People across the south Pacific islands, including New Caledonia, Tokelau, Samoa and Fiji, all reported spotting the same spiral phenomenon in the skies on Friday night, June 18.
The spectacular spiral formation baffled viewers, who recorded video and photographs of it and took to social media to share what they saw.
An expert has explained that the incredible koru-like phenomenon was actually a release of gas from a Chinese rocket.
Footage posted on social media shows the spiral shape expanding in size over a matter of seconds, before eventually vanishing in the night sky.
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According to New Caledonia's Astronomy Association, the culprit was a Chinese rocket that took off from Xichang launch centre on Friday.
"Jonathan McDowell, an American astronomer who lists all manoeuvres and orbital launches on the planet, has confirmed it was the second floor of a Chinese Long March 2 C rocket, which took off June 18 at 06 h25 UTC from Xichang launch center, with 4 satellites on board," Association Calédonienne d'Astronomie posted on Facebook.
"Amaury Bellee, who contacted him, explains: 'After completing its mission, the floor would have expelled his fuel (from UDMH and nitrogen peroxide) to passivate, i.e. avoiding it exploding into orbit due to the residual pressure in the tanks. This is the phenomenon you've been observing.'"
A further update from the association explains that the phenomenon had occurred before, in May, and will likely be seen again.
After exchanges with Jonathan McDowell, who is one of the best specialists in the world in terms of manoeuvres and orbital launches, we have confirmation that the spiral phenomenon observed on May 7 at 5 has the same type of origin as seen on June 18 at about 18 pm," the association wrote.
"Indeed, in all two cases, less than half an hour before, a rocket Long March 2 C was launched from the same location with the same parameters (a 34° orbit inclination with a southeast launch direction according to Joseph Remis, another subject specialist). So it was also a degassing as explained below. It is possible that in the future we will have the same show again provided it is done under the same lighting conditions, at dawn or dusk."
According to the same source, a similar launch is also scheduled for July so, should conditions allow, the same phenomenon could grace the skies again.