Astronomy Picture of the Day
Discover the cosmos!
Each day a different image or photograph of our fascinating universe is
featured, along with a brief explanation written by a professional astronomer.
2014 September 6
Moonbow Beach
Image Credit &
Copyright:
Rogelio Bernal
Andreo (Deep Sky Colors)
Explanation:
Like a rainbow at night,
a beautiful moonbow shines above the western horizon in this
deserted beach scene from Molokai Island,
Hawaii,
USA, planet Earth.
Captured last June 17 in early morning hours, the lights along
the horizon are from Honolulu and cities on the island of Oahu
some 30 miles away.
So where was the Moon?
A rainbow is
produced by sunlight internally reflected in
rain drops from the direction
opposite the Sun
back toward the observer.
As the light passes from air to water and back to air again, longer
wavelengths are refracted (bent) less than shorter ones
resulting in the separation of colors.
And so the moonbow is produced as raindrops reflect moonlight
from the direction opposite the Moon.
That puts the Moon directly behind the photographer,
still low and rising over the eastern horizon,
a few days past
its full phase.
Tomorrow's picture: There was the Moon.
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Authors & editors:
Robert Nemiroff
(
MTU) &
Jerry Bonnell (
UMCP)
NASA Official: Phillip Newman
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