Rainbow Airglow over the Azores . ... Airglow . Now air glows all of the time, but it is usually hard to see. ... The long-duration exposure nearly along the vertical walls of airglow likely made the undulating structure particularly visible. ... 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. ... NASA Web Site Statements, Warnings, and Disclaimers . ...