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Antarctic Circle

(Encyclopedia)Antarctic Circle, imaginary circle on the surface of the earth at 661⁄2°S lat., i.e., 231⁄2° north of the South Pole. It marks the southernmost point at which the sun can be seen at the winter s...

circle

(Encyclopedia)CE5 Circle circle, closed plane curve consisting of all points at a given distance from some fixed point, called the center. A circle is a conic section cut by a plane perpendicular to the axis of...

Antarctic Peninsula

(Encyclopedia)Antarctic Peninsula, glaciated mountain region of W Antarctica, extending c.1,200 mi (1,930 km) N toward South America. In the south, volcanic peaks rise to c.11,000 ft (3,350 m); other volcanic cones...

diurnal circle

(Encyclopedia)diurnal circle dīûrˈnəl [key], apparent path followed by a star due to the earth's rotation on its axis. The stars appear to move on the celestial sphere in concentric circular paths centered at t...

Arctic Circle

(Encyclopedia)Arctic Circle, imaginary circle on the surface of the earth at 661⁄2°N latitude, i.e., 231⁄2° south of the North Pole. It marks the northernmost point at which the sun can be seen at the winter ...

hour circle

(Encyclopedia)hour circle, in astronomy, a secondary axis in the equatorial coordinate system. The hour circle of a celestial body is the great circle on the celestial sphere that passes through both the body and t...

vertical circle

(Encyclopedia)vertical circle, in astronomy, the great circle on the celestial sphere that passes from the observer's zenith through a given celestial body. In the altazimuth coordinate system the altitude of a bod...

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