Lesson Plan - Get It!
Before GPS was created, humans had to use the stars to find their way at night. Polaris is known as the North Star because it can be used to easily find which direction is north.
- Could you find Polaris in the sky and use it to navigate your way if you were lost at night?
Read on to learn how!
If you walk toward Polaris' location in the sky, you are traveling north because Polaris is located directly above the Celestial North Pole.
Picture the earth's axis, which is the imaginary line around which the earth rotates:
Image by Silver Spoon, via Wikimedia Commons, is licensed under the CC BY-SA- 3.0 license.
The axis of the earth points directly at Polaris. In other words, if you were to extend the axis for roughly 433 light-years, you would eventually run into Polaris.
Because of its position, Polaris can be visible in the same place in the night sky at any time of night and during all seasons.
- Have you ever watched the movement of the stars at night?
Although the stars are actually fixed in the universe, they appear to move slowly across the sky because the earth is moving. This motion is best seen in a time-lapse video.
Watch North Star (Star Trails) Time-lapse HD!, from Jamie E, and see if you can identify the location of the North Star:
- Did you guess that Polaris is the center?
The location of Polaris causes all the other stars to appear to rotate around it as Polaris appears to remain motionless.
Polaris is only visible from the Northern Hemisphere. There is no South Star.
The star Sigma Octans is close but is just over one degree away from the South Celestial Pole. One degree might not sound like much, but when you are talking about the enormity of space, that one degree can make a big difference.
Polaris is not the brightest star in the sky, but it is the brightest star in the constellation Ursa Minor, also known as the Little Bear or Little Dipper.
Polaris can be found at the tip of the handle of the Little Dipper. However, the other stars in the Little Dipper are very faint and can be blocked out by a small amount of light pollution or even the light of a bright moon.
An easier way to locate Polaris on these nights is to use the Big Dipper, whose stars are much brighter.
Start by facing the north half of the sky. Try to find the Big Dipper, also known as Ursa Major, which looks like this:
Locate the two stars that make up the end of the ladle, Dubhe and Merak, also called the Pointer Stars.
Draw a line between these two stars and then extend the line roughly five times away from the dipper. Polaris will be very close to this point and is the brightest star in that section of the sky.
To review, watch Find North using the Stars - Ursa Major/Polaris - Navigation without a Compass from AlfieAesthetics:
Another fact that helps locate the North Star is that the altitude of Polaris is the same as your latitude on earth.
Remember that latitude refers to your distance from the equator. Lines of latitude run parallel to the equator, as seen below. The highest measure of latitude is 90°, found at the North and South Poles.
Altitude here is slightly different than our usual definition, which is the height above sea level. The altitude of Polaris refers to the angle at which we see it.
The horizon, the line where the land appears to meet the sky, is used as the bottom of our angle while Polaris is the top.
Watch Seth Horowitz explain How to Determine Your Latitude Using Celestial Observations:
Move on to the Got It? section to explore Polaris further.