In yesterday’s Cloud-a-Day, we explained how the rings of colour around the Sun that are known as a corona can appear as water droplets in a cloud act as tiny obstacles around which the sunlight bends, or diffracts. As if to prove the point that the sunlight doesn’t need to pass through the droplets to form the optical effect, here is a corona spotted by Agnieszka Kowalska near Kraków, Poland formed by tiny – and very opaque – particles of pollen.

The pollen was likely released by trees in the forests of Northern Europe, and its particles were likely very small and regular in size. Their effect of bending the different wavelengths of light by different amounts to separate the sunlight into rings of colour hinges on the size and shape of the minuscule obstacles, not on their clarity. Pollen coronas remind us that atmospheric optics aren’t the sole domain of clouds.