These ghostly wisps are called noctilucent clouds. They are perhaps the most rarely viewed cloud formation, only visible on Earth from higher latitudes after the Sun has dipped below the horizon, illuminating them from below. They are also the highest atmospheric clouds, at altitudes of nearly 50 miles above the Earth.
The origin of these “night-shining” clouds is debated, as they weren’t seen until after the Industrial Revolution. This jaw-dropping photo was captured from the International Space Station on June 13.