Explanation: The night of June 21 was the shortest night for planet Earth's northern latitudes, so at latitude 48.9 degrees north, Paris was no exception. Still, the City of Light had an exceptionally luminous evening. Its skies were flooded with silvery night shining or noctilucent clouds after the solstice sunset. Hovering at the edge of space, the icy condensations on meteoric dust or volcanic ash are still in full sunlight at the extreme altitudes of the mesophere. Seen at high latitudes in summer months, stunning, wide spread displays of northern noctilucent clouds are now being reported.
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This image shows a satellite view of noctilucent or “night shining” clouds on June 12, 2019. Noctilucent clouds draw their name from the fact that they appear in the twilight hour just after sundown. They float so high in the atmosphere that they are still lit by sunlight even after the Sun has dropped below the horizon for people on the ground. The image is centered on the North Pole and is based on data acquired by NASA’s Aeronomy of Ice in the Mesosphere (AIM) spacecraft. The instrument measures albedo, or the amount of light reflected back to space by the high-altitude clouds. The map is a composite view stitched together from several satellite passes. As Earth’s lower atmosphere warms with spring and summer, the upper atmosphere grows cooler. In the process, ice crystals collect on meteor dust and other particles, creating electric blue wisps on the edge of space—usually 80 to 85 kilometers (50 to 53 miles) in altitude. In the AIM map, noctilucent clouds appear in various shades of light blue to white, depending on the density of the ice particles.