Airglow is the light of excited atoms high in Earth’s atmosphere. Here’s an explanation from NASA Earth Observatory:
The phenomenon typically occurs when molecules (mostly nitrogen and oxygen) are energized by ultraviolet (UV) radiation from sunlight. To release that energy, atoms in the lower atmosphere bump into each other and lose energy in the collision. But the upper atmosphere is thinner, so atoms are less likely to collide. Instead they release their energy by emitting photons. The result is colorful airglow.
Yuri Beletsky Nightscapes captured this image in Banff National Park in Alberta, Canada. in October 2018. Yuri said:
Here you can see a view of a river, with the prominent Big Dipper just above the mountains. Airglow waves were all over the sky!
Thank you, Yuri!
Want to know more about airglow? Here’s a video from NASA.
Bottom line: Photo of airglow and Big Dipper over Banff National Park, Alberta, Canada, and video explaining airglow.
Eleanor Imster has helped write and edit EarthSky since 1995. She was an integral part of the award-winning EarthSky radio series almost since it began until it ended in 2013. Today, as Lead Editor at EarthSky.org, she helps present the science and nature stories and photos you enjoy. She also serves as one of the voices of EarthSky on social media platforms including Facebook, Twitter and G+. She and her husband live in Tennessee and have two grown sons.