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Atmospheric phenomenon
A
full Moon
rising through the Belt of Venus. (Note that the Moon is near the centre of the
field of view
, which means that the Sun must have set below the horizon behind the camera.)
The Belt of Venus as seen from an airliner at an altitude of 42,000 ft (13 km; 8.0 mi)
An animated sequence of the Belt of Venus at dusk, showing how its appearance evolves during evening twilight
The
Belt of Venus
– also called
Venus's Girdle
, the
antitwilight arch
, or
antitwilight
[1]
– is an
atmospheric phenomenon
visible shortly before
sunrise
or after
sunset
, during
civil twilight
. It is a pinkish glow that surrounds the observer, extending roughly
10?20°
above the
horizon
. It appears opposite to the
afterglow
, which it also reflects.
In a way, the Belt of Venus is actually
alpenglow
visible near the horizon during twilight, above the
antisolar point
. Like alpenglow, the
backscatter
of reddened
sunlight
also creates the Belt of Venus. Though unlike alpenglow, the sunlight
scattered
by fine
particulates
that cause the rosy arch of the Belt shines high in the atmosphere and lasts for a while after sunset or before sunrise.
[2]
As twilight progresses, the arch is separated from the horizon by the dark band of
Earth's shadow
, or the "twilight wedge". The pinkish glow is due to the
Rayleigh scattering
of light from the rising or setting
Sun
, which is then backscattered by particulates. A similar effect can be seen on a "blood moon" during a total
lunar eclipse
. The
zodiacal light
and
gegenschein
, which are caused by the
diffuse reflection
of sunlight from
interplanetary dust
in the
Solar System
, are also similar phenomena.
The Belt of Venus can be observed as having a
vivider
pink color during the winter months, as opposed to the summer months, when it appears faded and dim above the yellowish-orange band near the horizon.
[
citation needed
]
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
. Since the greatest
elongation
(
angular separation
between the Sun and a
Solar System
body) of
Venus
is only 45?48°, the
inferior planet
never appears in the opposite of the Sun's direction (
180° difference
in
ecliptic longitude
) from Earth and is thus never located in the Belt of Venus.
See also
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edit
]
References
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edit
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External links
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