Astronomy Vocabulary Mr. Ahearn 2013

Altitude The angular elevation of an object above the horizon

Antarctic Circle 66.5 degrees south Sun doesn’t rise on the winter solstice of the southern hemisphere Doesn’t set in the northern hemisphere

Arctic Circle 66.5 degrees north Sun doesn’t rise on the winter solstice in the northern hemisphere Doesn’t set in the southern hemisphere

Celestial Object Objects in sky beyond Earth’s atmosphere

Equinox A day that the sun rises due east and sets due west. Day and night are equal lengths. Vertical Rays at the equator.

Geocentric A model of the universe with the Earth @ the center

Heliocentric A model of the solar system with the sun at the center.

Revolution Movement of one object around another.

Rotation Spin around an axis (itself)

Solar Noon The time @ which the Sun reaches its highest point in the sky.

Solar Time Time based on observations of when the sun reaches its highest point and crosses a north-south line through the sky.

Summer Solstice June 21st northern hemisphere Dec 21st southern hemisphere Longest insolation Vertical rays @ Tropic of Cancer

Tropic of Cancer 23.5 degrees north Greatest latitude north of the equator reached by sun’s vertical rays.

Tropic of Capricorn 23.5 degrees south Greatest latitude south of equator reached by Sun’s vertical rays.

Vertical Ray Sunlight that strikes Earth’s surface @ angle of 90 degrees

Winter Solstice Dec 21 northern hemisphere June 21 southern hemisphere Shortest day of the year

Zenith Point in sky directly over observers head.