Astronomers at ESOs observatories often encounter zodiacal light. (640x360)

Zodiacal light is a faint, diffuse, and roughly triangular white glow visible in the night sky that appears to extend from the vicinity of the Sun along the ecliptic or zodiac. Sunlight scattered by interplanetary dust in the zodiacal cloud causes this phenomenon. Zodiacal light is best seen during twilight after sunset in spring and before sunrise in autumn, when the zodiac is at a steep angle to the horizon. However, the glow is so faint that moonlight and, or light pollution outshine it, rendering it invisible. The zodiacal light decreases in intensity with distance from the Sun, but in naturally dark skies, it is visible as a band completely around the ecliptic. In fact, the zodiacal light covers the entire sky and is largely responsible for the total natural skylight on a moonless, clear night. Another phenomenona faint, but slightly brighter, oval glowdirectly opposite of the Sun is the gegenschein.