Belt of Venus

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Moon seen through the Belt of Venus. Note that the full Moon is near the centre of the field of view, which means that the Sun must be behind the camera, just below the horizon.

The Belt of Venus, Venus's Girdle, twilight wedge,[1] or antitwilight arch is an atmospheric phenomenon visible shortly before sunrise or after sunset, during civil twilight, when a pinkish glow extending roughly 10–20° above the horizon surrounds the observer.

Like alpenglow, the backscatter of reddened sunlight also creates the Belt of Venus. Unlike the Belt of Venus, the direct illumination of clouds and aerosols that create the afterglow, which characterizes alpenglow, hover low in the atmosphere and create a red horizontal band visible soon after sunset or before sunrise. Unlike alpenglow, the sunlight refracted by the fine particulates that cause the rosy arch of the Belt hovers high in the atmosphere and persists long after sunset or before sunrise. In a way, the Belt of Venus is actually alpenglow visible above the horizon during twilight, near the antisolar point.

As twilight progresses, the glow is separated from the horizon by the dark band of Earth's shadow, or "dark segment." The arch's light pink color is due to the backscatter 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 the diffuse reflection of sunlight from the interplanetary dust in the Solar System, is also a similar phenomenon.

The name of the phenomenon alludes to the cestus, a girdle or breast-band, of the Ancient Greek goddess Aphrodite, customarily equated with the Roman goddess Venus.


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