A strange, spiraling light in the evening sky has many New Zealanders speculating about overseas travel. In fact, the phenomenon goes entirely back to earthly forces.

“It looked like a giant spiral galaxy just hanging in the sky and slowly drifting over it,” says hobby astronomer Alasdair Burns, describing the event that occurred on Sunday evening (local time) in southern New Zealand. What got many people excited but also confused: “A really scary feeling,” Burns later told the Guardian.

The various causes of phantoms have been debated on social media, from aliens to black holes to a new kind of advertisement in the night sky. But the assumption that came closest to reality was that the light in the sky came from a rocket test. These are “weird, but easy to explain”, said physicist Richard Easter in the Guardian. According to him, the spiral light phenomenon is a side effect of launching a satellite into space.

“When the propulsion stage is turned off after launch, water and CO2 are still released, which together form a cloud that is lit by the Sun,” explains Ether. “The orbit of the satellite and our relative position from the Sun produced these completely insane clouds that could be seen from the southern islands.” According to Eicher, a rocket from Elon Musk’s company SpaceX was responsible for the spiral light. SpaceX on Sunday launched a satellite into Earth orbit from the US state of Florida.