Residents of Russia's Sakhalin region recently saw a rare and beautiful sight: two bright suns appearing side by side in the sky. This event went viral on social media but is not an actual double sun. It is an optical illusion called a sundog or parhelia. Sundogs form when sunlight passes through flat, hexagonal ice crystals floating high in the atmosphere. These ice crystals, found in cirrus clouds or ‘diamond dust’ during very cold weather, bend the light and create bright spots near the real Sun. The name "parhelia" means "beside the Sun," fitting because sundogs appear next to the Sun, sometimes on both sides, making it look like there are two suns. The colors of sundogs often shift from red near the Sun to yellow and then blue on the edges. This happens because different light colors bend at different angles through the crystals. Sundogs most often appear when the Sun is low in the sky during sunrise or sunset, and in cold weather conditions like winter in Sakhalin. The hexagonal ice crystals needed to create sundogs are common in these chilly conditions. The term “sundog” comes from old myths where the bright spots were thought to follow the Sun like a dog follows its owner. Modern science explains sundogs clearly as light bending through ice crystals. This recent sundog sighting in Sakhalin is a vivid reminder of natural wonders. It shows how ordinary sunlight can create extraordinary sky shows when it meets ice in the air.