Circumpolar stars circle the celestial pole
The nearer you might be to both of Earth’s poles, the extra circumpolar stars you see. Circumpolar stars neither rise nor set however keep above the horizon in any respect hours of the day, each day of the yr. Even when you possibly can’t see them – when the sun is out and it’s daytime – these stars are up there. They’re circling endlessly across the sky’s north or south celestial pole.
For example, the celebs of the well-known Big Dipper asterism are circumpolar in any respect latitudes north of 41 degrees north latitude, which incorporates the northern half of the mainland United States and most of Europe.
No circumpolar stars at Earth’s equator
What number of circumpolar stars seem in your sky is determined by the place you might be. At Earth’s North and South Poles, each seen star is circumpolar. That’s, at Earth’s North Pole, each star north of the celestial equator is circumpolar, whereas each star south of the celestial equator stays under the horizon. On the Earth’s South Pole, it’s the precise reverse. Each star south of the celestial equator is circumpolar, whereas each star north of the celestial equator stays beneath the horizon.
On the Earth’s equator, no star is circumpolar as a result of all the celebs rise and set every day in that a part of the world. You’ll be able to (theoretically) see each star within the night time sky over the course of 1 yr. In observe, in fact, issues like clouds and horizon haze get in the best way.
Circumpolar stars and the place you reside
Locations between the equator and poles have some stars which are circumpolar, some stars that rise and set every day (just like the sun), and a few stars that stay under the horizon all yr spherical. Briefly, the nearer you might be to the North or South Pole, the better the circle of circumpolar stars; the nearer you might be to the Earth’s equator, the smaller the circle of circumpolar stars.
Right here is how you can decide what’s circumpolar out of your location. Subtract your latitude from 90 and also you get the declination of the objects that hardly skim above your northern (or southern) horizon. For example, from a latitude of 40° north, all the things north of a declination of +50° is circumpolar. From the Southern Hemisphere, at a latitude of 20° south, then all the things south of -70° declination is circumpolar, above your southern horizon.
We within the Northern Hemisphere are fortunate to have a reasonably shiny star, Polaris, practically coinciding with the north celestial pole: the purpose within the sky that’s at zenith (straight overhead) on the Earth’s North Pole.
Polaris at middle of circle
Draw an imaginary line straight down from Polaris, the North Star, to the horizon, and presto, you could have what it takes to attract out the circle of circumpolar stars in your sky.

For individuals within the Northern Hemisphere, Polaris practically pinpoints the middle of the nice massive circle of circumpolar stars on the sky’s dome; and the imaginary vertical line from Polaris to the horizon depicts the radius measure. (See the above chart, which has this line drawn in for you.)
Let your arm function a circle compass, enabling you to examine the circle of circumpolar stars together with your thoughts’s eye. Nearer to the equator, the circle of circumpolar stars grows smaller; nearer to the North Pole (or South Pole) the circle of circumpolar stars grows bigger.
Circumpolar stars in Southern Hemisphere
This system for finding the circle of circumpolar stars works within the Southern Hemisphere, as nicely. Nonetheless, it’s trickier to star-hop to the south celestial pole: the purpose on the sky’s dome that’s at zenith over the Earth’s South Pole. Practiced stargazers within the Southern Hemisphere depend on the Southern Cross, and key stars, to star-hop to the south celestial pole.
The Southern Cross is circumpolar anyplace south of 35 degrees south latitude; but, within the Northern Hemisphere, it’s the W or M-shaped constellation Cassiopeia that’s circumpolar in any respect locations north of 35 degrees north latitude.
Polaris and Cassiopeia
By the best way, Cassiopeia lies on the other facet of Polaris from the Massive Dipper. So from mid-northern latitudes, the Massive Dipper and Polaris enable you to find Cassiopeia.
If Cassiopeia is circumpolar in your sky, then the Southern Cross by no means climbs above your horizon. Conversely, if the Southern Cross is circumpolar in your sky, then the constellation Cassiopeia by no means climbs above the horizon.
As seen from the tropics (and part of the subtropics), neither the Southern Cross nor Cassiopeia is circumpolar. From this a part of the world, the Southern Cross rises over the southern horizon when Cassiopeia sinks under the northern horizon. Conversely, Cassiopeia rises over the northern horizon when the Southern Cross sinks under the southern horizon.
Circumpolar star path gallery


Steve Torrence made this video of circumpolar stars from close to the equator on June 21, 2016. Video through Wikimedia Commons.
Backside line: Circumpolar stars keep above the horizon all hours of the day, each day of the yr. Though you possibly can’t see them, they’re up even within the daytime.
Read more: Use the Southern Cross to find due south