Why We Use North Star (Polaris) for Navigation ?

Introduction :

Have You ever wondered why we use only North Star (Polaris) Navigation Purpose ? There are many stars visible in the night sky in various constellations, but when it comes to finding direction we look for the constellation of Ursa Minor of which Polaris belongs. Is Polaris the brightest star or nearest star (after sun) that’s why we use it to locate directions ?

Nowadays, there are many navigation websites and apps for locating oneself. However, this was not the case before GPS came into existence. People used the North Star for navigation purposes before the GPS came into existence. Even if you are stuck in an area where there is no connectivity then You can use the free apps which don’t require the internet for locating you.

Polaris :

Polaris is the brightest star in the constellation of Ursa Minor. The North is located at a distance of 433 light years away from us. Polaris is a triple star System.  Polaris is also known as the North Star. You can also call Polaris as North Star. It is 4.5 times heavier than the sun. Before advancing in technology, approximately everyone knew how to locate a Polaris. The Polaris was the only star by locating it you can find the direction.

Why Do We Use North Star (Polaris) for Navigation ?

Firstly, I cleared you that the North star is not the brightest or the nearest star. The brightest star is Sirius and the nearest star is Proxima Centauri. Hence, due to brightness and nearness, we don’t use Polaris to find directions.

As we all know that earth is rotating, therefore all objects in the night sky go on changing their position. Have you ever experienced it ? If not then go and watch the star by taking some building as a reference point for 10 to 15 minutes. You will find the star is moving with respect to the building. Therefore, every star and planet in the night changes their positions. 

Northern circumpolar stars appearing to revolve around the north celestial pole. Note that Polaris, the bright star near the center, remains almost stationary in the sky. The north pole star is constantly above the horizon throughout the year, viewed from the Northern Hemisphere. (Credit:Wikimedia Commons)

Luckily,  we have the North Star which lies just above the axis of rotation of earth. Axis of rotation is defined as the straight line through all fixed points of a rotating rigid body around which all other points of the body move in circles. Hence, the north pole star doesn’t change its position in the night sky. 

Credit:Wikimedia Commons

Vega :

Vega is the brightest star in the constellation of Lyra. Vega is the future North Star, it will replace Polaris after 13,000 years to become the North Star. It is located at a distance of 25 light-years from us. The vega is 2.1 times more massive than the Sun. Vega was the northern pole star around 12,000 BC and will become again around the year 13,727. 

Vega Will Become The North Star :

The status of North Star goes on changing after every 13,000 because the axis of earth undergoes Precessional wobbling. In day to day life you can experience this motion in a toy top. If you rotate the top then you can see that it wobbles slightly upon its axis. The same thing happens with earth, it wobbles like a slightly off-center spinning toy top. This is because of the Sun and Moon, that cause Earth to bulge at the equator affecting its rotation. Hence, The North Celestial Pole (NCP) is not fixed and the period of precession is 26, 000 years.

The simulation shows the precession wobbling of axis of rotation of earth. (Credit :NASA/JPL-Caltech)

In about 13,000 years due to precession of the axis of rotation of earth, Vega will become the North Star.  At that people will use Vega to find direction. But to feel unhappy for Polaris because after 26,000 years the Polaris will regain its status as North Star.  This process will continue. 

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