Belt of Venus

The Belt of Venus or Venus's Girdle or Twilight Wedge^[1] is an atmospheric phenomenon seen shortly before sunrise or shortly after sunset. The observer is, or is very nearly, surrounded by a pinkish glow (or anti-twilight arch) that extends roughly 10°–20° above the horizon.

Like alpenglow, backscattering 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 just after sunset or before sunrise. Unlike alpenglow, the sunlight refracted in the fine dust particles that create the rosy pinkish arch of the Belt of Venus hover high in the atmosphere and perpetuate it long after sunset or long before sunrise. 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.

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.

ALMA and Chajnantor at twilight. Lying between the two groups of antennas are the Earth's shadow and Belt of Venus phenomena.^[2]

Gallery

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  Full moon rising near Linz, Austria. Observed through the Belt of Venus.

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  Belt of Venus at 42,000 feet (13,000 m)

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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.

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  Belt of Venus photographed over a lake in Seattle, Washington.

See also

• Anticrepuscular rays
• Atmospheric refraction
• Blue hour
• Earth's shadow
• Golden hour or Magic hour

References

• Naylor, John (2002). Out of the blue : a 24-hour skywatcher's guide. Cambridge: Cambridge University Press. p. 72. ISBN 0-521-80925-8. 

External links

• NASA Astronomy Picture of the Day: The Belt of Venus over the Valley of the Moon (23 July 2006)
• NASA Astronomy Picture of the Day: The Belt of Venus Over Mercedes, Argentina (scroll to right of image for best view) (7 February 2012)
• Shadow of Earth, Belt of Venus as seen over Half Dome, Yosemite National Park, displayed in an interactive panorama. Scroll to the very bottom of the post to view, after all other Yosemite panoramas.

Parts of a day
	Dawn–Twilight–Sunrise Morning Daytime Evening Sunset–Twilight–Dusk Night
	Related articles: Belt of Venus Blue hour Golden hour Terminator Daylight Forenoon Noon Afternoon Midnight Midnight sun Polar night

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