Earth's Shadow and the Belt of Venus

Polish version is here

In astronomy, we often focus our attention on objects that are unimaginably distant from us, while extraordinary phenomena can occur right above our heads. One such spectacle is Earth’s shadow, visible in its atmosphere during sunrise or sunset.

Imagine Earth as a massive sphere illuminated by a relatively distant Sun (compared to Earth’s size). Like any object, Earth casts a shadow that extends far into space, and when the Moon happens to pass through it, we observe a lunar eclipse. However, it is less commonly known that Earth’s shadow also extends into its atmosphere.

When and Where to Observe?

The best conditions for observing Earth’s shadow are:

Just after sunset (on the eastern side of the sky) and just before sunrise (on the western side). During these times, sunlight strikes the atmosphere at an angle that makes the shadow more visible.
In locations with an unobstructed horizon, such as flat plains, coastlines, or large lakes.
From elevated areas like hills or mountains.

Observations

Fall 2023, at sunset – Jaworzno (Poland)

urban environment, mostly clear sky

Earth’s shadow appears as a dark band stretching along the horizon. Its color can vary depending on atmospheric conditions and the time of year. It most commonly appears bluish or violet due to the scattering of light by atmospheric gases and dust particles.

As mentioned above, hills and elevated areas are particularly suitable for observing Earth’s shadow, as they provide an unobstructed view of the entire horizon—the higher, the better. For my observation, I took a different approach by using a drone equipped with a camera, which has already proven valuable in many of my nature observations. However, I should note that using such devices requires compliance with applicable regulations.

A few minutes after sunset, I positioned the drone about 100 meters above my head and kept it stationary. I then rotated it along its vertical axis, capturing photographs of the entire horizon. By stitching these photos together, I created a 360-degree panorama, which had to be cut at some point to display it on a flat surface. In Photo 1, the panorama is aligned to face west, with the arrow indicating the point where the Sun had set below the horizon. At this time, the Sun is still just below the horizon, illuminating the sky with a beautiful evening twilight.

Photo 1 – without labels

Photo 1 – with labels

Although our attention typically focuses on the western sky during sunset, it is worth looking in the opposite direction. This view is shown in Photo 2, with the arrow now pointing east—opposite the twilight glow.

Photo 2 – without labels

Photo 2 – with labels

Earth’s shadow appears just above the horizon as a dark blue band extending across more than half the sky. During sunset, Earth’s shadow rises as the Sun sinks below the horizon (during sunrise, the sequence of events is reversed).

Closely associated with Earth’s shadow is a phenomenon known as the Belt of Venus. It appears as a pinkish-orange band, sometimes with a violet hue, just above the dark blue band of Earth’s shadow. This can be seen in Photo 2 and even more clearly in Photo 3, which shows a smaller section of the horizon opposite the setting Sun.

Photo 3 – without labels

Photo 3 – with labels

As shown, there is no sharp boundary between Earth’s shadow and the Belt of Venus—the colors gradually blend into each other. The Belt of Venus forms in the upper atmosphere, illuminated by light from the rising or setting Sun. This reddish hue results from the scattering of shorter wavelengths in the atmosphere. As the Sun sinks further below the horizon, the two bands become less distinct from each other. Eventually, Earth’s shadow and the Belt of Venus fade into the darkness of the night sky.

It is surprising how little-known these phenomena are, despite their frequent occurrence, as they can be observed twice each day under favorable conditions. Not only are these phenomena visually stunning, but they also serve as a reminder that we live on a piece of cosmic rock traveling through the Universe. Moreover, observing Earth’s shadow and the Belt of Venus provides an excellent opportunity to explore atmospheric and optical phenomena.

Photos 1, 2, 3 Parameters:

DJI mini 2 drone

Weird Science