Rainbow Airglow over the Azores
Explanation:
Why would the sky glow like a giant repeating rainbow?
Airglow.
Now air glows all of the time, but it is usually hard to see.
A disturbance however -- like an approaching storm -- may cause noticeable rippling
in the
Earth's atmosphere.
These gravity waves are
oscillations in air analogous
to those created when a
rock is thrown in calm water.
The long-duration exposure nearly along the vertical walls of
airglow likely made the undulating structure particularly
visible.
OK, but where do the colors originate?
The deep red glow likely originates from
OH molecules
about 87-kilometers high, excited by
ultraviolet light
from the Sun.
The orange and green
airglow
is likely caused by
sodium and
oxygen atoms slightly higher up.
The
featured image was captured during a
climb up
Mount Pico in the
Azores of
Portugal.
Ground lights originate from the island of
Faial in the
Atlantic Ocean.
A spectacular sky is visible through this banded airglow, with the central band of
our
Milky Way Galaxy running up the image center, and M31,
the
Andromeda Galaxy, visible near the top left.
Explore Your Universe:
Random APOD Generator
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.
