Airglow is the light of excited atoms high in Earth’s atmosphere. It’s usually too faint for the eye alone to see. But under very dark skies, photographers can capture it. Here’s how NASA’s Earth Observatory describes airglow:
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.
But some collisions can also create airglow. In fact, airglow is more common during solar maximum. That’s because the solar activity heats the upper atmosphere, which causes more collisions. Specifically, it causes more collisions that result in greenish light. Spaceweather.com said:
Although airglow does not require solar activity, there is a strong link to the solar cycle. As long ago as 1935, Lord Rayleigh realized that airglow peaks during years around solar maximum. Modern studies (e.g., 2011, 2015 and 2022) have confirmed the effect. Airglow is up to 40% brighter when the sun is most active.
Watch a video on airglow
And here’s another view of airglow from the International Space Station.
If you have a recent photo of airglow to share, send it to us!
View at EarthSky Community Photos. | Steve Price in Last Chance Desert, Utah, took this image on April 2, 2022. Steve wrote: “The Northern Hemisphere Milky Way season is on! My state is endowed with many dark-sky viewing locations: The Last Chance Desert is my favorite. There was green airglow now and then during my session, satellites galore, aircraft and several meteors, too. I’m pretty sure I captured at least one.” Thank you, Steve!View at EarthSky Community Photos. | Dan Bush in Albany, Missouri captured this stunning photograph of a bright meteor on June 2, 2022, and wrote: “I have an amateur astronomer-owned meteor monitoring station at my home in Albany, Missouri. The image shown is an image stack of several frames from one of last night’s bright meteors that showed up on several of my cameras. What appears to be high-thin cirrus clouds to the right in this image is actually airglow and was invisible to the unaided eye at the time. I have captured hundreds of bright meteors over the past decade with my monitoring station. I report my observations to the American Meteor Society.” Thank you, Dan!View at EarthSky Community Photos. | Cecille Kennedy in Cape Kiwanda State Natural Park, Oregon, captured this photo of the Milky Way on August 31, 2021. She wrote: “The bright green radiance to the right of the Milky Way, just over Chief Kiawanda Rock, is airglow, also called nightglow. Swedish physicist Anders Angstrom first identified the airglow phenomenon in 1868. It comes in different colors. The green airglow, fainter than zodiacal light, pervades the night sky from equator to pole. It usually appears 10-15 degrees above the horizon of the observer. The green airglow in the photo is not visible to my eyes, but the camera picked it up to my delight.” Thank you, Cecille!
Bottom line: Airglow is a light that occurs high in Earth’s atmosphere. It’s usually too dim to see with the eye, but photographers can capture glorious photographs of it.
Kelly Kizer Whitt has been a science writer specializing in astronomy for more than two decades. She began her career at Astronomy Magazine, and she has made regular contributions to AstronomyToday and the Sierra Club, among other outlets. Her children’s picture book, Solar System Forecast, was published in 2012. She has also written a young adult dystopian novel titled A Different Sky. When she is not reading or writing about astronomy and staring up at the stars, she enjoys traveling to the national parks, creating crossword puzzles, running, tennis, and paddleboarding. Kelly lives in Wisconsin.
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