At around 8am Tuesday, an unusual sunlight event excited people on the Hauraki Plains near Thames, with many wondering what had caused an unusual halo effect around the sun.

An HC Post reporter snapped pictures of the phenomenon, which eyewitnesses have described as looking like the Death Star from the movie Star Wars. Sadly for fans of the science fiction franchise, however, the explanation for the halo is fully grounded in known scientific fact.

Peter Little, expert meteorologist for meteorological operations at MetService, said the optical phenomenon is caused by "the refraction of light (in this case, sunlight) through ice crystals, and is known as a 22° halo". Little added that the type of clouds which were present this morning played a big part in the halo's formation.

"The cloud type associated with these halos is commonly cirrostratus."

Little directed interested people to the MetService site and a blog on atmospheric optics, which describes clouds high in the atmosphere combining with ice crystals and acting like prisms, separating the different wavelengths of light out from one another and sometimes creating a rainbow colour effect.

For further information, visit https://blog.metservice.com/atmospheric-optics.

- Jim Birchall, Bay of Plenty Times