–part 12 of the essay An astronomer in Texas–

A more zoomed-in photo reveals supernumaries. Rainbows are created by water drops of equal size, where light gets reflected inside the drop and, depending on the wavelength, exits the drop at a certain angle. However, if there are several similar-sized types of water drops in the sky, one can see such supernumaries where each order corresponds to a different particle size.