July 4, 2020
The story of your birthday began billions of years before calendars existed, in furnaces of light and clouds of dust.
Meeting in the Mesosphere
Birthday · July 4, 2020
A little universe, just for you
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APOD published July 4, 2020. Credit: Stephane Vetter. A publication-date match, not a photo taken on your date. Independent of NASA.
A sensitive video camera on a summit of the Vosges mountains in France captured these surprising fireworks above a distant horizon on June 26. Generated over intense thunderstorms, this one about 260 kilometers away, the brief and mysterious flashes have come to be known as red sprites. The transient luminous events are caused by electrical breakdown at altitudes of 50 to 100 kilometers. That puts them in the mesophere, the coldest layer of planet Earth's atmosphere. The glow beneath the sprites is from more familiar lighting though, below the storm clouds. But on the right, the video frames have captured another summertime apparition from the mesophere. The silvery veins of light are polar mesospheric clouds. Also known as noctilucent or night shining clouds, the icy clouds still reflect the sunlight when the Sun is below the horizon.
Image credit: Stephane Vetter