Glowing cloud

Noctilucent clouds, one of the highest clouds in the earth's atmosphere, stand out on the black background of the universe in an image taken from orbit.

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An astronaut on the International Space Station (ISS) took a picture of the cloud flying above the Tibetan plateau on June 13, Livescience said. The lower layers of the atmosphere are also illuminated in the image. The lowest floor, called the stratosphere, is light orange and red and is located near the horizon.

Noctilucent cloud layer in the photo that an astronaut
taken from ISS and published on June 25. (Photo: NASA)

As a rare form of clouds, noctilucent clouds are made up of ice crystals 76 to 85 km above the ground. They are only visible after the sun has just set or just before the sun has just risen. Because of the very high position, the noctilucent clouds still receive sunlight from the bottom up while the darkness covers the lower clouds. People often see the brightest clouds in late spring or early summer. Astronauts on ISS often see them above Canada, Northern Europe and Asia in the summer. The frequency of occurrence of noctilucent clouds in the northern hemisphere is higher than that of the southern hemisphere.

Although the number of glowing clouds has increased over the last few decades, their frequency has increased and decreased according to the sun's 11-year operating cycle. They increase sharply when the sun is in the 'gentle' stage, meaning blowing out less UV rays. According to experts, ultraviolet rays can destroy water - which is essential for the process of cloud formation - and maintain high temperatures that prevent ice particles from forming.

A recent study shows changes in temperature and gas composition in the atmosphere that make the cloud glow more and more bright.