STUNNING: Dying SpaceX rocket triggers giant spiral of light above UK and Europe during secret mission.

At around 8 p.m. local time (4 p.m. ET), people across the U.K. reported seeing the luminous swirl grow as it slowly streaked across the sky like something from a sci-fi movie, according to the BBC. The light show was most clearly visible above parts of England, including Lincolnshire, Yorkshire, Leicestershire, Suffolk and Essex, as well as in Wales and further afield in Sweden, Croatia, Poland, and Hungary.

Photographer Simon Minnican captured the ethereal scene in a stunning video that showed a bright spot appear and then grow in size before swelling into an ever-expanding vortex. The entire spectacle lasted around 12 minutes, with the spiral of light dissipating roughly 4 minutes after it unfurled.

There was initially some wild speculation about what had caused the unusual light show, with at least one observer blaming UFOs. However, experts quickly pointed out that it was a “SpaceX spiral” — an increasingly common phenomenon triggered by light reflecting off rocket fuel dumped into space by spinning SpaceX rockets before they reenter Earth’s atmosphere.

And here’s the video.