NASAのインスタグラム(nasagoddard) - 10月23日 03時03分

The night sky is never truly dark. If you removed light pollution, the Moon, stars, and galaxies, there would still be a very faint colorful glow. That’s airglow. With cameras, you can photograph it only on the darkest of nights. It’s about one-tenth as bright as the combined light of all the stars in the sky.

Red, green, purple, and yellow swaths of light in the atmosphere are seen in these photos and video of Earth’s limb shot from the International Space Station. They also feature auroras, star trails, city lights — and of course, that's our Earth below.

From above, airglow forms a luminous bubble encapsulating Earth. Appearing right at the boundary between Earth and space, airglow holds clues to how our atmosphere affects weather in space and how space weather affects humans on Earth. The bands of light span 50 to 400 miles above Earth’s surface, through a region called the ionosphere. This is where our GPS signals and astronauts travel.

What makes this region complicated is that it’s constantly changing. It reacts to both energy emanating from the Sun and weather near Earth’s surface. And as the ionosphere fluctuates, so can conditions in near-Earth space, where the Space Station orbits.

Airglow turns out to be a fantastic proxy not only for how particles move through the ionosphere, but also what kinds of particles even exist there — key information for helping us tease out how space and Earth’s weather interconnect.

And that’s a great reason for NASA to study this beautiful phenomenon.
Credit: NASA #nasagoddard #space #science #airglow #sun #moon #stars

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