Airglow Borealis
Explanation:
The best known
asterism in northern skies hangs over the Canadian
Rockies in this mountain and night skyscape taken last week from
Banff National Park.
But most remarkable is the amazing greenish airglow.
With airglow visible to the eye, but not in color,
the scene
was captured in two exposures with a single camera,
one exposure made while tracking the stars and one fixed to a tripod.
Airglow emission is predominately from atmospheric oxygen atoms at extremely
low densities.
Commonly recorded in color by sensitive digital cameras the eerie,
diffuse light is seen here in
waves across
the northern night.
Originating at an altitude similar to aurorae, the luminous airglow is
due
to chemiluminescence, the production of light through
chemical excitation and radiative decay.
Energy for the chemical excitation is provided during daytime by the
Sun's extreme
ultraviolet
radiation.
Unlike aurorae which are limited to
high latitudes,
airglow can be found
around the globe.
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.
