A thin green line of the aurora borealis (northern lights) crosses the top of this photograph, taken by an astronaut on the International Space Station. The moon appears as a white disc just above the aurora. Airglow appears as a blue-white cusp along the Earth’s limb. Russia’s capital city, Moscow, makes a splash of yellow light and is easily recognized by the radial pattern of its highways. Other cities are Nizhni Novgorod (400 kilometers from Moscow), Saint Petersburg (625 kilometers away), and Finland’s capital city Helsinki.