Does our Pole Star change from time to time?
It’s all about relativity!
You might have often read and heard about the North Star or the Pole Star, the star in the night sky that has been used to find the North direction since times immemorial.
A Pole Star, by definition, is the star in the night sky that is aligned to the Earth’s rotation axis.
Thus, as the Earth rotates, relative to us on Earth (ie, considering ourselves stationary), all the stars in the sky trace a circle — and we see the semi-circle as people see the other half in the other hemisphere — but the North Star traces a very small circle or almost remains at the same place in the night sky.
The Pole Star is what guided the early sea explorations and travels around the world and guides the coastal guards even today, as well as is widely used in astronomy for calibration of telescopes.
But have you ever wondered that the Pole star to which the “air shafts” in the Pyramids of Giza were aligned to for assisting the ascent to heaven is the same Pole Star as the one we use today?
And will it be the same one thousands of years from now?
Well, the answer is, unsurprisingly, NO.
Our Pole Star, or the North Star, keeps changing from time to time. While our current Pole Star is Polaris (α Ursae Minoris); Thuban (α Draconis) was closest to the North Pole about 2700 BCE, and the bright star Vega (α Lyrae) will be the star closest to the pole in 14,000 CE.
Why does our Pole Star change?
We know that the Earth revolves around the Sun in an elliptical orbit and also revolves on its own axis. But did you know that the Earth’s axis of rotation also performs a cyclic circular motion?
It is kind of like the wobbling motion of the spinning of a top — where the Earth’s axis traces a small circle in the heavens, and whichever star the axis points to at that particular time during the circular motion becomes our Pole Star. An interesting thing to note here is that the Earth’s axis maintains an angle of 23.5 degrees with respect to the line perpendicular to the plane of the orbit around the Sun — this is called the axial tilt!
The Earth’s axis takes around 26,000 years to complete one motion — which means humans or whatever life form exists on Earth 26,000 years from now — will again see Polaris as their North Star :P
This phenomenon, called the Precession of Equinoxes, has been known to us since the times of Greek civilization when it was discovered by the Greek astronomer Hipparchus.
I hope you found out something new and interesting about Earth’s Pole Star in this piece. After all, the star that we thought was always fixed and serves as our guiding light isn’t so fixed after all :)
Philosophically, it is an interesting take on how even the North Star for us as humans changes over time as we grow up in our lives — and it is totally okay for it to change — as long as it aligns with our values (just like the Earth’s axis still aligns with the plane of its orbit around the Sun) :P
Read about the last part in the Space Nuggets — Why the heck is a comet called C/2022 E3?
Why was this phenomenon called the Precession of Equinoxes? What role does it play in the Equinoxes and Solstices we witness on Earth? Stay tuned to learn about this and more in the next part of the series of Space Nuggets!
