June 11, 2019: On June 8th and 9th, many people who have never previously heard of “noctilucent clouds” (NLCs) found themselves eagerly taking pictures of them–from moving cars, through city lights, using cell phones and iPads. “I have never seen clouds like this before!” says Tucker Shannon, who took this picture from Corvallis, Oregon:
“I heard that they may have been seeded by meteoroids,” says Shannon.
That’s correct. NLCs are Earth’s highest clouds. Seeded by meteoroids, they float at the edge of space more than 80 km above the planet’s surface. The clouds are very cold and filled with tiny ice crystals. When sunbeams hit those crystals, they glow electric-blue.
Noctilucent clouds used to be a polar phenomenon. In recent years, however, researchers have noticed their electric-blue forms creeping south. Is it climate change? Or the solar cycle? No one knows for sure.
This past weekend, even veteran observers were stunned by the clouds’ intensity and southern reach. At one point, they were visible in Freedom, Oklahoma (latitude +36.7 N). As far as we know, that is the lowest latitude sighting ever. Other notable low-latitude sightings include San Francisco, California, and the Cedar Breaks National Monument in Utah.
Still images of NLCs capture only a fraction of their magic. These small videos recorded by Keven Lapp outside Edmonton, Alberta, show their hypnotic fine-structured rippling motions:
“This was one of the largest NLCs that I’ve ever seen,” says Lapp. “The time lapse was taken between 2:40 AM and 3:24 AM local time.”
At present, no one can predict exactly when these noctilucent clouds will re-appear. Recent events suggest that even mid-latitude observers should be alert. Observing tips: Look west 30 to 60 minutes after sunset when the sun has dipped below the horizon. If you see luminous blue-white tendrils spreading across the sky, you may have spotted a noctilucent cloud.