APOD: 2021 June 19 - Northern Summer Twilight

Good morning, Rallypoint. Today's Astronomy Picture of the Day (APOD) is titled "Northern Summer Twilight." Taken outside of Forrest, Manitoba (Canada) on June 14th, this tranquil scene features one of our old friends: noctilucent clouds. They are the highest clouds in Earth's atmosphere, located in the mesosphere at altitudes of around 76 to 85 km (249,000 to 279,000 ft). They are too faint to be seen in daylight, and are visible only when illuminated by sunlight from below the horizon while the lower layers of the atmosphere are in Earth's shadow. This composite image captures the clouds along with another summer favorite (at least of mine, anyway) in the foreground: fireflies. Aren't the colors wonderful?