What Is Diurnal Motion?

In astronomy, the term "diurnal motion" refers to the movement of stars around the Earth's celestial poles due to the planet's rotation on its axis. This movement is called a diurnal circle.

Throughout the course of a day, the stars appear to move in an arc from east to west. From the North Pole, the stars appear to move in a counterclockwise motion. When viewed from the South Pole, however, they move in a clockwise motion. Scientists photograph examples of diurnal motion by taking long-exposure photographs of the stars throughout the night. The diurnal path by which a star moves is determined by its declination.