An unusual “mother of pearl” cloud was spotted in skies above Scotland on Sunday evening and Monday morning, as low temperatures allowed sky-gazers to witness a rare spectacle. Nacreous clouds are one of the highest clouds, forming in the lower stratosphere over polar regions when the Sun is just below the horizon. A rare sight in the UK, these clouds are illuminated from below and often glow in vivid colours, which has led to them being referred to as “mother of pearl” clouds. They appear as large thin discs and are known mainly for the coloured light they reflect after sunset and before sunrise.
One BBC Weather watcher who spotted it said: “Absolutely fantastic Nacreous cloud caught at tonight’s sunset with some gulls flying over. What a fantastic sight to behold”.
According to the Met Office Nacreous clouds form in the lower stratosphere over polar regions when the Sun is just below the horizon, at heights of 68,500 – 100,000 feet.
They wrote: “The ice particles that form nacreous clouds are much smaller than those that form more common clouds. These smaller particles scatter light in a different way, which is what creates the distinctive luminescent appearance.
“Due to their high altitude and the curvature of the Earth’s surface, these clouds are lit up by sunlight from below the horizon and reflect it to the ground, shining brightly well before dawn and after dusk.
“They are most likely to be viewed when the Sun is between 1C and 6C below the horizon and in places with higher latitudes, such as Scandinavia and northern Canada.
“For this reason, they are sometimes known as polar stratospheric clouds. Nacreous clouds only form below -78C so are most likely to occur during the polar winter.”
Very low temperatures are required for them to form, making these clouds only visible from the UK when the cold air which circulates around polar regions in the stratosphere (known as the stratospheric polar vortex). It is then displaced and hovers temporarily over the UK.
While it’s not known exactly how regular – or irregularly – these clouds form, one of the last times such a spectacle was on show in Scotland was back in 2016.
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On Sunday evening and Monday morning, BBC Weather watchers in Scotland from Moray, the Highlands and Aberdeenshire sent in their photographs, with one user Helen citing the clouds as a: “strange thing in the sky”.
While stargazers as astonomy enthusiasts may have been treated to this latest spectacle in the sky, experts have warned that a “major issue” is looming as an abundance of satellites is threatening to “clog up” the night skies.
While satellites are used for crucial means, anything from internet connectivity and navigation to climate change observation studies, there is one problem that an excess of the technologies poses.
Tony Tyson, Professor of Physics and Astronomy at the University of California, Davis, was quoted in the Telegraph saying: “If you just went out in a dark place somewhere and looked at the sky in 2030 it would be a very macabre scene.The sky will be crawling with moving satellites and the number of stars that you would see are minimum, even in a very dark sky. It’s a major issue.”
Last week, The Royal Astronomical Society (RAS), the UK Space Agency (UKHSA), and the Department of Business met for the Dark and Quiet Skies conference in a call for closer regulation.
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There are more than 8,000 satellites orbiting the Earth as space companies launch at staggering rates. In fact, this is a four-fold increase since 2019. This rate will only continue to grow as the commercial global space industry grows.
Satellite launches are usually a flagship indicator of a nation’s burgeoning space sector. Take, for example, the interest around the UK’s first attempted rocket launch last month with Virgin Orbit from Spaceport Cornwall. The private firm’s rocket was meant to take nine satellites into low-Earth orbit, but failed to reach orbit after suffering an anomaly.
While this launch was not successful, SaxaVord, based in Scotland, is hoping to complete a launch by the summer and hopes to complete 30 satellite launches a year once its site in Shetland becomes fully operational.
There is huge excitement building for the UK’s burgeoning space sector, but the scale is much larger when names like SpaceX gets thrown into the mix. Elon Musk’s firm is poised to launch a further 44,000 for its Starlink internet constellation, for instance. All in all, around 400,000 satellites have been approved for Low Earth Orbit (LEO) around the world.
