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Credit & Copyright: Marcella Giulia Pace
Explanation:
Follow
a sunset on a clear day against a distant horizon and you might
glimpse green just as the Sun disappears from view.
The green flash
is caused by refraction of light rays traveling to the eye
over a long path through the atmosphere.
Shorter wavelengths refract more strongly than longer redder wavelengths
and the separation of colors lends a green hue to the last
visible vestige of the solar disk.
It's harder to see a
green flash from the Moon,
not to mention the diminutive disks
of Venus
and Mercury.
But a telescope or telephoto lens and camera can help
catch this tantalizing result of atmospheric refraction
when the celestial bodies are near the horizon.
From Sicily, the top panels were recorded
on March 18, 2019 for the Sun and May 8, 2020 for the Moon.
Also from the Mediterranean island,
the bottom panels were shot during the twilight apparition
of Venus and Mercury
near the western horizon on May 24.
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NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
Based on Astronomy Picture
Of the Day