Spirals of blue light in New Zealand night sky leave stargazers ‘kind of

New Zealand stargazers were left puzzled and awed by strange, spiralling light formations in the night sky on Sunday night.

Around 7.25pm Alasdair Burns, a stargazing guide on Stewart Island/Rakiura, received a text from a friend: go outside and look at the sky. “As soon as we actually went outside, it was very obvious what it was he was referring to,” Burns said.

He saw a huge, blue spiral of light amid the darkness. “It looked like an enormous spiral galaxy, just hanging there in the sky, and slowly just drifting across,” Burns said. “Quite an eerie feeling.”

Burns snapped a few images of the lights on long exposure, capturing the spiral from his phone. “We quickly banged on the doors of all our neighbours to get them out as well. And so there were about five of us, all out on our shared veranda looking up and just kind of, well, freaking out just a little bit.”

The country’s stargazing and amateur astronomy social media groups lit up with people posting photographs and questions about the phenomenon, which was visible from most of the South Island. Theories abounded – from UFOs to foreign rockets to commercial light displays.

“Premonition from our orbital black hole,” said one stargazer. “Aliens at it again,” commented another.

The reality was likely a little more prosaic, said Prof Richard Easther, a physicist at Auckland University, who called the phenomenon “weird but easily explained”.

Clouds of that nature sometimes occurred when a rocket carried a satellite into orbit, he said.

“When the propellant is ejected out the back, you have what’s essentially water and carbon dioxide – that briefly forms a cloud in space that’s illuminated by the sun,” Easther said. “The geometry of the satellite’s orbit and also the way that we’re sitting relative to the sun – that combination of things was just right to produce these completely wacky looking clouds that were visible from the South Island.”

Easther said the rocket in question was likely the Globalstar launch from SpaceX, which the company sent into low-earth orbit off Cape Canaveral in Florida on Sunday.

Burns had guessed the spiral was likely a rocket, having read about a similar phenomenon in 2009, when a Russian missile launch caused huge blue spirals over Norway. Even knowing the likely source, he said, it was a confronting sight. “None of us had ever seen anything like that before. It was spectacular.”