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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 ...
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 .
Polaris is the brightest star in the constellation of Ursa Minor (upper right). Big Dipper and Ursa Minor in relation to Polaris. A view of Polaris in a small telescope. Polaris B is separated by 18 arc seconds from the primary star, Polaris A. A 4 day time lapse of Polaris illustrating its Cepheid type variability.
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. Circumpolar stars are therefore visible from said location toward the nearest pole for the entire ...
The name of the star commonly used navigation publications and star charts. Bayer designation: Another name of the star which combines a Greek letter with the possessive form of its constellation's Latin name. Etymology of common name Etymology of the common name. SHA Sidereal hour angle (SHA), the angular distance west of the vernal equinox ...
Antikythera mechanism. The Antikythera mechanism (fragment A – front and rear); visible is the largest gear in the mechanism, about 13 cm (5 in) in diameter. The Antikythera mechanism ( / ˌæntɪkɪˈθɪərə / AN-tik-ih-THEER-ə, US also / ˌæntaɪkɪˈ -/ AN-ty-kih-) [1] [2] is an Ancient Greek hand-powered orrery (model of the Solar ...
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 ...
On the topographic maps of the U.S. Geological Survey (USGS), for example, a diagram shows the relationship between magnetic north in the area concerned (with an arrow marked "MN") and true north (a vertical line with a five-pointed star at its top), with a label near the angle between the MN arrow and the vertical line, stating the size of the ...