A “space jellyfish” is the glowing, bell-shaped exhaust plume that sometimes appears after a rocket launch, most often a SpaceX Falcon 9. The rocket’s engines release water vapor and carbon dioxide, and as the rocket climbs into colder, thinner air, that water vapor quickly freezes into ice crystals that trail behind it and spread into a jellyfish shape. The effect is easiest to see when a launch happens around twilight, just before sunrise or just after sunset, when the high-altitude plume is still lit by the sun while the sky below is dark; that sunlight can give the plume a rainbow-like, iridescent look. Launches in full darkness or full daylight rarely produce a visible jellyfish.
Source: FOX Weather — What is a ‘space jellyfish’ and what causes it?
Image: Twilight phenomenon in the wake of a Minotaur I launch from Vandenberg Air Force Base, California, Sept. 22, 2005. U.S. Air Force photo by Staff Sgt. LeeAnn Sunn-Wagner, public domain, via Wikimedia Commons.
