A pole star is a visible star, preferably a prominent one, that is approximately aligned with the Earth's axis of rotation; that is, a star whose apparent position is close to one of the celestial poles, and which lies approximately directly overhead when viewed from the Earth's North Pole or South Pole. A similar concept also applies to planets other than the Earth. In practice, the term pole star usually refers to Polaris, which is the current northern pole star, also known as the North Star.