Tropic of Capricorn

Tropic of Capricorn, imaginary line of latitude showing the southernmost point on the earth at which the sun can appear directly overhead. The sun's rays shine straight down on the Tropic of Capricorn on December 21 or 22, which is the winter solstice and the first day of winter in the Northern Hemisphere. Lying 23°27' south of the equator and running completely around the earth, the Tropic of Capricorn also marks the southern boundary of the Tropical Zone.