May 17
A beautiful green aurora slathers up the sky in this 2017 June snapshot from the International Space Station. Aurorae have the signature colors of excited molecules and atoms at the low densities that are found at extreme altitudes. Emission from atomic oxygen dominates this view. The glow is green at lower altitudes, but rarer reddish bands extend above the space station's horizon. The orbital scene was captured while passing over a point south and east of Australia, with stars above the horizon at the right belonging to the constellation Canis Major, Orion's big dog. Sirius, alpha star of Canis Major, is the brightest star near the Earth.
Image Credit & Copyright: Jack Fischer, Expedition 52, NASA
