Subscribe | UPI Odd Newsletter Subscribe ULAN BATOR, Mongolia, Jan. 22 (UPI) -- Photos that appear to show three suns rising over Mongolia captured an optical illusion caused by snow crystals in the air, scientists said. Researchers at a Mongolian meteorological center said the phenomenon, known as a parhelion or anthelion, occurs when sunlight passes through snow crystals in the air and is reflected as seeming duplicate suns, known as sundogs. Advertisement The researchers said the three-sun effect can only occur when temperatures drop below -22 degrees and there are clouds, vapor and ice crystals in the sky. Images of the sun flanked by sundogs on either side were captured Sunday across Mongolia.