The “Belt of Venus” is an atmospheric phenomenon that creates a pink band in the sky at sunrise and sunset. It is actually the area between Earth’s shadow and the blue sky. The belt is similar to alpenglow, which creates a reddish glow just over the horizon.
Facts about the Belt of Venus
- The Belt of Venus is an atmospheric optical phenomenon, but could also be considered a space phenomenon.
- The pink color in the belt is sunlight that is shining through denser atmosphere near the Earth’s surface, and being reflected off of atmosphere at the opposite end of the sky.
- The dark blue layer in the sky below the pink belt is Earth’s “shadow” being cast onto the atmosphere.
- It is visible at sunrise or sunset, but is more pronounced at sunset.
- It is best seen during the summer months, on clear and slightly hazy evenings.
- The Belt of Venus has several names, including antitwilight arch.
What causes the Belt of Venus?
Several factors contribute to the Belt of Venus phenomenon.
- Anti-twilight or Alpenglow forms. During sunset on clear evenings, the atmosphere around the horizon opposite of the Sun appears as a light shade of orange and pink. The pink color is sunlight that is shining through denser atmosphere near Earth’s western horizon, and reflecting off of atmosphere on the opposite side of the observer. The term for this reflection back towards the observer is backscattering.
This creates a pink “band” near the eastern horizon. The same pink light is often seen on mountain tops at sunset, which is where the term “Alpenglow” comes from.
- Earth’s shadow appears. As Earth rotates, sunlight ceases to reach parts of the atmosphere near Earth’s horizon on the side of the sky opposite the Sun. Earth’s shadow is being cast on the atmosphere, and it is no longer reflecting direct sunlight.
- Earth’s shadow rises. As Earth’s shadow continues to emerge, it makes the pink band appear to separate from the horizon. This gives the band more of a dramatic arch shape. We call this arch the Belt of Venus.
Intensity of the Belt
Backscatter causes the colors of the belt to become more pronounced and vivid right before the sun rises or just after it sets for the day. During sunrise and sunset, the effects of scattering are magnified, which is why a rising and setting sun typically has a spectacular red glow.
Best time to view the Belt
While this phenomenon can be seen at sunrise, the best time to find it is at sunset. As the Sun is setting in the West, the belt will be visible in the eastern sky (remember that it’s visible opposite the sun). The best conditions for getting a nice view are when the sky is clear, when there’s minimal wind and humidity, and when there are no obstructions on the horizon. When it’s visible, the belt will appear anywhere from 10° to 46° over the horizon line.
Why is it called the Belt of Venus?
It is called this due to an association of the phenomenon with the greek goddess Aphrodite and roman goddess Venus. It is not associated with the planet Venus.