Last night, 82 km above Earth's surface where our planet's atmosphere meets the vacuum of space, a ray of sunlight hit a wispy, rippling bank of icy noctilucent clouds (NLCs). They lit up, glowing electric-blue, producing this apparition over Queensferry, Scotland:

Noctilucent Clouds
© Adrian Maricic
A stitch of 2 images showing the lateral extent of the NLC display last night. A vivid, bright display, the best of the 2012 season so far for us in Scotland!

"A stitch of 2 images shows the broad extent of the display last night," says photographer Adrian Maricic. "It was bright and vivid, the best of the 2012 noctilucent cloud season so far for us in Scotland!"

Normally confined to Arctic latitudes, the intense NLCs of June 24-25, 2012, dipped all the way down to the south coast of England: "This was my first sighting of 2012," says Pete Lawrence, who photographed the southern edge of the bank from Selsey UK.

In recent years, the "habitat" of noctilucent clouds has been expanding. Breaking through the barriers of high-latitude that once kept them bottled up in the Arctic, NLCs have been sighted as far south as Colorado, Virginia, Kansas, and Utah. Here are some examples of sightings in the lower United States.

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've probably spotted a noctilucent cloud.