Another thing that sets circumpolar stars apart is that they do not rise into the sky or set. They always appear directly above the horizon, which is a line that you can see in the distance. Now is a good time to learn more about circumpolar stars and what they are.
Latitude and Altitude
The main thing that will determine what circumpolar stars you can see is your current latitude. Experts determine the latitude of a location by looking at the altitude that a spot is in regards to Polaris, which is one of the sky’s brightest stars. Polaris sits exactly 55 degrees higher than the horizon. When stars have an altitude of 35 degrees, they will sit slightly above the horizon and skim this line. A circumpolar star must have a latitude or altitude of 35 degrees or more.
One thing you should know about circumpolar stars is that they are always visible in the sky. As the stars do not rise or set, they remain bright and twinkling at all hours of the day and night. This does not mean that you can walk outside right now and see the stars though. They are only visible when you’re standing on or near one of the Earth’s poles. The Big Dipper is an asteristm within the constellation of Ursa Major, that includes Polaris. If you have a latitude of around 41 degrees, you can see all the stars in this constellation. Locations in which you can view this constellation include parts of Europe and North America.
Circumpolar stars and where they appear in the sky can depend on the current season. During the spring, the Big Dipper will appear directly above you with Polaris slightly below. In winter, the Big Dipper moves to the right of Polaris and then moves to the left of this star in the summer. When you locate Polaris in the fall, you can move your eyes down or south of the star to locate the Big Dipper. Other constellations will move in similar ways. You can even track the stars in a constellation and see how their locations change from one season to the next.
North Pole vs. South Pole
When your travels take you to the North Pole and the South Pole, you shouldn’t expect to see the same stars. What you can see will depend on the circumpolar equator. This is an imaginary line that wraps around the planet and splits it in half. On the South Pole, stars that are south of this line are circumpolar. Stars on the North Pole are only circumpolar if they sit north of this line.
Rotation of the Earth
Circumpolar stars exist because of the way the Earth rotates. As the Earth moves around its axis, it follows a circular path around one of the poles. Depending on how close you are to either pole, these stars may appear to move in small circular paths or not move at all. Long exposure photos taken of circumpolar stars show white streaks in the sky that form small circles. The highest of those stars appear as small circles, but the stars that are closer to the planet form larger circles.
Can You See All Circumpolar Stars in the United States?
As the United States is far from both the North and South poles, you cannot see all the circumpolar stars in the sky from your home. Acrux is a star system that forms the Southern Cross and is more than 300 light-years away. This star is not visible from most spots in the US but may appear to those who live in the south. Polaris is the main circumpolar star that you can view, though it may depend on how much light and environmental pollution is nearby. Circumpolar stars are essentially stars that do not rise or set that are visible on the North and South Poles.