Gegenschein

Gegenschein is a faint, diffuse glow in the night sky that appears opposite the Sun. It is caused by sunlight scattering off dust particles in the zodiacal cloud, a disk-shaped collection of dust and debris orbiting the Sun. The zodiacal cloud is concentrated along the ecliptic, the apparent path of the Sun across the sky. Gegenschein is most visible in very dark locations, far from light pollution, and is typically observed as a hazy patch of light.

The intensity of gegenschein varies depending on the density of the zodiacal dust and the observer's position relative to the Sun. It is generally fainter than zodiacal light, which is a similar phenomenon but appears closer to the Sun. While gegenschein is a natural phenomenon, it can sometimes be confused with faint terrestrial atmospheric phenomena or even faint nebulae. Its study helps astronomers understand the distribution and composition of interplanetary dust.