Antarctic Circle

The parallel of latitude at about 66°33′ south, marking the approximate northern limit of the region where the Sun can remain above or below the horizon for 24 hours.

Axial tilt: The angle between a rotating body's spin axis and the perpendicular to its orbital plane. Earth’s tilt makes the Sun stay above or below the horizon for a full day beyond this latitude.
Latitude: The angular distance of a point north or south of the equator, measured in degrees. The circle is defined by its south latitude.
Antarctica: Earth’s southernmost continent, largely covered by a thick ice sheet and surrounded by the Southern Ocean. The Antarctic Circle crosses the continent and helps distinguish its polar interior.
Antarctic Peninsula: The long peninsula extending north from the Antarctic mainland toward South America. The circle crosses its southern portion, making it a prominent land crossing.
Polar day: A period when the Sun remains above the horizon for at least 24 hours. Locations south of the circle experience polar day around the December solstice.
Parallels of latitude: Imaginary circles around Earth formed by points sharing the same latitude. The Antarctic Circle is one such parallel.
Antarctic Treaty System: The international agreements governing peaceful activity, scientific cooperation, and environmental protection in Antarctica. Its geographic scope concerns Antarctica, a continent partly bounded by the circle.
Dumont d'Urville Station: A French research station on Adélie Land in East Antarctica. It lies south of the circle, where seasonal polar day and night occur.
Polar night: A period when the Sun remains below the horizon for at least 24 hours. Locations south of the circle experience polar night around the June solstice.
Equator: The great circle at 0° latitude, equidistant from the North and South Poles. Its plane anchors the latitude system used to locate the Antarctic Circle.

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