The Earth looks stunning! A new photograph from European Space Agency (ESA) astronaut Thomas Pesquet shows our beloved planet wrapped in its atmosphere, and surrounded by a background of glittering stars. Honestly, it’s like an artwork that came to life! Pesquet managed to capture the night side of Earth from the Cupola of the International Space Station (ISS):
"A few night pictures from the Cupola: sometimes star lights battle it out with city lights for who's the brightest and more beautiful," Pesquet wrote on Flickr. "I'm just lucky to get to be the judge."
The glowing atmosphere, not mentioned by Pesquet, is also astonishing. It's called nightglow, and it's created by natural processes.
Earth's sky is never completely dark, not even at night, and not even once you've extracted light pollution, starlight, and diffuse sunlight. The molecules in the atmosphere are constantly undergoing various processes, which causes them to faintly glow across a range of wavelengths.
Nightglow, which appears at night, occurs when molecules and particles broken apart during the day by solar radiation (a process called photoionization) recombine, releasing their excess energy in the form of photons. On Earth, this occurs in layers – the blue-green layer at the outer edge is oxygen and nitrogen.
At a lower altitude, the red-gold layer is called the sodium layer. This is where meteors break apart, releasing sodium into the atmosphere. Photoionization and recombination of sodium atoms then produces a distinctive golden glow.
Image credit: ESA/NASA-T. Pesquet