Stargazers in New Zealand got a stellar surprise on Sunday night when they saw strange spirals of blue light in the heavens. The country’s amateur astronomers put forward different explanations for what might be causing the unusual phenomenon ranging from UFOs to commercial light displays, The Guardian reports. Stargazing guide Alasdair Burns told the newspaper he and his nonplussed neighbors were left “freaking out just a little bit” by the lights in the sky, adding that the experience was “quite an eerie feeling.” But Prof Richard Easther, a physicist at Auckland University, explained that the unusual marvel was likely caused by a SpaceX’s Globalstar launch from Florida on Sunday. “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.