Fred Giannaris, age 12, of Lansing, Mich., for his question:
Does the Big Dipper ever rise and set?
Over Lansing, the capital city of Michigan, Polaris the North Star is always 43 degrees above the horizon. This is about halfway between the horizon and the top of the sky overhead. All the other stars move around Polaris while it stays still, marking an exact spot in the heavens. Over Houston, Texas, Polaris is only 30 degrees above the horizon and over the Florida Keys only 25 degrees. Over the North Pole, Polaris hangs 90 degrees above the horizon, which is exactly overhead.
At the North Pole, Polaris is in the very center of the sky and all the stars move around and around. They all remain above the horizon and none of them ever rise and set, Every 24 hours, all the stars in the heavens parade once around the North Star in the center of the sky. At this point on the globe, we say that all the stars and constellations are circumpolar, meaning around the pole.
As we move south, Polaris appears a little lower in the sky. All the stars still continue to circle around it once every 24 hours, but the big circle overhead is slightly tipped. Polaris no longer appears quite at the center. Some of the constellations must dip below the horizon. As we move still further south, Polaris is still lower in the sky. A mariner can always tell his latitude from the place of Polaris in the sky. Lansing is on latitude 43 degrees north, and here Polaris is 43 degrees above the horizon. Houston is about 30 degrees latitude north and the Florida Keys about 25 degrees latitude north.
The further south we go, the lower Polaris is in the sky. This means that fewer stars are circumpolar and more of them rise and set. At the equator, all the stars rise and set and none of them are circumpolar.
In southern Florida, the Big Dipper rises and sets, In temperate latitudes there are several circumpolar constellations which we can easily see. It is a good idea to learn their names so that you can use them as guide posts to identify other stars and constellations.
The Big Dipper, of course, is familiar to all of us, Its pointer stars point to Polaris, which is in the Little Dipper. Between the Big Dipper and the Little Dipper sprawls a long, twisting constellation called Draco, the Dragon, On the opposite side of Polaris from the Big Dipper is a brilliant constellation, shaped like an M or a W. This is Cassiopeia., the Queen between the Queen and the Dragon is the constellation Cepheus, the King. Less brilliant than the Queen, this constellation looks like a square box with a pointed top. All these constellations are circumpolar in temperate latitudes north of the equator.