Explanation:
What if the atmosphere above you became one gigantic lens?
This actually happens when a nearly transparent sheet of
pyramid shaped ice crystals
falls from the sky in a common orientation.
These ice-crystals act together like millions of miniature ice mirrors, with external and internal reflections from different faces creating
arcs and halos of different radii.
An amazing display of pyramid ice crystal halos was
captured
on June 5 above
Tampere,
Finland.
Visible above are
very unusual sun halos
of 9, 18, 20, 23, and 24 degrees.
In contrast, thin and flat falling ice crystals will
produce a halo of
22 degrees only.
The high clouds containing the ice crystals are faintly visible, as are some
sundogs.
The usual Sun image was covered behind a light post,
and the above image was significantly digitally sharpened.
It is not currently known how large areas of nearly uniform
pyramidal ice crystals form.
digg_url = 'http://apod.nasa.gov/apod/ap080618.html'; digg_skin = 'compact';
