Rare clouds located on the edge of space have been spotted in the night skies over Washington state.
Noctilucent clouds, silvery-blue tendrils that glow in the dark, are the rarest and highest cloud type. Before sunrise on July 1, vivid sightings were reported from Seattle and the community of Keller located in the northeastern part of the state. Since the end of June, they’ve also been seen over the western Canadian provinces of British Columbia and Alberta, along with the countries of Britain, Germany, Denmark and Poland.
And that’s just some of the locations.
Each summer, it’s not unusual for noctilucent clouds to make occasional appearances in the northern sky. During the past few weeks, however, scientists have recorded more frequent appearances than any time in the past 15 years, according to NASA, which studies the mysterious clouds with help from a satellite launched in 2007.
Noctilucent clouds form when extremely cold water vapor congregates around dust from meteors and then freezes into tiny ice crystals. Previously, the clouds were known to appear at higher latitudes near the north and south poles. But in recent years satellite images have been capturing them in at latitudes as far south as central California and Oklahoma.
Not only are the clouds being seen at lower latitudes, but they are also more frequent, according to NASA’s satellite data. And this summer’s uptick exceeds previous spikes going back to 2007, the agency has stated.
Noctilucent clouds form about 50 miles from Earth. Because they’re so high in the sky, they’re able to catch the sun’s lingering light when the lower sky is dark, according to Gavin Pretor-Pinney, author of “The Cloudspotter’s Guide” and founder of the Cloud Appreciation Society.
The fact that they’re being seen at lower latitudes and more frequently “has led some scientists to speculate they are indicators of climate change,” he wrote. Another theory is that an increasing number of rocket launches are leaving behind dust particles that contribute to the clouds’ formation.
Regardless of what’s causing them, noctilucent clouds are ghostly beautiful, and now is the peak time to view them. Visible to the naked eye, they’re most likely to appear 30 minutes to two hours after sunset or 30 minutes to two hours before sunrise. Just head outside and look north.
Keep in mind that unlike the northern lights, they’re notoriously unpredictable. One night they’re in full display. The next night they’re not. So if you’re hoping to see them, check the sky from time to time when the weather is clear within the two-hour period after sunset or before sunrise. Keep in mind, however, that most of the recent sightings have occurred closer to sunrise than sunset.
To get an idea of the amount of excitement being generating among skywatchers, check out the Facebook page Noctilucent Clouds Around the World, www.facebook.com/groups/nlcaroundtheworld.
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