Ice crystals bend sun’s rays into ring
In the sky above eastern Antarctica, airborne ice crystals sculpt the sun’s rays into a ring.
This phenomenon, called a 22-degree halo, is the result of sunlight passing through tiny, six-sided ice cylinders in high-altitude clouds. The crystals act like prisms, bending incoming light 22 degrees off course. Millions of crystals at various orientations can cast a full circle of light around the sun. While dramatic over polar regions, these halos can occur worldwide, even at the equator. Some halos are decorated with bright spots known as sun dogs or mock suns.
Italian photographer Enrico Sacchetti captured this halo in 2013 over Concordia Station, a joint Italian-French research base on the Antarctic Plateau, one of the coldest places on Earth. While ice in the air puts on a light show, the ice surrounding the station provides researchers an opportunity