1. "To get the noctilucent clouds you need temperatures that are about 20 degrees Kelvin colder than what we see on average up there," Wickwar said.

2. Pictured above earlier this month, a network of noctilucent clouds cast an eerie white glow after dusk, above the the city of Edmonton, in Alberta, Canada.

3. The clouds are also called noctilucent, or "night-shining, " clouds because they are usually seen at twilight.

4. The preparation technique and application of noctilucent powder and noctilucent glaze were introduced in this paper.

5. People first spotted the noctilucent clouds a few years after the 1883 eruption of the Krakatoa super-volcano in Indonesia created spectacular sunsets from ash in the atmosphere.

6. Noctilucent clouds were first observed in 1885 by an amateur astronomer.

7. Noctilucent clouds appear about 80 kilometres above the Earth in each hemisphere's summer.

8. Noctilucent clouds are a fundamentally new phenomenon in the temperate mid-latitude sky, and it's not clear why they've migrated down from the poles.

9. Much about noctilucent clouds has been discovered only over the past few years, while how they form and evolve remains a topic of active research.

10. THE comings and goings of noctilucent or "night shining" clouds in the extreme upper atmosphere may be linked to the sun's rotation.

11. Polar mesospheric, or noctilucent ("night shining"), clouds usually are seen at twilight, following the setting of the sun below the horizon and darkening of Earth's surface.

12. Rare earth noctilucent fibers are a kind of new materials, provided with special function.

13. The recent observations of noctilucent clouds at all kinds of latitudes provide an extra impetus to understand what is going on up there.

14. Polar mesospheric clouds are also known as noctilucent or "night-shining" clouds—a property that is clearly visible in this astronaut photograph.

15. Noctilucent clouds are ragged extensions of a more widespread and more permanent layer which forms over the summer polar area at the mesopause.

16. Photographers and other sky watchers in Omaha, Paris, Seattle, and other locations have run outside to capture images of what scientists call noctilucent ("night shining") clouds.

17. It is the season for viewing Polar Mesospheric Clouds, and with our high beta-angle we were able to capture this thin layer of noctilucent clouds at sunset (6-25-2010).

18. In this paper, the illuminant principle and functional characters of rare earth noctilucent fibers were summarized, and then analyze its wearability and application area.

19. Captured by flickr user, breff 3. A rendering of the noctilucent clouds created from data obtained by Russel's NASA project, AIM.

20. The sky over Omaha on July 14th, snapped by Mike Hollingshead at Extreme Instability 2. A rendering of the noctilucent clouds created from data obtained by Russel's NASA project, AIM.