The North Star

Polaris, also known as the North Star, is located at the very tip of the group of stars called the Little Dipper.  As you may have guessed from its name, the North Star is always located in the direction of North. But why does this happen for this one particular star?

If we imagine the Earth being at the center of a globe and the celestial bodies laying on the shell of that sphere, we have what is known as the “celestial sphere.”  By extending an imaginary line of Earth’s axis out to the celestial sphere, we get the North and South Celestial Poles (for the Northern and Southern Hemispheres, respectively).  The North Celestial Pole points at the North Star, making it appear stationary in the sky even as Earth spins on its axis. (The Southern Hemisphere does not have a bright enough star located near the South Celestial Pole, so this phenomenon does not occur for Southern Hemisphere observers.)

A common misconception about Polaris is that it is the brightest star in our sky.  In actuality, it is not a very bright star and can be challenging to find if you are in an area with a lot of light pollution like a city.  One of the easiest ways to find the North Star is by using the Big Dipper, since it is bigger and more recognizable than the Little Dipper. As shown in the picture below, you can use the two outer cup stars of the Big Dipper to find the North Star.

As with all heavenly bodies, God created them for “signs and seasons” (Genesis 1:14) and the North Star played a role of particular historical importance as a “sign.”  During the period of slavery in the United States, many slaves escaped to freedom by following the North Star. Though most slaves could not read or write, they were taught in their childhood to be able to locate the North Star.  Using the simple directions “walk towards the North Star”, many slaves were able to find their freedom in northern states.

Circumpolar Stars

As the Earth rotates daily on its axis, the stars seem to make circular arcs around the North Celestial Pole and therefore the North Star.  Stars farther from the North Star make larger circles and eventually go below the horizon. However, as you get closer to the North Star the stars’ circle paths will become smaller.  If you were to take a long exposure of the northern night sky, you would see that a certain zone of stars appear to circle around the North Star and never go below the horizon. This zone of stars is called the circumpolar region and the stars in it will always be above the horizon, no matter the time or the season. 

The circumpolar region varies depending on an observer’s latitude.  If you are at 32° latitude, the radius of circumpolar stars from the North Star is 32°.  At the North Pole (90° latitude), the North Celestial Pole (and therefore the North Star) is located directly overhead at the zenith.  This means that at the North Pole every star visible is circumpolar. On the other hand, at the Equator (0° latitude), the celestial pole lies on the horizon there are no circumpolar stars.  Every star in the sky will eventually set.