Did you see a glowing purple spiral in the night sky?

A glowing, swirling spiral of blue and purple was seen across the UK and also in parts of Europe on Monday night.

But what was it?

The cloud-like shape appeared for several minutes before disappearing, and experts think it was caused by leftover fuel from a rocket launch in the United States.

The rocket, called Falcon 9, was launched by SpaceX, the company owned by Elon Musk.

The launch, a classified US government mission, took place in Florida at 1:50pm local time, or 5:50pm UK time.

In a post on X, SpaceX said: "Falcon 9's first stage has landed on LZ-1 in Florida".

Physicist and space expert Professor Brian Cox reposted, saying: “For everyone asking about the strange spiral shape in the sky earlier - it was associated with this launch”.

The Falcon 9 is a reusable rocket. After launching into space, it releases what is called its payload - which is the equipment it’s carrying, such as a satellite - which then continues its journey into Earth's orbit.

Once that’s happened, the rocket turns around and heads back home. As it comes down, it releases any leftover fuel. The fuel freezes quickly because it's so high up in the sky.

The spiral shape happens because of the rocket's movement, and when light hits the frozen fuel, it reflects to display the colourful swirling pattern people saw from the ground.

The Met Office, which monitors UK weather, explained what had happened on social media, saying: “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.”