91Èȱ¬

Residents across the UK have been amazed by rare sights in the sky on Tuesday and Wednesday evenings.

Looking like a "portal to the next dimension" or possibly a spaceship, the shimmering colours of nacreous cloud were spotted.

One of the highest clouds in our atmosphere, they are often referred to as "mother-of-pearl", and are rarely spotted in the UK because of the exceptional conditions needed.

Nacreous cloud form in very cold conditions over polar regions and within the stratosphere, around 12-19 miles (19-31km) high, far above our normal clouds.

91Èȱ¬ Weather Watcher SazzyJ "spotted this cloud iridescence from our garden in Edinburgh late afternoon. We'd never seen anything like it before".

"A portal to the next dimension" said Weather Watcher SkyWatcher.

Another commented "Brief, eerie and bright cloud illumination at sunset this evening. Unsure exactly what. No filter, no spaceship."

Occasionally cold polar air, locked in place by strong winds high up in the atmosphere - called the polar vortex - weakens and allows this colder air to sink south to our latitude.

Formed in air that is around -80C, tiny ice crystals refract sunlight, giving the cloud pearly colours - the reason why it is also called mother-of-pearl.

Nacreous clouds are mostly seen a couple of hours either side of sunset or sunrise and, being so high, they are still lit by sunlight which makes them appear even brighter in our evening sky.

Because of the height and temperature needed this cloud is also known as Polar Stratospheric Cloud.

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