Has Polaris Always Been Our Pole Star?

Short Answer: No, it hasn’t always been our pole star! To understand the reason behind this let’s go back to our childhood when we enjoyed playing with a top. Let’s dive in and observe how it rotates.

Did you notice it wobble (an unsteady movement from side to side) before it came to an end? This wobble is also known as the precession of the top and this happens for all rotating bodies including Earth. Our planet completes one rotation in 24 hours, a revolution in 365 days, and a precession in 26,000 years!

The precession of our planet is majorly influenced by Sun and Moon’s gravitational influence also known as Lunisolar Precession and minorly by other planets in our solar system.

Due to this motion, the celestial pole precesses in 26,000 years. This precession causes pole stars to change every 2000 – 4000 years. Before we could understand which stars were the pole stars in the past, we must understand What a Pole Star is? What features distinguish a normal star from a pole star? A pole star is a position in the sky that is always in the polar direction. A North Pole star can be seen in the northern direction and similarly, a south pole star in the southern direction.

As most of the older civilizations grew in the northern hemisphere we have much more knowledge and idea about the North Pole star. Still, we have less evidence of which star used to be the north pole star. Over here we tried to figure out the possible north pole star. So we took three considerations.

1. The Star must be close to the North Celestial Pole with a declination (angular distance of a point north or south of the celestial equator) not less than 80°
2. The Star must have a magnitude less than 4.
3. Historical/mythical stars were also taken

The table below shows the possible north pole star and years associated with it.

The declination given in the table gives us an idea about how close those stars were to being a pole star. We can even understand that Polaris has been a perfect pole star for thousands of years. Bright stars like Vega and Deneb were once pole stars.

Historical context: We know the story of Dhruv Bal, where he was given the special position of a north pole star in the sky. So, this means that the position of Dhruv Tara has changed since the date of the story.

In the above image, we can even see Vega being the Pole star or at least being near to the north celestial pole.

The Pyramids were built around the year 2500 BCE pointing toward the dark sky patch to which stars revolve at night, which means that there was no pole star at that time.

South pole stars are not much discussed as north pole stars either because there were no advanced civilizations in the southern hemisphere or there was never a necessity to travel down south. But a similar exercise can be done for the south celestial pole as well and we came up with the following stars.

ENJOYED READING THIS? CONSIDER READING OUR BLOG ON THE TYPES OF STARS.

READ MORE ABOUT THE POLARIS HERE.