On October 7, an astronaut on the International Space Station — orbiting 250 miles over Australia — witnessed the Earth wrapped in a sparkling bright orange color. The scene inspired him to whip out his camera, so that he could capture the mysterious airglow that appeared to be enveloping our planet.
As Live Science reports, the orange color — known as airglow — is a “luminescence” that comes from the many varied chemical reactions that take place high up in Earth’s atmosphere. These reactions end up as bands of light that extend from 50 to 400 miles throughout the atmosphere.
When light from the sun creates ultraviolet radiation, this radiation can sometimes take molecules of oxygen, sodium, nitrogen, and ozone — energizing them. During this energizing process, the different molecules collide with each other. The more they collide, the more energy they lose.
It is this utter depletion of energy that creates the magnificent effects of airglow, which looks impressively like an effervescent shield over Earth — much like the one most recently witnessed on board the International Space Station.
In a statement, NASA have explained that besides being beautiful, airglow is also enormously useful to scientists when it comes to learning more about the movement of particles.
“Airglow reveals some of the workings of the upper reaches of our atmosphere. It can help scientists learn about the movement of particles near the interface of Earth and space, including the connections between space weather and Earth weather. Satellites offer one way to study this dynamic zone. NASA’s Ionospheric Connection Explorer (ICON) satellite will help scientists understand the physical processes at work where Earth’s atmosphere interacts with near-Earth space.”
— SPACE.com (@SPACEdotcom) November 7, 2018
Because of the extreme faintness of airglow, which is one billion times dimmer than sunlight, NASA notes that this phenomenon is best witnessed in the dark of night. However, airglow can be seen at any time of day, and has different names which correspond to these times.
“Technically speaking, airglow occurs at all times. During the day it is called ‘dayglow’, at twilight ‘twilightglow,’ and at night ‘nightglow.’ There are slightly different processes taking place in each case, but in the image above the source of light is nightglow.”
And while airglow is oftentimes cast in a vibrant orange or yellowish light, at other times it can take on a much different hue. This was the case back in 2016, when a photographer was visiting the Azores Islands and witnessed airglow that was every color of the rainbow, as Space reported at the time.
However, regardless of the color presented, airglow is a spectacular phenomenon — a phenomenon which one astronaut aboard the International Space Station was very lucky to witness earlier last month.