June 21, 2019: What do you get when you mix the summer solstice with one of the deepest Solar Minima in a century? Extreme noctilucent clouds.
“On June 21st, at least 80% to 90% of our sky was covered by bright electric-blue waves,” reports Jacob Kuiper of Steenwijk, The Netherlands. “It was unbelievable, so bright and vast. For sure, this was the most extreme display I have seen in 35 years of observing NLCs.”
“I’ve been waiting 10 years to see these clouds in Paris,” says photographer Sylvain Weiller. “Finally, the NLCs are back!”
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.
This close-up photo taken by Sebastian Voltmer of Spicheren, France, shows the clouds’ tell-tale wave structure:
This summer, extra moisture in the mesosphere has super-charged noctilucent clouds, allowing them to be sighted as far south as Rome, Italy; Los Angeles, California; and Paris, France. No one can predict exactly when they will appear. Tonight could be the night where you live.
Observing tips: Look west 30 to 60 minutes after sunset (or before sunrise) when the sun is just below the horizon. If you see luminous blue-white tendrils spreading across the sky, you may have spotted a noctilucent cloud.