This was
your sky.

A Seemingly Square Sun

The Sun is round, but in this picture, Earth's atmosphere makes it appear almost square. A layer of air near the Earth was so warm it acted like a giant lens, creating increasingly distorted paths for sunlight to reach the camera. This is similar to how a long, flat highway can appear to be covered with water in the distance. In that case, light from the blue sky is unusually refracted by warm air just above the dry road.