Large Magellanic Cloud (LMC, right) and Small Magellanic Cloud (SMC, left), with bands of red airglow in the night sky over mountains in the Atacama desert, Chile. The LMC and SMC are satellite galaxies of our galaxy the Milky Way. The LMC is around 163,000 light years away, while the SMC is closer at about 199,000 light years away. Airglow is a phenomenon where a planetary atmosphere emits a faint glow when atoms are excited by sunlight. The banding of this glow is caused here by gravity waves in the atmosphere, where weather systems generate large waves as buoyant air masses rise and sink due to the effects of gravity, often as a flow of air meets mountains.