APOD: 2026 October 27 – Noctilucent Clouds over Sweden

Discover the cosmos!Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. Explanation:Sometimes it's night on the ground but day in the air. As the Earth rotates to eclipse the Sun,sunset rises upfrom the ground. Therefore, at sunset on the ground, sunlight still shines oncloudsabove. Underusual circumstances, a pretty sunset might be visible, but unusualnoctilucent cloudsfloat so high up they can be seen well after dark. Normally too dim to be seen,theymay become visible just after sunset during the summer when illuminated by sunlight from below the horizon.Noctilucent clouds are the highest clouds and are known more technically aspolar mesospheric clouds. Featured here as they appeared in early August, a network of blue noctilucent clouds was captured in the distant sky above a field of green grass nearLinköping,Sweden, with trees instark silhouetteacross the horizon. Much aboutnoctilucent cloudshas beendiscoveredonly in the past two decades, whilehow they form and evolveremains a topic ofactive research.Tomorrow's picture:round and round