Cosmology, the study of the universe. It is both a scientific subject and a philosophical one.
Year, a unit of time. It is based on the time it takes the earth to make one revolution around the sun. See more »
Zenith, the point in the heavens that is directly above the head of the observer. See more »
Zodiac, an imaginary belt in the sky extending some 8 on either side of the ecliptic, the apparent annual path of the sun among the stars. See more »
Zodiacal Light, a faint glow that appears along the zodiac above the western horizon after sunset and above the eastern horizon before sunrise. See more »