The mystery of a pair of lights crossing the sky over the Bay of Islands has been solved by a reader from the Waikato.
John Burns, of Onewhero, has established that the mystery lights were caused not by extra-terrestrial visitors but a piece of space junk and a satellite which by chance passed over the Far North on a similar path just seconds apart.
Paihia man Rob Clarke contacted the Advocate after seeing a pair of lights pass overhead at 9.40pm on Sunday. They were bright, travelled slowly but steadily, and diverged slightly as they crossed the sky from south to north. They were silent so could not have been aircraft.
Mr Clarke said he had had nothing stronger to drink than a cup of tea and did not believe in little green men, but he was curious to know what was responsible for the lights.
Mr Burns read the story online and, with a little research on the astronomy website heavens-above.com, found a Viking rocket body left over from a French space launch in 1986 crossed the sky over Paihia starting in the south at 9.40pm and disappearing over the northern horizon at 9.55pm.
A US Department of Defence weather satellite followed just seconds later, tracing almost the same path and taking just a minute longer to cross the sky.
Although the two objects are 50km apart - the satellite is orbiting about 850km above the Earth, the rocket at 800km - they would have appeared close together. They were almost certainly the cause of the lights Mr Clarke saw, Mr Burns said.
Satellites do not create light of their own but reflect the sun. They are bright enough to be seen easily, especially from a place like Paihia with clear skies and few streetlights.
Mr Burns, a computer programmer by day and amateur astronomer by night, said spotting a satellite was nothing unusual at this time of year. About 20,000 pieces of space debris bigger than 5cm are orbiting the Earth, a few thousand of which are big enough to be seen with the naked eye in the right conditions. A collision between two satellites in 2009 added another 6000 pieces of space debris, he said.
Another reader contacted the Advocate to say some satellites travel in pairs, such as those launched by Nasa last year to study the Earth's magnetic field. Bill Boyce, of Warkworth, photographed the satellites on Saturday night as they traced a double path across the sky.
Many readers also responded on the Advocate's Facebook page, where the most popular theory was that the lights had been caused by Chinese lanterns with one reader reporting that three had released around 9.45pm to celebrate a wedding. Lanterns, however, are unlikely to follow such a steady path across the sky.