Around 3000 BC, Thuban was the closest star to the celestial north pole, meaning it was the northern polar star. However, due to the precession of the Earth's axis, the position of the celestial north pole slowly shifts over time.
Today, Polaris (the current north star) is the closest star to the celestial north pole. However, in the future, Thuban will again be the northern polar star, although that won't happen for several thousand years.
