Cosmic Rays, high-energy radiation consisting chiefly of subatomic particles moving at nearly the speed of light.
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 »