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Credit & Copyright: Juan Carlos Casado
Explanation:
Have you ever seen a halo around the Moon?
This fairly common sight occurs when high thin clouds containing millions of tiny
ice crystals cover much of the sky.
Each ice crystal acts like a miniature lens.
Because
most
of the crystals have a similar
elongated hexagonal shape,
light entering one crystal face and exiting
through the opposing face refracts 22 degrees,
which corresponds to the radius of the Moon Halo.
A similar
Sun Halo
may be visible during the day.
The town in the foreground of the
above picture is
San Sebastian,
Spain.
The distant planet
Jupiter
appears by chance on the
halo's upper
right.
Exactly
how ice-crystals form
in clouds remains under
investigation.
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NASA Web Site Statements, Warnings, and Disclaimers
NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
Based on Astronomy Picture
Of the Day
Publications with keywords: Moon - halo
Publications with words: Moon - halo
See also: