The
Belt of Venus or
Venus's Girdle is an
atmospheric phenomenon seen at
sunrise and
sunset. Shortly after sunset or shortly before sunrise, the observer is, or is very nearly, surrounded by a pinkish glow (or
anti-twilight arch) that extends roughly 10°–20° above the horizon. It is similar to
alpenglow as they both are caused by backscattering of reddened sunlight. The only difference is that alpenglow is characterized by afterglow and is a red horizontal band visible just after sunset or before sunrise due to direct illumination of
clouds and
aerosols low in the atmosphere, whereas the Belt of Venus is a rosy pinkish arch visible long after sunset or long before sunrise, caused by
backscattering of
refracted sunlight due to fine dust particles high in the atmosphere. In a way, the Belt of Venus is a true
alpenglow visible at twilight near the
anti-solar point. Often, the glow is separated from the horizon by a dark layer, the
Earth's shadow or "dark segment." The arch's light pink color is due to
backscattering of reddened light from the rising or setting
Sun. A very similar effect can be seen during a total
solar eclipse. The
zodiacal light, which is caused by reflection of sunlight from the
interplanetary dust in the
solar system, is also a similar phenomenon.