Astronomy

Identifying and Understanding the North Star



Tweet
Rex Trulove's image for:
"Identifying and Understanding the North Star"
Caption: 
Location: 
Image by: 
©  

To many people, the North Star is Polaris, a bright star easily located in the northern night sky for most of the northern hemisphere. What many people don't realize is that Polaris actually isn't always, and hasn't always been, the North Star.

It is currently easy to identify the North Star, because it appears almost directly above the North Pole. With time-lapse photography, looking directly up from the North Pole, the only star that wouldn't appear to move would be Polaris right now, recognized as the North Star. All others will produce circular paths on the time-lapse plate. Polaris is also very bright in the northern sky.

Through much of the northern hemisphere, Polaris is one of the few stars that is observable on virtually any cloudless night, regardless of season, owing to its position. This fact has long made the star important to navigation, especially at sea. However, relying on it for millennium as the North Star it isn't without problems.

The earth is inclined about 23.5 degrees on it's axis, currently. However, the earth's tilt changes with time. This gives the earth a distinct wobble as it moves through space. This can be imagined if you think of a spinning top that isn't exactly vertical. The topmost part of the top spins in a slow circle, encompassing a whole circle, rather than a pointing only at a specific spot.

Like the top, the north pole of the earth slowly (in terms of human beings) describes a circle every 23,000 years approximately. This means that gradually Polaris will no longer be seen as directly above the pole, and eventually Vega will become the North Star. Again, after 23,000 years from now, Polaris will once again become the North Star.

Still, the north star is important to navigation in the northern hemisphere, and has been for centuries, since from the aspect of the earth, and from night to night, it is the only star that doesn't appear to move in the night sky as the earth rotates. What this also means is that throughout the year, even as constellations change in position as the earth rotates around the sun, if you can see the North star, it will always appear to be in the same location. In turn, this also means that once you identify the North Star, you can use it to identify the constellations that are visible in the sky.

Best of all, because of the slow procession of the wobble, if you can identify the North star as a child, you will be able to find it in the same place as an aged person, if you are in the same location. This tends to lend a feeling of permanence to the cosmos. This gives the star importance to spiritual and psychological aspects of our life, and not just to the practical aspect of navigation.

In fact, Polaris also has another practical aspect. Since it is celestially above the North Pole, in the northern hemisphere, it is possible to figure out the latitude of your position, by figuring out how far north of the zenith Polaris appears. This can mean that even if you are lost, if you can see Polaris and can figure out how far north it is from directly overhead, you can at least figure out your latitude.

Throughout history, even before they were named, there were many important stars to mariners and other travelers; Rigel, Sirius, Betelgeuse, and Vega for instance. All can be easily identified, and all are bright. However, none of these has proved to be more important than our current North Star, Polaris. None are easier to identify, either, and since the bright North Star doesn't seem to move in the sky, all that is necessary is a clear sky. The progression of the seasons makes little difference.

If you make any effort to be able to identify any one star, the North Star is the one to select.

Tweet
More about this author: Rex Trulove

From Around the Web




ARTICLE SOURCES AND CITATIONS