of Ursa minor in February evenings, when facing north. Draco the dragon lies below Ursa Minor, and just to the left of the Big Dipper. Camelopardalis, the giraffe, lies high in the evening sky, above Cassiopeia.
Another couple of bright stars are circumpolar even though parts of their constellations are not. Mirfak, in Perseus, and Deneb, in Cygnus, are bright stars that are always above our horizon.
Enjoy February’s night skies!
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