Sicilian photo featured as NASA’s photo of the day: “Tramonto” on Earth
The title of the Nasa’s image of the day “Shadows of the Night” has a noir flavor, framing a crucial moment on Earth, perhaps the most celebrated by poets: the sunset. Sicilian astrophotographer Dario Giannobile captured the colors of the Dantean “hour that turns towards desire” in the Plemmirio reserve in Siracusa. “I reconstructed the scene,” explains Giannobile, “to show the evolution of colors during dusk.”
The colors, divided into bands, are caused by direct sunlight reflecting off the air and aerosols in the Earth’s atmosphere, from multiple reflections that sometimes involve a reddened sunset, and from refraction. In practice, these bands can be diffuse and difficult to distinguish, and their colors can depend on the colors near the setting Sun. Finally, the Sun sets completely and the sky darkens. “Time,” Giannobile adds, “flows from the first strip on the left to the last on the right. Starting from the first moment, we can recognize the bright colors in the upper part of the sky. As time passes, we observe the formation of two distinct color zones. The first, at the bottom, is the shadow that the Earth projects on the lower layers of the atmosphere.
The Sun is so low that its rays are blocked by the horizon on which it sets and cannot illuminate the anti-twilight. This band is blue in color and is called the Blue Band or Earth’s Shadow. The rays that do manage to illuminate the upper part of the sky create a pink coloration known to experts as the Belt of Venus. As time passes, the Belt of Venus and the Blue Band are replaced by other formations: the Horizon Band in a pale blue, the Red Band, and a second Earth’s Shadow. How these last two bands form is still the subject of study.
«Tramonto» sulla Terra: è di un siciliano la foto del giorno sul sito della Nasa
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