An unusual shape in the West Coast sky is the result of mainland Chinese astronautical activity.

People living across the Pacific Northwestern region reported a spinning spiral in the sky on June 18, 2021.

Some witnesses compared the shape to the inter-dimensional portal from Marvel Studios’s “Doctor Strange” superhero movie.

A spiral appears in the South Pacific sky on June 18, 2021. (Courtesy Caledonian Astronomical Association/Facebook)

Astronomers eventually identified the shape as fuel a Chinese Communist Party (CCP) rocket dumped while taking off. Flammable material was discharged during the first stage of liftoff to help prevent the Long March 2C from bursting in space due to residual pressure in the fuel tanks. This created a spiral pattern in the sky.

The rocket’s mission was to deliver four new satellites into low-earth orbits of about 600km (372.8 miles) above sea level, at a 35-degree inclination.

The Caledonian Astronomical Association (CAA) recorded a video of the spectacle, showing the spiral spinning and expanding before it finally faded out. The footage was viewed more than 37,000 times and liked 220 times on Facebook at the time of publication.

This is not the first time the spiral appeared in the South Pacific sky. A previous CCP rocket created the same shape back on May 7. The spiral could be seen in Vanuatu and the New Caledonian settlements of Yate, Thio, and La Tontouta.

“The spiral is when the rocket is tumbling end over end while venting its fuel–it is then exactly like a garden sprinkler,” U.S. astronomer Jonathan McDowell told the Daily Mail.

“In space the spiral stays perfect over hundreds of miles because there is no air to mess up the shape–that is why it looks surprising to us. We are not used to seeing such perfect geometries because, on Earth, there is always wind or friction to distort things,” he added.

The remarks came after the astronomer spent two days investigating the origins of the spiral shape that CAA had reported. McDowell confirmed the CCP’s launch happened just minutes before the shape appeared.

“The only space launch that day took off from China, just 15 minutes or so earlier,” he said according to the publication. “We know the orbit of that rocket because the U.S. space force tracked it once it reached orbit.”

CAA compared the spiral to a shape that formed above Northern European skies about 12 years earlier.

“Based on our initial research, the only similar but even more dramatic phenomenon is the Norway Spiral in 2009,” the association said on Facebook.

A Russian missile launch formed the Norway Spiral after veering off course and spiraling around in the sky.