Seeing Stars: Elusive night-shining clouds
Keith Wilson has had a lifelong interest in the night sky and has written for space and astronomy publications in the UK and USA. He lives under the dark night skies of the Isle of Gigha.
The sky never really gets dark this month here in the west of Scotland which gives us a chance to spot something rare in the sky.
This month and next are the best times of the year for sighting an elusive night sky event called noctilucent or night-shining clouds. These are our highest clouds which gleam blue and silver across our night sky.
But what have these clouds got to do with studying outer space? Well, it is believed these clouds are formed from something that comes from beyond Earth. Most clouds we see in the sky are found up to 15km above us but night-shining clouds are much higher - at 80km - nearly in space.
These clouds are ripply and electric-blue and are sometimes visible an hour or two after sunset in a north-west direction.
Scientists think the clouds are frosted meteor dust, made when crystals of ice form on fine dust particles from meteors which enter our atmosphere from space. Fine dust from eruptions of volcanoes can also create night-shining clouds.
The clouds can only form when temperatures are low and when there’s water vapour available high above us to form ice crystals.
You can’t see meteor dust as it is so tiny but it might surprise you to know that up to 200 tons of dust from space pours down on Earth every day. Some of this dust is likely in your gutters.
The dust comes from planet forming debris, disintegrating comets and colliding asteroids. Scientists studying ice in the polar regions find it is packed with this space dust.
Cosmic dust may affect our climate by either scattering or absorbing light from the sun. If light reflects away from us, the planet gets colder but if it’s absorbed we get warmer.
Hopefully we will see night-shining clouds rather than grey clouds this summer. If you spot some, please take a photograph and send it in to the Courier as we would love to see them.