Explanation:
Sometimes falling ice crystals make the atmosphere into a
giant lens causing arcs and halos to appear around the Sun or Moon.
This past Saturday night was just such a time near
Madrid,
Spain,
where a winter sky displayed not only a bright Moon but
as many as four rare lunar halos.
The brightest object, near the top of the above image, is the Moon.
Light from the Moon
refracts through tumbling
hexagonal ice crystals into a
22 degree halo
seen surrounding the Moon.
Elongating the 22 degree arc horizontally is a
circumscribed halo caused by
column ice crystals.
More rare, some moonlight refracts through more distant tumbling ice crystals to form a (third)
rainbow-like arc 46 degrees from the Moon and appearing here
just above a picturesque winter landscape.
Furthermore, part of a whole
46 degree circular halo
is also visible, so that an extremely rare -- especially for the Moon --
quadruple halo
was actually imaged.
The snow-capped trees in the foreground line the road
Puerto de Navacerrada in the
Sierra de Guadarrama mountain range near Madrid.
Far in the background is a famous winter skyscape that includes
Sirius, the
belt of Orion, and
Betelgeuse all visible between the inner and outer arcs.
Halos and arcs typically last for minutes to hours,
so if you do see one there should be time to invite family, friends or neighbors to
share your unusual lensed vista of the sky.
Quick Poll:
Have you ever seen a lunar halo?
