People in the Kempen District of Antwerp Province and eastern Flemish Brabant witnessed a beautiful sight last night: noctilucent clouds or night shining clouds. These are tenuous cloud-like phenomena in the earth’s upper atmosphere.
Marc Van den Broeck of the Urania observatory told VRT:
"These are clouds of ice crystals at an altitude of 80 kilometres. At night they reflect sunlight from behind the horizon " and that resulted in the amazing sight witnessed by people in Gierle (Lille – Antwerp Province) on Wednesday night.
Amateur photographer Bart Medaer posted a beautiful timelapse video showing night shining clouds on Twitter. It’s a phenomenon that means there is still light after sunset, but only high up in the sky.
Images also surfaced from Oplinter (Tienen – Flemish Brabant). "This is the first quality observation of night shining clouds I’ve seen this year," says Urania’s Marc Van den Broeck.
Ice crystals at an altitude of 80 kilometres
Night shining clouds occur much higher in the sky than normal clouds. "Ordinary veil clouds occur about 10 to 12 kilometres above the ground. Night shining clouds occur at altitudes of up to 80 kilometres in the sky. They consist of ice crystals that reflect light from the sun that is already behind the horizon in front of us. Because they occur at such high altitudes, they still capture the sunlight. The sky stays bright even two hours after sunset and also from two hours before sunrise onwards."
The phenomenon is visible only in clear weather between mid-May and mid-July. "Basically, these are the last days of the year when you have a chance to see night shining clouds. After mid-July, the sun sinks too low below the horizon," Van den Broeck concludes.