Why does our pole star change?

Question

And in 10,000 AD what star will be our pole star?

Answer 1

Think about a childs spinning top. As long as it was spinning fast the gyro effect kept it upright. As it slowed down, it started to wobble. Consequently the toy's top , if extended, would start to draw a circle on the ceiling. Well we are not slowing down (in our lifetime) but the earth wobbles in the same way. Our north pole is drawing a large circle in the starry sky. The major stars involved are polaris, Vega and Thurban.

Answer 2

The answers above about the changing north star are correct. What I find interesting is why it changes. First, our Moon does orbit around the equator but has an orbit inclined at about 30 degrees. Second, the daily rotation of the Earth creates cetrifugal force that causes it to bulge at the equator. When the Moon is north of the equator, the tidal forces acting on the bulge tend to pull the south pole toward the Moon. Half an orbit later, when the Moon is south of the equator, the same action pulls the north pole away.

The odd part is that the pulling does not directly tilt the Earth. The Earth acts like a gyroscope so that the force of the Moon gives a sideways wobble (precession) to the axis. This resulting motion is exactly the same reason why a spinning top with a tilted axis begins to wobble due to the downward force of gravity pulling on the axis. For the Earth, one complete rotation of the pole around the sky takes about 26000 years. Just a few years agos, our axis passed as close to Polaris (the current north star) as it ever gets. In 10,000 AD there really won't be a pole star. By then, Polaris will be 38 degrees from the pole (its one degree away now) and we will be headed toward Deneb but that will be 8 degrees off. A few more thousand years and the bright star Deneb will be within a degree of the pole.. About 4000 years after that, Vega, one of the brightest stars of all takes the honors.

Answer 3

While the tilt of Earth remains fairly constant at 23.5 degrees, where the North Pole points to in space changes gradually - it's a wobble called precession. Toy tops do this, too, but much faster! One complete wobble takes about 26,000 years. At some point Vega will be the pole star, but I thought that was in 14,000 AD.

Answer 4

It looks like third-magnitude delta Cygni will be the nearest star to the north celestial pole in 10,000 AD, though it won't be as close as Polaris is now.

Answer 5

In 14000 AD it'll be Vega.