Zodiacal Light and the False Dawn

As seen on Astronomy Picture of the Day an unusual triangle of light is visible along the ecliptic before dawn and after dusk under dark skies, specially in pre-dawn sky of late Summer and early Autumn and just after dusk in late winter and early spring (considered for northern hemisphere and the opposite for southern viewers). Once considered a false dawn, this triangle of light is actually Zodiacal Light, light reflected from interplanetary dust particles. The triangle is clearly visible in this image taken in Namibia. Zodiacal dust orbits the Sun predominantly in the same plane as the planets: the ecliptic. Zodiacal light is so bright at those mentioned time of year because the dust band is oriented nearly vertical at sunrise or sunset, so that the thick air near the horizon does not block out relatively bright reflecting dust.