People across Europe spotted a mysterious blue blob floating in the night sky on Monday.
Videos posted on social media showed the spiral shining bright above the United Kingdom, Croatia and Poland.
The U.K.’s National Meteorological and Climate agency says it was likely caused by a SpaceX Falcon 9 rocket launch earlier that day. The rocket’s frozen exhaust plume appears to be spinning in the atmosphere, reflecting sunlight and causing the spiral to appear, they said.
