What was the glowing blue spiral seen in the night sky above Europe?

A glowing blue spiral was spotted in European skies on Monday evening, causing a stir on social media. 

The swirls were seen across Europe with reports of sightings from the United Kingdom, France, Norway, Germany, Ukraine, Denmark, and Poland. 

The spiral was visible for several minutes before it faded. 

The phenomenon was likely caused by the aftermath of a SpaceX rocket launch in the United States, according to the Met Office, the UK’s national meteorological and climate agency. 

“The rocket’s frozen exhaust plume appears to be spinning in the atmosphere and reflecting the sunlight, causing it to appear as a spiral in the sky,” it said on X. 

The Elon Musk-owned aerospace company noted that one of its Falcon 9 rockets took off on Monday from Florida at around 1.50 pm local time, (6:50 pm CET).

The company said the launch was carried out on a classified US government mission on behalf of the country’s National Reconnaissance Office, which was confirmed by the Kennedy Space Center on X. 

How did the swirls form?

As the Falcon 9 is a reusable two-stage rocket, it releases its payload into space, such as a satellite, before returning to Earth. 

As the first stage comes back, it ejects leftover fuel, which forms a swirl pattern because of the rocket’s movements and freezes due to the altitude.

It is then visible on Earth as light reflects off the frozen fuel.