ESO telescope captures red sprites - an elusive form of lightning occurring well-above storm clouds

The European Southern Observatory's Picture of the Week shows red sprites - an elusive form of lightning that occurs well-above storm clouds, discharging electricity high up in Earth's atmosphere at an altitude of 50-90km. This mesmerizing picture was taken at the platform of ESO's 3.6m telescope at La Silla in the middle of Chile's Atacama desert.

Capturing red sprites on camera is a real challenge because of their elusive nature. According to ESO, the first photographic evidence for them was only taken in 1989.

These mysterious bursts of light occur much higher in the sky than regular lightning. Another unusual feature of sprites is that they are cooler than the white lightning we usually see and appear much fainter.

This Picture of the Week captures a very elusive phenomenon: red sprites. This is a form of lightning occurring well-above storm clouds, discharging electricity high up in Earth's atmosphere at an altitude of 50-90km.🔗 https://t.co/uykgr4AjUZCredit: @zdenek_bardon / @ESO pic.twitter.com/XAovz0Y64j

— ESO (@ESO) August 22, 2022

The green hue in this picture is called airglow - diffuse bands of light that stretch 50 to 400 miles into our atmosphere. The phenomenon occurs all around the Earth, all the time, but can only be seen in very dark skies where there is no light pollution.

According to NASA, airglow occurs when atoms and molecules in the upper atmosphere, excited by sunlight, emit light to shed their excess energy. Or, it can happen when atoms and molecules that have been ionized by sunlight collide with and capture a free electron. In both cases, they eject photon to relax again.

Airglow is similar to auroras, but where auroras are driven by high-energy particles originating from the solar wind, airglow is energized by ordinary, day-to-day solar radiation. Airglow carries information on the upper atmosphere's temperature, density, and composition, but it also helps trace how particles move through the region itself.