Zodiacal cloud

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. It is caused by sunlight scattered by space dust in the zodiacal cloud. It 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 phenomenon—a faint, but slightly brighter, oval glow— directly opposite of the Sun is the gegenschein.

The dust forms a thick pancake-shaped cloud in the Solar System collectively known as the zodiacal cloud, which occupies the same plane as the ecliptic. The dust particles are between 10 and 300 micrometres in diameter, most with a mass around 150 micrograms.

In the mid-latitudes, the zodiacal light is best observed in the western sky in the spring after the evening twilight has completely disappeared, or in the eastern sky in the autumn just before the morning twilight appears. The zodiacal light appears as a column, brighter at the horizon, tilted at the angle of the ecliptic. The light scattered from extremely small dust particles is strongly forward scattering, although the zodiacal light actually extends all the way around the sky, hence it is brightest when observing at a small angle with the Sun. This is why it is most clearly visible near sunrise or sunset, when the sun is blocked, but the dust particles nearest the line of sight to the sun are not. The dust band that causes the zodiacal light is uniform across the whole ecliptic.

...
Wikipedia