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Астронет: Астрономическая картинка дня Серебристые облака над Эдмонтоном http://variable-stars.ru/db/msg/1252924/eng |
Credit & Copyright: Greg Scratchley
(RASC Edmonton)
Explanation:
Sometimes it's night on the ground but day in the air.
As the Earth rotates to eclipse the Sun,
sunset rises up from the ground.
Therefore, at sunset on the ground,
sunlight still shines on clouds above.
Under usual circumstances, a
pretty sunset
might be visible, but unusual
noctilucent clouds float so high up they
can be seen well after dark.
Normally too dim to be seen,
they may become visible at sunset during late summer
when illuminated by sunlight from below.
Noctilucent clouds are
the highest clouds known and thought to be part of
polar mesospheric
clouds.
Pictured
above earlier this month,
a network of
noctilucent
clouds cast an eerie white glow after dusk, above the the city of
Edmonton, in
Alberta,
Canada.
Much about
noctilucent clouds has been discovered only over the past few years, while how
they form and evolve remains a
topic of active research.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.