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Pole star. A pole star is a visible star that is approximately aligned with the axis of rotation of an astronomical body; that is, a star whose apparent position is close to one of the celestial poles. On Earth, a pole star would lie directly overhead when viewed from the North or the South Pole .
Earth's rotation. Earth's rotation or Earth's spin is the rotation of planet Earth around its own axis, as well as changes in the orientation of the rotation axis in space. Earth rotates eastward, in prograde motion. As viewed from the northern polar star Polaris, Earth turns counterclockwise . The North Pole, also known as the Geographic North ...
The north and south celestial poles are the two points in the sky where Earth 's axis of rotation, indefinitely extended, intersects the celestial sphere. The north and south celestial poles appear permanently directly overhead to observers at Earth's North Pole and South Pole, respectively. As Earth spins on its axis, the two celestial poles ...
Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulge due to centrifugal force. As stars are not solid bodies, they can also undergo differential ...
The azimuth is the angle formed between a reference direction (in this example north) and a line from the observer to a point of interest projected on the same plane as the reference direction orthogonal to the zenith. An azimuth ( / ˈæzəməθ / ⓘ; from Arabic: اَلسُّمُوت, romanized : as-sumūt, lit. 'the directions') [1] is the ...
Diurnal motion (from Latin diurnus 'daily', from Latin diēs 'day') is an astronomical term referring to the apparent motion of celestial objects (e.g. the Sun and stars) around Earth, or more precisely around the two celestial poles, over the course of one day. It is caused by Earth's rotation around its axis, so almost every star appears to ...
In the star chart to the right, declination is shown by the radial coordinate, starting at 90° north in the center and decreasing to 30° north at the outer edge. Sidereal hour angle is shown as the angular coordinate, starting at 0° at the left of the chart, and increasing counter-clockwise.
Circumpolar star trails in a long-exposure photo of several hours. The stars near the celestial pole leave shorter trails with the long exposure. A circumpolar star is a star that, as viewed from a given latitude on Earth, never sets below the horizon due to its apparent proximity to one of the celestial poles.