APOD: 2026 October 27: Noctilucent Clouds over Sweden

Blue noctilucent clouds spread across the sky above a field near Linkoping, Sweden, in early August 2026 in this Astronomy Picture of the Day. They are the highest clouds, technically polar mesospheric clouds, and become visible after sunset in summer when sunlight from below the horizon lights them. Much about them has only been discovered in the past two decades, so look for them after summer sunsets.