It’s been a couple years since the Department of Awesome Natural Phenomena first discovered a stunning atmospheric optical phenomemon known as Light Pillars, when extremely cold weather makes it look like aliens are dropping in for a visit. In fact the appearance of light pillars is sometimes the cause of false UFO reports.

Instead of visitors from another world, light pillars are the result of many flat, hexagonal ice crystals in the air that collectively function as a giant mirror. They reflect light from the sun, moon, or even street lights upwards and/or downwards to create the appearance of a radiant column of light. The larger the ice crystals, the stronger the effect.

Head over to My Modern Metropolis for a few additional photos.

Photos by Eventarian, Mybackwardswalk, u_sofronov, Ronn & Marketa Murray, Mia Heikkilä, Christoph Geisler, Adam Kraft, NASA, Tristan Greszko, and Joey Holliday respectively.

[via My Modern Metropolis]