Sunlight appears white to the human eye, but it contains a spectrum of colors. Under ordinary circumstances, those colors overlap so closely that we perceive them as a single bright source. When sunlight passes through or reflects from particular structures, however, its different wavelengths can be separated or directed along different paths.
This is the foundation of many atmospheric optical phenomena, including rainbows, halos, sundogs, and certain colorful arcs around the Sun.
Ice crystals play a particularly important role in the upper atmosphere. They form in cold clouds, including many cirrus clouds, which often appear as thin, wispy streaks high above the ground. These clouds may seem delicate, but their crystals can produce striking optical effects when sunlight reaches them at the appropriate angles.
A familiar example is the halo: a luminous ring or partial ring around the Sun or Moon. The most common solar halos are associated with sunlight refracting through ice crystals, often producing a ring with a radius of approximately 22 degrees around the Sun. The ring may be white or display subtle colors, with reddish tones on the inner edge and bluish tones farther out.
Another familiar phenomenon is the sundog, sometimes called a parhelion. Sundogs appear as bright patches to the left and right of the Sun, often at approximately the same elevation. Under suitable conditions, they can show vivid colors, with red closest to the Sun and other colors extending outward.
These phenomena can occur in skies that appear otherwise clear. A person might see a bright blue sky, scattered clouds, and an unexpectedly colorful feature without realizing that tiny ice crystals are present in a thin, high-altitude cloud layer.
Could a halo or sundog explain the luminous form over Ikaria?
Possibly, but the geometry matters. A conventional halo generally appears as a ring or arc centered around the Sun, while a sundog is usually located to one side. Neither normally resembles a complete, human-shaped figure. The unusual vertical structure in the photographs would require a more specific explanation, potentially involving a different optical effect, a combination of effects, or the way the image was captured.
A more general concept is atmospheric dispersion. When light passes through a transparent material, different wavelengths can be refracted by slightly different amounts. This separates colors, just as a glass prism can divide white light into a spectrum. Ice crystals can act like tiny prisms, redirecting sunlight and producing colorful displays.
The appearance depends on the crystal's shape and orientation, the direction of the incoming sunlight, and the angle from which the light reaches the observer. Some optical displays are highly dependent on geometry. Move a few steps, and the colors may become weaker, shift position, or disappear altogether.
The camera introduces another layer of complexity. Digital sensors record light differently from the human eye, and intense highlights can overwhelm the sensor's ability to preserve detail. When the brightest portion of an image becomes overexposed, it may turn almost pure white. Fine structures within the light can disappear, while the surrounding edges retain enough color to create a striking outline.
This is especially relevant when the luminous region is extremely bright. The center may appear to have a defined head-like shape, even if the original light source has no such structure. A glowing central area can merge with nearby streaks, while the camera's exposure settings emphasize the contrast between the white core and the colored edges.
Lens flare is another possible contributor. When bright sunlight enters a camera lens, some of the light can reflect between internal optical surfaces or scatter within the lens system. These reflections may produce bright patches, streaks, halos, or colored shapes that are not present in precisely the same form to the naked eye.
Lens flare can be particularly prominent when the Sun is inside or near the camera's field of view. The effect depends on lens design, coatings, the angle of the incoming light, and the presence of dust or other optical irregularities. Smartphone cameras can produce distinctive flare patterns, especially when photographing intense sunlight.
This does not mean that the images are necessarily artificial or that the phenomenon never existed in the real sky. It means that a photograph can contain both a genuine atmospheric display and additional visual effects created during capture.
There is also an important distinction between a rainbow and a halo. A conventional rainbow forms when sunlight interacts with water droplets, usually after refraction, internal reflection, and refraction again. Its position depends on the relationship between the Sun, the droplets, and the observer. Ice-crystal halos arise through different optical geometry and often appear in different parts of the sky.
The rainbow-like streaks in the photographs cannot be confidently classified as a conventional rainbow from appearance alone. Their origin would need to be assessed using the location of the Sun, the orientation of the colorful bands, and the surrounding clouds.
The most scientifically useful question is therefore not simply, "Why is the light colorful?" It is, "What combination of source, atmospheric particles, viewing angle, and camera behavior would produce this particular arrangement of colors?"
Answering that question requires more than a dramatic image. It requires context.
And in a place like Ikaria, where the sky meets a broad expanse of the Aegean Sea, that context may be especially important.