Two bright yellow "suns" seemingly appeared in the sky over south-western China, baffling locals. A cyclist from Chengdu, Sichuan province, recorded footage of the puzzling sight in the early morning hours of 18 July. He spotted the almost blinding phenomenon while biking down a busy street.Both "suns" in the video seem to have a perfectly round shape and a vibrant yellow colour, with the second one being slightly smaller than the first one and sitting directly underneath. The man said that it was the first time he has ever seen something like this, and witnessing it felt amazing. Although this is not the first time a double sun image has been spotted, scientists have still a lot to discover about this peculiar phenomenon. Astronomers suspect is it most likely a case of a rare mirage, an illusion caused by light refraction which creates a displaced image of faraway objects or the sky.The phenomenon has become known as an atmospheric optical illusion. It happens when light is bent or refracted by the atmosphere. Another type of atmospheric optical illusion that can cause two suns to appear is a sundog. A sundog is a bright patch of light that appears on either side of the sun, which is caused by the refraction of sunlight by ice crystals in the atmosphere.