photo #6926074

When sunlight shines through the prism-like ice crystals of high Cirrostratus clouds, it can be refracted into bright rings of light known as halos. A couple are present in this display spotted by Wynne Young over Costa Mesa, California, US. If Wynne had pointed one arm towards the Sun and the other to any point on the large circle of light around it, her arms would have made an angle of 22 degrees. The angle is always the same for this light effect, which is why it is known as a 22-degree halo. The effect happens as sunlight bends, or refracts, as it passes through the angled faces of ice crystals in the cloud that are in the shape of tiny hexagonal columns – like minuscule unsharpened pencils of glass, tumbling through the lofty, frigid air.While the 22-degree halo is a common optical effect in ice-crystal clouds, a much rarer halo is also present in Wynne’s display. This is the smaller 9-degree halo, which appears as a fainter ring that is closer to the Sun (with an angle of 9 degrees between Sun and halo). A ring of light like this only appears if some of the pencil-like ice crystals have more pointed ends. Instead of flat faces, one or both of their ends taper like six-sided pyramids. This means sunlight can shine through faces at different angles to standard hexagonal columns. When you’re on the lookout for halos like these, try taking a photo of the Sun and studying that so you never have to look directly at the Sun, which is eye-damagingly bright through thin cloud like Cirrostratus.