Noctilucent Clouds Hop the Atlantic
In 2015, the first reports of noctilucent clouds (NLCs) came from Europe. Now the clouds have hopped the Atlantic, and Canadians are seeing them, too. "Despite the full Moon in the opposite part of the sky, the NLC display was quite noticeable," reports Alister Ling, who sends this picture from Edmonton, Alberta:
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 first appeared in the 19th century after the eruption of super-volcano Krakatoa. At the time, people thought NLCs were caused by the eruption, but long after Krakatoa's ash settled, the clouds remained. In recent years, NLCs have intensified and spread with summer sightings as far south as Utah and Colorado. This could be a sign of increasing greenhouse gases in Earth's atmosphere.
Observing tips: Look west 30 to 60 minutes after sunset when the Sun has dipped 6o to 16o below the horizon. If you see luminous blue-white tendrils spreading across the sky, you may have spotted a noctilucent cloud.
Observing the sky can be thought of as a form of entertainment, too.