north celestial pole		pair of quantities, right ascension and declination (2wds)
summer solstice		a human grouping of stars in the night sky into a recognizable pattern
right ascenstion		date on which the Sun crosses the celestial equator moving northward, near March 21(2wds)
galaxy		point on the celestial sphere directly above Earth's North Pole (3wds)
seasons		the period of time between the instant when the Sun is directly overhead to the next time it is directly overhead (2wds)
astronomical unit		imaginary sphere surrounding Earth (2wds)
solar day		changes in average temperature and length of day that result from the tilt of the Earth's axis
celestial sphere		celestial coordinate used to measure longitude on the celestial sphere (2 wds)
declination		celestial coordinate used to measure latitude above and below the celestial equator on the celestial sphere
ecliptic		one of eight bodies that orbit the Sun, visible to us by reflected sunlight
zodiac		point on the ecliptic where the Sun is at its northernmost point above the celestial sphere (2wds)
celestial coordinates		date on which the Sun crosses the celestial sphere moving southward, near Sept . 22 (2wds)
autumnal equinox		the average distance of Earth from the Sun (2wds)
tropical year		gravitationally bound collection of a large number of stars
planet		the time interval between one vernal equinox and the next.(2wds)
celestial equator		the time needed between successive risings of a given star (2wds)
south celestial pole		the projection of Earth's equator onto the celestial sphere (2wds)
triangulation		point on the celestial sphere directly below Earth's South Pole (3wds)
vernal equinox		the twelve constellations on the celestial sphere through which the Sun appears
parallax		the apparent motion of a relatively close object with respect to a more distant background
constellation		method of determining distance based on the principle of geometry
sideral year		the apparent path of the Sun